sixteenth international summer school on vacuum, electron and ion

NINETEENTH INTERNATIONAL SUMMER SCHOOL ON VACUUM, ELECTRON AND ION TECHNOLOGIES

21 - 25 September 2015 SOZOPOL, BULGARIA

PROGRAM

ABSTRACTS

Editors: M. Dimitrova, M. Damyanova, Ch. Ghelev and E. Vasileva

INSTITUTE OF ELECTRONICS BULGARIAN ACADEMY OF SCIENCES

72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria Phone: +359 2 875 0077, Fax: +359 2 975 32 01, http://www.ie-bas.dir.bg

The Institute of Electronics carries out research and educational activities in the

fields of Physical Electronics, Quantum Electronics and Radiophysics. The research is focused on: studying the processes of generation and control of beams of electrons, ions and photons, and especially on their interaction with matter; development of experimental and industrial equipment for surface modification, thin-film deposition and analysis; welding and melting of metals; low-temperature plasma, and plasma-chemical processes; plasma-assisted formation of thin films and coatings; interaction of laser radiation with matter and thin-film formation; development of laser sources and systems for spectroscopy, metrology, modification and analysis of materials; non-linear optical phenomena in fibers and semiconductors; generation and propagation of electromagnetic waves; non-linear phenomena in a wide MW-frequency range; scattering of electromagnetic waves from homogeneous and inhomogeneous media, signal detection, data acquisition and processing; development of electronic systems for the MW and optical ranges; systems for remote sounding of the atmosphere and sensing of the sea and Earth surface.

DUTCH INSTITUTE FOR FUNDAMENTAL ENERGY RESEARCH

FOM Institute DIFFER, De Zaale 20, 5612 AJ Eindhoven, The Netherlands Phone: +31 (0) 40 333 49 99, https://www.differ.nl/en

DIFFER was started in 2012 as the focal energy research activity of the Dutch

organisation for scientific research NWO and of its physics branch FOM, the foundation for fundamental research on matter. The institute expands the previous FOM Institute for Plasma Physics Rijnhuizen into a multidisciplinary national home for basic energy research. We perform fundamental energy research in the fields of nuclear fusion and solar fuels, actively working together with academic researchers. DIFFER also connects to research and development at enterprises and industries. To accelerate technology innovation, we are building an active national community on energy research.

DIFFER has two fusion research programs, which both address high priority topics in the European Fusion Roadmap. We explore the intense plasma surface interactions expected at the wall of future fusion power plants with our unique high-flux plasma generators Magnum-PSI and Pilot- PSI.

On the shorter timescale, the big challenge in the energy transition is to integrate fluctuating sustainable electricity in an infrastructure which demands predictable power production. This is closely connected to the issue of global energy storage and transport, and at DIFFER we aim to tackle this challenge by converting intermittent sustainable energy into fuels. For instance, DIFFER investigates the splitting of water into hydrogen or the activation of carbon dioxide into carbon monoxide, and the processing of these products into a hydrocarbon fuel. The research involves the synthesis and design of novel materials and processes to obtain scalable, efficient and cost-effective systems.

NINETEENTH INTERNATIONAL SUMMER SCHOOL ON VACUUM, ELECTRON AND ION TECHNOLOGIES 21 – 25 September 2015, Sozopol, Bulgaria

ORGANIZED BY

INSTITUTE OF ELECTRONICS

BULGARIAN ACADEMY OF SCIENCES, SOFIA, BULGARIA

DUTCH INSTITUTE FOR FUNDAMENTAL ENERGY RESEARCH EINDHOVEN, THE NETHERLANDS

CHAIRS OF THE SCHOOL M. Dimitrova, Institute of Electronics, Bulgarian Academy of Sciences, Sofia, Bulgaria M.C.M. van de Sanden, Dutch Institute for Fundamental Energy Research, Eindhoven, The Netherlands INTERNATIONAL ADVISORY COMMITTEE N. Guerassimov Bulgarian Academy of Sciences, Sofia, Bulgaria M. Dimitrova Czech Academy of Sciences, Prague, Czech Republic R. Panek Czech Academy of Sciences, Prague, Czech Republic Th. Czerwiec Institut Jean Lamour (IJL), Ecole des Mines de Nancy, Nancy, France W. Möller Forschungszentrum Dresden-Rossendorf, Dresden, Germany B. Rauschenbach IOM and Leipzig University, Leipzig, Germany H. Kersten IEAP University of Kiel, Kiel, Germany D. Mataras University of Patras, Patras, Greece V. Guerra Instituto Superior Técnico, Lisboa, Portugal G. Dinescu National Institute for Laser, Plasma and Radiation Physics,

Magurele Bucharest, Romania Z. Petrovic Institute of Physics, Belgrade, Serbia M. Mozetic "Jozef Stefan" Institute, Ljubljana, Slovenia K. Larsson Uppsala University, Uppsala, Sweden I. Katardjiev Uppsala University, Uppsala, Sweden M.C.M. (Richard) van de Sanden

Dutch Institute for Fundamental Energy Research (DIFFER), Eindhoven, The Netherlands

M. Ürgen Istanbul Technical University, Istanbul, Turkey A. Ehiasarian Sheffield Hallam University, Sheffield, UK I. Petrov University of Illinois, Urbana, IL, USA

CO-FINANCED BY the MINISTRY OF EDUCATION AND SCIENCE of BULGARIA

Nineteenth International Summer School VEIT 21 – 25 September 2015, Sozopol, Bulgaria

4

LOCAL ORGANIZING COMMITTEE Ch. Angelov, M. Damyanova, M. Dimitrova (Chair), Ch. Ghelev, E. Vasileva

MAIN SCIENTIFIC TOPICS: • THIN FILMS DEPOSITION • SURFACES AND THIN FILMS PROCESSING AND ANALYSIS • COATINGS FOR ADVANCED APPLICATIONS • PLASMA-SURFACE INTERACTION AND PLASMA DIAGNOSTICS • MODELING AND COMPUTER SIMULATION

PLENARY AND POSTER SESSIONS: A: PLASMA-SURFACE INTERACTION AND PLASMA DIAGNOSTICS.

MODELING AND COMPUTER SIMULATION B: SURFACES AND THIN FILMS PROCESSING AND ANALYSIS

C: THIN FILMS DEPOSITION. COATINGS FOR ADVANCED APPLICATIONS

ABBREVIATIONS: TL – TOPIC LECTURE PR – PROGRESS REPORT OP – ORAL PRESENTATION PA – POSTER SESSION A PB – POSTER SESSION B PC – POSTER SESSION C


PROGRAM

MONDAY, 21 SEPTEMBER 10:00 OFFICIAL OPENING

10:10 – 11:20 PLENARY SESSION 1 Chairman: S. Gateva

Title of the lecture

10:10 TL-1 M. Mozetic Tailoring surface properties of delicate ma-terials by neutral reactive plasma species

11:00 OP-1 T. Bogdanov Theoretical investigation of coaxial dis-charge based on 1d fluid model

11:20 – 11:45 COFFEE BREAK

11:45 – 13:05 PLENARY SESSION 2 Chairman: P. Hovsepian


11:45 PR-1 R. Panek Recent results in edge plasma studies on the COMPASS tokamak

12:15 PR-2 M. Berta Li-beam diagnostic system for the COM-PASS tokamak

12:45 OP-2 P. Marinova Reaction kinetics, heavy particles and rate coefficients in HF and MW discharges in ar-gon at atmospheric pressure

13:05 LUNCH

15:30 – 16:40 PLENARY SESSION 3 Chairman: R. Panek


15:30 PR-3 J. Gunn Heat loads on tungsten divertor targets in ITER

16:00 OP-3 E. Yordanova Measurements of nonlinear susceptibility of multicomponent glassy matrix processing by using femto second z-scan method

16:20 OP-4 S. Karatodorov Optical emission spectroscopy of plasma produced by laser ablation of ferrous sulfide


17:00 – 19:00 POSTER SESSION A

Plasma-surface interaction and plasma di-agnostics. Modeling and computer simula-tion

20:00 WELCOME PARTY


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TUESDAY, 22 SEPTEMBER 10:00 – 11:20 PLENARY SESSION 4

Chairman: M. Mozetič


10:00 TL-2 J. Gerlach Ion-beam assisted deposition of thin films

10:50 PR-4 G. Henrion High time-resolution optical investigations of PEO discharges: towards a better under-standing of what is going on during plasma electrolytic oxidation of light alloys

11:20 – 11:45 COFFEE BREAK 11:45 – 13:05 PLENARY SESSION 5

Chairman: M. Urgen


11:45 PR-5 N. Puac OES and mass spectrometry characteriza-tion of atmospheric pressure plasma jets

12:15 PR-6 G. Dinescu Atmospheric pressure processing with cold radiofrequency plasma jets

12:45 OP-5 A. Kuzminova Fabrication of metal oxide nanoparticles us-ing gas aggregation source combined with auxiliary oxygen RF plasma

13:05 LUNCH 15:30 – 16:50 PLENARY SESSION 6

Chairman: G. Dinescu


15:30 PR-7 M. Urgen Effect of different bias modes on structure and properties of coatings and diffusion lay-ers produced by cathodic arc PVD

16:00 OP-6 A. Kovalenko Gradual annealing effect and thermal stabil-ity of bulk-heterojunction solar cells using DPP(TBFu)2 derivatives as donor materials

16:20 OP-7 G. Tsigaras Detection of power formation in SiH4/H2 glow discharge

16:40 I. Petrov IUVSTA


17:00 – 19:00 POSTER SESSION B

Surfaces and thin films processing and anal-ysis.


WEDNESDAY, 23 SEPTEMBER 10:00 – 11:20 PLENARY SESSION 7

Chairman: J. Gerlach


10:00 TL-3 I. Petrov Control of micro- and nanostructures in transition metal nitrides: recent advances

10:50 PR-8 N. Ghafoor Structuring on a nanoscale to manufactur-ing hard thin films

11:20 – 11:45 COFFEE BREAK 11:45 – 13:05 PLENARY SESSION 8

Chairman: J. F. Pierson


11:45 PR-9 V. Chirita From Ab-initio design to synthesis of multi-functional thin film coatings with enhanced hardness and toughness

12:15 PR-10 P. Hovsepian Three approaches to producing application tailored Me-carbon films

12:45 OP-8 B. Blagoev Resistivity in Al doped ZnO nanolayers ob-tained by atomic layer deposition

13:05 LUNCH 15:30 – 16:40 PLENARY SESSION 9

Chairman: Z. Petrovic


15:30 PR-11 O. Yordanov Fractal vs random field characterization of complex morphologies and patterns

16:00 OP-9 V. Vrakatseli Comparative study of RF reactive magne-tron sputtering and SOL-GEL deposition of UV induced superhydrophilic TiOx thin films

16:20 OP-10 A. Ayrapetov Stand for coating deposition and coat-ing/material testing


17:00 – 19:00 POSTER SESSION C Thin films deposition. Coatings for ad-vanced applications

THURSDAY, 24 SEPTEMBER 10:00 – 11:20 PLENARY SESSION 10

Chairman: I. Petrov


10:00 TL-4 V. Guerra Mesoscopic models as a tool to describe and interpret surface phenomena


8

10:50 PR-12 J. F. Pierson Local epitaxial growth effect in reactively sputtered oxide thin films


11:45 – 13:05 PLENARY SESSION 11 Chairman: H. Kersten


11:45 PR-13 M. Gleeson Surface interactions of plasma-generated species

12:15 PR-14 G. van Rooji Plasmolysis as a novel approach to CO2-to-fuel conversion

12:45 OP-11 V. Sauchyn Investigation of arc spot motion along the electrodes in a plasma torch

13:05 LUNCH 14:00 EXCURSION 20:00 OFFICIAL DINNER FRIDAY, 25 SEPTEMBER 10:00 – 11:20 PLENARY SESSION 12

Chairman: V. Guerra


10:00 TL-5 H. Kersten Non-conventional plasma and sheath diag-nostics

10:50 PR-15 A. Sobota Atmospheric pressure plasma jets in helium – the electric field and the charge delivered to a dielectric surface


11:45 – 12:35 PLENARY SESSION 13 Chairman: N. Guerassimov


11:45 PR-16 V. Ignatova ASML: Pushing the boundaries of what is physically possible in precision engineering

12:05 OP-12 S. Boyadjiev WO3 nanoparticles and WO3/TiO2 core-shell nanocomposites prepared by annealing and atomic layer deposition (ALD) for gas sens-ing, photocatalytic and electrochromic ap-plications

12:25 CLOSING

13:00 LUNCH


ABSTRACTS TOPIC LECTURES Page TL–1 M. Mozetič Tailoring surface properties of delicate

materials by neutral reactive plasma spe-cies

21

TL–2 J.W. Gerlach Ion-beam assisted deposition of thin films

22

TL–3 I. Petrov Control of micro- and nanostructures in transition metal nitrides: recent advances

23

TL–4 V. Guerra

Mesoscopic models as a tool to describe and interpret surface phenomena

24

TL–5 H. Kersten, S. Bornoldt, A. Spethmann, V. Schneider, T. Trottenberg

Non-conventional plasma and sheath di-agnostics

26

PROGRESS REPORTS Page PR–1 R. Panek, J. Adamek, P. Bilkova,

P. Cahyna, R. Dejarnac, M. Dimitrova, P. Hacek, J. Havlicek, M. Hron, M. Imrisek, M. Komm, T. Markovic, M. Peterka, J. Seidl, J. Stockel, P. Vondracek, V. Weinzettl and the COMPASS team

Recent results in edge plasma studies on the COMPASS tokamak

29

PR–2 M. Berta, G. Anda, A. Bencze, D. Dunai, P. Hacek, J. Krbec, R. Panek, G. Veres, S. Zoletnik

Li-beam diagnostic system for the COM-PASS tokamak

30

PR–3 J. P. Gunn Heat loads on tungsten divertor targets in ITER

31

PR–4 G. Henrion, A. Nominé, S.C. Troughton, J. Martin, A.V. Nominé, T.W. Clyne, T. Belmonte

High time-resolution optical investi-gations of PEO discharges: towards a better understanding of what is going on during plasma electrolytic oxida-tion of light alloys

32

PR–5 N. Puač, D. Maletić, N. Selaković, G. Malović and Z.Lj. Petrović

OES and mass spectrometry charac-terization of atmospheric pressure plasma jets

33

PR–6 G. Dinescu Atmospheric pressure processing with cold radiofrequency plasma jets

34


10

Page

PR–7 M. Ürgen, S. Öncel Effect of different bias modes on structure and properties of coatings and diffusion layers produced by cathodic arc PVD

34

PR–8 N. Ghafoor Structuring on a nanoscale to manufactur-ing hard thin films

35

PR–9 V. Chirita From Ab-initio design to synthesis of multifunctional thin film coatings with enhanced hardness and toughness

36

PR–10 P. Eh. Hovsepian and A. P. Ehiasarian Three approaches to producing appli-cation tailored Me-carbon films

37

PR–11 O. Yordanov Fractal vs random field characterization of complex morphologies and patterns

38

PR–12 J.F. Pierson, Y. Wong, J. Ghanbaja, F. Soldera, D. Horwat, F. Mücklich

Local epitaxial growth effect in reactively sputtered oxide thin films

39

PR–13 M.A. Gleeson, T. Zahria, A.W. Kleyn, and M.C.M van de Sanden

Surface interactions of plasma-generated species

40

PR–14 G.J. van Rooij, D.C.M. van den Bekerom, N. den Harder, T. Minea, G. Berden, W.A. Bongers, R. Engeln, M.F. Graswinckel, E. Zoethout, and M.C.M. van de Sanden

Plasmolysis as a novel approach to CO2-to-fuel conversion

41

PR–15 A. Sobota, E.T. Slikboer, O. Guaitella Atmospheric pressure plasma jets in he-lium – the electric field and the charge delivered to a dielectric surface

42

PR–16 V. Ignatova ASML: Pushing the boundaries of what is physically possible in precision engi-neering

43

CONTRIBUTED PAPERS

ORAL PRESENTATIONS

Page

OP–1 T. Bogdanov, E. Benova Theoretical investigation of coaxial dis-charge based on 1d fluid model

47

OP–2 P. Marinova, M. Atanasova, E. Benova

Reaction kinetics, heavy particles and rate coefficients in HF and MW discharges in argon at atmospheric pressure

48


Page OP–3 G. Yankov and E. Iordanova Measurements of nonlinear susceptibility

of multicomponent glassy matrix processing by using femto second z-scan method

49

OP–4 S Karatodorov, V Mihailov and M Grozeva

Optical emission spectroscopy of plasma produced by laser ablation of ferrous sul-fide

49

OP–5 A. Kuzminova, J. Hanus, A. Shelemin, O. Kylian and H. Biederman

Fabrication of metal oxide nanoparticles using gas aggregation source combined with auxiliary oxygen RF plasma

50

OP–6 A. Kovalenko, J. Honová, M. Vala, S. Luňák, L. Fekete, I. Kratochvílová, P. Horáková, L. Dokládalová, L. Kubáč and M. Weiter

Gradual annealing effect and thermal sta-bility of bulk-heterojunction solar cells using DPP(TBFu)2 derivatives as donor materials

51

OP–7 G. Alexiou, G. Tsigaras, A. Kalampounias, E. Amanatides, D. Mataras

Detection of power formation in SiH4/H2 glow discharge

52

OP–8 B. S. Blagoev, D. Z. Dimitrov, V. B. Mehandzhiev, J. B. Leclercq, P. K. Sveshtarov

Resistivity in Al doped ZnO nanolayers obtained by atomic layer deposition

53

OP–9 V.E. Vrakatseli, E. Amanatides and D. Mataras

Comparative study of RF reactive magne-tron sputtering and SOL-GEL deposition of UV induced superhydrophilic TiOx thin films

54

OP–10 A.A. Ayrapetov, L.B. Begrambekov A.E. Evsin, A.V. Grunin, A.A. Gordeev, A.M. Zakharov, A.M. Kalachev, Ya.A. Sadovskiy, P.A. Shigin

Stand for coating deposition and coat-ing/material testing

55

OP–11 V. Sauchyn, I. Khvedchyn Investigation of arc spot motion along the electrodes in a plasma torch

56

OP–12 S. Boyadjiev, V. Georgieva and I. M. Szilágyi

WO3 nanoparticles and WO3/TiO2 core-shell nanocomposites prepared by anneal-ing and atomic layer deposition (ALD) for gas sensing, photocatalytic and elec-trochromic applications

57


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POSTER SESSION A: PLASMA-SURFACE INTERACTION AND PLASMA DIAGNOSTICS. MODELING AND COMPUTER SIMULATION Page PA–1 I. Bozhinova, S. Iordanova,

A. Pashov Investigation of the hydrogen neutrals in discharge source used for production of metal hydrides

61

PA–2 A. Georgiev, A. Pashov, D. Michailova, St. Zapryanov and A. Blagoev

A study of sputtered tungsten atoms by laser induced fluorescence

61

PA–3 V. Mihailov, S. Karatodorov and O. Ivanov

Laser ablation threshold determination by surface photo-charge effect

62

PA–4 V. Tankova, K. Blagoev, M. Grozeva, G. Malcheva

Qualitative and quantitative laser-induced breakdown spectroscopy of bronze objects

62

PA–5 D. Yordanova, G. Malcheva, V. Tankova, A. Pirovska, M. Grozeva

LIBS analysis of valuable precious met-al museum objects

63

PA–6 M. Stefanova, P. Pramatarov, A. Saifutdinov and A. Kudryavtsev

Identification of metal samples by colli-sional electron spectroscopy (CES)

63

PA–7 S. I. Slaveeva, T. P. Chernogorova, K. A. Temelkov

Determination of spatially- and time-resolved electron temperature in nano-second pulsed longitudinal discharge

64

PA–8 K. A. Temelkov, S. I. Slaveeva and Yu. I. Fedchenko

Theoretical study on thermal conductiv-ity of various gas mixtures through ge-neralized Lennard-Jones interaction po-tential for application in gas-discharge lasers

65

PA–9 M. Mitov, V. Videkov, Tsv. Popov, K. Raykov, A. Bankova

Investigation of parameters of gas dis-charge in an argon-oxygen mixture for optimization of the growth of oxide films

66

PA–10 D. López-Bruna, Tsv. Popov, E. de la Cal

Monte Carlo estimates of edge particle sources in TJ-II plasmas

67

PA–11 A. Kasilov, L. Grigor’eva, V. Chechkin, A. Beletskii, R. Pavlichenko, A. Lozin, M. Kozulya, N. Zamanov, Y. Mironov, V. Voitsenya

Peripheral plasma characteristics in the URAGAN-3M torsatron

68

PA–12 M. Dimitrova, N. Puac, N. Skoro, K. Spasic, G. Malovic, Tsv. Popov, F. Dias, Z. Lj. Petrovic

Radial profile of the electron energy distribution function in RF capacitive gas discharge plasma

69


Page PA–13 M. Dimitrova, V. Weinzettl,

J. Matejicek, Tsv. Popov, S. Marinov, S. Costea, R. Dejarnac, J. Stöckel, J. Havlicek and R. Panek and the COMPASS team

Power flux density in the divertor re-gion of the COMPASS tokamak in oh-mic ELMy H-modes

69

PA–14 M. Dimitrova, E. Hasan, P. Ivanova, E. Vasileva, Tsv. Popov, R. Dejarnac, J. Stöckel, P. Junek and R. Panek and the COMPASS team

Electron energy distribution function in the divertor region of the COMPASS tokamak

70

PA–15 P. Ivanova, M. Dimitrova, Tsv. K. Popov, D. López-Bruna, P. Vondráček, R. Dejarnac, J. Stöckel, M. Aftanas, P. Böhm, P. Bílková, P. Junek, M. Hron and R. Panek and the COMPASS team

Radial profile of the plasma parameters measured by horizontal reciprocating Langmuir probes in the COMPASS to-kamak

71

PA–16 M. Damyanova, S. Sabchevski, I. Zhelyazkov, E. Vasileva, E. Balabanova, P. Dankov, P. Malinov

Development of problem-oriented soft-ware packages for numerical studies and computer aided design (CAD) of gyrotrons

72

PA–17 M. Damyanova, U. Hohm, E. Balabanova, D. Barton

Thermophysical properties of CF4/O2 and SF6/O2 gas mixtures

73

PA–18 I. Asenova and E. Valcheva Intersubband optical absorption in ni-tride superlattice grown by MBE

74

PA–19 E. Koleva, V. Dzharov, M. Kardjiev, G. Mladenov

Automation of the electron beam weld-ing process

74

PA–20 E. Koleva, L. Koleva, D. Todorov, G. Mladenov

Electron beam characterization by to-mographic approach

75

PA–21 I.P.Levchuk, V.I.Maslov, I.N.Onishchenko, A.M.Yegorov, V.B.Yuferov

Vertical plasma turbulence suppression in crossed electrcal and magnetic fields due to finite lifetime of electrons and ions and due to finite system length

76

PA–22 I.P. Levchuk, V.I. Maslov, I.N. Onishchenko

Providing homogeneous and identical focusing of train of short relativistic electron bunches by Wakefield plasma lens

77

PA–23 M. Nikovski, Zh. Kiss'ovski, E. Tatarova

Model of surface-wave discharge with fixed profile of gas temperature

78


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Page PA–24 E. Taskova, E. Alipieva and

G. Todorov Stray magnetic field influence on the CPT resonance in a coated Rb vacuum cell

78

PA–25 T. Gyergyek, J. Kovačič A self-consistent one-dimensional mul-tifluid model of the plasma-wall transi-tion in the presence of two species of negatively biased particles

79

PA–26 H. Nichev, M. Petrov, K. Lovchinov, N. Tyutyundzhiev

Open DSS simulations of power fluctu-ations induced by a rooftop PV genera-tor on a building LV electrical grid

80

POSTER SESSION B: SURFACES AND THIN FILMS PROCESSING AND ANALYSIS Page PB–1 S. Muhl, J. Cruz, J. Restrepo Plasma induced heating of the substrate

during magnetron sputtering

83

PB–2 T. Nurgaliev, B. Blagoev, V. Strbik, S. Chromik, M. Sojkova

Investigation of resistive properties of HTS/manganite bi-layers

83

PB–3 V. Štrbík, Š. Beňačka, Š. Gaži, M. Španková, V. Šmatko, Š. Chromik, N. Gál, M. Sojková and M. Pisarčík

Transport properties of YBa2Cu3Ox/La0.67Sr0.33MnO3 nanojunc-tions

84

PB–4 M. Sojková, V. Štrbík, Š. Chromik, M. Španková, T. Nurgaliev, B. Blagoev

Fabrication of hybrid thin film structures from HTS and CMR materials

85

PB–5 P.A. Atanasov, N.E. Stankova, N.N. Nedyalkov, T.R. Stoyanchov, Ru.G. Nikov, N. Fukata, J.W. Gerlach, D. Hirsch, B. Rauschenbach

Properties of nanosecond laser processed polydimethylsiloxane (PDMS)

85

PB–6 G. Atanasova, N. Stoeva, R. Nickolov, I. Spassova

Preparation and characterization of cop-per catalysts supported on mesoporous silica-carbon nanocomposites

86

PB–7 A.Og. Dikovska, G.B. Atanasova, G.V. Avdeev

Thin nanocrystalline zirconia films pre-pared by pulsed laser deposition

87

PB–8 A.Og. Dikovska, G.V. Avdeev, G.B. Atanasova

Effect of Al2O3 on the low temperature degradation of Y-PSZ thin films

87


Page PB–9 R.G. Nikov, A.S. Nikolov,

N.N. Nedyalkov, E.L. Pavlov, P.A. Atanasov, M.T. Alexandrov, D.B. Karashanova

Investigation of the aging process of noble metal nanostructures fabricated by nanosecond laser ablation in water

88

PB–10 Ru.G. Nikov, N.N. Nedyalkov, P.A. Atanasov

Laser nanostructuring of Ag films depo-sited on different substrates

89

PB–11 N. Nedyalkov, M. Koleva, R. Nikov, Y. Nakajima, A. Takami, M. Terakawa

Laser-induced optical properties changes in gold doped materials

89

PB–12 N.E. Stankova, P.A. Atanasov, Ru.G. Nikov, R.G. Nikov, N.N. Nedyalkov

Laser-assisted processing of PDMS elas-tomer as a material for precise neural interface engineering

90

PB–13 A. Nikolov, T. Koutzarova, R. Nikov, N. Nedyalkov, N. Stankova, S. Kolev, P. Peneva, D. Karashanova and D. Kovacheva

Study of barium hexaferrite nanostruc-tures produced by laser ablation in water

90

PB–14 A. Daskalova, C. Nathala, W.Husinsky

Pump-probe investigation of femtose-cond laser induced modification of bio-polymer thin films

91

PB–15 A.A. Grechnikov, V.B. Georgieva, N.Y. Donkov, A.S. Borodkov, A.V.Pento, Tc.A.Yordanov

Comparison of different substrates for laser-induced electron transfer desorp-tion/ionization of metal complexes

92

PB–16 J. Walkowicz, V. Zavaleyev, E. Dobruchowska, D. Murzynski, A. Zykova, V. Safonov, S.Yakovin, N. Donkov

Corrosion properties of zirconium-based ceramic coatings for micro-bearing and biomedical applications

93

PB–17 N. Donkov, A. Zykova, V. Safonov, A.Goltsev, T. Dubrava, I. Rossokha, S. Yakovin, D. Kolesnikov, I. Goncharov

Surface modification of tantalum pen-toxide coatings deposited by magnetron sputtering and further correlation with cell adhesion and proliferation in in vitro tests

94

PB–18 A. Bankova, V. Videkov, K. Raykov, B. Tzaneva, M. Mitov

Investigation of the mechanical stability of anodic aluminum oxide with vacuum-deposited thin metal film

95

PB–19 V. Donchev, M. Milanova, J. Lemieux, N. Shtinkov, I.G. Ivanov

Surface photovoltage and photolumines-cence study of thick Ga(In)AsN layers grown by liquid-phase epitaxy

96

PB–20 E. Halova, N. Kojuharova, S Alexandrova, A Szekeres

Interface characterization of nanoscaled SiOx layers grown on RF plasma hydro-genated silicon

97


16

Page PB–21 A. Bencurova, K.Vutova,

A.Konecnikova, P.Nemec, P. Hrkut, E.Koleva, I. Kostic, G. Mladenov

Study of the CSAR62 new positive tone electron beam resist at 40 keV electron energy

98

PB–22 L. Nedelchev, D. Nazarova, N. Berberova, G. Mateev, V. Salgueiriño, D. Schmool

Enhanced photoanisotropic response in azopolymer doped with elongated goe-thite nanoparticles

99

PB–23 N. Berberova, D. Nazarova, L. Nedelchev, B. Blagoeva, D. Kostadinova, V. Marinova, E. Stoykova

Photoinduced variation of the Stokes parameters of light passing through thin films of azopolymer-based hybrid organ-ic/inorganic materials

99

PB–24 M. Ormanova, V. Angelov, P. Petrov

Investigation of thermal processes in electron-beam surface modification by means of a scanning electron beam

100

PB–25 S. Valkov, D. Dechev, N. Ivanov, P. Petrov

Electron-beam induced surface alloying of titanium with aluminium

101

PB–26 M. Berova, M. Sandulov, T. Tsvetkova, D. Karashanova and L. Bischoff

Structural modification of Ga+-ion im-planted ta-C film

101

PB–27 M. Berova, M. Sandulov, T. Tsvetkova and L. Bischoff

Vibrational spectroscopy of Ga+-ion im-planted ta-C films

102

PB–28 D. Dimitrov, L. Komsalova, D. Lilova, M. Sendova-Vassileva, G. Popkirov , P. Vitanov, I. Gadjov, M. Ganchev

Chemical bath deposition of TiN sul-phide thin films

103

PB–29 S. Kaschieva, Ch. Angelov, S.N. Dmitriev

MeV Electron Irradiation of Si-SiO2 Structures with Magnetron Sputtered Oxide

104

PB–30 K. Raykov, V. Videkov, A. Bankova

Wire bonding on vacuum deposited thin metal film over nanostructured alumi-num oxide

104

PB–31 K.T. Popov, V.G. Sears and B.J. Jones

Gold distribution on latent fingermarks developed by vacuum metal deposition

105

PB–32 T. Hristova-Vasileva, I. Bineva, A. Dinescu, D. Nesheva, D. Arsova, B. Pejova

Thickness influence on the morphology and the sensing ability of thermally de-posited tellurium films

106


POSTER SESSION C: THIN FILMS DEPOSITION. COATINGS FOR ADVANCED APPLICATIONS Page PC–1 R.A. Wilhelm, E. Gruber,

R. Heller, S. Facsko, F. Aumayr Slow highly-charged ions transmission through carbon nanomembranes and gra-phene

109

PC–2 P.G. Sennikov, R.A. Kornev, S.V. Golubev

Plasma-assisted CVD production of iso-topes of group IV and VI elements in the form of thin films, nanoparticles and bulk material

110

PC–3 N. Lukat, E. von Wahl, H. Kersten Mass-spectrometry investigation of plasma for parylene C deposition

111

PC–4 D. Nicheva, V. Ilcheva, T. Petkova, I. N. Mihailescu, G. Popescu-Pelin, G. Socol, C. Ristoscu, P. Petkov

Influence of the preparation method on the optical properties of GeS1.2 – AgI films

112

PC–5 I.I. Maronchuk, D.D. Sankovitch, H. Nichev, D. Dimova-Malinovska

Study of the morphology of Ge quantum dots grown by liquid phase epitaxy

112

PC–6 H. Nichev, N. Georgiev, M. Petrov, K. Lovchinov, D .Dimova-Malinovska, V. Bojinov

Arenecarboximide derivatives as dye-sensitizers applied in thin film solar cells

113

PC–7 Zh. Dimitrov, M. Nikovski, Zh. Kiss'ovski

Deposition of carbon nanostructures on metal substrates at atmospheric pressure

114

PC–8 G. Georgieva, D. Dimov, M. Vala, M. Weiter, G. Dobrikov, and I. Zhivkov

Vacuum deposited organic solar cell structures

114

PC–9 T. Nurgaliev, E. Mateev, L. Slavov, B. Blagoev, G. Gajda, I. Nedkov

Magnetron sputtering of Fe-oxide mag-netic films on dielectric and supercon-ducting substrates

115

PC–10 I. Hilmi, E. Thelander, Ph. Schumacher, J. W. Gerlach, B. Rauschenbach

Influence of the pulsed laser deposition parameters on the properties of epitaxial GST films on Si(111)

116

PC–11 T. Ivanova, A. Harizanova, A. Petrova

Morphological and optical investigation of Sol-Gel ZnO films

117


18

Page PC–12 T. Ivanova, A. Harizanova,

T. Koutzarova, B. Vertruyen Synthesis and properties of ZnO:Al thin films prepared by SOL-GEL method

118

PC–13 R. Andreeva, E. Stoyanova, A. Tsanev, D. Stoychev

Influence of the surface pretreatment of aluminium on the processes of formation of cerium oxides protective films

119

PC–14 N.I. Balalykin, J. Huran, M.A. Nozdrin, A.A. Feshchenko, A.P. Kobzev, V. Sasinková

Transmission photocathodes based on stainless steel mesh and quartz glass coated with N doped DLC thin films prepared by reactive magnetron sputter-ing

120

PC–15 S. Gozzinia, A. Lucchesinia, C. Marinellia, L. Marmugi, S. Gateva, S. Tsvetkov, S. Cartaleva

Transformation of electromagnetically induced transparency into absorption in thermal K optical cell with spin preserv-ing coating

121

PC–16 L. Duta, G.E. Stan, M. Anastasescu, H. Stroescu, M. Gartner, Zs. Fogarassy, N. Mihailescu, C. Luculescu, S. Bakalova, A. Szekeres, I.N. Mihailescu

Structural, optical and vibrational proper-ties of nanostructured aluminum nitride films synthesized by multi-stage pulsed laser deposition

122

PC–17 M. Duta, J. Calderon-Moreno, S. Preda, P. Osiceanu, S. Mihaiu, M. Zaharescu, M. Gartner, S. Simeonov, D. Spasov, A. Szekeres

Electrical properties of p-type In-N co-doped ZnO thin films deposited on dif-ferent substrates

123

PC–18 D. Stoyanova, S. Kitova, J. Dikova, M. Kandinska, A.Vasilev, I. Zhivkov, A. Kovalenko

Impact of the active layer nano-morphology on the efficiency of organic solar cells based on a squaraine dye as a donor

124

PC–19 M. Sendova-Vassileva, G. Popkirov, P. Vitanov, G. Grancharov, V. Gancheva, H. Dikov, E. Lazarova

Optimization of the series resistance in bulk heterojunction polymer solar sells

125

PC–20 Ch. Dikov, P. Vitanov, T. Ivanova Optical and electrical properties of nano-laminate dielectric structures

125

POST DEADLINE CONTRIBUTION

PA–27 K. Ivanov, T. Bogdanov, E. Benova

Theoretical study of surface-wave-discharges in vacuum–plasma and di-electric–plasma configurations

127


TOPIC LECTURES

TL–3

CONTROL OF MICRO- AND NANOSTRUCTURES IN TRANSITION

METAL NITRIDES: RECENT ADVANCES

Ivan Petrov


21

TL–1 TAILORING SURFACE PROPERTIES OF DELICATE MATERIALS BY NEUTRAL

REACTIVE PLASMA SPECIES

M. Mozetič

Department of Surface Engineering, Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia

Non-equilibrium gaseous plasma contains a variety of charged as well as neutral reactive parti-cles. Their concentration depends on the production and loss rates. The production is often pre-dominantly by electron impact – electrons from the high energy tail of the distribution function are capable of ionizing, dissociating and exciting gaseous molecules. The production therefore depends on the electron density and temperature. The loss rate of reactive particles in plasma at low pressure is often by surface reactions. The probability for such reactions depends on the type of particles and material facing plasma. Positively charged ions are accelerated across the sheath next to the surface, lose at least a fraction of their kinetic energy upon impinging on the surface so they cannot re-enter the gas phase. The probability for surface neutralization of posi-tive ions is thus close to unity. Neutral reactive particles do not feel an electric force so they can be trapped on the surface only providing a rather strong chemical bond is established upon interaction with a solid material. Different materials exhibit different affinity to bond neutral particles so the surface loss depends on the type of the material. Of particular interest are radi-cals, such as molecular fragments including neutral atoms. These particles will interact exten-sively with materials capable of chemisorbing atoms but will be just reflected from the surface providing no suitable anchor site is available. The first types of materials are called catalysts while the others are inert. The density of molecular fragments including neutral atoms in the gaseous plasma therefore depends on the surface reactions rather than on the electron density and temperature. Obviously, the flux of neutral reactive particles onto the surface of a treated object immersed into gaseous plasma could be adjusted by placing a material of selected cata-lytic property next to the object. An alternative is treatment of the objects in the flowing after-glow where the charged particles are absent. Tailoring the concentration of neutral radicals by selective catalysts allows for a functionaliza-tion of materials by specific functional groups. A high concentration of such functional groups is unstable so they may decay quickly if a material is exposed to plasma itself. In order to avoid this unwanted effect the materials are rather exposed to plasma afterglows. Such a treatment allows for an optimal functionalization of polymer materials without side-effects otherwise likely to occur upon treatment of polymers by gaseous plasma. Several examples of application of in bio-medicine will be presented.


22

TL–2

ION-BEAM ASSISTED DEPOSITION OF THIN FILMS

J.W. Gerlach

Leibniz Institute of Surface Modification (IOM), Permoserstrasse 15, D-04318 Leipzig, Germany

In modern human life thin and ultrathin films play a tremendous role, a fact, which is in many

cases unbeknownst to the person using them. For the deposition of such films, which possess

highly specific properties and functionalities, a variety of different physical and chemical vapor

phase techniques is available. Ion-beam-assisted deposition (IBAD) is an effective physical

vapor deposition technique. It provides manifold possibilities to intentionally modify or deter-

mine the physical properties of the prepared thin films. The technique is characterized by the

simultaneous bombardment of the growing thin film with energetic ions during the deposition

process. The typical ion energies used with IBAD range from several 10 eV to several 10 keV.

Apart from the preparation of pure single elemental films (using noble gas ion bombardment),

IBAD is particularly well suited for the deposition of compound thin films (e.g. nitrides,

oxides) by using reactive gas ions (e.g. nitrogen, oxygen). This stems from the separation and

the resulting good controllability of the different particle fluxes being involved in the film

growth process. Furthermore, the technique allows for the application of in situ analysis me-

thods in order to investigate the growth process in detail.

In this lecture, a short overview of the IBAD technique is given. Principles and basics of the

technique are addressed. Typical components of an IBAD system are presented and the most

prominent process parameters are related to them. The ion bombardment induced effects at and

below the sample surface are explained. Special weight is put into the dependence of the dif-

ferent ion bombardment induced processes on the ion energy. The requirements in order to de-

posit high quality epitaxial thin films by IBAD are explained as well. All explanations are illu-

strated by results obtained from IBAD films. The lecture closes with a short outlook on future

developments of the IBAD technique.


23

TL–3

CONTROL OF MICRO- AND NANOSTRUCTURES IN TRANSITION METAL NITRIDES: RECENT ADVANCES

Ivan Petrov

Frederick Seitz Materials Research Laboratory and Materials Science Department, University

of Illinois, Urbana, Illinois 61801 Department of Physics (IFM), Linköping University, SE-581 83 Linköping, Sweden

[email protected]

Polycrystalline TiN and related transition-metal nitride (TMN) thin films are typically de-

posited by reactive magnetron sputter deposition and employed as diffusion barriers in microe-

lectronics as well as hard, wear-, and corrosion-resistant coatings in mechanical and optical

applications. We use a combination of HR-XRD, TEM, HR-XTEM, AFM, and STM analyses

to characterize micro- and nanostructures. We will review the fundamental film growth proc-

esses - nucleation, coalescence, competitive growth, and recrystallization - and their role in thin

film microstructure evolution as a function of substrate temperature. Special attention will paid

to in-situ substrate treatment by ion-irradiation and its effect on film microstructure and adhe-

sion. Using spontaneous natural patterning processes, we show that self-organized nanostruc-

tures consisting of commensurate nanolamellae, nanocolumns, nanospheres, and nanopipes can

be synthesized to further extend the range of achievable properties. All of these structures are a

result of kinetic limitations and require low growth temperatures combined with low-energy

(less than the lattice atom displacement potential), very high flux, ion irradiation during deposi-

tion. We will also review recent advances in the selective use of metal ions during HIPIMS co-

sputtering to extend the attainable structures and properties in metastable TMN with examples

of Ti(1-x)AlxN, Ti(1-x)SixN, ad Ti(1-x)TaxN. We probe the effects of (i) metal versus rare-gas ion

irradiation as well as (ii) the type of metal ion uses (Ti vs Me). We employ a metastable NaCl-

structure Ti0.39Al0.61N as a model system to demonstrate that switching from Ar+- to Al+-

dominated bombardment eliminates phase separation, minimizes renucleation during growth,

reduces the high concentration of residual point defects, and thus results in dense, single-phase,

stress-free films.1

For metastable alloys, TiAlN and TiSiN, mechanical properties are shown to be deter-

mined by the average metal-ion momentum transfer per deposited atom .2 Irradiation with

lighter metal-ion (Me = Al+ or Si+ during Me-HIPIMS/Ti-DCMS) procures fully-dense single-

phase cubic Ti1-x(Me)xN films.3 In contrast, with higher-mass film constituents such as Ti,


24

easily exceeds the threshold necessary for phase segregation which results in precipitation of

second w-AlN or Si3N4 phases.

With the TiTaN system we show that synchronized pulsed ion bombardment in the hy-

brid system with the heavy-metal ions (Ta) permits to grow dense, hard, smooth, and stress-

free thin films at lowered substrate temperature, with no external heating.4

Overall, we demonstrate that using synchronous bias to select the metal-rich portion of

the ion flux opens new dimension for ion-assisted growth in which momentum can be tuned by

selection of the metal ion in the hybrid/cosputtering configuration and stresses can be eliminat-

ed/reduced since the metal ion is a component of the film.

1G. Greczynski, J. Lu, M. Johansson, J. Jensen, I. Petrov, J.E. Greene, and L. Hultman, Va-cuum 86 (2012) 1036 2G. Greczynski, J. Lu, J. Jensen, I. Petrov, J.E. Greene, S. Bolz, W. Kölker, Ch. Schiffers, O. Lemmer and L. Hultman, JVSTA 30 (2012) 061504-1 3G. Greczynski, J. Lu, J. Jensen, I. Petrov, J.E. Greene, et al, Thin Solid Films, 556 (2014) 87 4G. Greczynski, J. Lu, I. Petrov, J.E. Greene, S. Bolz, W. Kölker, Ch. Schiffers, O. Lemmer and L. Hultman, JVSTA 32 (2014) 041515 TL–4 MESOSCOPIC METHODS AS A TOOL TO DESCRIBE AND INTERPRET SURFACE

PHENOMENA

Vasco Guerra

Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa

1049-001 Lisboa, Portugal This work addresses the question of modelling heterogeneous molecule formation on silica or

Pyrex surfaces. Despite the impressive evolution of semi-classical molecular dynamics calcula-

tions in recent years [1,2], its application to realistic conditions of molecule formation on silica

surfaces is still difficult. Moreover, the direct coupling with complex gas-phase chemistry

models remains unpractical. In this context, “coarse-grained” mesoscopic models describing

the surface in terms of fractional coverages of different adsorption sites, albeit the lack of a true

predictive capacity, continue to form powerful tools to describe and interpret surface phenom-

ena.


25

Two complementary approaches are explored. The first one relies on a deterministic descrip-

tion where the time-evolution of the adsorbed species and adsorption sites is ruled by a system

of reaction-rate differential equations associated with different elementary processes [3,4]. The

second one is to use a stochastic dynamical Monte Carlo scheme, as outlined in [5,6].

The formation of NO2 molecules on a Pyrex tube of inner radius 1 cm, as a result of NO oxida-

tion by previously adsorbed O atoms on the wall [7,8] is taken as a case study, but other sys-

tems are investigated as well. It is shown that dynamical Monte Carlo methods, in particular

with an algorithm based on local update with lists, can be effectively used to simulate surface

kinetics and coupled gas phase and surface chemistries. These methods are particularly suited

to studying systems where surface diffusion of physisorbed atoms and/or molecules plays an

important role.

Acknowledgments This work was partially funded by Portuguese FCT – Fundação para a Ciência e Tecnologia, under Project UID/FIS/50010/2013.

References [1] M. Rutigliano, C. Zazza, N. Sanna, A. Pieretti, G. Mancini, V. Barone and M. Cacciatore, J. Phys. Chem. A 113 (2009) 15366–75. [2] A. Bogaerts, M. Eckert, M. Mao and E. Neyts, J. Phys. D: Appl. Phys. 44 (2011) 174030. [3] B.F. Gordiets and C.M. Ferreira, AIAA J. 36 (1998) 1643–51. [4] V. Guerra, IEEE Trans. Plasma Sci. 35 (2007) 1397–412. [5] K.A. Fichthorn and W.H. Weinberg, Chem. Phys. 95 (1991) 1090–6. [6] V. Guerra J. Loureiro, Plasma Sources Sci. Technol. 13 (2004) 85–94. [7] O. Guaitella, M. Hübner, S. Welzel, D. Marinov, J. Röpcke and A. Rousseau, Plasma Sources Sci. Technol. 19 (2010) 45026. [8] V. Guerra, D. Marinov, O.Guaitella and A. Rousseau, J. Phys. D: Appl. Phys. 47 (2014) 224012.


26

TL–5

NON-CONVENTIONAL PLASMA AND SHEATH DIAGNOSTICS

H. Kersten, S. Bornoldt, A. Spethmann, V. Schneider, T. Trottenberg

Institute for Experimental and Applied Physics, University of Kiel, Kiel, Germany

In addition to well-established plasma diagnostic methods (Langmuir probes, optical emission

spectroscopy, mass spectrometry etc.) we perform examples of “non-conventional” diagnostics

[1] which are applicable to technological plasma processes for particle formation, surface

structuring and thin film deposition:

i) The total energy influx from plasma to substrates can be measured by special calorimetric

probes (passive or active, respectively) as well as by fluorescent micro-particles. Examples for

rf-discharge and magnetron sputtering will be provided [2-5]. By comparison with model

assumptions on the involved plasma-surface mechanisms, the different contributions to the

total energy influx can be separated.

ii) For a variety of thin film applications it is essential to determine the sputtering yield as well

as the angular distribution of sputtered atoms. For this purpose we developed a novel and rather

simple method, the so-called sputtering-propelled instrument (SPIN) [6]. It is stack nearly

without friction and exposed to a vertical ion beam, rotating due to momentum transfer by the

released particles, i.e. sputtered target atoms and reflected ions. Comparison of the

measurements with simulation yields valuable information on the sputtering mechanisms and

support validation of related sputter codes. The angular distribution of sputtered particles was

also measured by a sensitive pendulum which is commonly used for thrust measurements in

ion beam sources for space propulsion systems.

REFERENCES: [1] T. Trottenberg et.al., Plasma Phys. Control Fusion 54(2012) 124005. [2] H. Maurer, H. Kersten, J. Phys. D: Appl. Phys. 44(2011) 174029. [3] I. Levchenko, M. Keidar, S. Xu, H. Kersten, K. Ostrikov, JVSTB 31(2013) 050801. [4] K. Nishiyama et.al., J. Nucl. Mat. 438(2013), S788-S791. [5] H. Kersten, H. Deutsch, H. Steffen, et.al., Vacuum 63(2001) 385-431. [6] J. Rutscher T. Trottenberg, H. Kersten, Nucl. Instr. Meth. Phys. Res. B 301(2013) 47-52.


PROGRESS REPORTS

PR–9

STRUCTURING ON A NANOSCALE TO MANUFACTURING HARD THIN FILMS

Naureen Ghafoor


29

PR–1

RECENT RESULTS IN EDGE PLASMA STUDIES ON THE COMPASS

TOKAMAK

R. Panek, J. Adamek, P. Bilkova, P. Cahyna, R. Dejarnac, M. Dimitrova, P. Hacek,

J. Havlicek, M. Hron, M. Imrisek, M. Komm, T. Markovic, M. Peterka, J. Seidl, J. Stockel,

P. Vondracek, V. Weinzettl and the COMPASS team

Institute of Plasma Physics AS CR, Prague, Czech Republic

COMPASS is a compact tokamak (R = 0.56 m, a = 0.2 m) operated in divertor plasma configu-

ration with an ITER-like plasma cross-section. COMPASS operates with a plasma current of

up to 0.4 MA and a toroidal magnetic field in the range of 0.9 – 2.1 T. It has been equipped by

two new neutral beam injectors, which provide power of 2 × 0.4 MW at the beam energy of 40

keV for additional plasma heating and which enable co- or balanced injection. COMPASS op-

erates in an ohmic as well as NBI assisted H-mode accompanied by Type-I and Type-III Edge

Localized Modes (ELMs) in the frequency range of 80 – 1 000 Hz.

The main focus of the COMPASS scientific program is on the edge, SOL and divertor

physics supported by a comprehensive new diagnostic system. Characterization of H-mode and

ELMs using several newly developed diagnostic techniques, which allow for unique measure-

ments of the plasma parameters in the pedestal, SOL and divertor regions, will be shown.

In addition, COMPASS is equipped with a system of coils for generation of magnetic perturba-

tions (MP) with a toroidal mode number of n = 2. The plasma response to applied magnetic

perturbation in L- and H-mode by 100 diagnostic saddle loops covering the whole vacuum ves-

sel will be presented. In addition, the changes in divertor plasma during the application of MP

will be shown.


30

PR–2

Li-BEAM DIAGNOSTIC SYSTEM FOR THE COMPASS TOKAMAK

M. Berta1,2,3 G. Anda2, A. Bencze2, D. Dunai2, P. Hacek3, J. Krbec3, R. Panek3, G. Veres2, S. Zoletnik2

1Széchenyi István University, Győr, Hungary

2Wigner RCP, Budapest, Hungary 3Institute of Plasma Physics CAS, v.v.i., Prague, Czech Republic

Detailed information about the electron density profile and its fluctuations is very valuable and

important for operation of tokamaks. Li-beam diagnostic method is one of the useful

techniques of electron density measurement.

The COMPASS tokamak is equipped with a completely new Li-beam diagnostic system, which

has been extended with a novel Li-ion detector for plasma edge current fluctuation

measurement.

The energy of the incident beam can be varied from 10 − 120 keV. The ion current extracted

from the emitter is between 1 − 5 mA. The observation system has three branches.

At the bottom of the machine is placed an 18-channel, radially distributed system of avalanche

photodiodes with appropriate optics for fast profile and fluctuation measurement.

On the top of the COMPASS tokamak there is a CCD camera installed for slow density profile

measurements, and an ion detector − called atomic beam probe − for plasma edge current

fluctuation measurements.

With this system we are able to reconstruct the electron density profile every 4 microsecond

with 1 − 2 cm spatial resolution. The density fluctuations dynamics can be followed with a

time resolution of 500 nanosecond. The ion detection system is in test operation, but its

expected time resolution is about 10 − 20 μs, the spatial resolution is in the submillimeter

range, and will be able to resolve 10% of the edge plasma current's changes.

Besides of the diagnostic system's description, experimental results demonstrating the system's

capabilities will also be presented.


31

PR–3

HEAT LOADS ON TUNGSTEN DIVERTOR TARGETS IN ITER

J. P. Gunn

CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France. The International Thermonuclear Experimental Reactor (ITER) will begin operation with a full

tungsten (W) divertor consisting of solid W monoblocks (MB) bonded to CuCrZr water-

carrying cooling tubes. The "Heat and Nuclear Load Specifications" (HNLS) is the ITER

Project Level document that defines the maximum thermal loads to which plasma-facing com-

ponents can be subjected, based on the best current knowledge from both physics modelling

and observations on current devices. The maximum manageable heat loads to the divertor are

imposed by engineering knowledge about material/technology limits, and validated by tests in

high heat flux devices. In steady state (SS), the maximum inter-ELM heat load allowed by the

HNLS is qHNLS = 10 MW/m2. During the lifetime of the first divertor, which is supposed to

survive until the end of the first full D-T campaign, slow transient (ST) re-attachment events

may occur due principally to loss of detachment control. During each of these events, the di-

vertor can sustain qHNLS = 20 MW/m2 for up to 10 s. Concerning fast transients (FTs), e.g. edge

localized modes (ELMs), it is the surface heat flux factor which is of interest, because we wish

to compare it to the melting threshold of W, εmelt = 48 MJ/m2s1/2. The heat flux factor is given

by the energy flux density normal to the MB surface, divided by the square root of the FT rise

time ΔtELM = 250 µs.

All the heat loads described above are specified in the HNLS in terms of heat flux normal to an

ideal, axisymmetric, unshaped divertor surface, but MB shaping, potential misalignments, and

castellation lead inevitably to local heat flux peaking. The actual power flux delivered to any

point on the MB surface must be calculated by integrating the distribution functions at the

sheath entrance, modified to describe shadowing by surface features. Surface heat loads on

several ITER monoblock design options are derived using physics-based modelling. Power

flow into gaps, target tilting, and monoblock shaping would lead to peak temperatures that can

exceed the tunsgten recrystallization temperature during inter-ELM detached regime, and poss-

ible edge melting during slow transient reattachment. Furthermore, the margin against global

surface melting due to mitigated ELMs would be lost.


32

PR–4

HIGH TIME-RESOLUTION OPTICAL INVESTIGATIONS OF PEO DISCHARGES: TOWARDS A BETTER UNDERSTANDING OF WHAT IS GOING ON DURING

PLASMA ELECTROLYTIC OXIDATION OF LIGHT ALLOYS

G. Henrion1, A. Nominé2, S.C. Troughton3, J. Martin1, A.V. Nominé2, T.W. Clyne3, T. Belmonte1

1Institut Jean Lamour, CNRS – Université de Lorraine, Nancy, France

2The Open University, Department of Physical Sciences, Milton Keynes, United Kingdom 3Department of Materials Science & Metallurgy, Cambridge University, United Kingdom

The Plasma Electrolytic Oxidation (PEO) is a particular electrochemical process to produce protective oxide ceramic coatings on light-weight metals as aluminium, magnesium or titanium. The process is carried out in a liquid conductive electrolyte and high current density (some 10s of A.dm-2) and voltage (some 100s of V) are applied to the working electrode. This leads to the development of micro-discharges (MDs) on the sample surface due to dielectric breakdown. It is admitted that MDs are the main contributors that allow oxidation to pursue beyond the usual limits encountered in anodizing.

Although several investigations have been carried out to improve the efficiency of the PEO process, and despite the considerable interest in this process, there is still no clear understanding of the underlying discharge mechanisms that make possible metal oxidation up to hundreds of µm through the ceramic layer. Indeed, these mechanisms are complex because they occur in a multi-phase medium with multiple interphases.

Using optical tools with high time-resolution may help to characterize the MDs and therefore propose descriptive breakdown mechanisms and resulting oxidation of the material.

After a brief review of the recent progress in PEO process investigation, the presentation will focus on the latest results related to optical emission spectroscopy of PEO discharges together with high-speed video imaging of single PEO discharges. It will particularly be shown that discharges occur as cascades with duration of some tens of micro-seconds, and that successive cascades tend to ignite at the same location over one half-cycle of the AC current. Another issue that will be addressed concerns the mutual behavior of discharges and gas bubbles. Does the discharge ignite in a gas bubble or is the bubble a consequence of the discharge ignition? In fact, the question is still open and light may come from video images of both discharges and bubbles.

In light of these results, the breakdown-growth mechanisms will be discussed by describing both the physical behaviour of the plasmas and the growth of the oxide coating.


33

PR–5

OES AND MASS SPECTROMETRY CHARACTERIZATION OF ATMOSPHERIC PRESSURE PLASMA JETS

N. Puač, D. Maletić, N Selaković, G. Malović and Z.Lj. Petrović

Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia

Fast time-resolved ICCD imaging is one of the easiest and, also, the most important ways to

investigate time/space development of plasma in plasma jet systems. From these high-speed

images, it can be seen that plasmas in plasma jets are not always continuous, but they some-

times appear as plasma packages that propagate from the glass tube filled with a flow of helium

into the surrounding atmosphere. These plasma packages, the so called “plasma bullets” or

PAPS (pulsed atmospheric pressure streamers), are not yet fully understood. It is assumed that

photons and Penning ionization play the main role in propagation of “plasma bullets”. We have

investigated PAPS development and propagation for various electrode set-ups [1, 2]. It was

shown that an optimal configuration can be found in order to get the maximum travelling dis-

tance of PAPS. Also, while inside the electrodes plasma has a ring-like shape and it is mainly

travelling along the walls of the glass tube. On the other hand, inside the glass tube (inter-

electrode region) plasma is confined to the center of the tube and the main emission is originat-

ing from that volume. When plasma comes in contact with the ambient air, the discharge vol-

ume increases and plasma acquires a sphere-like shape before its starts to travel in open air. At

all times, the PAPS are connected with the main discharge inside the tube with a trail of a very

small emission. Since the main reason for the development of these atmospheric plasma de-

vices are applications, particularly in medicine and biology, it is necessary to make detailed

diagnostics of the plasma and, most importantly, examine its chemical composition. We have

used a Hiden HPR 60 mass-energy analyzer for the integrated and time-resolved measurements

of the neutral and ionic species originating from an atmospheric-pressure plasma jet.

Acknowledgments: This research has been supported by the Ministry of Education, Science and Technological Development, Republic of Serbia, under projects III41011 and ON171037. 1. N Puač, D Maletić, S Lazović, G Malović, A Đorđević and Z Lj Petrović 2012 Appl. Phys.

Lett. 101 24103 2. D Maletić, N Puač, N Selaković, S Lazović, G Malović, A Đorđević and Z Lj Petrović

2015 Plasma Sources Sci. Technol. 24 025006 (9pp)


34

PR–6 ATMOSPHERIC PRESSURE PROCESSING WITH COLD RADIOFREQUENCY

PLASMA JETS

G. Dinescu1,2

1National Institute for Laser, Plasma and Radiation Physics, Atomistilor 409, 077125, Magurele- Bucharest, Romania

2Physics Department, University of Bucharest, Atomistilor 405, Magurele, Romania

We present the principles and various discharge configurations for producing cold ra-diofrequency plasmas at atmospheric pressure, like plasma jet sources of DBD (Dielectric Bar-rier Discharges) and DBE type (Discharges with Bare Electrodes) and their utilization in engi-neering, biology and medicine, environment, and nanotechnology. The applicative potential of those plasmas is exemplified with: polymer surface modification in order to control the wet-tability, cleaning and etching, patterning the cells growth on surface, promoting the adhesion of dental prostheses, operation in liquid phase for chemical decomposition, functionalization of carbon nanowalls, and synthesis of metallic nanoparticles.

PR–7

EFFECT OF DIFFERENT BIAS MODES ON STRUCTURE AND PROPERTIES OF COATINGS AND DIFFUSION LAYERS PRODUCED BY CATHODIC ARC PVD

M. Ürgen1, S. Öncel2

1Istanbul Technical University, Department of Metallurgical and Materials Engineering, 34469,

Maslak, Istanbul-Turkey

2Nanomate Surface Tech Inc. DES San. Sit. 116. Str. No:22 34776 Y.Dudullu, Umraniye Istanbul

Cathodic arc plasmas are capable of highly ionizing the metal vapors created by the arcs

travelling on the cathode surface. Thus the plasmas created in this manner are rich in both metal ions and electrons. In the conventional cathodic arc PVD (CAPVD) process, a negative DC or pulse bias is applied to substrate surfaces for achieving a dense and very well adherent coatings on the substrate.

In the first part of this presentation, the effects of the negative bias magnitude and mode will be discussed. Specific examples will be given for TiN and TiAlN coatings produced by using high-voltage pulse bias. In the second part of the talk, a recent method developed in our group will be presented. In this method, contrary to conventional applications, we aimed to utilize both the electrons and ions


35

in the CA plasma by the application of AC bias to the substrates. The method allows heating the substrate in a controlled manner by tuning the electron current passing through the sub-strate. Thus it becomes possible to alloy the substrate with the depositing metal or alloy and to minimize the stress in the hard coating. Several applications of the method related to surface alloying (aluminizing of nickel, titanium and steel) and low stress nitride based coatings (TiN) will be given and discussed. PR–8

STRUCTURING ON A NANOSCALE TO MANUFACTURING HARD THIN FILMS (From structural design to deformation mechanisms)

Naureen Ghafoor [email protected]

Nanostructured Materials, Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden

“Man is a tool-using animal...” − this statement has often been described in history to distin-guish the technological abilities of humans from those of other creatures. Today, more than 2.5 million years after the earliest discovery of tools, tool technology still stays a decisive factor in our evolution. Among the many factors that determine the functionality of a tool is its hard-ness. It is a fundamental property and may be the most crucial one. Thanks to the contemporary progress in scientific methodology, today we are able to uncover the hardening mechanisms in old known materials. This knowledge can be used to manufacture even harder materials, in-cluding very thin films deposited onto tools, for better cutting performance under harsh condi-tions. In this lecture, a general concept of hardness in a few bulk materials will be reviewed with the main focus on nanostructuring. Two-phase complex nanostructures from immiscible transition metal nitrides Zr1-xAlxN1 and Zr1-xSixN2 alloys as well as Zr1-xAlxN/ZrN and Zr1-xSixN/ZrN su-perlattices were realized with a thin-film deposition technique called magnetron sputtering. The growth, structure, and hardness relationship will be presented. We have explored a range of obtainable self-organized structures in these materials. The phase evolution, decomposition, and mechanical properties of the films as a function of the structural design and growth para-meters will be discussed. There will be an emphasis on the necessity to perform theoretical calculations and profound structural characterization of the complex nanostructures in addition to the syntheses to devel-op future thin films for cutting tools.

1 N. Ghafoor, L. Johnson, D. Klenov, J. Demeulemeester, P. Desjardins, I. Petrov, L. Hultman, M. Odén, APL Materials 1 (2) (2013) 022105. 2 N. Ghafoor, I. Petrov, D.O. Klenov, B. Freitag, J. Jensen, J.E. Greene, L. Hultman, M. Odén, Acta Materialia 82 (0) (2015) 179.


36

PR–9 FROM AB-INITIO DESIGN TO SYNTHESIS OF MULTIFUNCTIONAL THIN FILM

COATINGS WITH ENHANCED HARDNESS AND TOUGHNESS

V. Chirita

Thin Film Physics, IFM, Linköping University, Sweden

Enhanced toughness in hard and superhard thin films is a primary requirement for present day ceramic hard coatings, known to be prone to brittle failure during in-use conditions, in modern applications. Density Functional Theory (DFT) investigations predicted significant improve-ments in the hardness/ductility ratio of several pseudobinary B1 NaCl structure transition-metal nitride alloys, obtained by alloying TiN or VN with NbN, TaN, MoN and WN [1, 2]. The ini-tial calculations reveal that the electronic mechanism responsible for toughness enhancement stems from the high valence electron concentration (VEC) of these alloys, which, upon shear-ing, leads to the formation of alternating layers of high and low charge density oriented ortho-gonal to the applied stress, and ultimately allows a selective response to tetragonal and trigonal deformations.

Recently, these results have been validated experimentally [3]. Single-crystal V0.5Mo0.5N/MgO(001) alloys, grown by dual-target reactive magnetron sputtering together with VN/MgO(001) and TiN/MgO(001) reference samples, exhibit hardness > 50 % higher than that of VN, and while nanoindented VN and TiN reference samples suffer from severe cracking, the V0.5Mo0.5N films do not crack. New DFT calculations address the issue of lattice ordering effects on the mechanical properties of these pseudobinary alloys, and concentrate on V0.5Mo0.5N, V0.5W0.5N, Ti0.5Mo0.5N and Ti0.5W0.5N alloys. The results reveal that while the de-gree of electronic structure layering, i.e. the formation of alternating layers of high and low charge density upon shearing, becomes less pronounced in disordered configurations, the over-all VEC effect is not affected. The essential feature in the disordered alloys, as initially re-ported for ordered alloys, is the increased occupancy of electronic d-t2g metallic states, which allows the selective response to tensile/shearing stresses, and explains the enhanced toughness confirmed experimentally for V0.5Mo0.5N films.

[1] D. G. Sangiovanni et. al. Phys. Rev. B 81, 104107 (2010). [2] D. G. Sangiovanni et. al. Acta Mater. 59, 2121 (2011). [3] H. Kindlund et. al, APL Materials 1, 042104 (2013).


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PR–10

THREE APPROACHES TO PRODUCING APPLICATION TAILORED Me-CARBON FILMS

Papken Eh. Hovsepian and Arutiun P. Ehiasarian

HIPIMS Technology Centre, Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK

The lecture discusses three approaches to producing metal carbon films to address triboological problems in key industrial applications. The first approach utilizes the effects of dynamic segregation and self-organization growth mechanisms in Cr-C films to achieve high wear resistance. High ion irradiation during coating growth of C-based coatings can produce clusters of almost pure carbon surrounded by a hard Me-carbide phase. The clusters are arranged in a nanoscale multilayer structure with an abnor-mally large spacing between the individual layers of 25 nm. Cr-C films with carbon clusters when used as a top coat on TiAlCrYN have shown excellent performance in dry machining of Ni-based alloys. The second approach utilizes the effect of low shear strength interfaces in nanoscale multilayer structured V-C based films to control coating wear mechanism. In TiAlCN/VCN coatings car-bon segregates laterally during the coating growth to produce a weak phase at the interface be-tween the individual layers of TiAlCN and VCN. The low shear strength carbon based inter-faces prevent built up edge formation when machining Al and Ti alloys. The third approach utilizes tribochemical reactions to achieve low friction and high wear resis-tance of Me-C films in boundary lubrication and at elevated temperatures. Mo-W- C coatings were deposited by a combined nonreactive HIPIMS and DC-sputtering technique. In pin-on-disc tests at room temperature lubricated conditions using non-formulated engine oil (Mobil1 10W-60), the coatings showed a friction coefficient of µ = 0.033, which was lower than that reported for a number of DLCs. At 200oC and lubricated conditions, the friction coefficient remained low at 0.05 compared to 0.08 measured for state-of-the-art DLC coating under the same conditions. Raman spectroscopy of the wear debris revealed that in lubricated conditions the wear product contained a MoS2 phase. In boundary lubrication condition, the friction be-havior of the Mo-W doped C coatings is influenced by the formation of solid lubricants via tri-bochemical reactions at the asperity contacts due to high flash temperatures. Mo-W-C films are potential candidates to prolong the life time of automotive components.


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PR–11

FRACTAL VS RANDOM FIELD CHARACTERIZATION OF COMPLEX MORPHOLOGIES AND PATTERNS

Oleg I. Yordanov

Institute of Electronics, Bulgarian Academy of Sciences. 72 Tsarigradsko Chaussee blvd, Sofia

1784, Bulgaria

Fractal methods, and their generalization multifractal methods, are becoming increasingly popular for characterization of complex structures in a variety of science and technology areas. An important example is provided by the surface roughness, which in turn affects a number of physical processes. The fractals own their du jour to the simplicity of methods as well as to the availability of algorithms and software for evaluation of the fractal dimension(s). A number of drawbacks exist, however, which substantially limit the applicability and the usefulness of the fractal models. The most serious one is related to the interpretation of the results: the fractal estimation provides just values of exponent(s)/dimension(s), evidence (sometimes rather poor) of a scaling, which is hard to link with relevant physical characteristics and processes. Another major problem comes from the lack of methods for statistical validation of the results obtained rooted in the fact that the probability distributions of the fractal dimensions is almost never known. In this report, we review the development and present some new results for an alternative ap-proach based on modelling of complex patterns using approximate scale-invariant random fields [1,2]. The fields of interest are constructed from their spectral (Fourier) representations and involve single- or multi-segment, power-law, piece-wise continuous functions. In contrast to the fractal methods, the stochastic field modelling renders a richer and more adequate de-scription of the complex structures, including variances, autocovariance and structures func-tions, root mean derivatives, curvature, etc. A particular focus in the report is given to the sta-tistical estimations of these functions from empirical data as well as to the computer simula-tions of the fitted fields. Both represent new facets of the methodology and are key steps for the models’ statistical verification. [1] Yordanov O.I. and N.I. Nickolaev, Phys. Rev. E, (Rapid Comm.), 49, p. R2517 (1994). [2] O. Yordanov and I. Atanasov, European Phys. Jour. B, 29, p. 211 (2002).


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PR–12

LOCAL EPITAXIAL GROWTH EFFECT IN REACTIVELY SPUTTERED OXIDE THIN FILMS

J.F. Pierson1, Y. Wong1, J. Ghanbaja1, F. Soldera2, D. Horwat1, F. Mücklich2

1Institut Jean Lamour, Université de Lorraine, Nancy, France

2Department for Materials Science, Saarland University, Saarbrücken, Germany The texture of thin films strongly influences their functional properties (hardness, oxidation resistance, electrical resistivity, optical properties…). In reactively sputtered thin films, the texture of the coatings can be tuned by the deposition conditions, such as bias voltage, total pressure, reactive gas flow rate… However, the deposition parameter window to get a specific texture can be narrow and during the synthesis of the coating a small change in the conditions may induce a drastic change of the film texture. In this presentation, the Cu-O and Ni-O systems are studied to show their ability to grow at room temperature and on glass substrates oxide films with a texture that is independent on the deposition conditions. Among the various deposition conditions, the total pressure is found to have a strong effect on the preferred orientation of Cu2O films: [100] at a low pressure and [111] at a high pressure [1]. Using a two-step deposition procedure, a highly textured Cu2O thin film with a controlled orientation can be formed independently of the deposition conditions. Provided that it has a sufficient thickness, this layer acts as a seed layer that determines the crystal orientation of a second layer grown even after air exposure and/or without specific cleaning of the surface prior to deposition [2]. High-resolution transmission electron microscopy analyses evidence that the top layer grows in homoepitaxy with the seed layer with a microstructure consisting of single crystal columns crossing the interface between the layers. The same behavior has been obtained for NiO thin films. Finally, this local epitaxial growth effect has been used to grow NiO films with [111] texture on a previously deposited Cu2O film [3].

[1] Y. Wang et al., Appl. Surf. Sci. 335 (2015) 85

[2] Y. Wang et al., Acta Mater. 76 (2014) 207

[3] Y. Wang et al., submitted


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PR–13

SURFACE INTERACTIONS OF PLASMA-GENERATED SPECIES

M.A. Gleeson1, T, Zahria2, A.W. Kleyn3, and M.C.M van de Sanden1

1Dutch Institute for Fundamental Energy Research (DIFFER), De Zaale 20, 5612 AJ,

Eindhoven, The Netherlands. 2Materials Innovation Institute (M2i), P.O. Box 5008, 2600 GA Delft, The Netherlands.

3Center of Interface Dynamics for Sustainability, Chengdu Development Center for Science and Technology, 355, Tengfei Er Road, Chengdu, Sichuan 610207, People’s Republic of China.

This progress report presents recent developments in plasma-materials interaction research at the Dutch Institute for Fundamental Energy Research (DIFFER). The work is primarily focussed on plasma-surface interactions and the utilization of UHV techniques to investigate the same. The plasma state can produce reactive or activated species that can drive unconventional reactions and reduce barriers to chemical conversions that may be high under conventional chemical conditions. However, the plasma is a complex environment and disentangling the significance of the contribution from various processes is extremely challenging. To circumvent this, an approach is adopted that separates plasma generation from the surface interaction. This is illustrated by presenting a recent work on the interaction of hyper-thermal nitrogen with ruthenium [1], which produced a clear-cut demonstration of Eley-Rideal (ER) (direct abstraction) reaction for a “heavy atom” system. The evidence for ER reaction along with the details it reveals about the reaction system are discussed. We will also give an introduction to recently initiated projects on the role that surfaces and materials can play in realizing plasma-assisted conversion of CO2 for the purpose of solar fuels production. This work is part of a core line of research at the DIFFER institute.

[1] “Eley-Rideal Reactions with N Atoms at Ru(0001): Formation of NO and N2”, Teodor Zaharia, Aart W. Kleyn, and Michael A. Gleeson, Phys. Rev. Lett. 113, 053201. DOI: PhysRevLett.113.053201

http://dx.doi.org/10.1103/PhysRevLett.113.053201


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PR–14

PLASMOLYSIS AS A NOVEL APPROACH TO CO2-TO-FUEL CONVERSION

G.J. van Rooij,a D.C.M. van den Bekerom,a N. den Harder,a T. Minea,a G. Berden,b W.A. Bongers,a R. Engeln,c M.F. Graswinckel,a E. Zoethout,a and M.C.M. van de Sandena,c

aDutch Institute for Fundamental Energy Research, P.O. box 6336, 5600 HH Eindhoven, The Netherlands; Tel: +31 (0) 40 333 49 99 ; E-mail: [email protected]

bRadboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands.

cDepartment of Applied Physics, Plasma and Materials Processing Group, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.

Sustainable energy generation by means of wind or from solar radiation through photovoltaics or concentrated solar power will be a significant part of the energy mix in 2025. Intermittency (due to e.g. day/night cycle) as well as regional variation of these energy sources requires means to store and transport energy on a large scale. A promising option is creating artificial solar fuels (or CO2 neutral fuels) with sustainable energy, which can easily be deployed within the present infrastructure for conventional fossil fuels. A candidate raw material would be CO2 itself (fitting in carbon capture and utilization, CCU, strategies). Presently, no efficient schemes are yet available for the conversion of CO2 into fuels. A plasma chemical approach potentially offers high energy efficiency (up to 90%) due to selectivity in the reaction processes that can be tailored via its inherently strong out-of-equilibrium processing conditions. At the same time, it is characterized by efficient and fast power switching, low investment costs, no scarce materials required, and high power density, which are all advantageous for addressing intermittency. In this presentation, the plasma chemical approach will be introduced and examples will be discussed of research carried out at the DIFFER to ultimately enable a scale up to industrial applications. In particular, a common microwave reactor approach is evaluated experimentally with Rayleigh scattering and Fourier transform infrared spectroscopy to assess gas temperatures (exceeding 104 K) and conversion degrees (up to 30%), respectively. The results are interpreted on the basis of estimates of the plasma dynamics obtained with electron energy distribution functions calculated with a Boltzmann solver. It indicates that the intrinsic electron energies are higher than is favorable for preferential vibrational excitation due to dissociative excitation, which causes thermodynamic equilibrium chemistry still to dominate the initial experiments. Novel reactor approaches are proposed to tailor the plasma dynamics to achieve the non-equilibrium in which vibrational excitation is dominant.


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PR–15

ATMOSPHERIC PRESSURE PLASMA JETS IN HELIUM – THE ELECTRIC FIELD AND THE CHARGE DELIVERED TO A DIELECTRIC SURFACE

A. Sobota1, E.T. Slikboer1, O. Guaitella2

1EPG, Eindhoven University of Technology, Postbus 513, 5600MB Eindhoven, The

Netherlands

2LPP, Ecole Polytechnique,Route de Saclay, 91128 Palaiseau CEDEX, France The family of non-thermal atmospheric pressure discharges has been the focus of intense

research of a large number of research groups in the last fifteen years, as they are easy and

cheap to assemble and run, and exhibit properties that can be used in surface treatment or

biological applications. In this discharge family, the non-thermal atmospheric pressure plasma

jet commands a good deal of attention.

The mentioned applications all involve the presence of a surface (target for treatment) in the

vicinity of the discharge, and it has been shown that in many cases the presence of the surface

alters the properties of the discharge. There are many types of surfaces to consider, from

metals, dielectrics, to liquid surfaces, and they all leave a different mark on the discharge

properties. Still, most of the research has been done on plasma jets expanding freely into the

open air.

This paper reports on the electric field and charge measurements delivered to a dielectric

surface by an atmospheric-pressure plasma jet working in the bullet mode in helium. Imaging

will be presented alongside the measurements of charge, as it will be evident that the charge

distribution on the dielectric surface will mirror the observations obtained by imaging. The

central results contain the charge packed in one ionization wave leaving the capillary towards

the target, around 20 pC. The associated electric fields vary between 3×105 and 6×105 V/m.


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PR–16

ASML: PUSHING THE BOUNDARIES OF WHAT IS PHYSICALLY POSSIBLE IN PRECISION ENGINEERING

V.A. Ignatova

| On-product Overlay Performance – Modeling| ASML Netherlands B.V. Building 21 C2.039 | De Run 6501, 5504 DR Veldhoven | The Netherlands

T +31 61 13 452 572| F +31 40 268 5577 | E velislava.ignatova @asml.com | I http://www.asml.com

ASML is a successful high-tech company headquartered in the Netherlands, which manufac-tures complex lithography machines. ASML is a technology leader and supplier to all leading chip manufacturers around the world. The steady progress of the world’s technological evolu-tion through faster, smarter, more energy-efficient yet more affordable chips is to a large extent the result of technological breakthroughs at ASML. One of the breakthroughs is the recently launched holistic lithography approach, which links the lithography machines (scanners) to the metrology and computational lithography design context. Customer device shrink roadmap is leading litho approaches for 7 nm technology to drive for high density design to support advanced – mobile – applications. Based on metrology and control SW we are moving from process window detection, through computational litho-graphy design context, towards process window enhancement and process window control. Litho-Insight (LIS) is an ASML application product for process control on all domains – over-lay, focus and dose. There are number of steps to derive process corrections from wafer data: measurement with ASML’s metrology tool YieldStar, determination of corrections in the Litho InSight application and applying these corrections on the scanner. This calls for a holistic ap-proach on OV process control where we split and quantify the systematic and noise contribu-tions to all variations in the data at each of the steps. ASML spends more than 1 billion Euros per year on R&D, our people have the freedom and the resources to push boundaries of known technology. They work in close-knit, multidiscipli-nary teams and each day they listen to, learn from and exchange ideas with each other. It’s the ideal environment for professional development and personal growth.

http://www.asml.com/


ORAL PRESENTATION OF CONTRIBUTED PAPERS

OP–6

DETECTION OF POWDER FORMATION IN SiH4/H2 GLOW DISCHARGES

G. Alexiou, G. Tsigaras, A. Kalampounias, E. Amanatides, D. Mataras


47

OP–1

THEORETICAL INVESTIGATION OF COAXIAL DISCHARGE BASED ON 1D FLUID MODEL

T. Bogdanov, E. Benova

St. Kliment Ohridski University of Sofia, Sofia, Bulgaria

Microwave discharges sustained by travelling electromagnetic waves have been inten-sively investigated in the past decades both theoretically and experimentally. The cylindrical surface-wave-sustained discharge (SWD) has been studied in detail. The coaxial structure is a relatively new type of a plasma source, which was proposed recently [1,2]. In the coaxial struc-ture the plasma is produced outside the dielectric tube in a low-pressure chamber and a metal rod is arranged at the dielectric tube axis.

The possible configurations depend on the radial distribution of different materials, such as metal, vacuum, dielectric and plasma. We studied two configurations: metal–dielectric–plasma and metal–dielectric–dielectric–plasma.

The purpose of this work is to present theoretical investigations of a coaxial surface-wave-sustained discharge (CSWD) at given configurations. The basic relations in our 1D fluid model are the local dispersion relation and the wave energy balance equation obtained from Maxwell’s equations [3]. The plasma is axially inhomogeneous and the dispersion relation yields the so called phase diagrams – dependences between the normalized plasma density and the dimensionless wave number. Axial profiles of the plasma density, wave power, electric and magnetic field components are presented, too. From the behavior of the phase diagrams and the axial profiles at different discharge configurations, we can obtain information about the ability of the wave to sustain the plasma and about the wave and plasma characteristics.

References [1] E. Räuchle, J. Phys. IV France 8, 99 (1998) [2] S. Gritsinin, I. Kossyi, N. Malykh, M. Misakyan, S. Temchin, and Y. Bark, Preprint No

1, Russian Academy of Science, General Physics Institute, Moscow, 1999 [3] E. Benova, Z. Neichev, Czechoslovak J. Phys. 52, D659-D665 (2002) Acknowledgments This work was supported by Project BG051 PO 001-3.3.06-0057, Operational Program Human Resources Development 2007—2013 and partially supported by the Fund for Scientific Re-search at Sofia University under Grant No 187/2015.


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OP–2

REACTION KINETICS, HEAVY PARTICLES AND RATE COEFFICIENTS IN HF AND MW DISCHARGES IN ARGON AT ATMOSPHERIC PRESSURE

P. Marinova, M. Atanasova, E. Benova

Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier blvd., Sofia

1164, Bulgaria The enormous variety of applications of plasmas originates from their capability to produce large fluxes of photons and radicals. Plasma provides handy sources for surface treatment, sur-face modification etc. The latest applications require that the plasma sources be small, inexpen-sive and with sufficiently high concentrations of charged particles and chemically active spe-cies. Moreover, applications like medical plasmas need to be sustained in open air, and to have considerably low gas temperature. An adequate solution to the above requirements is offered by the atmospheric pressure surface-wave-sustained discharges (SWDs). These discharges are usually plasma into non-equilibrium conditions and the prediction of the chemical composition and the plasma properties becomes difficult as they can no longer be described by the classical distribution laws of statistical physics. The detailed knowledge of the discharge characteristics and their dependence on the externally controlled parameters required by the practical applications can be provided in economical and reliable way by a self-consistent model. For SWDs, the model consists of two parts – electro-dynamics of the wave sustaining the discharge coupled with the plasma kinetics. Basis of the kinetic model are Boltzmann’s equation and the particles balance and energy balance equa-tions. We applied the model to argon plasma at atmospheric pressure. Under high pressure conditions, a more detailed energy level diagram of argon should be con-sidered and a large numbers of elementary processes should be taken into account. The follow-ing species are included in our model Ar, Ar(4s), Ar(4p), Ar(3d), Ar(5s), Ar(5p), Ar(4d), Ar(6s), Ar2*, Ar+, Ar2+, and Ar3+. All the excited states are considered as blocks of levels with effective energy ∑

=

=m

jjkk muu

1, / where uk,j is the energy of each level in the block k and m is

their number. Additionally, averaged population is used. By means of the model, the rate coefficients for direct and stepwise ionization and excitation, the electron-neutral collision frequency, the excited atoms population and the ions densities are obtained and presented in this study. The numerical calculations are carried for the following discharge conditions: plasma radii – 0.05 cm, 0.1 cm and 0.2 cm, surface wave frequencies – 2 GHz, 1.5 GHz, 1 GHz and 0.5 GHz. The electron energy distribution functions at different plasma densities are also obtained. The calculations confirm that the function is close to Max-wellian for high (~ 1015 cm–3) electron densities, but deviates from Maxwell’s distribution for lower ionization ratios ne / N. Acknowledgements: This work was supported by Project BG051 PO 001-3.3.06-0057 Opera-tional Program Human Resources Development 2007-2013 and partially supported by the Fund for Scientific Research at Sofia University under Grant No 187/2015.


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OP–3

MEASUREMENTS OF NONLINEAR SUSCEPTIBILITY OF MULTICOMPONENT GLASSY MATRICES BY USING FEMTO SECOND Z-SCAN METHOD

G. Yankov and E. Iordanova

Institute of Solid State Physics, Bulgarian Academy of Science 72, Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

e-mail: [email protected]

The synthesis of any new solid-state material for laser applications and optical telecommunications necessitates extensive research and provokes a broad scientific response. Multi glassy matrices possessing variable nonlinear optical properties are one such an example. Such mediums are interesting in the cases of optical switches and optical memories. The earliest works dealing with tellurite glasses, numerous syntheses and studies of have been conducted of new multicomponent glassy matrices possessing various nonlinear properties. In the present work we report on the us of the z-scan method for non-linear coefficient measurement of the synthesized glasses. This methodology is based on the transformation of phase distortion into an amplitude distortion by using the Kerr effect.

The introduced z-scan method has the following advantages: • the diffraction problems are avoided by applying a CCD camera instead the typically

used power meter and diaphragm; • simultaneous measurement of the nonlinear constants is possible; • by using femtosecond laser, the influence of any thermal effects is minimized. The data obtained allow us to derive the nonlinear absorption (NLA) and nonlinear refraction (NLR). The nonlinear optical coefficients of fused silica was measured and compared with the known data cited in the literature. The values of n2 and of the glasses were determined. OP–4

OPTICAL EMISSION SPECTROSCOPY OF PLASMA PRODUCED BY LASER ABLATION OF FERROUS SULFIDE

S. Karatodorov, V, Mihailov and M. Grozeva

Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

In this work, optical emission spectroscopy studies on laser ablation plasma from a FeS target in vacuum are reported. The aim of the work is to correlate the plasma emission with the resulting deposition on unheated metallic substrates at different laser pulse energies and different distances to the target. In order to achieve this goal, a thorough knowledge of the plasma emission behavior is needed. Here the plasma behavior is characterized in space and

mailto:[email protected]


50

time by measuring the main plasma parameters – electron density and electron temperature. The plasma emission is recorded in the interval 0 ÷ 1000 ns after the laser pulse at three different positions above the target – 1 mm, 2.5 mm and 5 mm. From the spectra obtained, the electron temperature is calculated by the Boltzmann plot method using a set of 15 Fe I lines with known emission line parameters. A different set of Fe I lines is used to calculate the electron density by the Stark broadening of the emission lines. OP–5

FABRICATION OF METAL OXIDE NANOPARTICLES USING GAS AGGREGATION SOURCE COMBINED WITH AUXILIARY OXYGEN RF PLASMA

А. Kuzminova, J. Hanus, A. Shelemin, O. Kylian and H. Biederman

Charles University Prague, Faculty of Mathematics and Physics, Prague, Czech Republic

Vacuum-based techniques for production of metal and metal oxide nanoparticles (NPs) have been constantly developed and studied for many years. The magnetron sputtering or physical vapor deposition methods are widely used to prepare metal NPs. These methods can be com-bined with gas aggregation sources (GAS) of different constructions that have been extensively investigated for the last few decades. Applying oxygen, as a reactive gas, in a working gas ad-mixture may allow one to produce metal oxide NPs. However, this approach can also lead to undesirable effects, such as oxidation or poisoning of the magnetron target, which in turn may cause instability of the process or a decrease of the deposition rate. Therefore, we proposed to separate the oxidation process from the formation of metal NPs. In this case, we used gas ag-gregation source for fabrication of Ti or Ag nanoparticles. The nanoparticles formed then passed through auxiliary oxygen RF plasma, where they were oxidized, and were finally depo-sited on the substrate positioned in the main deposition chamber (Fig. 1). A planar magnetron with a metal target (Ag, Ti) was mounted inside the aggrega-tion chamber, where argon at elevated pressure was used as a working gas. The auxiliary plasma was maintained by an external circular electrode attached onto a glass tube that was mounted on the end of the aggregation chamber. RF power was applied to electrodes at 5 and 10 W using argon/oxygen as a working gas mixture. The pressure inside of the main deposition chamber was 1 Pa. Measurements of the chemical composition, morphology and optical properties of the NPs produced have shown that the additional oxygen RF plasma caused substantial oxidation of both Ti and Ag. The possible use of oxidized Ag-AgO/Ag2O NPs in antibacterial applications will be discussed.

Acknowledgement: This research has been sup-ported by the Czech Science Foundation through Project 13-09853S.

Figure 1. Schematic representa-tion of the set-up used for fabrica-tion of metal oxide nanoparticles


51

OP–6

GRADUAL ANNEALING EFFECT AND THERMAL STABILITY OF BULK-HETEROJUNCTION SOLAR CELLS USING DPP(TBFU)2 DERIVATIVES AS

DONOR MATERIALS

Alexander Kovalenkoa, Jana Honováa, Martin Valaa, Stanislav Luňáka, Ladislav Feketeb, Irena Kratochvílováb, Petra Horákovác, Lenka Dokládalovác, Lubomír Kubáčc and Martin

Weitera

a Brno University of Technology, Faculty of Chemistry, Materials Research Centre, Purkyňova 118, 612 00 Brno, Czech Republic.

b Institute of Physics, Academy of Sciences Czech Republic v.v.i, Na Slovance 2, CZ-182 21, Prague 8, Czech Republic.

c Centre for Organic Chemistry Ltd., Rybitví 296, CZ-533 54 Rybitví, Czech Republic. Currently, polymer and small molecules (SMs) bulk-heterojunction (BHJ) organic solar cells (SCs) exceeding 11 % power conversion efficiency (PCE) and lifetimes above 1000 h under continuous illumination are attracting particular interest due to their flexibility, color tunability and, predominantly, potentially low production cost. Considering SMs as a donor material, de-spite of the recent successful results, they still lag behind the polymer BHJ solar cells. Howev-er small-molecules BHJ SCs do not depend on a polymer weight distribution, thus do not suf-fer from batch-to-batch differences. One of the most promising structural class of the donors in BHJ SCs - diketopyrrolopyrrole (DPP) derivatives - show excellent photovoltaic performance both as a part of polymers or dimers, because of a low band gap, enabling them to absorb a large portion of the solar spectrum, as well as an ability to be further-functionalized to match the parameters required for the photovoltaic applications. Among the DPP monomers, DPP(TBFu)2 ethyl-hexyl alkylated derivative showing high power-conversion efficiency (PCE) up to 4.4 - 4.8% with PC70BM and 4.0% with PC60BM, represents the most successful de-sign. Applying a solvent annealing for the DPP(TBFu)2: PC70BM blend 5% of PCE can be ex-ceeded, which is, up to now, the highest reported PCE among the monomeric DPP derivatives. Consequently, relatively easily (as compared to e.g. bis-DPPs) obtainable DPP(TBFu)2 is often used as a benchmark compound in the current research dealing with new SM donors, acceptors or tandem cells. The attempts to modify DPP(TBFu)2 structure using different heteroatoms brought only lower PCE. DPP(TBFu)2 belongs to SM donors, for which the relationships be-tween the structure and various aspects of the photovoltaic activity such as hole mobility were understood to the most detailed extent. PCE of BHJ SCs using DPP(TBFu)2 as a donor is known to be extremely sensitive to tempera-ture annealing. Furthermore, to the best of our knowledge, PEDOT:PSS is the only hole-selective contact (HSC) reported in the previous studies. Here we report a new method of the gradual annealing, causing the progressive reorganization of the donor-acceptor bulk-heterojunction, improving the solar cells performance. It is known that the MoO3 used as HSC instead of PEDOT:PSS can improve in some cases PCE of BHJ SCs, so we studied its effect in detail, including the thermal stability of the contacts. Moreover, we have tested the new DPP(TBFu)2 derivatives with ethyl-hexyl solubilization groups substituted by ethyl-hexyl ace-tate and diethyl acetal groups. It was expected that the electron-accepting effect of these substi-tuents could stabilize HOMO level of a donor and thus improve the open-circuit voltage of the cell.


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OP–7

DETECTION OF POWDER FORMATION IN SiH4/H2 GLOW DISCHARGES

G. Alexiou, G. Tsigaras, A. Kalampounias, E. Amanatides, D. Mataras

Plasma Technology Laboratory, Department of Chemical Engineering, University of Patras

Hydrogenated microcrystalline (μc-Si:H) and amorphous (a-Si:H) silicon thin films have attracted particular attention due to their application to optoelectronic devices. The method that is commonly used for the production of these films, is plasma enhanced chemical vapor deposition (PECVD) using radio frequency (RF), through capacitively coupled silane/hydrogen discharges. In the deposition of these films, it is important to increase the deposition rate while maintaining the high quality of the film. Many parameters of the discharge affect the deposition rate and the deposited film quality. RF power, as well as the working pressure have been increased to achieve higher deposition rates. However, these two parameters have the common drawback of increasing the powder formation in the discharge which affects the film’s quality. For this reason, fast powder detection in SiH4/H2 discharges is of special interest. Different techniques have been proposed to detect the powder formation in silane/hydrogen discharges. In this work, we used different techniques in order to monitor the nucleation and formation of dust in SiH4/H2 discharges. The thin films were deposited in a capacitively coupled, ultra-high vacuum (10-8 Torr base vacuum) parallel plate reactor under different conditions of pressure and RF power. Corning 7059 glasses were used as substrates at a constant temperature of 200 oC. The SiH4 concentration in H2, the total flow rate and the interelectrode distance were kept constant. Raman crystallinity and in-situ laser reflectance interferometry (LRI) were used in order to estimate the crystalline volume fraction and the deposition rate, respectively. The formation of particles was found to produce instabilities in both the electrical and optical properties of the discharge. These instabilities were monitored through different time–resolved plasma diagnostics, as forward and reflected power measurements, discharge current harmonics, self-bias voltage (Vdc), optical emission spectroscopy (OES) and laser light scattering (LLS). These techniques were compared in terms of their sensitivity and their applicability for early point detection of the particles nucleation phase. The advantages and disadvantages of the techniques are discussed, together with the effect of particles formation on the film quality and deposition rate.


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OP–8

RESISTIVITY IN Al DOPED ZnO NANOLAYERS OBTAINED BY ATOMIC LAYER DEPOZITION

Blagoy S. Blagoev, Dimiter Z. Dimitrov, Vladimir B. Mehandzhiev, Jerome B. Leclercq,

Peter K. Sveshtarov

Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd, 1784 Sofia, Bulgaria

Transparent conducting oxides (TCO) have been extensively investigated in recent years due to their applications in electronics, optoelectronics and photovoltaics. Zinc oxide (ZnO) is one of the most competitive semiconductors because of its high transmittance in the visible range and low dc resistivity. Small additions of Al as a dopant element to ZnO films strongly decrease the resistance without worsening the optical properties. Atomic layer deposition (ALD) is one of the most suitable techniques for obtaining uniform ultra thin films on large areas. The dopant incorporation with atomic precision could be easily performed by ALD. In this work we present ZnO nanolayers with different concentration of Al dopant grown by atomic layer deposition. For deposition of ZnO films and Al addition we used liquid precursors DEZ and TMA respectively alternating with H2O. In spite of the great number of publications for ZnO:Al, there is no enough information on studying the resistivity of samples prepared by ALD. We investigated in more detail the influence of the Al dopant on samples’ resistivity.


54

OP–9

COMPARATIVE STUDY OF RF REACTIVE MAGNETRON SPUTTERING AND SOL-GEL DEPOSITION OF UV INDUCED SUPERHYDROPHILIC TiOx THIN

FILMS

V.E. Vrakatseli, E. Amanatides and D. Mataras

University of Patras, Department of Chemical Engineering Plasma Technology Laboratory

Titania (TiO2) thin films possess unique properties, such as photocatalytic activity and pho-toinduced hydrophilicity, which is the ability of TiO2 surfaces to alternate their wetting charac-teristics from hydrophobic or relatively hydrophilic to super hydrophilic under UV irradiation. Superhydrophilic / amphiphilic TiO2 thin films are of particular interest because of the great prospects for many new applications, such as self-cleaning, anti-fogging and anti-ice surfaces. Nevertheless, their application on non-thermal resistive polymeric substrates demands a low temperature deposition method. The different deposition methods applied could severely influ-ence the resulting thin film’s structure, properties and functionality, but they also have limita-tions, advantages and disadvantages of various aspects. Therefore, the choice of a proper me-thod for the deposition of the desired TiO2 film is of significant importance related to its prop-erties, applicability and resulting quality. In this work, ΤiOx and TiOx-like thin films were deposited on PEEK (Polyether ether ketone) substrates by the two most common low-temperature deposition methods and the resulting films were compared in terms of their properties and photoinduced hydrophilicity. TiOx thin films were deposited in a homemade ultra-high vacuum radio frequency (13.56 MHz) magnetron sputtering reactor using a Ti target, Ar as the buffer gas and O2 as the reactive gas. The effect of RF plasma sputtering parameters, such as the plasma power and the Ar/O2 composition, on the deposited films was evaluated. On the other hand, titanium tetrasio-propoxide (TTiP) alcoholic solutions (TTiP/iPrOH/H2O and TTiP/MetOH/Η2Ο) were spin coated on the PEEK substrates. The sol-gel spin-coating deposited thin films were examined after they were physically dried at room temperature, but also after they were treated by low temperature Ar/O2 atmospheric pressure plasma using a plasma jet source. Both methods resulted in adhesive, transparent and UV induced superhydrophilic TiOx and TiOx-like thin films. The RF reactive magnetron sputtered thin films and the TTIP sol gel de-posited films were compared in terms of their UV induced hydrophilicity, hydrophilicity per-sistence in dark, as well as their optical and structural properties.


55

OP–10

STAND FOR COATING DEPOSITION AND COATING/MATERIAL TESTING.

A.A. Ayrapetov, L.B. Begrambekov , A.E. Evsin, A.V. Grunin, A.A. Gordeev, A.M. Zakharov, A.M. Kalachev, Ya.A. Sadovskiy, P.A. Shigin

National Research Nuclear University «MEPhI», Moscow, Russia

The paper describes a new laboratory stand constructed for film deposition and for testing of deposited films and materials under pulsed and constant heat, ion and electron irradiation. The film is formed on substrates by atoms sputtered from targets of different materials by ions of argon plasma ignited between heated tungsten cathode and anode. The energy and current of the ions sputtering targets can be varied separately. This makes possible deposition of coating with various components, multi-layer coating etc. To investigate the ability of the deposited films to trap hydrogen isotopes they are added to plasma during the film deposition. A mass-spectrometer is used to measure the composition of the residual and working gasses. The low residual pressure allows for less than 0,1 % of impurities in deposited coatings. The substrates of dimensions 15×15 mm2 are water cooled during deposition and their temperature can be fixed during deposition between 300 K and 900 K. Before and during deposition, the substrate with the deposited film cab be irradiated by plasma ions for achieving better adhesion and better structural property of the film, respectively. For testing of any material samples or deposited films by plasma electron or ion irradiation they are biased, correspondingly, positively or negatively. Hydrogen is used as a working gas for plasma discharge thus reducing sample sputtering by ion irradiation. The parameters of the sample irradiation can be varied over wide limits by changing the plasma density, bias potential and relative position of sample and plasma chamber. The energies of the ions or electrons can be up to 25 keV. Up to 4000 W (40 MW/m2 power density in the case of a 1 cm2 sample) of power could be applied during both continuous and pulsed regimes. Pulses of 1-99 % duty cycle at 0-500 Hz can be applied to the sample. Heating of the samples up to 2500 °C is available. A pulsed particle load can be combined with a steady-state load. Thermal cycling of the sample is realized by irradiation of the substrate’s backside by electron or ion beams. The heating flux can irradiate the whole sample or be focused at its center (spot of ~4 mm2). Sample dimensions up to 100 mm in diameter are possible. The backside of the tested samples can be actively cooled. Acknowledgements: This work was supported by the Competitiveness Growth Program of the Federal Autonomous Educational Institution of Higher Professional Education National Research Nuclear University MEPhI and by the Ministry of Education and Science of the Russian Federation (agreement contract 14.575.21.0049 of 27.06.14).


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OP–11

INVESTIGATION OF ARC SPOT MOTION ALONG THE ELECTRODES IN A PLASMA TORCH

V. Sauchyn1, I. Khvedchyn1

1 Luikov Heat and Mass Transfer Institute of the National Academy of Sciences of Belarus

The process was investigated of the arc spot motion along the surface of cylindrical electrodes in a plasma torch with gas vortex stabilization of the arc. Experiments were conducted with a model of the plasma torch with onesided outflow. The design of the plasma torch allows us to place a metal foil with a thickness of 0.1 mm inside the electrodes. Arc spots are moved due to the gas vortex flow. They leave tracks on the foil as a results of overheating. The geometrical parameters of the tracks were measured, such as arc spots size, distance be-tween two consecutive spots, tracks length and direction. All this data were correlated with os-cillograms of the arc current and voltage. The parameters of the arc spots movement along the electrodes depend to a large extent on the plasma forming gas consumption and arc current strength. It should be mentioned that the anode and cathode arc spots are different. Two mechanisms of arc spot movement can be de-fined in the case of a cathode spot. The first one is when there is continuous gliding and track is inseparable. The second one is discontinuous arc jumping caused by shunting of arc with elec-trode surface. The first mechanism is about 30 % arc movement and decreases with plasma forming gas consumption and decreasing of current strength. Life time of arc spot in one place varies widely from 10-5 to 10-3 seconds. So the size of tracks vary too from 10-7 to 10-5 mm2. With plasma forming gas consumption increasing cathode arc spots make smooth lines. The distance of spot jump increases insignificant. With increasing of current strength up to 200 A arc spot splitting to 2 or more spots takes place. Life time of new spots is up to some microse-conds. It should be point out that increasing of plasma forming gas consumption decreases probability of arc spot splitting and needs to increase current strength to start the process. Anode arc spots as opposed to cathode ones move only by jumping. Distance between two spots is about 1-5 mm and doesn’t depend on plasma forming gas consumption and current strength. Shape of spot is close to circle with smooth border. Its diameter is from 0.2 to 3 mm. Life time of arc spot in one place varies from 10-5 to 2·10-4 seconds. Anode arc spot can split as the cathode one. It should be mentioned that the splitting process needs less current strength and dependence on plasma forming gas consumption is weak. Longitudinal and circular velocity of arc spot movements was observed quantity depending on plasma forming gas consumption and current strength. Velocity of cathode arc spot movement exceeds anode one.


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OP–12

TRANSITION METAL OXIDES NANOPARTICLES, NANOFIBERS AND CORE-SHELL NANOCOMPOSITES PREPARED BY ANNEALING, ELECTROSPINNING AND ALD FOR GAS SENSING, PHOTOCATALYTIC AND ELECTROCHROMIC

APPLICATIONS

S.I. Boyadjiev1, V.B. Georgieva2, I.M. Szilágyi1,3

1 MTA-BME Technical Analytical Chemistry Research Group, Szent Gellért tér 4, Budapest, H-1111, Hungary, e-mail: [email protected]

2 “Georgi Nadjakov” Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria, e-mail: [email protected]

3 Budapest University of Technology and Economics, Department of Inorganic and Analytical Chemistry, Szent Gellért tér 4, Budapest, H-1111, Hungary, e-mail: [email protected] Many transition metal oxides are widely used for gas sensing, photocatalytic and electrochromic applications. Their properties might be improved by making composites of them with other semiconductor oxides. In the present study, two approaches to prepare core-shell nanocomposites of several transition metal oxides were used. By combining annealing and atomic layer deposition (ALD), pure WO3 and core/shell WO3/TiO2 nanoparticles were prepared and tested as gas sensors, photocatalysts and electrochromic materials. The performance of these nanocomposites can be increased by preparing them as nanofibers with a high specific surface. In this direction, pure ZnO and TiO2, as well as core/shell ZnO/TiO2 and TiO2/ZnO nanofibers were prepared by electrospinning, annealing and ALD, and also tested for gas sensing and photocatalysis. The composition, structure and morphology of the pure and composite nanoparticles and nanofibers were characterized by TG/DTA-MS, TEM, SEM-EDX, XRD, UV-Vis, FTIR and Raman spectroscopies. We investigated how the semiconductor oxides interacted with each other when a pure oxide particle or fiber was covered with an ultra-thin film of other oxide and how exchanging the core and shell materials influenced their properties.

Fig. 1. TEM image of a core/shell composite WO3/TiO2 nanoparticle


POSTER SESSION A:

PLASMA-SURFACE INTERACTION AND PLASMA DIAGNOSTICS. MODELING AND

COMPUTER SIMULATION

PA–2 A STUDY OF SPUTTERED TUNGSTEN ATOMS

BY LASER INDUCED FLUORESCENCE

A. Georgiev, A. Pashov, D. Michailova, St. Zapryanov and A. Blagoev


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PA–1

INVESTIGATION OF THE HYDROGEN NEUTRALS IN DISCHARGE SOURCE USED FOR PRODUCTION OF METAL HYDRIDES

I. Bozhinova, S. Iordanova, A. Pashov

Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 J. Bourchier blvd. 1164 Sofia, Bulgaria

The main properties are examined of a discharge tube designed for production of metal hy-drides (in particular NiH), which are of interest in astronomy. The results from laser absorption measurements reveal the optimum gas composition and pressure and discharge current at which the highest concentration of NiH species is achieved in the tube volume [1]. Under the optimal working conditions, however, the emission from the center of the tube is significant, contrary to our expectations. The dark center of the tube is suitable for laser-induced fluores-cence measurements. Moreover, when heating the cathodes, the NiH absorption signals drop. These observations guided us to examine experimentally some of the elementary processes in the gas discharge and how the NiH molecules are formed in this source. This contribution is devoted to an investigation of the hydrogen neutrals by using optical emis-sion spectroscopy. We used the interferometric setup from Ref. [2] to estimate the temperature of various groups of hydrogen atoms. The measurements show that the change of the main dis-charge parameters (gas pressure and current) changes the relative intensity of the atomic and molecular lines and the temperature of the atoms. The complicated line shape of the hydrogen H spectral line is examined in detail. The connection between the parameters of the neutral hydrogen particles and the production of NiH is discussed. References: [1] I. Bozhinova, St. Kolev, M. Dimitrova, Tsv. Popov, and A. Pashov, Discharge tube with coaxial geometry for efficient production of metal hydrides, Rev. Sci. Instrum. 84, Issue 9, 093107 (2013); http://dx.doi.org/10.1063/1.4820959 (9 pages), ISSN: 0034-6748, IF=1.602 [2] S. Iordanova and A. Pashov. ”Spectral diagnostics based on Doppler-broadened Hline shape in a single element of a matrix source”. AIP Conf. Proc., 1655:040012, 2015. PA–2

A STUDY OF SPUTTERED TUNGSTEN ATOMS BY LASER INDUCED FLUORESCENCE

A.Georgiev, A. Pashov, D. Michailova*, St. Zapryanov and A. Blagoev

University of Sofia, 5 J Bourchier blvd., 1164 Sofia, Bulgaria

* Technical University of Eindhoven, The Netherlands We report on a spectroscopic method for determination of the density of sputtered tungsten atoms. The method is based on registration of the fluorescence at 3024,9 Ǻ following laser ex-citation of the WI 2879,4 Ǻ resonance line. The tungsten atoms are sputtered in a hollow ca-thode tube of a special rectangular geometry in order to increase the atomic density in the cen-

http://rsi.aip.org/resource/1/rsinak/v84/i9

http://link.aip.org/link/doi/10.1063/1.4820959


62

tral region. The hollow cathode is placed in a White multi pass cell, which influences also the geometry of the cathode. The discharge is operated in a pulsed regime with a repetition rate of 20 Hz and a pulse duration of 3 ms. The laser pulses (generated by a system of a pulsed Nd:YAG pump laser and a dye laser with a frequency doubler) are synchronized with the dis-charge, but a delay between the discharge and the Q-switch of the Nd:YAG laser can be intro-duced. This delay, the duration of the current pulse and the laser intensity can be varied; one can thus study the fluorescence of the W atoms in an afterglow mode. The laser-induced fluo-rescence is collected in a direction perpendicular to the laser beam, filtered by a 35 cm mo-nochromator and registered by a photomultiplier. We will present the decay of the W density for delays up to 2.5 ms. The method for estimation of the atomic density from the registered signals as well as the possibility to make quantitative measurements will be discussed. PA–3

LASER ABLATION THRESHOLD DETERMINATION BY SURFACE PHOTO-CHARGE EFFECT

V. Mihailov, S. Karatodorov and O. Ivanov

Institute of Solid State Physics, Bulgarian Academy of Sciences,

72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

Experimental results are presented concerning a new technique for measurement of the laser ablation threshold by using the surface photo-charge effect. To demonstrate the utility of the proposed technique, the effect of laser power on both the magnitude and time evolution of the surface photo-charge voltage in Si are investigated. It has been established that there are two regimes characterizing the laser-target interaction which depend on the laser intensity. When the laser pulse energy is less than the laser ablation threshold, there is no destruction of the surface. At the same time, a strong and quickly relaxing photo-induced signal is observed. With increasing the laser pulse energy beyond this limit, destruction of the surface starts and craters are being formed accompanied by a dramatic change in the shape of the signal. A small increase in the amplitude is accompanied by a significant broadening of the signal and the appearance of a second component with opposite polarity. Hence, by varying the laser intensity applied, the pulsed laser-induced signal can be used for in situ monitoring of the onset of surface damage. PA–4

QUALITATIVE AND QUANTITATIVE LASER-INDUCED BREAKDOWN SPECTROSCOPY OF BRONZE OBJECTS

V. Tankova, K. Blagoev, M. Grozeva, G. Malcheva

Institute of Solid State Physics, 72 Tzarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

Laser-induced breakdown spectroscopy (LIBS) is an analytical technique for qualitative and quantitative elemental analysis of solids, liquids and gasses. In this work, the method was ap-plied to investigating archeological bronze objects. The analytical information obtained by


63

LIBS was used for qualitative determination of the elements in the material used for manufac-turing the objects under study. Quantitative chemical analysis was also performed after gene-rating calibration curves with standards of similar matrix composition. Quantitative estimation of the elemental concentration of the bulk of the samples and of the surface layer of the objects was performed. Results of the quantitative analyses gave indications about the manufacturing process of the objects. PA–5

LIBS ANALYSIS OF VALUABLE PRECIOUS METAL MUSEUM OBJECTS

D. Yordanova1, G. Malcheva1, V. Tankova1, A. Pirovska2, M. Grozeva1

1 Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia, Bulgaria 2 Maritza-Iztok Archaeological Museum, Radnevo, Bulgaria

Laser induced breakdown spectroscopy (LIBS) is a versatile elemental analysis method with a great potential in the field of artworks. The unique capabilities of this laser-based method permit one to perform investigations of cultural heritage monuments, which has not so far been possible by conventional laboratory techniques. We report results of a qualitative elemental analysis of two precious metal artefacts of different periods, found in the region of Stara Zagora: silver pectoral and gold pectoral. Elemental composition analysis was conducted at characteristic spots on the surface and in depth. As the investigated objects are of high value, the desire was to obtain reliable spectra for analysis causing as less damage as possible. That is why during this study we limited the measurements up to five shots at a spot, causing a crater hardly visible by a naked eye. The elemental composition of the two artefacts differed: the ancient (B.C.) artefact (the silver pectoral) hd been manufactured of high-quality silver with traces of copper and gold, while the ancient (B.C.) artefact (the gold pectoral) had been manufactured of high-quality gold with traces of copper and silver. The measurements were performed by a LIBSCAN 25 portable system for near-field measurements. PA–6

IDENTIFICATION OF METAL SAMPLES BY COLLISIONAL ELECTRON SPECTROSCOPY (CES)

M. Stefanovaa, P. Pramatarova, A. Saifutdinovb and A. Kudryavtsevb

aInstitute of Solid State Physics, Bulgarian Academy of Sciences,

72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria bSt.Petersburg State University, 7-9 Universitetskaya nab., St.Petersburg, 199034, Russia

The non-local plasma of a short (without positive column) dc Ar microdischarge at interme-diate pressures is utilized for the detection and identification of atoms from Au samples. The identification of the analyzed metal is carried out by using the electron energy spectra of groups of fast nonlocal electrons − characteristic electrons released in the Penning ionization of


64

the Au atoms by Ar metastable atoms and molecules. The recently developed collisional elec-tron spectroscopy (CES) method for gas analysis allows one to measure the energy spectra of the Penning electrons and to determine their energy εp in the collisional mode at intermediate and high pressures [1, 2]. In nonlocal plasma [3], the different groups of electrons lose negligi-ble portion of their energy by collisions in the volume and behave independently of each other over the specific discharge dimension. As a result, sharp peaks in the EEDF are formed. The recorded EEDF in main gas Ar at pressures 10 – 50 Torr with small admixture of Au atoms are characterised by the presence of well expressed peaks, at the energies of the Penning electrons appearance, which are 2.3 eV and 1.2 eV. The acquisition of the electron energy spectra is per-formed using an additional electrode − a sensor located at the boundary of the discharge vo-lume. Using the measured energy of the maxima εpAu, and ionization potential εiAu, identifica-tion of the Au atoms is accomplished. Cathode sputtering is used for atomization of the metal under analysis. Absolute calibration of the energy scale is made by using the characteristic Ar maxima due to pair collisions between Ar metastable atoms and molecules, and super-elastic collisions. This study demonstrates the possibility of creating a novel microplasma analyzer for atoms from metal samples.

[1] A. A. Kudryavtsev, A. B. Tsyganov and A. S. Chirtsov, Patent of Russian Federation 2,

422,812 (27 June 2011) [2] A. Kudryavtsev, P. Pramatarov, M. Stefanova and N. Khromоv, J. of Instrumentation IOP,

JINST, 2012, 7 PO7002, 1– 13. [3] L. D. Tsendin, Plasma Sources Sci. Technol. 1995, 4, 200-211. PA–7

DETERMINATION OF SPATIALLY- AND TIME-RESOLVED ELECTRON TEMPERATURE IN NANOSECOND PULSED LUNGITUDINAL DISCHARGES

S. I. Slaveeva1, T. P. Chernogorova2, K. A. Temelkov1

1Metal Vapor Lasers Laboratory, Institute of Solid State Physics,

Bulgarian Academy of Sciences, 72, Tzarigradsko Chaussee, 1784 Sofia, Bulgaria 2Faculty of Mathematics and Informatics, Sofia University,

3 James Bourchier blvd., 1164 Sofia, Bulgaria [email protected]

The electron temperature, together with the gas temperature and the electron density are the most fundamental plasma parameters that play a very important role in understanding the nu-merous phenomena in gaseous discharges, laser physics, plasma technologies, gas-discharge mass spectroscopy, absorption and emission spectroscopy, and plasma in general.

Elastic and inelastic electron-heavy particle collisions, such as electron impact excitation, de-excitation, and ionization, as well as three-body recombination, depend thoroughly on the elec-tron temperature. Measurements of the electron temperature by Langmuir probes are not appli-cable to high-voltage and high-current nanosecond pulsed longitudinal discharges (NPLDs). Laser Thomson scattering measurements of the electron temperature have been proved to be effective but challenging because of the low signal and excessive stray light, as well as the complicated experimental setup.


65

Under conditions of a local thermodynamic equilibrium, measurement of the relative intensities of some He and Ne spectral lines, originating from different upper levels, enabled us to deter-mine the stationary electron temperature, as well as the time-resolved electron temperature in the discharge afterglow, in a NPLD in He, Ne and Ne-He mixtures [1]. This type of discharge is widely used for excitation of high-power metal and metal halide vapor lasers oscillating in the deep ultraviolet (DUV), visible, near infrared (NIR) and middle infrared (MIR) spectral ranges. Using the experimental results obtained for the stationary electron temperature [1], and deriving using the Wiedemann-Franz law the electronic thermal conductivity as well, an ana-lytical solution of the steady-state heat conduction equation was found for a uniform input.

A 2D (r, t) numerical model was developed for determination of the spatially- and time-resolved electron temperature in various NPLDs used for excitation of the abovementioned high-power metal and metal halide vapor lasers. The preliminary results showed that the elec-tronic thermal conductivity as derived using the Wiedemann-Franz law results in obtaining an unreasonable solution of the nonstationary heat conduction equation for electrons. Scanning the electronic thermal conductivity, radial and time dependences of the electron temperature, which reflect the physical reality, were obtained. References: [1] K.A. Temelkov, S.I. Slaveeva, N.K. Vuchkov, “Analytical Calculation of Gas Temperature and Experimental Determination of Electron Temperature in Gas Discharge in He-Ne Mix-tures”, IEEE Transactions on Plasma Science, vol. 39, no. 3, pp. 831-835, 2011. PA–8

THEORETICAL STUDY ON THERMAL CONDUCTIVITIES OF VARIOUS GAS MIXTRES THROUGH GENERALIZED LENNARD-JONES INTERACTION

POTENTIAL FOR APPLICATION IN GAS-DISCHARGE LASERS

K. A. Temelkov, S. I. Slaveeva and Yu. I. Fedchenko

Metal Vapor Lasers Laboratory, Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences

72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria [email protected]

One of the main problems of plasma physics is to determine characteristic constants for

basic processes in plasma, such as asymmetric charge transfer, Penning ionization, elastic and inelastic electron-heavy particle collisions, heat conduction, diffusion and radiative transitions. This will be very helpful in understanding and predicting numerous phenomena in gaseous dis-charges, laser physics, plasma technologies, spectroscopy, and plasmas in general. The above-mentioned processes determine the creation of population inversion and output parameters in a number of high-power metal and metal halide vapor lasers oscillating in the deep ultraviolet (DUV), visible, near infrared (NIR) and middle infrared (MIR) spectral ranges.

The characteristic constants for the heavy particle processes depend on the gas temperature. In particular, for metal or metal halide vapor lasers, the thermal mode, as well as the radial temperature distribution, are of considerable importance for the stability of the laser


66

operation and also for the achievement of high output characteristics, because it controls not only the laser level kinetics, but also the concentration of the active particles, i.e. particles on whose transition laser oscillation is obtained. The experimental techniques for gas temperature measurements using measurements of the Doppler spectral lines broadening and the focal distance of a thermal lens are definitely imprecise.

The constants B and a, which determine the thermal conductivity allometrically ex-pressed, could be obtained through fitting the existing experimental data. Unfortunately, except for rare gasses, data for the thermal conductivities of chemical elements of our interest are either very scarce in the literature or are within a narrow temperature range, which is not of interest. That is why it is necessary to calculate the thermal conductivities in order to obtain the gas temperature distribution via solving the heat conduction equation. The generalized (m-n) Lennard-Jones interaction potential, namely ϕ(r) = A.r –n – B.r –m, is used to calculate the thermal conductivities of helium, neon, copper, bromine, hydrogen and strontium.

The thermal conductivities of binary gas systems are calculated on the basis of the empirical method of Brokaw, combination rules for Lennard-Jones interaction potential and Wassiljewa’s formula for the case of gas discharges in helium and neon with small admixtures of copper, bromine, hydrogen and strontium. The binary gas mixtures considered, i.e. the pressures of the two gas components, are optimal for achieving maximal output characteristics of the lasers excited in a nanosecond pulsed longitudinal discharge in these mixtures.

PA–9

INVESTIGATION OF PARAMETERS OF GAS DISCHARGE IN AN ARGON-OXYGEN MIXTURE FOR OPTIMIZATION OF THE GROWTH OF OXIDE FILMS

M. Mitov1, V. Videkov1, Tsv. Popov2, K. Raykov1, A. Bankova1

1Technical University of Sofia, 8 Kliment Ohridski blvd., 1000 Sofia, Bulgaria

2Faculty of Physics, St. Kliment Ohridski University of Sofia, 5, J. Bourchier blvd., 1164 Sofia, Bulgaria

The oxide film properties and the methods of their production are of great interest. Oxide films find many applications in micro and nano electronics. They can be a part of the chip structure, an insulator in supercapacitors, mechanical elements in micro-electro-mechanical systems, a dielectric base for micro modules and many others. The paper presents an investigation of gas discharge parameters in an argon-oxygen mixture during growth of an oxide films under dif-ferent discharge conditions. The results obtained allow optimization of the discharge in order to obtain uniform oxide layers with an exact thickness. Using the film being grown as a Langmuir probe allows us to monitor the film thickness in real time.


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PA–10 MONTE CARLO ESTIMATES OF EDGE PARTICLE SOURCES IN TJ-II PLASMAS

D. López-Bruna1, Tsv. Popov2, E.de la Cal1

1 Laboratorio Nacional de Fusión, CIEMAT, 28040 Madrid (Spain)

2 Faculty of Physics, University of Sofia, Sofia (Bulgaria) The evaluation of the sources in magnetic confinement fusion devices is a difficult and complex task. In most cases, source terms do not conform to flux surfaces and a three-dimensional (3D) calculation is mandatory. This is especially true in the case of particle sources, which involve the motion of neutrals through the vacuum vessel (VV) and the contained plasma, together with the atomic physics and some description of the plasma-wall interaction. In medium sized or large tokamak plasmas, a one-dimensional calculation can be sufficient to yield a first approximation of the neutrals distribution and the corresponding electron source [1], although detailed results near the divertor require 3D calculations. Matters are commonly more complicated in stellarators. The TJ-II Heliac is somewhat singular because the plasma-wall interaction is strong in a complicated VV geometry. For example, in addition to the possible insertion of poloidal limiters, typical plasmas are limited by the “hard core”, a metallic case that protects the central conductors [2]. We present 3D calculations of the effects of gas puffing, limiter insertion and wall conditioning (boronized or lithiumized wall coating) based on the EIRENE Monte Carlo code [3] adapted to the TJ-II geometry [4]. The output consists of 3D distributions for neutrals and ionized species, and estimates of diagnostic measurements in the appropriate geometry, so that the calculations can be compared with experimental measurements. The importance of performing 3D calculations is stressed when the experiments involve specific geometries, like gas puffing valves, diagnostic chords or solid angles through which radiation is collected. Examples are given for (i) the evolution of Hα light during a radiative collapse following the L-H transition, (ii) CX spectra at a specific time of a discharge, (iii) helium 760 mm light recorded near a gas-puffing valve in He-plasmas and (iv) electron source from ionization of neutrals in relation with electric probe measurements. References [1] S. Rehker, H. Wobig, Plasma Phys. 15 1083 (1973) [2] C. Alejaldre et al., Fusion Technol. 17 131 (1990) [3] D. Reiter, The EIRENE code user manual (including: B2-EIRENE interface) (2005), http://www.eirene.de/html/manual.html [4] J. Guasp, A. Salas, Manual for the use of Eirene at Ciemat, http://www.eirene.de/html/recent reports.html


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PA–11 PERIPHERAL PLASMA CHARACTERISTICS IN THE URAGAN-3M TORSATRON

A. Kasilov, L. Grigor’eva, V. Chechkin, A. Beletskii, R. Pavlichenko, A. Lozin, M. Kozulya,

N. Zamanov, Y. Mironov, V. Voitsenya

Institute of Plasma Physics, National Science Center “Kharkov Institute of Physics and Tech-nology”, Kharkov, Ukraine [email protected]

In the = 3/ m= 9 Uragan-3M (U-3M) torsatron (R0 = 100 cm, a ≈ 12 cm, ι( a )/2π ≈ 0.3, Вφ ≲ 1 Т), hydrogen plasma is produced and heated by RF fields in the Alfvén range of fre-quencies (ω ≲ ωci). In the work reported, to introduce RF power into the plasma, an unshielded frame-like antenna is used with a broad spectrum of generated parallel wavelengths [1]. The plasma parameters distributions (electron density ne, electron temperature Te, floating potential Vf) are studied by Langmuir probes in the space between the helical winding cases and the last closed flux surface in a poloidal torus cross-section far from the antenna and in two cross-sections in the region of antenna location, one of them crossing the area bounded by the anten-na frame. The measurements are carried out in two discharge regimes [2], one of them (regime 1) is characterized by a low average density en ~ (1–3)×1012 cm-3, a high electron temperature (Te

rad up to 800 eV) and a large plasma loss from the confinement volume (by the diverted plasma flow magnitude), while a higher density en ≲ 7×1012 cm-3, a lower temperature (tens eV) and a low plasma loss are inherent to the other regime (regime 2). Comparing the values of the electron density in the divertor flows and peripheral plasma, it was deduced that plasma divertor flows are predominantly formed by the plasma outgoing from the confinement vo-lume. The up-down asymmetry of the plasma divertor flows in the U-3M torsatron is con-firmed [3]. Due to the characteristic properties of the device, such as enclosing the whole mag-netic system into a large vacuum chamber, a specific structure of the edge field lines ensuring the helical divertor magnetic configuration and the method of RF plasma production and heat-ing with the antenna placed in a short section of the torus, strong toroidal and radial inhomoge-neities are inherent to the peripheral plasma in U-3M. Unlike the Vf, ne and Te spatial distribu-tions far from the antenna, the distributions of these parameters close to the antenna, as well as their absolute values, are strongly disturbed by the near antenna field. [1] О.М. Shvets, I.A. Dikij, S.S. Kalinichenko, A.I. Lysojvan, et al. Nucl. Fusion 26 (1986) 23. [2] V.V. Chechkin, L.I. Grigor’eva, R.O. Pavlichenko, et al. Plasma Phys. Reports 40 8 (2014) 601. [3] V.V.Chechkin, L.I. Grigor’eva, M.S. Smirnova, et al. Nucl. Fusion 42 192 (2002).



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PA–12 RADIAL PROFILE OF THE ELECTRON ENERGY DISTRIBUTION FUNCTION IN

RF CAPACITIVE GAS DISCHARGE PLASMA

M. Dimitrova1, N. Puac2, N. Skoro2, K. Spasic2, G. Malovic2, Tsv. Popov3, F. Dias4, Z. Lj. Petrovic2

1 Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko

Chaussee blvd., 1784 Sofia, Bulgaria 2Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia

3Faculty of Physics, St. Kliment Ohridski University of Sofia, 5, J. Bourchier Blvd., 1164 Sofia, Bulgaria

4 Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, 1049-001 Lisboa, Portugal

Low temperature (non-equilibrium) plasmas are the basis for a number of technologies, old, current and future. The success story is, of course, plasma etching, which, together with photo-lithography, is the basis for miniaturization of integrated circuits; other major applications in-clude surface alloying, thin film deposition, plasma displays, modification of the properties of polymers and organic materials. Recently, the most promising seems to be the field of plasma-based medical applications. Non-equilibrium plasmas are difficult to describe by universal theories, so that joint efforts are needed in diagnostics and modelling in order to understand their properties and use that knowledge to control, design and optimize applications. The im-portance of the research is that it will facilitate applications while maintaining the scientific effort on the fundamental aspects of non-equilibrium plasmas: the relative simplicity of the ex-periments makes them excellent tools in studying non-equilibrium plasmas.

This paper reports experimental results on a low-pressure argon capacitive RF discharge at different conditions, as gas pressure in the range 3 ÷ 30 Pa and different power 10 ÷ 100 W. The measured IV characteristics were processed by two different second derivative probe tech-niques for determination of the plasma parameters and the electron energy distribution func-tion. The radial profile of the main plasma parameters are presented. Acknowledgements: This research has been supported by the JOINT RESEARCH PROJECT between the Academy of Sciences and Arts of Serbia and the Institute of Electronics BAS BG. PA–13

POWER FLUX DENSITY IN THE DIVERTOR REGION OF THE COMPASS TOKAMAK IN OHMIC ELMY H-MODES

M. Dimitrova1,2, V. Weinzettl1, J. Matejicek1, Tsv. Popov3, S. Marinov3, S. Costea4, R.

Dejarnac1, J. Stöckel1, J. Havlicek1, R. Panek1 and the COMPASS team

1 Institute of Plasma Physics, Academy of Sciences of the Czech Republic, 3, Za Slovankou, 182 00 Prague 8, Czech Republic

2 Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee, 1784 Sofia, Bulgaria

3 Faculty of Physics, St. Kliment Ohridski University of Sofia, 5, J. Bourchier blvd., 1164 Sofia, Bulgaria


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4 Institute for Ion Physics and Applied Physics, University of Innsbruck, 25 Technikerstr., A-6020 Innsbruck, Austria

We report experimental results obtained by Langmuir probes embedded in the divertor tiles on the COMPASS tokamak. Measurements of the current-voltage (IV) probe characteristics were performed during ohmic ELMy H-modes in deuterium plasmas, toroidal magnetic field BT = 1.15 T, plasma current Ip = 300 kA and line-averaged electron density ne = 5×1019 m−3. The data obtained between the ELMs were processed by the recently published first-derivative probe technique for precise determination of the plasma potential and the electron energy distribution function (EEDF) [1,2]. The spatial profile of the electron temperature shows that the EEDF at the high-field side is Maxwellian with a temperature of 6 − 10 eV; however, in the private flux region it differs from the Maxwellian but can be approximated by a bi-Maxwellian distribution. The electron temperatures and densities obtained were used to evaluate the radial distribution of the parallel power flux density as being of the order of 0.05 − 9 MW/m2, and the electron pressure, 0.3 − 40 Pa. The experimental conditions were used to investigate the plasma interaction with tungsten samples, with or without pre-grown He fuzz. The samples were observed by using the fast framing Photron APX camera with the aim to trace ELM-induced arcs on the sample surface and estimate a critical power flux for an arc production depending on different surface properties. Acknowledgements: This research has been supported by the Czech Science Foundation grant No. 14-12837S, by the International Atomic Energy Agency (IAEA) Research Contract No 17125/R0, R1 and R2 as a part of the IAEA CRP F13014 on “Utilisation of a Network of Small Magnetic Confinement Fusion Devices for Mainstream Fusion Research”, by the JOINT RESEARCH PROJECT between the Institute of Plasma Physics v.v.i., AS CR and the Institute of Electronics BAS BG; and by MSMT Project # LM2011021. References [1] Popov Tsv K et al, Plasma Phys. Control. Fusion 51 (2009), 065014 [2] Dimitrova M et al, Contrib. Plasma Phys. 54 No. 3 (2014) 255 PA–14 ELECTRON ENERGY DISTRIBUION FUNCTION IN THE DIVERTOR REGION OF

THE COMPASS TOKAMAK

M. Dimitrova1,2, E. Hasan2,3, P. Ivanova2, E. Vasileva2, Tsv. Popov3, R. Dejarnac1, J. Stöckel1, R. Panek1 and the COMPASS team

1 Institute of Plasma Physics, Academy of Sciences of the Czech Republic,

3, Za Slovankou, 182 00 Prague 8, Czech Republic 2 Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences,

72, Tsarigradsko Chaussee, 1784 Sofia, Bulgaria 3 Faculty of Physics, St. Kliment Ohridski University of Sofia,

5, J. Bourchier blvd., 1164 Sofia, Bulgaria

http://www.ipp.cas.cz/Staff/generic_gr.php?IDG=00176


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The plasma parameters during an L-mode hydrogen discharge in the COMPASS tokamak with a toroidal magnetic field BT =1.15 T and a line-averaged electron density ne = 6×1019 m−3 and with a plasma current variation from 209 kA to 100 kA were studied in the divertor region. It is shown that as the plasma current decreases, the position of the outer strike point changes within a few millimeters. In contrast, the position of the inner strike point is shifted towards the high-field side by about 5 cm. The electron energy distribution function (EEDF) for 209 kA at the high-field side and the private region is Maxwellian with a temperature in the range of 5 - 9 eV, while around the outer strike point and the low-field side it is bi-Maxwellian with a low-energy electron group (4 - 5 eV) and higher energy electrons (10 - 20 eV). As the plasma current decreases, the appearance of the bi-Maxwellian EEDF is shifted towards the low-field side; at a plasma current of 100 kA the EEDF is Maxwellian in the whole divertor region. Acknowledgements: This research has been supported by the International Atomic Energy Agency (IAEA) Research Contract No 17125/R0, R1 and R2 as a part of the IAEA CRP F13014 on “Utilisation of a Network of Small Magnetic Confinement Fusion Devices for Mainstream Fusion Research”, by the JOINT RESEARCH PROJECT between the Institute of Plasma Physics v.v.i., AS CR and the Institute of Electronics BAS BG; by a project BG051 PO001-3.3.06-0057 and by MSMT Project # LM2011021. PA–15

RADIAL PROFILE OF THE PLASMA PARAMETERS MEASURED BY A HORIZONTAL RECIPROCATING LANGMUIR PROBE IN THE COMPASS

TOKAMAK

P. Ivanova1, M. Dimitrova1,2, Tsv. K. Popov3, D. López-Bruna4, P. Vondráček2, R. Dejarnac2, J. Stöckel2, M. Aftanas2, P. Böhm2, P. Bílková2, M. Hron2 and R. Panek2

1 Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences,

72, Tsarigradsko Chaussee blvd,, 1784 Sofia, Bulgaria 2 Institute of Plasma Physics, Academy of Sciences of the Czech Republic,

3, Za Slovankou, 182 00 Prague 8, Czech Republic

3 Faculty of Physics, St. Kliment Ohridski University of Sofia, 5, J. Bourchier blvd., 1164 Sofia, Bulgaria

4 Laboratorio Nacional Fusión, CIEMAT, Complutense 40 – 28040 Madrid, Spain

The radial distribution of the main plasma parameters in the scrape-off-layer of the COMPASS tokamak was studied in an L-mode regime using a new electrical probe mounted on a horizontal manipulator. The new probe head consists of two probe tips: one is oriented parallel, and the other, perpendicular to the magnetic field lines. The radial profiles of the plasma potential and the electron energy distribution functions, i.e., the electron temperatures and densities, were derived from the Langmuir probe current-voltage characteristics measured by applying the first-derivative probe technique (FDPT) [1]. During the experiment, three different shots with accretive average density (density scan) and three shots with different plasma current (current scan) were studied. The plasma parameters evaluated by the FDPT using the parallel and the perpendicular probe tips showed satisfactory agreement. The simplified kinetic solver for neutrals included in the ASTRA package [2] was used to study the ionization of neutral deuterium atoms in the vicinity of the last closed flux surface. The influence of the ionization on the formation of the electron energy distribution


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function is discussed [3]. Acknowledgements: This research has been supported by the GACR grant No. P205/11/2341, by the International Atomic Energy Agency (IAEA) Research Contract No 17125/R0, R1 and R2 as a part of the IAEA CRP F13014 on “Utilisation of a Network of Small Magnetic Con-finement Fusion Devices for Mainstream Fusion Research” and 7th IAEA Joint Experiment; by the JOINT RESEARCH PROJECT between the Institute of Plasma Physics AS CR and the Institute of Electronics BAS BG; and by MSMT Project # LM2011021. References [1] Tsv. K. Popov, P. I. Ivanova, J. Stockel and R. Dejarnac, 2009 Plasma Phys. Control. Fusion 51, 065014 "Electron energy distribution function, plasma potential and electron density measured by Langmuir probe in tokamak edge plasma" [2]. Pereverzev G V and Yushmanov P N, 2002 ASTRA Automated System for Transport Analysis, Tech. Rep. IPP, Max Plank Institut für Plasmaphysik, Garching, February 5/98 [3] Tsv K Popov et al. 2015 Plasma Phys. Control. Fusion (submitted) "Bi-Maxwellian electron energy distribution function in the vicinity of the last closed flux surface in fusion plasma" PA–16

DEVELOPMENT OF PROBLEM-ORIENTED SOFTWARE PACKAGES FOR NUMERICAL STUDIES AND COMPUTER AIDED DESIGN (CAD) OF

GYROTRONS

M. Damyanova1, S. Sabchevski1, I. Zhelyazkov2, E. Vasileva1, E. Balabanova1, P. Dankov2, P. Malinov2

1Institute of Electronics of the Bulgarian Academy of Sciences,

72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria 2Faculty of Physics, St. Kliment Ohrdidski University of Sofia, Association EURATOM-

INRNE, 5, James Bourchier blvd., 1164 Sofia, Bulgaria

Gyrotrons are the most powerful sources of coherent CW (continuous wave) radiation in the frequency range situated between the long-wavelength edge of the infrared light (far-infrared region) and the microwaves, i.e., in the region of the electromagnetic spectrum, which is usual-ly called THz-gap (or T-gap) since the output power of other devices (e.g., solid-state oscilla-tors) operating in this interval is by several orders of magnitude lower. In recent years, the unique capabilities of the sub-THz and THz gyrotrons have opened the road to many novel and future promising applications in various physical studies and advanced high-power terahertz technologies. We present the current status of the problem-oriented software packages (most notably GYROSIM and GYREOSS) used for numerical studies, computer-aided design (CAD) and optimization of gyrotrons for various applications. They consist of a hierarchy of codes specialized to modelling and simulation of different subsystems of the gyrotrons (EOS, reso-nant cavity, etc.) and are based on adequate physical models, efficient numerical methods and algorithms. The performance of the simulation tools developed is illustrated by results of nu-merical experiments and benchmarking tests. Finally, we conclude with an outlook for the fu-ture elaboration and extension of the computational modules of the underlying computer codes.


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PA–17

THERMOPHYSICAL PROPERTIES OF CF4/O2 AND SF6/O2 GAS MIXTURES

M. Damyanova1, U. Hohm2, E. Balabanova1, D. Barton3

1Institute of Electronics of the Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

2Institut für Physikalische und Theoretische Chemie der TU Braunschweig, Hans-Sommer-Str. 10, D-38106 Braunschweig, Germany

3Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40,

48149 Münster, Germany

The determination of reliable thermophysical data of pure gasses and gas mixtures is an important but in many cases cumbersome experimental and computational task. Such data related to the transport (viscosity, diffusion) and equilibrium (second virial coefficient) properties are needed in many practical applications. The fluorinated gasses and gas mixtures e.g. CF4/O2 and SF6/O2 are widely used for dry etching of silicon, some silicides, polymers etc. [1-3]. Also, there is evidence that the mixture SF6/O2 plays a significant role in studying the convective and diffusive intrapulmonary gas transport [4]. Despite the intensive use of CF4/O2 and SF6/O2 in practical applications, still little is known about their thermophysical properties, especially in wide ranges of temperature and composition. The aim of this work is to calculate and present recommended values for the viscosity, diffusion and second virial coefficients of CF4/O2 and SF6/O2 gas mixtures. The calculation of the transport and virial coefficients of the pure substances CF4, SF6 and O2 is based on an (n-6) Lennard-Jones temperature dependent potential model, discussed in [5]. In this work we use our previously suggested Hohm-Zarkova-Damyanova (HZD) mixing rules [6], which have been shown to yield reasonable interaction potentials between unlike molecules and, subsequently, reliable thermophysical properties of binary gas mixtures at low pressures. The data for the viscosity, diffusion and second virial coefficients for both mixtures are obtained in a wide temperature range between 200 K and 1000 K. We compare our findings to the available experimental and theoretical data. In general good agreement is observed.

[1] Yu. N. Grigoryev and A. G. Gorobchuk, Russian Microelectronics 36(5) (2007) 321 [2] T. P. Chow and G. M. Fanelli, J. Electrochem. Soc. 132(8) (1985) 1969 [3] J. Meichsner, M. Schmidt, R. Schneider, H. Wagner, Nonthermal Plasma Chemistry and Physics, CRC Press, (2012) [4] R. C. Tai, H. Chang, and L. Farhi, Resp. Physiology 40 (1980) 253 [5] L. Zarkova, U. Hohm, and M. Damyanova, J. Phys. Chem. Ref. Data 35(3) (2006) 1331 [6] U. Hohm, L. Zarkova, and M. Damyanova, Int. J. Thermophys. 27(6) (2006) 1725


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PA–18 INTERSUBBAND OPTICAL ABSORPTION IN NITRIDE SUPERLATTICE GROWN

BY MBE

I. Asenova1, E. Valcheva

1Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier blvd., 1164 Sofia, Bulgaria

We present a theoretical study of the intersubband absorbance of the wurtzite AlN/GaN superlattice. The structure is characterized by macroscopic in-layer polarization, which breaks down the symmetry of the potential profile, thus making the parity-based transition rules invalid. As a result, the “allowed” transitions are shown to be exceeded in intensity by the “forbidden” ones. All our considerations are made within the assumption that no bias is applied to the device. The theoretical model we utilize for our calculations is based on the envelope-function approximation, while the bound state energies of the system are calculated via the transfer matrix formalism. PA–19

AUTOMATION OF THE ELECTRON BEAM WELDING PROCESS

E. Koleva1,2, V. Dzharov1, M. Kardjiev1, G. Mladenov1

1Institute of Electronics, Bulgarian Academy of Sciences

2University of Chemical Technology and Metallurgy, Sofia The electron beam has been developed over the years into a flexible and economic manufacturing tool. Due to the deep penetration in the work-piece, the electron beam is able to generate a narrow weld with a minimal thermally affected zone and without the usage of welding consumables. The high-vacuum required by the method prevents the heated and melted material from being oxidized and affected by atmospheric pollutants. With the advanced development of computer control, the number of electron-beam applications has significantly increased. In what concerns the electron-beam welding (EBW) technologies, the EBW plants were developed into complex equipment containing highly-stabilized power sources and electronic blocks, a reliable and effective vacuum system, a technologcal chamber with a precision 3D manipulator, thus becoming truly software controlled programmed manufacturing tools with high efficiency and excellent reproducibility. The technological data gathered during the process enable quality monitoring and support the improvement of the testing process of the manufactured components; also, the data are recorded for future analysis of the relations of the adjusted process parameters and the weld quality and stability. In this work, the automatic control is considered of the vacuum and cooling systems of the equipment located in IE-BAS for electron-beam welding, evaporation and surface modification, together with the electron-beam formation and motion. A project is developed for the control and management based on existing and additional technical means of automation. Optimization of the indicators, which are critical for the time period needed for reaching a working regime and stopping the operation of the installation, is performed using


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experimentally obtained transient characteristics. The control of the beam formation and the motion over different trajectories is designed and simulated. The automation of the available equipment aims to improve its efficiency and the repeatability of the results obtained, as well as stabilization of the process parameters. PA–20

ELECTRON BEAM CHARACTERIZATION BY TOMOGRAPHIC APPROACH

E. Koleva1,2, L. Koleva2, D. Todorov, G. Mladenov1

1Institute of Electronics, Bulgarian Academy of Sciences

2University of Chemical Technology and Metallurgy, Sofia

The characterization of the radial and angular space distribution of particle trajectories (or the respective current distributions) in high-power electron beams is an important scientific and practical task, connected with improving the quality of the electron-beam technologies, creating standards of electron-beam welding machines and permitting transfer of concrete electron-beam welding technologies from one equipment to another. To apply the advantages of electron-beam welding, it is necessary to know the properties of the electron beam. There only exist standards for measuring the electron-beam current and accelerating voltage as beam characteristics applicable to the acceptance inspection of an electron-beam welding machine or to research. These parameters cannot characterize the quality of the electron-beam produced in terms of the ability to transport it over long distances and to focus it into a small spot with a minimum divergence. Tomography is a technique for reconstruction of a two-dimensional object image from a set of its one-dimensional projections, measured as an array of line integrals (or slices) of the object studied. This technique is widely used in different scientific areas, starting from medical applications, materials science etc. There, a Fourier transformation from real to frequency space and a subsequent back Fourier transformation permit one to reconstruct the beam cross-section current density image (beam radial intensity profile) with its asymmetry features. During the last decade, measurements were proposed of the profile of intense electron beams by an enhanced modified Faraday cup. We developed further this tomography evaluation to obtain the beam emittance, containing the beam current distribution in the cross-section studied, together with the angular distribution of the beam electrons there. The emittance (or the reciprocal value − the brightness normalized to one volt) is an invariant quantity along the beam and could be used as а standard characteristic, for prognosis and optimization, as well as for transfer of technologies from one electron beam equipment to another. In this work, based on the tomographic approach, the 3D beam radial current density distribution is reconstructed and the angular beam distribution and the beam emittance are estimated when variyng the electron beam parameters: If – focusing current, Ie – beam current, Uv – venelt voltage and the distance H to the measuring device. By implementing regression analysis, the dependences of these beam quality characteristics on the electron-beam parameters are estimated. The tomographic algorithm for beam reconstruction is optimized through comparison of the simulation results for different experimental equipment sets. A graphical user interface for visualization and investigation of the electron-beam characteristics is developed.


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PA–21

VERTICAL PLASMA TURBULENCE SUPPRESSION IN CROSSED ELECTRICAL AND MAGNETIC FIELDS DUE TO FINITE LIFETIME OF ELECTRONS AND IONS

AND DUE TO FINITE SYSTEM LENGTH

I.P.Levchuk, V.I.Maslov, I.N.Onishchenko, A.M.Yegorov, V.B.Yuferov

NSC Kharkov Institute of Physics & Technology, 61108 Kharkov, Ukraine

The plasma in crossed radial electrical and longitudinal magnetic fields has a rotating drift. In the case of multicomponent plasma, the plasma column rotation leads to a spatial separation of the ion component.This principle is a fundamental method for the separation of heavy and light fractions of the ions in the rotating plasma with a positive potential on the cylindrical axis of the longitudinal magnetic and radial electric field (the system E×B). The possibility to use rotating-plasma devices for substance separation promotes the plasma investigations and development of facilities for substance separation into mass groups and elements. In plasma [1-3], a turbulence has been excited in crossed radial electrical and longitudinal magnetic fields by a gradient of the external magnetic field. This turbulence is a distributed vorticity. In this work, the excitation and damping of similar vortical turbulence, excited in cylindrical plasma in crossed radial electrical and longitudinal magnetic fields [4], is investigated theoretically. The dispersion equation was derived describing the instability development of vortex turbulence excitation in cylindrical plasma in crossed radial electric and axial magnetic fields with taking into account the longitudinal inhomogeneity and the finite time of the electrons and ions leaving the plasma. It is shown that the finite length of the system and the finite time of the electrons and ions leaving the plasma lead to the appearance of an instability threshold and to a decrease of the rate of its development.

[1] A.Goncharov, A.Dobrovolsky, A.Kotsarenko, A.Morozov, I.Protsenko // Journal «Physica Plasmy». 1994, v. 20, pp. 499.

[2] A.Goncharov, I.Litovko, Electron Vortexes in High-Current Plasma Lens // IEEE Trans. Plasma Sci. 1999, v. 27, pp. 1073.

[3] V.I.Maslov, A.A.Goncharov, I.N.Onishchenko, Self-Organization of Non-Linear Vortexes in Plasma Lens for Ion-Beam-Focusing in Crossed Radial Electrical and Longitudinal Magnetic Fields // Invited Paper. In Proceedings of the International Workshop "Collective phenomena in macroscopic systems", G. Bertin, R. Pozzoli, M. Rome' & K.R. Sreenivasan Eds. World Scientific, Singapore, 2007, pp. 20-25.

[4] V.B.Yuferov, A.S.Svichkar, S.V.Shariy, T.I.Tkachova, V.О.Ilichova, V.V.Katrechko, A.I.Shapoval, S.N. Khizhnyak, About Redistribution of Ion Streams in Imitation Experiments on Plasma Separation // Problems of Atomic Science and Technology. Ser.: Physics of Radiation Damage and Radiation Material. 2013, 5 (87), pp. 100-103.


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PA–22

PROVIDING HOMOGENEOUS AND IDENTICAL FOCUSING OF TRAIN OF SHORT RELATIVISTIC ELECTRON BUNCHES BY WAKEFIELD PLASMA LENS

I.P. Levchuk, V.I.Maslov, I.N.Onishchenko

NSC Kharkov Institute of Physics & Technology, 61108 Kharkov, Ukraine

Focusing relativistic electron bunches by wakefield, excited in the plasma, is important and interesting (see [1-2]). The focusing of bunches by wakefield, excited in plasma by resonant train of relativistic electron bunches (the repetition frequency of the bunches ωm coincides with the plasma frequency ωm = ωp), is inhomogeneous [3, 4]. A mechanism of focusing in plasma, in which all bunches of train are focused identically and uniformly, has been proposed and investigated by numerical simulation in [3, 4]. This plasma wake lens for short relativistic electron bunches is studied in the present work analytically and by numerical simulation by lcode [5]. Unbound nonmagnetized homogeneous plasma is considered. Rectangular in longitudinal direction bunches (i.e. the bunch current is constant along the bunch axis) are considered in a fixed current approximation. We consider homogeneous focusing of train of short bunches. We show that all bunches of the train are focused identically and uniformly. It is also shown that there are two wakefield plasma lenses for a train of short bunches. In the first lens, achieving identical and uniform focusing necessitates that the length of first bunch ∆ξb1 be chosen equal to the half of wavelength ∆ξb1=λ/2; all other bunches should be short, ∆ξb<λ/2, and the charge density of all other bunches should be more than twice as large as the charge density of the first bunch n1 = ni/2, i = 2, 3, ... In the second lens, achieving identical and uniform focusing necessitates that the charge density of the first bunch be smaller by a factor of

2 than the charges of the other bunches, and the spatial interval between the first and the second bunches should be equal to (n+1/8)λ, n = 1, 2, … The intervals between all bunches in both lenses must be multiples of the wavelength δξ=pλ, p = 1, 2, …, in order to achieve a longitudinal wakefield Ez = 0 and a radial focusing field Fr =const along the bunch. The first bunch only is in the finite decelerating field Ez ≠ 0. The other bunches are in a longitudinal electric field equal to zero Ez = 0. Then, the first bunch only exchanges energy with the wakefield. The subsequent bunches do not interchange energy with the wakefield and the amplitude of the wakefield does not change along the train. The radial wake force Fr in the areas of bunches location is approximately constant along the bunches.

[1] Ya. Fainberg, M. Ayzatsky, V.Balakirev et al., Focusing of Relativistic Electron Bunches at

the Wakefield Excitation in Plasma. Proceedings PAC’97. 12-16 May, 1997 Vancouver, Can-ada. V. II. P. 651-653.

[2] H. Suky et al., Proc. of PAC. New York, 1999. [3] K.V.Lotov, V.I.Maslov, I.N.Onishchenko, O.M.Svistun. Problems of Atomic Science & Tech-

nology. 2012. 3(79). P. 159-163. [4] V.I.Maslov, I.N.Onishchenko, I.P. Yarovaya. Problems of Atomic Science & Technology.

2013. 1(83). P. 134- 136. [5] K.V.Lotov. Phys. Plasmas. 1998, V. 5, N 3, P. 785-791.


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PA–23 MODEL OF SURFACE-WAVE DISCHARGE AT ATMOSPHERIC PRESSURE WITH

FIXED PROFILE OF GAS TEMPERATURE

M. Nikovski1, Zh. Kiss'ovski1, E. Tatarova2

1 Faculty of Physics, St. Kl. Ohridski University of Sofia

5, J Bourchier blvd., 1164 Sofia, Bulgaria 2 Institute of Plasmas and Nuclear Fusion, Instituto Superior Tecnico, University of Lisbon,

1049-001 Lisbon, Portugal E-mail: [email protected], [email protected]

In this study, a model is presented of a surface-wave sustained discharge at 2.45 GHz at

atmospheric pressure. A small plasma source creates a plasma column in a dielectric tube and a plasma torch is observed above the top of the tube if the absorbed power is higher than 11 W [1]. The plasma parameters and the axial profile of the gas temperature change significantly in the presence of the substrate above the plasma torch. The model includes a dispersion relation of azimuthally symmetric surface waves in the plasma column in the dielectric tube and in the plasma torch [2]. The electron Boltzmann equation under local approximation is solved, together with heavy particle balance equations at a fixed axial profile of the gas temperature [3]. A detailed collisional-radiative model is developed for an argon discharge at atmospheric pressure, which includes 21 rate balance equations for excited Ar atoms [(Ar(1s5-1s1), Ar(2p10 -2p1), Ar(2s3d), Ar(3p)], for positive Ar+ and Ar2

+ ions and for excited molecules [4]. The changes in the EEDF shape and the mean electron energy along the plasma column are investi-gated and the axial structures of the discharge and torch regions are obtained.

[1 ] Kiss’ovski Zh, Ivanov A, Kolev M, Lishev St, Koleva I (2009) J Phys.D: App. Phys 42 182004-10 [2] D. Tsyganov, N. Bundaleska, E. Tatarova, C.M. Ferreira, (2013) Int. J of Hydrogen Energy 38 (2013) 14512-14530 [3] J Henriques, A Ivanov, Zh. Kiss’ovski, E Tatarova, C. M. Ferreira, Bulletin of APS (2011), 64th Annual GEC, v. 56, N 15, p 35 [4]. Kiss’ovski Zh , Ivanov A., Iordanova S and Koleva I 2011 J Phys. D: Appl. Phys., 44, 205203 PA–24

STRAY MAGNETIC FIELD INFLUENCE ON THE CPT RESONANCE IN A COATED Rb VACUUM CELL

E. Taskova, E. Alipieva and G.Todorov

Academician Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences,

72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria The interaction of a resonant laser beam with an atomic absorption medium creates population redistribution and interference between the atomic levels. This anisotropy of the medium is ex-




79

perimentally observed as coherent population trapping (CPT) or electromagnetically induced transparence (EIT) [1]. Due to the small sub-natural width of the CPT and EIT resonances they find wide application in metrology, quantum optics, atom cooling. In this work we present a systematic investigation of the influence of the stray magnetic fields (MF) on the CPT resonances obtained on Zeeman sublevels of D1 line of 87Rb in a paraffin-coated vacuum cell. The cell coating preserves the coherence created in the atomic media. Consequently, the CPT resonance registered is some orders of magnitude narrower than the one obtained in a cell without coating. The non-compensated magnetic field which is able to destroy or change dramatically the CPT resonance shape is in the range of some mG. Figure 1 shows the shape of the CPT resonance in the presence of a stray magnetic field (red line) and when the stray magnetic field is compensated (black line). The population, longitu-dinal and transverse alignment contribute to the fluorescence signal.

The influence of the stray MF on each of these components is modeled by a standard semiclassical description of the atomic system by the statistical operator in density matrix representation. The irreducible tensor operator (ITO) formalism program for numerical modeling of this effect is used. The numerical calculations are based on the model presented in [2]. The comparison of the obtained theoretical line shape of the resonances with the experiments shows good agreement.

Figure 1. Influence of stray MF on the CPT resonances shape; (a) with stray MF and (b) without stray MF.

[1] E.B. Alexandrov, M.P. Chaika, G.I. Hvostenko “Interference of atomic states,” Sptinger-

Verlag (1991). [2] V. Polischuk, V.Domelunksen, E. Alipieva, G. Todorov, “Modelling of nonlinear interac-

tion of 87Rb atoms with polarized radiation”, Bulg. J. Phys. 39 150-164 (2012). Acknowledgements: This work has received partial funding from the 7th EU Framework Programme: "Coherent optics sensors for medical applications-COSMA" (Grant Agreement No: PIRSES-GA-2012-295264). PA–25

A SELF-CONSISTENT ONE-DIMENSIONAL MULTIFLUID MODEL OF THE PLASMA-WALL TRANSITION IN THE PRESENCE OF TWO SPECIES OF

NEGATIVELY BIASED PARTICLES

T. Gyergyek1,2, J. Kovačič2

1University of Ljubljana, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana, Slovenia

2Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia


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The plasma-wall transition in the presence of either negative electrons or energetic electron population is a subject of great interest and is still an area of very active research in magnetized [1,2] as well as non-magnetized plasmas [3,4]. An approach that is used by many authors [1-4] is to assume that the continuity and momentum exchange equations are valid for the positive ions, while the Boltzmann relation is assumed for the negative particles. In this work, each of the three particle species present in the plasma is treated by its own pair of continuity and momentum exchange equations. In this sense, the model is fully self-consistent, since there is no an a-priori assumption on the density of any of the particle species. There are two negative and one positive particle species present in the plasma. The model is one dimensional. A set of seven ordinary differential equations is derived and solved numerically. The solutions give the density and fluid velocity profiles for all particle species as well as the potential and electric field profile. Elastic collisions between different particle species can be taken into account. The same model can be used for the analysis of either plasma with two-electron temperature distributions, or electronegative plasma that contains electrons and negative ions. Some basic properties of the model are illustrated and the role of collisions and consistency of the source terms is investigated. The Bohm criterion under various conditions is obtained.

[1] K. Yasserian, M. Aslaninejad and M. Ghoraneviss, Phys. Plasmas, 16, 023504 (2009). [2] M. M. Hatami and B. Shokri, Phys. Plasmas, 20, 033506 (2013). [3] J. I. Fernandez Palop, J. Ballesteros, M. A. Hernandez and R. Morales Crespo, Plasma Sources Sci.

Technol. 16, S76–S86 (2007). [4] J. I. Fernandez Palop, J. Ballesteros, M. A. Hernandez and R. Morales Crespo, J. Appl. Phys. 91,

2587-2593 (2002). PA–26

OPEN DSS SIMULATIONS OF POWER FLUCTUATIONS INDUCED BY A ROOFTOP PV GENERATOR ON A BUILDING LV ELECTRICAL GRID

Hristo Nichev, Miroslav Petrov, Konstantin Lovchinov, Nikolay Tyutyundzhiev

Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences

72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria The high extent of proliferation of photovoltaic (PV) installations in urban areas raises the problem of power quality and voltage stability during external atmospheric fluctuations. If not properly designed, densely populated PV installations, connected in a remote node of the grid, may degrade the power quality or multiply the power fluctuations. A computer simulation of power flows in a bidirectional grid can reveal weak points in the grid. It can imply measures for mitigation of fluctuations and creation of algorithms for energy management of future “smart grids”. This report gives and overview of the bilateral impact between a decentralized generator and a LV grid. Daily profiles of the electrical load in a building and the generated power are ex-tracted from grid monitoring devices. Based on experimental data, software simulations are performed in an open DSS environment − an open-source simulation tool. Keywords: Photovoltaic systems, PV power generation, Impact on grid stability, Smart grids.


POSTER SESSION B:

SURFACES AND THIN FILMS PROCESSING AND ANALYSIS

PB–10

LASER NANOSTRUCTURING OF Ag FILMS DEPOSITED ON DIFFERENT SUBSTRATES

Ru. G. Nikov, N. N. Nedyalkov, P. A. Atanasov


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PB–1

PLASMA INDUCED HEATING OF THE SUBSTRATE DURING MAGNETRON SPUTTERING

S. Muhl, J. Cruz, J. Restrepo

Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Cd.

Universitaria, Av. Universidad 3000, México, DF 04510, México It is known that the substrate, or more importantly, the surface of the deposit, are heated by the plasma during magnetron sputtering. However, there have been few detailed reports of this process, which can involve a combination of bombardment by ions, electrons, excited and neutral species, and absorption of visible and UV radiation. Here we report a study of the substrate heating during DC magnetron sputtering of a 4” aluminium target as a function of: the plasma power, the Ar gas pressure and the substrate bias (floating, earthed and negatively biased). Additionally, we studied the heating during argon-nitrogen reactive sputtering as a function of the nitrogen concentration. For sputtering of aluminium, the substrate could reach temperatures greater than 200 oC and the temperature distribution over the 4” substrate holder was not uniform; the highest temperatures were found in front of the racetrack and the lowest, at the edge of the target. For reactive sputtering, the temperature increased strongly for nitrogen concentrations of > 8 %. Both aluminium and aluminium nitride thin films were deposited using the sputtering conditions studied, and the coating characteristics depended on where the substrate was located. The properties of the films were analyzed using SEM and X-ray diffraction and the film thickness was measured using a stylus profilometer. PB–2 INVESTIGATION OF RESISTIVE PROPERTIES OF HTS/MANGANITE BILAYERS

T. Nurgaliev1, B. Blagoev2, V. Strbik3, S. Chromik3, M. Sojkova3

1Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria

2Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria

3Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovak Republic

Manganites show a broad spectrum of physical properties and frequently demonstrate a coexistence of the spatially separated different electronic and magnetic states at the same time. The electromagnetic properties of high temperature superconducting (HTS) YBa2Cu3O7-x

(YBCO) depend strongly on the oxygen content x in the CuO chains; depending on x, the


84

YBCO can be in insulating antiferromagnetic or in superconducting states. The characteristics of both materials are very sensitive to the influence of external factors, such as temperature, magnetic field, stresses and strains. A variety of additional new effects arises in HTS/manganite heterostructurs due to different coupling mechanisms across the interface. In this work we considered peculiarities of the resistive characteristics of the manganite (La0.7Ca0.3MnO3 (LCMO), La0.7Sr0.3MnO3 (LSMO)) films and HTS/manganite (YBCO/LCMO, YBCO/LSMO) bilayers deposited on different substrates. In particular, LSMO films sputtered onto LaAlO3 (LAO) substrates with a strip-like twin structure demonstrated anisotropy of the resistance at room temperatures. The conductive properties of the bilayers are determined by the contribution of the conductivities of the individual HTS and manganite layers and by the interaction peculiarities of the layers in the interface. Modeling allowed us to obtain additional information on the characteristics of the individual layers of the bilayer structures. PB–3

TRANSPORT PROPERTIES OF YBa2Cu3Ox/La0.67Sr0.33MnO3 NANOJUNCTIONS

V. Štrbík, Š. Beňačka, Š. Gaži, M. Španková, V. Šmatko,, Š. Chromik, N. Gál, M. Sojková and M. Pisarčík

Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava, Slovakia

A metallic ferromagnet (F) in a close proximity with a superconductor (S) can transport supercurrent over a long distance (long-range proximity effect, LRPE) through conversion of opposite-spin singlet Cooper pairs (CP) into equal-spin triplet CP, which are not broken by the exchange energy of F. The optimal conditions for the conversion are still not clear; however, it is accepted that key points in this process include high interface transparency and magnetic inhomogeneity at the SF interface. The objects of our contribution are SF nanostrips (a length of about 1500 nm and a width of about 300 nm) and lateral SFS nanojunctions based on high critical temperature YBa2Cu3Ox (YBCO) and half-metallic La0.67Sr0.33MnO3 (LSMO) thin films. We applied a Ga+ focused ion beam for patterning SF nanostrips, as well as SFS nanojunctions, after removing part of the YBCO film in a slot of width of less than 50 nm. The temperature dependences of the samples resistance R(T) show a critical temperature TCn ≈ 89 K of the SF nanostrips; however, the SFS junctions at T < TCn show a residual resistance R < 100 Ω, corresponding to dirty LSMO (ρ ≈ 10-3 Ω cm) present in the slot; therefore, the LRPE was not present in the SFS junctions until now. Progress in these investigations will be presented.


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PB–4

FABRICATION OF HYBRID THIN FILM STRUCTURES FROM HTS AND CMR MATERIALS

M. Sojková1, V. Štrbík1, Š. Chromik1, M. Španková1, T. Nurgaliev2, B. Blagoev2

1Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9,

841 04 Bratislava, Slovakia


Perovskite materials (high-temperature superconductor (HTS) and half-metallic ferromagnetic manganite with colossal magnetoresistance (CMR)) demonstrate a number of interesting properties from both theoretical and application points of view, including the spin-polarized DC current injection effect from a ferromagnetic CMR to a HTS film. As HTS we used YBa2Cu3Ox (YBCO) and Tl2Ba2Ca1Cu2Ox (TlBCCO) thin films, and as CMR, La1-xSrxMnO3 (LSMO) or La1-xCaxMnO3 (LCMO), all with a nominal thickness in the range of 50-300 nm. The films were prepared by magnetron sputtering, laser pulsed ablation techniques, and in the case of TlBCCO, by a two-step thallination process. The hybrid HTS/CMR structures were fabricated using wet etching and “lift-off” processes. We will present some structural and electrical properties of the HTS/CMR heterostructures. PB–5

PROPERTIES OF NANOSECOND LASER PROCESSED POLYDIMETHYLSILOXANE (PDMS)

P.A. Atanasov1*, N.E. Stankova1, N.N. Nedyalkov1, T.R. Stoyanchov1, Ru.G. Nikov1,

N. Fukata2, J. W. Gerlach3, D. Hirsch3, B. Rauschenbach3

1Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsaridradsko Chaussee blvd., Sofia 1784, Bulgaria.

2International Center for Materials for NanoArchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1Namiki, Tsikuba 305-0044, Japan

3Leibniz Institute of Surface Modification (IOM), Permoserstrasse 15, D-04318 Leipzig, Germany

* [email protected]

Medical grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial in medi-cine and for preparation of high-technology devices because of its remarkable properties: me-chanical flexibility and stability; high dielectric constant and breakdown field; optical transpa-rency in the ultraviolet (UV) – visible (VIS) spectral regions; biocompatibility and biostability; simple and inexpensive fabrication. High-definition tracks and electrodes can be fabricated by UV or VIS ns- or fs-laser pulse processing with subsequent metallization in order to get altera-tions of the chemical composition and structural morphology of the ablated traces. The impor-tance of knowing the changes of the morphology, structure and chemical properties of the la-ser-processed material will help to understand the nature of the laser-matter interaction.



86

In this work, we present experimental results on the change of the morphology, chemical com-position and structure of the PDMS processed by UV, VIS and IR ns-laser pulses. The processing of medical grade PDMS elastomer is accomplished using the fundamental (λ = 1.064 µm), 2nd HG (λ = 532 nm) or 4th HG (λ = 266 nm) of a Q-switched Nd:YAG laser (pulse duration τ = 15 ns and repetition rate of 10 Hz). The as-processed material is studied by XRD, SEM, µ-Raman analyses and 3D laser microscopy in order to get information for the in-fluence of the different processing parameters as laser wavelength, fluence and number of con-secutive pulses on its properties. Key words: PDMS-elastomer, optical properties; UV, VIS, and IR ns-laser processing; XRD, µ-Raman, XPS, SEM analyses and 3D laser microscopy; PB–6

PREPARATION AND CHARACTERIZATION OF COPPER CATALYSTS SUPPORTED ON MESOPOROUS SILICA-CARBON NANOCOMPOSITES

G. Atanasova1, N. Stoeva 1, R. Nickolov2, I. Spassova1

1Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia,

Bulgaria

2University of Chemical Technology and Metallurgy, Sofia, 1756 Sofia, Bulgaria

In view of better catalytic performance, enhanced activity and selectivity, the composite catalysts are of interest and have been extensively studied recently in the field of heterogeneous catalysis. These composite catalysts, prepared by one or more active components supported on a support are of interest because of the possible interaction between the catalytic components and the support materials that could ensure the preparation of composite catalysts with much improved properties. In this case, it is important to study the possible cooperation in the nanocomposite catalysts between the different catalytic components or between the catalytic components and the support. Mesoporous silica-carbon nanocomposites have drawn more attention because of the combination of multi-functionality, well-controlled pore structure, high surface areas, tuneable pore morphology facilitating the diffusion of the reagents and the reaction products inside the pores. Mesostructured silica-carbon nanocomposites were prepared by tri-constituent co-assembly of previously prepared resol (phenol-formaldehyde clay), silica oligomers from acid-catalysed hydrolysis of TEOS, and triblock copolymer Pluronic F127 via the EISA method in ethanol solution. The composites were synthesized with various silica: carbon ratios using different quantities of TEOS and resol. The copper active phase was loaded on the supports by vacuum evaporation of CuCO3Cu(OH)2 in ammonia with subsequent thermal treatment in argon. The catalysts were characterized by XRD (low-angle and wide-angle), XPS, TEM, AAS and low-temperature nitrogen adsorption. A relationship was found between the composition of the support and the specific surface area, total pore volume, mean pore diameter. XPS investigations proved the cooperation between the support and the supported copper phases in order how the support maintains the active catalyst phase. It was found that different silica: carbon ratios in the composites provoke different Cu+ and Cu2+ content on the surface. Acknowledgments: The work was financed by the National Science Fund Project E02/2- 2014.


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PB–7

THIN NANOCRYSTALLINE ZIRCONIA FILMS PREPARED BY PULSED LASER DEPOSITION

A.Og. Dikovska1*, G.B. Atanasova2, G.V. Avdeev3

1Institute of Electronics, Bulgarian Academy of Sciences,

72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria 2Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences,

Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria 3Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences,

Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria

Zirconium oxide (ZrO2) is a transition metal oxide, which offers several interesting technologi-cal applications due to its properties, such as high melting point, high refractive index, good thermal, chemical and mechanical stabilities, wide band gap, high dielectric constant and elec-trical resistivity. It finds applications in optical coatings, protective coatings and insulating lay-ers, catalyst for alcohol synthesis, in fuel cells as well as in thermal barrier coatings. ZrO2 has three well-defined polymorphs under different conditions of temperature: monoclinic, tetra-gonal and cubic. These high temperature phases can be retained at room temperature by doping with some suitable oxides, such as aluminium oxide, yttrium oxide, magnesium oxide, and cal-cium oxide. In the present work, zirconia thin films were prepared on different (silicon, quartz, and steel) substrates by the PLD technique at different substrate temperatures and partial oxygen pres-sures. The substrate temperature was varied from room to 600 oC, and the oxygen pressure, from vacuum to 0.1 mbar. The effect of the substrate temperature and oxygen pressure on the formation of m-zirconiaand t-zirconia phases was investigated by Raman spectroscopy. The formation of a cubic phase of ZrO2 was also investigated. The variation in the optical proper-ties was studied and discussed in relation with the microstructure of the zirconia films. PB–8

EFFECT OF AL2O3 ON THE LOW TEMPERATURE DEGRADATION OF Y-PSZ THIN FILMS

A.Og. Dikovska1*, G.V. Avdeev2, G.B. Atanasova3


72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria 2Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences,

Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria 3Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences,

Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria *[email protected]

Zirconia is one of the most important structural ceramics. In particular, yttria partially stabi-lized zirconia (Y-PSZ) with excellent mechanical properties have been widely used in many


88

industrial fields. However, the phase transformation from tetragonal (t) to monoclinic (m) oc-curring on the surface of Y-PSZ at the low temperatures of 100 ~ 400 C usually produces mi-cro-cracks and macro-cracks and results in an abrupt decrease in strength. This is called low-temperature degradation, which seriously affects the application of Y-PSZ. The research on improving the degradation resistance of Y-PSZ has lately made considerable progress. For ex-ample, controlling the grain size, doping by metal oxides and stabilizing by surface engineering technologies, are effective techniques improving the degradation resistance of Y-PSZ. Adding particles with a high elastic modulus to Y-PSZ has been considered as one of the most accessi-ble techniques for inhibiting the low temperature degradation. It has been indicated that adding Al2O3 particles into Y-PSZ not only improves its mechanical properties at room temperature, but also inhibits the low-temperature degradation. In this work, zirconia and zirconia composites were prepared in thin-film form by pulsed laser deposition (PLD). The microstructure, phase composition, and tetragonal to monoclinic trans-formation behavior were investigated and discussed as a function of the Al2O3 content. A study is presented of the low-temperature degradation, called also ageing phenomenon, in zirconia-alumina films. The influence of the yttria content in zirconia composites and microstructure on the ageing mechanisms is also discussed. PB–9 INVESTIGATION OF THE AGING PROCESS OF NOBLE METAL NANOSTRUCURES

FABRICATED BY NANOSECOND LASER ABLATION IN WATER

R.G. Nikov1, A.S. Nikolov1, N.N. Nedyalkov1, E.L. Pavlov1, P.A. Atanasov1, M.T. Alexandrov2, D.B. Karashanova3


72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria 2Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences,

G. Bonchev Street, bl. 25, Sofia 1113, Bulgaria 3Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences,

G. Bonchev Street, bl. 109, Sofia 1113, Bulgaria Colloids of noble metal nanostructures were produced by pulsed laser ablation of solid targets in water. The fundamental (λ = 1064 nm) and the second (λ = 532 nm) harmonics of a Nd:YAG laser system were utilized in the ablation process. The colloids produced were stored in a cuvette at a constant temperature during the ageing process. The changes in the volume of the colloids produced were studied by measuring the optical extinction spectra. These spectra were taken at different heights of the cuvette and their changes at different time periods after fabrication were traced. They were used to assess the ageing process of the colloids expressed in sedimentation and aggregation of the nanostructures. To visualize the effect of these two processes, transmission electron microscopy was used. Ultrasonic treatment of the colloids was applied to achieve modification of the already created clusters and recover the optical properties of the colloids as closely as possible to these on the day of preparation. As a result, some of the aggregates were completely disintegrated while others fragmented into smaller ones. The aim was to establish the optimal storage conditions of the colloids in view of preserving their original characteristics.


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PB–10

LASER NANOSTRUCTURING OF Ag FILMS DEPOSITED ON DIFFERENT SUBSTRATES

Ru.G. Nikov1, N.N. Nedyalkov1, P.A. Atanasov1


72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria

This paper presents results on nanostructuring of Ag thin films by a laser-assisted technique. The thin films are fabricated by on-axis pulsed laser deposition technology on glass, metal and polymer substrates. The as-deposited films are then irradiated by nanosecond laser pulses deli-vered by a Nd:YAG laser system operated at λ = 355 nm. The characteristics of the film mod-ifications obtained are also studied as a function of the laser pulse parameters and the film thickness. Under certain conditions, the laser treatment may lead to a decomposition of the Ag film into a discrete nanostructure on the substrate composed of nanoparticles. The optimal con-ditions for fabrication of nanoparticles with a narrow size distribution on the different sub-strates are defined. The modification of the film morphology is studied by means of scanning electron microscopy of the sample surface. The optical properties study based on structure’s transmission spectra shows that film decomposition into nanoparticles results in a clear dip in the spectra. This effect is related to efficient plasmon excitation. The shape and position of the plasmon band are found to depend on both the laser processing parameters and the substrate material. The fabricated structures can be used in the design of plasmonic solar cells, sensors and SERS devices. PB–11

LASER-INDUCED OPTICAL PROPERTIES CHANGES IN GOLD-DOPED MATERIALS

N.Nedyalkov1,2, M. Koleva2, R. Nikov2, Y. Nakajima1, A. Takami1, M. Terakawa1

1Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi Koho-

ku-ku, Yokohama-shi Kanagawa-ken, 223-8522, Japan 2Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee,

1784 Sofia, Bulgaria This work presents results on laser processing of Au doped oxide thin films. Using a pulsed laser deposition technique, SiO2/Au and Al2O3/Au thin films are deposited. The rotating target used for deposition consists of two sectors containing the oxide material and gold. By changing the area of the sectors, films with different content of gold are obtained. The deposited films are then irradiated by laser pulses with different parameters – wavelength, fluence, pulse dura-tion, number of pulses. The optical properties of the processed areas are studied on the basis of their transmission spectra. It is shown that under certain processing conditions the laser irradia-tion induces clear coloring and a dip in the transmission spectra of the initially transparent films. The analyses performed based on TEM, SEM, XRD, and EDX, show that this effect is related to the formation and dynamics of gold nanoparticles caused by the interaction with the laser pulses. The influence of the processing condition on the characteristics of the formed par-ticles and the mechanism of their formation are discussed. The structures fabricated can be ap-plied to the design of new optical materials and in plasmonics.


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PB–12

LASER-ASSISTED PROCESSING OF THE PDMS ELASTOMER AS A MATERIAL FOR PRECISE NEURAL INTERFACE ENGINEERING

N.E. Stankova, P.A. Atanasov, Ru.G. Nikov, R.G. Nikov, N.N. Nedyalkov

Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., Sofia

1784, Bulgaria

Direct laser writing based on nanosecond laser processing of the PDMS elastomer has been performed for production of stretchable micro-channels with high structuring accuracy for MEMS, NEMS and MEAs devices. This technology could especially facilitate a high-resolution, high-density integrated system solution for neural and muscular surface interfacing. Systematic experiments have been conducted to characterize how the laser beam parameters (wavelength, fluence, and number of pulses) affect the optical properties and the chemical composition in the laser treated areas. Remarkable changes of the optical properties and the chemical composition have been observed. Despite the low optical absorption of the native PDMS for UV, VIS and NIR wavelengths, successful laser treatment has been accomplished due to the incubation process occurring below the polymer surface. By increasing the fluence and the number of pulses, chemical transformations have been revealed in the entire laser treated area. The incubation reaches saturation after a certain number of pulses and efficient laser ablation of the material begins. This process is a complex function of the wavelength, fluence, number of pulses and the material properties as well. Also, a laser lift-off (LLO) process has been employed to fabricate micro-channeled Au, Ni, and Pt electrodes. This method could increase the electrical conductance of the as-produced electrodes, hence, improve the capacitive components of the electrode-tissue interface interaction. PB–13 STUDY OF BARIUM HEXAFERRITE NANOSTRUCTURES PRODUCED BY LASER

ABLATION IN WATER

A. Nikolov1, T. Koutzarova1, R. Nikov1, N. Nedyalkov1, N. Stankova1, S. Kolev1, P. Peneva1, D. Karashanova2 and D. Kovacheva3

1 Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784, Bulgaria

2 Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 109, 1113 Sofia, Bulgaria

3 Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev str., bl. 11, 1113 Sofia, Bulgaria

The method of nanosecond pulsed laser ablation in liquid is employed to produce nanostruc-tures of barium hexaferrite. The target fabricated by sol-gel auto-combustion is immersed in double distilled water. A Nd:YAG laser system is used for the ablation procedure. Different colloids are fabricated by variying the laser wavelength and fluence. The influence of these


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technological parameters on the morphology of the nanostructures produced is investigated. The fundamental (λ = 1064 nm), second (λ = 532 nm), third (λ = 355 nm) and fourth (λ = 266 nm) harmonics were used in the experiments, with the and fluence being changed from several J/cm2 to tens of J/cm2. The stability of the colloids during their ageing is also investigated. The optical transmission of the colloids in the near UV and visible regions was measured to esti-mate the effiency of the ablation procedure. Their stability during the ageing process is also investigated. The shape of the nanostructures and their size distribution are visualized by using TEM analysis. XRD, SAED and HRTEM are utilized to examine the material phases of the nanostructures obtained. The nanoscale magnetic ferrites are of particular interest due to their chemical compatibility with biological tissues and the unique combination of electronic and magnetic properties. PB–14

PUMP-PROBE INVESTIGATION OF FEMTOSECOND LASER INDUCED MODIFICATION OF BIOPOLYMER THIN FILMS

A. Daskalova 1, C. Nathala 2,3, W. Husinsky 2

1Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd.,

1784 Sofia, Bulgaria 2IAP, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria

3Femtolasers Productions GmbH, Fernkorngasse10, 1100 Vienna, Austria

Femtosecond lasers can be applied for fast and precise modification of thin biofilms. Previous studies on surface modification of biopolymers have shown that laser irradiation is a suitable method for production of thin layer of a porous biomaterial matrix. Structuring the surface of a biomaterial into arrays with micro- and nanoscale features and architectures defines new roadmaps to advanced applications of biomaterials in biology and medicine. The dynamics of the formation of laser-induced surface foam on thin gelatin films upon irradiation by fs-laser pulses (30 fs pulse duration) is studied by pump-probe experiments. In order to analyze the influence of temporally distributed energy deposition nn the foam formation, a Michelson interferometer was used for generating multiple double-pulse sequences at 800 nm. We explored the possibility of structuring the biopolymer thin film by applying different time-delays between the separate pulses; the resulting porous morphologies were characterized by scanning electron microscopy. This interaction regime allows tailoring of the surface modification by adaptive temporal separation. We used delay times varying from 0 to 10 ps and a number of pulses from 10-100. The time-resolved results show that by optimizing the temporal interval between the consecutive pulses, as well as the other laser parameters (energy, beam homogeneity, fluence), one could choose an appropriate regime to eliminate excessive photo-thermal and photomechanical effects and obtain the desired surface structure and a controlled porosity. Confocal microscopy images of modified zones were obtained in order to examine the topography at the zones of interaction. Acknowledgments This work was supported by the Bulgarian National Science Fund (NSF) under project DMU 03/15/2011, and a Bulgaria/Austria bilateral project DNTS Austria/01/1/2013-2015.


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PB–15 COMPARISON OF DIFFERENT SUBSTRATES FOR LASER-INDUCED ELECTRON

TRANSFER DESORPTION/IONIZATION OF METAL COMPLEXES

A.A. Grechnikov1, V.B. Georgieva2, N.Y. Donkov3, A.S. Borodkov1, A.V. Pento4, Tc.A. Yordanov2

1Vernadsky Institute of Geochemistry and Analytical Chemistry of RAS, 19 Kosygin str.,

119991 Moscow, Russia, 2Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72

Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria 3Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd.,

1784 Sofia, Bulgaria 4“Energomashtekhnika” Ltd., prospect Vernadskogo, 123, b. 2, 119571 Moscow, Russia

Laser-induced electron transfer desorption/ionization (LETDI) is a novel variant of the laser desorption/ionization technique. In LETDI, the analytes are preliminarily deposited on a surface of a solid state substrate − an ion emitter. The emitter surface is subjected to a pulsed laser radiation. This produces ions of the analytes, which are then analyzed by a mass spectrometer. The ionization mechanism is based on electron transfer from the excited adsorbed analyte molecule to the semiconductor material. The physical and chemical properties of the substrate are known to play a critical role in the LETDI process. However, no sufficient data is available to enable one to specify the properties that would make a substrate a good ion emitter. In this report, we compare the analytical performance of different substrates, including metal materials, graphite, amorphous silicon (α-Si) and titanium dioxide (TiO2) films for laser-induced electron transfer desorption/ionization of several metal coordination complexes with common organic reagents. All results were obtained by a laboratory-built LETDI-mass spectrometer based on a time-of-flight reflectron (0.9 m) with orthogonal ion injection via a gas-filled radio-frequency quadrupole. A diode-pumped Nd:YAG-laser with 355-nm wavelength (third harmonic), 0,37-ns pulse duration and 500-Hz repetition rate was used for desorption-ionization. To investigate the mechanism of LETDI, we studied experimentally and theoretically the dependence of the ion yield and the surface temperature on the fluence of the incident radiation. The temperature was estimated using a numerical solution of a one-dimensional heat conduction problem with a heat source distributed in time and space. It was found that at the same temperature, the ion yield from different substrates varies in the range of three orders of magnitude. The direct comparison of all studied substrates revealed that LETDI from TiO2 films and α-Si is a better choice for producing molecular ions of metal coordination complexes.


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PB–16

CORROSION PROPERTIES OF ZIRCONIUM-BASED CERAMIC COATINGS FOR MICRO-BEARING AND BIOMEDICAL APPLICATIONS

J. Walkowicz1, V. Zavaleyev1, E. Dobruchowska1, D. Murzynski1, A. Zykova2, V. Safonov2 ,

S.Yakovin3, N. Donkov4

1Institute of Technology and Education, Koszalin University of Technology, Koszalin, Poland 2National Science Center „Kharkov Institute of Physics and Technology“, Kharkov, Ukraine

3Department of Physical Technologies, Kharkov National University, Kharkov, Ukraine 4Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko

Chaussee blvd., 1784 Sofia, Bulgaria

Excessive metal wear debris, which causes osteolysis and, consequently, a loosening of the prosthesis, has caused the resurgence of the use of metal bearings in total and module joint ar-throplasty. Modification of metal materials by means of ceramic coating deposition is an effec-tive way of alternative bearing surfaces formation. The ZrN and ZrO2 ceramics and nanocom-posite oxynitride coatings are widely used as protective coatings against wear, diffusion and corrosion. The corrosion and wear resistance properties of modern coatings play a key role in the future efficient applications for micro-bearings and for biomedical needs. The aim of the present study was to study the effect of compositional, structural and morpho-logical properties of ZrN, ZrO2 and oxynitride ZrON films on the corrosion characteristics of the ceramic coatings produced. Stainless steel (AISI 316) discs with a diameter of 32 mm and a thickness of 3 mm were used as substrates. The process of ZrO2, ZrN and oxynitride ZrON coatings deposition by magnetron sputtering was performed in a high-vacuum pumping system with a base pressure of about 10-3 Pa. The magnetron discharge power was 4 − 5 kW. An ICP source for oxygen activation with RF power of up to 1 kW was applied. The main parameters of deposition process were the following: Ar pressure Par = 2.3×10-1 Pa, oxygen mass flow rate q = 35 sccm, nitrogen mass flow rate q = 27 sccm, magnetron voltage Um = 500 − 520 V, magnetron current Im = 7.0 − 7.6 А, total pressure P = 2.8 − 3.0×10-1 Pa, coating deposition rate 6 − 8 μm/hour. An ion source was used to clean the samples surface before deposition. The coatings thickness was measured by Calotest. The adhesion properties, hardness and elas-tic modulus were evaluated by standard methods with the use of the Revetest (CSM Instru-mets) and the Rockwell test with a diamond type C Rockwell indenter. To determine the mi-cro-hardness, a Fischerscope® HM2000 tester was applied. The surface roughness parameters were measured by a Hommel Werke T8000profilometer. The surface morphology and topography were observed by optical microscopy and a JSM 5500 LV electron scanning microscope. The chemical composition of the coatings was analyzed by energy dispersive X-ray (EDX) spectroscopy (Oxford Link ISIS 300). For potential metric stu-dies, all samples were washed in ethanol in an ultrasonic bath before the measurements. The active area of the sample was 0.287 cm2. All samples were kept in contact with the electrolyte (isotonic NaCl (0.9%), 50 ml) for one hour before the measurements. The potential was in the range 0.7 – 0.8 V for the reference sample and 0.5 – 1.0 V for all samples with deposited coat-ings, the sweep rate was 1 mV/s and the reading density, 3 mV. The temperature during the measurements was kept at 25 ± 1 °C. The values of the corrosion potential (Ecor) and the corro-sion current density (Icor) weree estimated using the method of the Tafel slopes extrapolation. The results demonstrate an improvement of the corrosion characteristics of metal surfaces coated by ceramic coatings. The corrosion resistance parameters increased in the cases of oxy-


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nitride and oxide coatings. The development of new low-cost and innovative bearing surfaces with enhanced corrosion characteristics is very challenging forfuture micro-bearing, joints re-placement and other biomedical applications. The study was supported within the 7th European Community Framework Program, ImBeing-FP7-.PEOPLE-2013-IRSES-612593 PB–17

SURFACE MODIFICATION OF TANTALUM PENTOXIDE COATINGS DEPOSITED BY MAGNETRON SPUTTERING AND FURTHER CORRELATION

WITH CELL ADHESION AND PROLIFERATION IN IN VITRO TESTS

N. Donkov1, A. Zykova2 , V. Safonov2, A. Goltsev3, T. Dubrava3, I. Rossokha3,., S.Yakovin4, D. Kolesnikov5, I. Goncharov5

1Emil Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko

Chaussee blvd., Sofia, Bulgaria 2National Science Center “Kharkov Institute of Physics and Technology“, Kharkov, Ukraine

3Institute for Problems of Cryobiology and Cryomedicine NASU, Kharkov, Ukraine 4Department of Physical Technologies, Kharkov National University, Kharkov, Ukraine .

5Belgorod State National Research University, Belgorod, Russia The clinical application of cell therapy methods requires the improvement of the traditional tissue engineering approaches. Tantalum and tantalum-based compounds are promising for biomedical applications due to their good dielectric properties. The aim of the present work was to study the effect of argon-ion and electron-beam surface treatment on the structure and surface properties of tantalum pentoxide (Ta2O5) coatings deposited by reactive magnetron sputtering and, further, the correlation between the surface characteristics and the cell adhesion and proliferation. Ta2O5 coatings were deposited on Petri dishes glass substrates in a high-vacuum pumping sys-tem with a base pressure of about 10-2 Pa by ion source-assisted magnetron sputtering. Oxygen for the reactive deposition was delivered through an ICP plasma source at q = 60 sccm; the magnetron voltage was Um = 700 V, with magnetron current of about Im = 5,7 А. For other substrates, the deposition process was carried out with simultaneous bombardment of the growing film by argon ions using an ion source. The ion source parameters were as follows: magnetic field current 1.5 A, ion acceleration voltage 2.5 kV, ion source current 30 mA. A primary electron beam was created by a UL-119 type electron gun. The energy of the reflected electrons was 20 kV, the current density on the sample surface, 14 mA /cm2, the irradiation time, 1500 s. The structural parameters of the as-deposited and post-treated coatings were investigated by means of transmission electron microscopy using JEOL JEM 2100. The surface topography and roughness parameters of the oxide ceramic coatings were evaluated by scanning electron microscopy (QUANTA 600 FEG) and atomic force microscopy. X-ray diffraction coating profiles were observed by means of a DRON-3 diffraction device. X-ray photoelectron spectroscopy was carried out using an ESCALAB MkII (VG Scientific) electron spectrometer with a AlKalpha X-ray source (excitation energy hν = 1486.6 eV). The total surface free ener-gy, polar and dispersion parts were estimated by applying the Wu and Owens-Wendt-Rabel-Kaeble’ methods.


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Culturing of bone marrow (BM) cells was performed with a density of 0.5 − 1×104 cells/cm2. After passage, the cells were removed by a trypsin-EDTA solution (Sigma-Aldrich, USA).The structural and functional characteristics of the BM cells were evaluated. Visual control of the cell cultures was carried out using a Primo Star light phase-contrast microscope (Zeiss, Germa-ny) and an Axiovert 40C inverted microscope (Zeiss, Germany). The BM cells’ adhesive po-tential was also evaluated. It was shown that the tantalum pentoxide coatings after electron beam irradiation can increase cell adhesive and proliferative potential in comparison to as-deposited coatings. In contrast, the argon ions bombardment during coating deposition process reduces the adhesive and proliferative potential of BM cells. The study was supported within the collaboration Program BAS-NASU and project No. 24-04-15 NASU. PB–18

INVESTIGATION OF THE MECHANICAL STABILITY OF ANODIC ALUMINUM OXIDE WITH VACUUM DEPOSITED THIN METAL FILM

A. Bankova, V. Videkov, K. Raykov, B. Tzaneva, M. Mitov

Technical University of Sofia, 8, St. Kliment Ohridski blvd., 1000 Sofia, Bulgaria

E-mail: [email protected] Nanostructured anodic aluminum oxide (AAO) is widely used in micro and nano electronics. AAO is used in a variety of sensors and microelectromechanical systems (MEMS). In the last few years, the use of AAO as a substrate has become more and more common. Some applica-tions require that conductive tracks or conductive areas with a specific shape be formed on the AAO substrate. In this work we investigated the mechanical stability of anodic aluminum oxide with a thin metal film deposited on it in vacuum. Thin metal film meanders were depo-sited through a metal mask on free-standing membranes of AAO. The ends of the meanders were wire-bonded to provide electrical contact. Using a series of mechanical bends, we inves-tigated the stability ot the metal film on the AAO substrate and the stability of the system "AAO - thin metal film". By measuring the resistivity of the metal film, we investigated the maximum angle of deflection and the maximum elongation of the AAO substrate before the metal tracks are broken. The results can be used as a reference for the design of MEMS devices incorporating similar structures.


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PB–19

SURFACE PHOTOVOLTAGE AND PHOTOLUMINESCENCE STUDY OF THICK Ga(In)AsN LAYERS GROWN BY LIQUID-PHASE EPITAXY

V. Donchev1, M. Milanova2, J. Lemieux3, N. Shtinkov3, I.G. Ivanov4

1 Faculty of Physics, St. Kliment Ohsridski University of Sofia, 5, J.Bourchier blvd., 1164

Sofia, Bulgaria 2Central Laboratory of Applied Physics, 59 St. Petersburg blvd, 4000 Plovdiv, Bulgaria

3 Department of Physics, University of Ottawa, Ottawa, ON, K1N 6N5, Canada 4, Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping,

Sweden The addition of nitrogen in small concentrations is known to shift the absorption edge of III-V materials to the longer wavelengths, which makes dilute III-V nitrides promising materials for third-generation multi-junction solar cells. We present an experimental and theoretical study of Ga(In)AsN layers with thickness around 1 μm, grown by liquid phase epitaxy (LPE) on n-type GaAs substrates. The samples were studied by surface photovoltage (SPV) spectroscopy in the metal-insulator-semiconductor geometry mode [1] and by photoluminescence spectroscopy. Theoretical calculations of the absorption spectra were carried out using a full-band tight-binding approach in the sp3d 5s*sN parameterisation [2]. The SPV spectra measured at room temperature are sensitive to the optical absorption spectrum of the structures and clearly show a red shift of the absorption edge with respect to the absorption of the GaAs substrate. The shift is of the order of 50 − 60 meV. The analysis of the SPV amplitude and phase spectra provides information about the alignment of the energy bands across the structures. Photoluminescence measurements performed at 2 K show a red shift of the emission energy of 50 − 60 meV with respect to GaAs, in good agreement with the SPV results. Theoretical calculations of the electronic structure and the spectral dependence of the dielectric constant were carried out for different nitrogen concentrations and show a good agreement with the experimental data. The results obtained contribute to a better understanding of the physical properties of dilute nitride materials grown by LPE and their potential for optoelectronic applications. [1] L. Kronik, Y. Shapira Surface photovoltage phenomena: theory, experiment, and

applications. Surf. Sci. Rep., 37, 1-206 (1999). [2] N. Shtinkov, P. Desjardins, R.A. Masut, Empirical tight-binding model for the electronic

structure of dilute GaNAs alloys, Phys. Rev. B 67: 081202 (R)/1-4 (2003).


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PB–20

INTERFACE CHARACTERIZATION OF NANOSCALED SiOx LAYERS GROWN ON RF PLASMA HYDROGENATED SILICON

E. Halova1, N. Kojuharova1, S Alexandrova1, A Szekeres2

1Department of Applied Physics, Technical University of Sofia, 1797 Sofia, Bulgaria

2Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria 3Department of Solid State Physics and Microelectronics, St. Kliment Ohridski University of

Sofia, 1164 Sofia, Bulgaria Email: [email protected]

Control and characterization of the defects at the interfaces in single or multilayered structures is an important issue in modern semiconductor devices. The incorporation of hydrogen into a semiconductor structure is known for its beneficial effect, such as stabilization of the device’s characteristics mainly through gettering of impurity defects. In silicon technology, hydrogena-tion has been widely used in the past decade in lower concentrations for improving the defect and leakage characteristics and in higher concentrations for future nanoelectronic applications, such as exfoliation of silicon in smart cut processes, increasing the carrier life-time in solar cells, etc. The aim of the present work is characterization of the interface between rf plasma hydrogen-ated (100) p-Si wafers and the overgrown SiOx by thermal oxidation at 850oC. The interface traps density spectra are supposed to depend on the amount of incorporated hydrogen. For this purpose, plasma hydrogenation of the Si wafers was conducted either without heating the Si substrates or heating them up to 300 oC and the interface traps density spectra were examined in detail. The thickness of the SiOx layers varied depending on the hydrogenation level, but was in the nanoscale range below 10 nm, as determined from the ellipsometric measurements. In order to examine the interface traps, MOS capacitors were built incorporating the Si/SiOx structures. As a characterization tool, multiple frequency C-V and G-V measurement tech-niques were used. A generalized C-V curve was generated by applying the three-frequency method to the C-V and G-V characteristics taken at a variety of frequencies ranging from 50 Hz to 300 kHz. In this curve, the in-series resistance and the leakage through the oxide layer was accounted for. The energy spectra of the interface traps were extracted by comparing the ex-perimental and the generalized C-V curves. Ellipsometric data and the capacitance in strong accumulation of the C-V curves were used to calculate the thickness and the dielectric con-stants of the oxide layers. The analysis of the electrical characteristics showed that the C-V and G-V curves of the MOS structures with SiOx layer grown on Si treated in plasma exhibit a small oxide charge and low leakage currents typical for a high-quality dielectric layer. The interface density spectra showed the presence of localized interface traps energetically distributed in the Si bandgap. The positions and the height of the trap levels in the Si bandgap depended on substrate hydro-genation temperature and were related to particular structural defects at the interface and in a thin region inside the oxide. The conclusions are well correlated with the results on the oxide mechanical stress level, oxide composition and Si-O ring structure and the composition of the interfacial region from our previous detailed multi-angle spectral ellipsometric and IR studies.

mailto:%[email protected]


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PB–21

STUDY OF THE NEW CSAR62 POSITIVE TONE ELECTRON BEAM RESIST AT 40 kEV ELECTRON ENERGY

R. Andok1, K. Vutova2, A. Bencurova1, E.Koleva2, P. Nemec1, P. Hrkut1,

I. Kostic1, G. Mladenov2

1Institute of Informatics, Slovak Academy of Sciences, Dubravska 9, 84507 Bratislava, Slovakia

2Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

One of the few “top-down” methods for fabrication of nanodevices is the e-beam lithography, which allows flexible patterning of devices with a nanoscale resolution down to less than 10 nm. A thinner, more resistant to etching, and more sensitive e-beam resists are required for the better control, linearity, and uniformity of the critical dimensions of structures for fabrica-tion of nanodevices. Within the last decade, researchers have made a significant effort to im-prove the resolution limits of the nanoscale e-beam lithography. The resist material properties are an important factor governing the resolution. This work deals with the investigation and simulation of the characteristics of the AR-P 6200 (CSAR 62) positive beam resist (Allresist). The investigations are performed for a 400-nm layer of the CSAR 62 positive e-beam resist onto a Si substrate for the case of an electron energy of 40 keV. The contrast and sensitivity characteristics are obtained experimentally for various development conditions. The energy deposition function (EDF) is an important parameter in e-beam lithography. The EDF (characterizing resist modification after e-beam exposure), which can reflect the absorbed energy distribution in both lateral and depth direction (3-dimensional), is required for calcula-tion of accurate resist profiles. The scattering trajectories of electrons in CSAR 62 and in the Si substrate are obtained by Monte Carlo (MC) simulation to calculate discrete data for EDF. The

proximity effect parameters (βf, βb, ηE) for a point e-beam source are calculated through the MC technique. Discrete data for EDF at the resist-substrate interface (at the depth of 400 nm) are compared with an analytical approximation using a sum of two Gaussians (Figure 1). The variation of the proximity effect parameters’ values along the resist depth is evaluated in order to calculate 3D-EDF, taking into account the development process simulation.

Figure 1 Comparison between the discrete data obtained () and its analytical fit (solid line). The CSAR 62 is characterized by a similar resolution; however, it exhibits a higher sensitivity and a significantly improved plasma etch resistance in comparison to the widely used high-resolution positive e-beam resist PMMA (poly-methyl-methacrylate).


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PB–22

ENHANCED PHOTOANISOTROPIC RESPONSE IN AZOPOLYMER DOPED WITH ELONGATED GOETHITE NANOPARTICLES

L. Nedelchev1, D. Nazarova1, N. Berberova1, G. Mateev1, V. Salgueiriño2, D.

Schmool3

1Institute of Optical Materials and Technology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

2Department of Applied Physics, University of Vigo, 36310, Vigo, Spain 3Laboratory PROMES CNRS, University of Perpignan, 66100 Perpignan, France

*Corresponding author: [email protected] We present a study of the photoinduced birefringence in nanocomposite films of an azopolymer (PAZO) doped with nanoparticles (NP) of the magnetic material Goethite (α-FeOOH). The NP have an elongated shape with a size 15×150 nm, i.e. a ratio of 1:10. Samples with different concentrations of the NP in the azopolymer were prepared by varying the con-centration from 0 % (non-doped azopolymer film) to 15 %. An unusual dependence of the birefringence on the concentration was observed in the present experiments – two peaks of enhancement at 1 % and at 10 % concentration. Our previous studies with ZnO and SiO2 NP have indicated only one peak of increase at low concentrations – 0.5 % and 2 % respectively. This effect could be related with the elongated shape of the nanoparticles and the presence of two characteristic NP sizes – 15 and 150 nm. Moreover, the birefringence increase for the samples with 10 % NP concentration compared with the non-doped samples is rather significant – nearly 70%. PB–23

PHOTOINDUCED VARIATION OF THE STOKES PARAMETERS OF LIGHT

PASSING THROUGH THIN FILMS OF AZOPOLYMER-BASED HYBRID ORGANIC/INORGANIC MATERIALS

N. Berberova, D. Nazarova, L. Nedelchev, B. Blagoeva, D. Kostadinova, V.

Marinova, E. Stoykova

Institute of Optical Materials and Technology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Corresponding author: [email protected] Hybrid materials synthesized by combining polymers and inorganic nanoparticles (NP) re-ceived considerable attention recently due to their advantageous electrical, optical, or mechani-cal properties. Here we present a polarimetric study of thin films prepared from photoaniso-tropic hybrid materials: azopolymer (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt]) doped with different concentrations of ZnO NP with sizes below 50 nm. To obtain the complete information about the polarization response of these thin films, we determined the kinetics of the Stokes parame-ters of light passing through the films on illumination with linearly polarized light within the


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absorbance band of the material, namely, 473 nm. Using the Stokes parameters, the birefrin-gence values are calculated as a function of time and compared for films with different NP concentrations. PB–24

INVESTIGATION OF THERMAL PROCESSES IN ELECTRON-BEAM SURFACE MODIFICATION BY MEANS OF A SCANNING ELECTRON BEAM

M. Ormanova1, V. Angelov2, P. Petrov1,

1Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd.,

1784 Sofia, Bulgaria 2Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72, Tsa-

rigradsko Chaussee blvd., 1784 Sofia, Bulgaria

In this work we present an investigation of the thermal processes during surface modification of steels performed by means of a scanning electron beam. A model was developed for descrip-tion of the thermal processes taking place in the electron-beam material processing realized by a scanning electron beam. The model is based on solving the heat-transfer equation by means of Green functions. The thermal field was calculated, as well as the size the zone of structural changes in instrumental steel samples. In order to evaluate the applicability of the thermal model, we carried out experiments on sam-ples of instrumental steel W 320 (0.31 % C, 0.30 % Si, 0.35 % Mn, 2.9 % Cr, 2.8 % Mo, 0.5 % V). The size of the samples was 20×20×4 mm. The experiments were conducted by means of a Leybold Heraeus EWS 300/15-60 electron-beam installation using a scanning electron beam for sample processing. The technological parameters of the processing were: accelerating voltage U = 55 kV, scanning beam current I = 40 mA, sample motion speed V = 4 cm/s, focus-ing current If = 484 mA, frequency of electron-beam deflection f = 1 kHz, scanning beam di-ameter d = 0.1 mm. The comparison of the experimentally observed zones of thermal treatment with the theoreti-cally calculated ones and the corresponding structural changes showed a very good agreement.

Keywords: electron beam processing, thermal model, Green functions


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PB–25

ELECTRON-BEAM INDUCED SURFACE ALLOYING OF TITANIUM WITH ALUMINIUM

S. Valkov, D. Dechev, N. Ivanov, P. Petrov

Institute of Electronics, Bulgarian Academy of Sciences 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

A summary is presented of the investigations on the mechanism of an alloyed layer formation during electron-beam surface alloying of titanium with Al. Surface alloys were produced by a two-step process: first, Al films were deposited on commercially pure Ti substrates by DC magnetron sputtering in Ar atmosphere, which was followed by treatment by a scanning elec-tron beam. Before the aluminium film deposition, the Ti substrates were cleaned by sputtering for ten minutes. The electron-beam treatment was carried out using a Leybold Heraeus installa-tion (EWS 300/15-60). The crystallographic structure of the samples prepared was characterized by X-ray diffraction with Cu Kα characteristic radiation (1,54 Å). The experiments were performed on a fully au-tomated Seiferd&Co diffractometer with a scintillation detector and a flat graphite monochro-mator on the diffracted beam. The samples were further characterized by Raman spectroscopy and scanning electron microscopy (SEM). The dependence was analyzed of the phase composition and the crystallographic parameters of the specimens on the different technological parameters of the electron beam treatment. It was been found that the presence of several possible intermetallic Ti-Al phases (Ti3Al, AlTi, Al3Ti), responsible for important mechanical properties of the samples, strongly depend on the technological parameters of the electron-beam treatment. Other important crystallographic pa-rameters, such as lattice parameters, crystal texture, etc, were also evaluated; it was found that they also strongly depend on the technological parameters of the electron-beam treatment. PB–26

STRUCTURAL MODIFICATION OF Ga+-ION IMPLANTED TA-C FILMS

M. Berova1, M. Sandulov1, T. Tsvetkova1, D. Karashanova2 and L. Bischoff3

1Institute of Solid State Physics, Bulgarian Academy of Sciences 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

2 Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences Acad. G. Bontchev str., bl. 109, 1113 Sofia, Bulgaria

3Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O.B. 51 01 19, 01314 Dresden, Germany

Thin film samples (d ~ 40 nm) of tetrahedral amorphous carbon (ta-C), deposited by filtered cathodic vacuum arc (FCVA), were implanted with Ga+ at an ion energy E = 20 keV and ion doses D = 3×1014 ÷ 3×1015 cm-2. The Ga+-ion-beam induced structural modification of the im-planted material results in a considerable change of its optical properties consisting in a signifi-cant shift of the optical absorption edge to the lower photon energies, which is accompanied by


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a considerable increase of the absorption coefficient (photo-darkening effect) in the photon en-ergy range measured (0.5 ÷ 3.0 eV). These effects could be attributed to the Ga+-ion-beam in-duced structural modification, in the form of introduction of additional defects and increased graphitization, as well as the formation of Ga atoms clustering, as revealed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) measurements. These underlying structural changes define the optical photo-darkening effect observed, which could be applied to for information archiving, in the area of high-density optical data storage while using focused Ga+ ion beams. PB–27

VIBRATIONAL SPECTROSCOPY OF Ga+-ION-IMPLANTED TA-C FILMS

M. Berova1, M. Sandulov1, T. Tsvetkova1 and L. Bischoff2

1Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

2Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O.B. 51 01 19, 01314 Dresden, Germany

In the present work, low-energy Ga+-ion-beam implantation was used for modification of the structural and optical properties of tetrahedral amorphous carbon (ta-C) thin films. Thin film samples (d ~ 40 nm) of ta-C, deposited by filtered cathodic vacuum arc (FCVA), were im-planted with Ga+ at an ion energy E = 20 keV and ion doses D = 3×1014 ÷ 3×1015 cm-2. The Ga+-ion-beam-induced structural modification of the implanted material results in a consider-able change of its optical properties consisting in a significant shift of the optical absorption edge to the lower photon energies as obtained from optical transmission measurements. This shift is accompanied by a considerable increase of the absorption coefficient (photo-darkening effect) in the measured photon energy range (0.5÷3.0 eV). These effects could be attributed both to additional defect introduction and increased graphitization, as well as to accompanying formation of bonds between the implanted ions and the host atoms of the target, as confirmed by infra-red (IR) and Raman measurements. The optical contrast thus obtained (between im-planted and unimplanted film material) could applied to information archiving, in the area of high-density optical data storage, while using focused Ga+ ion beams.


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PB–28

CHEMICAL BATH DEPOSITION OF THIN TIN SULPHIDE FILMS

D. Dimitrov1, L. Komsalova1, D. Lilova2, M. Sendova-Vassileva1, G. Popkirov1, P. Vitanov1, I. Gadjov2, M. Ganchev1

1Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences

72 Tsarigradsko Chaussee blvd, 1784 Sofia, Bulgaria 2University of Chemical Technology and Metallurgy

8 Climent Ohridsky blvd, 1756 Sofia, Bulgaria Tin sulphide is an attractive binary semiconductor with favorable electro-physical properties and abundant elements and can be deposited as thin films by simple preparation methods. In order to understand the possibilities for its application in photovoltaic devices, a chemical bath deposition approach to form SnS thin layers on soda lime glass substrates at different temperatures and solution compositions was developed. Differential scanning calorimetry was used to reveal the thermo-chemical behavior of the as-deposited SnS and the possibility for suitable annealing treatment. The DSC analysis showed a well-defined temperature interval of heat absorbing (endothermic) reaction of 150 oC – 166 oC where the (re)crystallisation of the as-formed SnS takes place. X–ray diffractometry of SnS deposited at different temperatures showed an improvement in the crystal structure. A totally amorphous material, as obtained at 60 oC, underwent a gradual transtion at 70 oC and 90 oC to well-defined patterns of orthorhombic Herzenbergite syngony. The XRD pattern of already DSC-processed SnS (from 50 oC up to 220 oC at a rate of 10 oC/min) showed the full spectrum of the related powder diffraction file for Herzenbergite. Optical investigations of as-deposited and annealed SnS thin films showed a region of absorption near 400 – 600 nm and were used to estimate the band gap for allowed transitions. The optical band gaps for samples annealed at different temperatures from 100 oC up to 260 oC were calculated. Raman spectra of the same films showed typical vibrations for the SnS phase and another one at the higher temperatures related to the SnS2 phase, which could explain the variation of the estimated band gap observed as the temperature was raised.


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PB–29

MeV ELECTRON IRRADIATION OF Si-SiO2 STRUCTURES WITH MAGNETRON SPUTTERED OXIDE

S. Kaschievaa, Ch. Angelovb, S.N. Dmitrievc

a Institute of Solid State Physics, Bulgarian Academy of Sciences

72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria b Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences

72 Tsarigradsko Chaussee blvd.,1784 Sofia, Bulgaria c Joint Institute for Nuclear Research, Flerov Laboratory of Nuclear Reactions

Dubna, Moscow Region 141980, The Russian Federation

MeV electrons influence on the characteristics of a Si-SiO2 structure with magnetron sputtered oxide was studied by ellipsometry and the thermally stimulated current technique. The MOS structures used in this study were fabricated on <100> oriented p-Si substrates of 12.75-17,25 Ω cm resistivity. Magnetron sputtered oxides with different thicknesses of 20 nm and 100 nm were deposited. Both groups of samples were irradiated by 23 MeV electrons. The oxide thicknesses and the TSC characteristics of the MOS sample were measured before and after irradiation by doses of 4.80×1015 and 4.8×1016 cm-2. The activation energy and the con-centration of the defects generated by MeV electrons were also evaluated. It was shown that the trap concentration increases as the electron irradiation dose was increased. The main peak in the TSC characteristics gives information about the main radiation defects at the Si-SiO2 in-terface of the structures. These defects can be related to the vacancy-boron complexes which are associated with the main impurities in the p-Si substrate. This study supports our results reported earlier for MeV electron irradiated Si-SiO2 structures with thermally grown oxide. However, the effects observed are more pronounced for the magnetron sputtered oxide. A possible reason is the more effective increase of the oxygen con-centration at the Si-SiO2 interface after MeV electron irradiation. This is connected also with the higher concentration of defects generated in the magnetron sputtered oxide during its depo-sition. PB–30

WIRE BONDING ON VACUUM DEPOSITED THIN METAL FILM OVER NANOSTRUCTURED ALUMINUM OXIDE

K. Raykov, V. Videkov, A. Bankova

Technical University of Sofia, 8, St. Kliment Ohridski blvd., 1000 Sofia, Bulgaria

In recent years, nanostructured anode aluminum oxide (AAO) has been widely used in various areas of human activity. In micro- and nano-electronics AAO is used in a variety of sensors and microelectromechanical systems (MEMS). Its unique properties and its low cost make it an attractive material for use in the electronics industry. With the development of MEMS devices, a large number of solutions have been proposed involving a semiconductor structure on a beam or membrane of AAO. It is also possible to form conductive tracks on the AAO surface, where


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the problem arises of implementing electrical contacts between the semiconductor structure on the AAO substrate and the tracks. Wire bonding is a well known process for realizing electrical contacts, also because the size of the wire is highly suitable for this purpose. This work investigates various types of wire bonds on metal layers of different thickness deposited in vacuum on substrates of AAO. A study of the wire bonds characteristics was conducted, as well as of the behavior of nanostructured AAO during and after the wire bonding process. PB–31 GOLD DISTRIBUTION ON LATENT FINGERMARKS DEVELOPED BY VACUUM

METAL DEPOSITION

K.T. Popov1,2, V.G. Sears3 and B.J. Jones1,2,4

1School of Materials, University of Manchester, United Kingdom

2University of Huddersfield, United Kingdom 3CAST, Home Office, United Kingdom

4Science, Abertay University, Dundee, United Kingdom

Fingermark development is one of the key methods for forensic identification. A latent finger-print is formed from the material left on a surface after being touched and is often invisible. In order to be visualized, the latent fingerprint needs to be developed, by one of a range of tech-niques. One such development method is vacuum metal deposition (VMD), a two-step process of sequential evaporation and deposition of gold followed by zinc in vacuum. This method is particularly useful for old and environmentally exposed fingermarks. In normal development, the exposed gold particles between the fingermark ridges and around the fingermark serve as nucleation sites for zinc deposition, while on the ridges no zinc is deposited as the gold par-ticles submerge into the fingermark material. In some instances, however, problematic devel-opments occur: reverse development (zinc only on the ridges), empty prints (no zinc on both the ridges and space between them but surrounding the fingermark) and overdevelopment (zinc is deposited everywhere). This work studies the gold distribution on fingermarks and the sub-strates on which they are deposited. Scanning electron microscopy reveals that between the ridges the gold appears as a uniform nanoparticle distribution, while on the fingermark ridge there are random shaped granules or no gold particles resolvable. In addition, the presence of an irregular area surrounding the finger-mark ridges is revealed. Here the gold particles appear with a reduced contrast. The presence and size of this area is related to the fingermark donor and substrate and is linked to the pres-ence of a thin layer of deposited material surrounding the fingermark ridge, revealed by atomic force microscopy. These results allow us to propose a model for the gold distribution on the fingermarks and how this affects the resultant fingerprint development.


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PB–32 THICKNESS INFLUENCE ON THE MORPHOLOGY AND THE SENSING ABILITY

OF THERMALLY DEPOSITED TELLURIUM FILMS

T. Hristova-Vasileva1, I. Bineva1, A. Dinescu2, D. Nesheva1, D. Arsova1, B. Pejova3

1 Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

2 National Institute for R&D in Microtechnologies – IMT Bucharest, 126 Erou Iancu Nicolae str., 077190 Bucharest, Romania

3 Faculty of Natural Sciences and Mathematics, Sts. Cyril and Methodius University, P.O. Box 162, 1001 Skopje, Macedonia

Tellurium films with nominal thicknesses of 30, 90 and 300 nm were prepared by thermal eva-poration in vacuum at a low deposition rate of 0.3 nm/s. The morphology evolution with the increase of the film thickness was observed by scanning electron microscopy and atomic force microscopy (Fig. 1). Nanorods with a width of about 40 nm is observed on the thinnest films surface whose root-mean-square roughness (Sq) is ~7 nm – Fig. 1a. On the 90-nm thick films, the formations grow in priority to the z- direction to nanoblades with the same width and length of about 100 nm (Fig. 1b). The further increase of the thickness leads to an increase of the 2D nanoobjects width and length and formation of stacked nanosheet structure (Fig. 1c). The Sq increases with the thickness. Preliminary investigations of the sensing ability of the as-deposited tellurium films with different thicknesses towards water (H2O), ethanol (C2H5OH), acetone (C3H5OH), and ammonia (NH3) vapors were performed by measuring the vapor induced changes in the film dark current. The films show appreciable response only to ammonia vapors; their sensitivity is almost equal for the 30 and 90 nm thick films, and decreases significantly for the thickness of 300 nm.

Fig. 1. SEM microphotographs (magnification of 100 000 times) of Te films with nominal thickness of a) 30, b) 90 and c) 300 nm.

Acknowledgements: The authors acknowledge the support of the Bulgarian Academy of Sciences (contracts ISSP-VK 03/14 and the bilateral projects with the Romanian Academy of Sciences and with the Macedonian Academy of Sciences and Arts), as well as of the National Science Fund (contract DMU 0391/2011).

a) b) c)


POSTER SESSION C:

THIN FILMS DEPOSITION. COATINGS FOR ADVANCED APPLICATIONS

PC–1

SLOW HIGHLY CHARGED ION TRANSMISSION THROUGH CARBON NANOMEMBRANES AND GRAPHENE

R.A. Wilhelm, E. Gruber, R. Heller, S. Facsko, F. Aumayr


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PC–1

SLOW HIGHLY-CHARGED IONS TRANSMISSION THROUGH CARBON NANOMEMBRANES AND GRAPHENE

R.A. Wilhelm1, E. Gruber2, R. Heller1, S. Facsko1, F. Aumayr2

1Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials

Research, Dresden, Germany, EU

2 Institute of Applied Physics, Technical University of Vienns, Vienna, Austria, EU Slow highly-charged ions (HCI) showed in many studies their efficiency in forming surface nanostructures, especially on insulating surfaces [1]. Here we report on the transmission of HCI through carbon foils with a thickness of only 1 nm and less (graphene). At these thicknesses, the neutralization of the slow HCI is not completed in the solid and, thus, effects of pre-charge-equilibrium stopping of slow ions can be addressed experimentally. We found that transmitted highly-charged Xe ions with charge states between Q = 10 and Q = 30 show a bimodal charge state distribution, i.e. one part of the ions is transmitted in low exit charge states combined with a large charge exchange enhanced kinetic stopping. The other part of the ions, however, shows only a very small charge exchange with almost no kinetic energy loss [2]. Both charge exchange regimes are attributed to different impact parameter regimes, i.e. close collisions lead to extremely large charge exchanges and distant collisions are connected with weak ion-target interactions. Thus, our measurements reveal that sub-surface neutralization of HCI proceeds in a step-like fashion, i.e. either the ion approaches a target atom closely and correspondingly neutralizes almost completely (∆Q > 20 for Q = 30), or it passes through the material almost unchanged (∆Q < 5) until it hits a target atom at some larger depth. A bimodal charge state distribution could therefore not be observed for larger target thicknesses [3], except for the inverse case of a swift heavy ion charging up during transmission through a silicon single crystal under random vs. channeling direction [4]. Gas phase experiments on the other hand cannot lead to slow HCI neutralization in one single scattering event using light target atoms (e.g. carbon), because here only atomically bound electrons can contribute to the neutralization process (6 electrons in case of carbon) rather than de-localized electrons in a solid target. [1] Aumayr, F., Facsko, S., et al., Single ion induced surface nanostructures: a comparison between slow highly charged and swift heavy ions. J. Phys. Condens. Matter 23, 393001 (2011) [2] Wilhelm, R. A., Gruber, E. et al., Charge Exchange and Energy Loss of Slow Highly Charged Ions in 1 nm Thick Carbon Nanomembranes. Phys. Rev. Lett. 112, 153201 (2014) [3] Schenkel, T., Briere, M et al., Charge State Dependent Energy Loss of Slow Heavy Ions in Solids. Phys. Rev. Lett. 79, 2030–2033 (1997) [3] Dauvergne, D., Scheidenberger, A., et al. Charge states and energy loss of 300-MeV/u U73+ ions channeled in a silicon crystal. Phys. Rev. A 59, 2813–2826 (1999).


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PC–2

PLASMA-ASSISTED CVD PRODUCTION OF ISOTOPES OF GROUP IV AND VI ELEMENTS IN THE FORM OF THIN FILMS, NANOPARTICLES AND BULK

MATERIAL

P.G. Sennikov1, R.A. Kornev1, S.V. Golubev2.

1 G.G. Devyatykh Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhny Novgorod, The Russian Federation, [email protected]

2 Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, The Russian Federation

In the chemical vapor deposition (CVD) process, the starting molecules of gasses and vapors are “chemically activated” due to the resistive heating before deposition. In plasma-enhanced chemical vapor deposition (PECVD), chemical activation is achieved by supplying electrical power to a gas at a reduced pressure, typically between 10 mTorr and 10 Torr. At these pres-sures, the application of a sufficiently high voltage creates a visible glow-discharge plasma (called low-temperature non-isothermal plasma). The electrical power is coupled into the gas through the mediation of the plasma electrons. The energetic electrons in the plasma ionize the gas to a minor extent. On the contrary, a much larger fraction of the gas is chemically activated by the electrons. The increased chemical activity of the gas results primarily from dissociation of the molecules into radicals. These species are unsaturated and therefore capable of chemical reactions at high rates resulting in formation of solid and gaseous products. Depending on the experimental conditions, the solid deposits possess different chemical and phase structure. The PECVD method is widely used for laboratory and industrial production of different chemical substances and elements. The advantage of this approach is clearly demonstrated in the case of precursors with high-energy chemical bonds. Inorganic fluorides of different elements belong to this group of sub-stances. Besides, fluorine is monoisotopic, hich is why volatile fluorides are used in centrifugal processes of isotopic separation (enrichment). The classical illustration of this approach is the isotopic enrichment of uranium hexafluoride. This report summarizes the main results of recent investigations carried out at the Institute of Chemistry of High-Purity Substances and the Institute of Applied Physics of the Russian Academy of Sciences in Nizhny Novgorod in creating the physico-chemical background of plasma-chemical production of chemically and isotopically pure of groups IV and VI elements (silicon, germanium, sulfur, molybdenum) from their enriched fluorides. The main features are discussed of the plasma-chemical reactions of hydrogen reduction of the isotopically enriched tetrafluorides SiF4 и GeF4 in HF, UHF and ECR discharges resulting in deposition of silicon and germanium in the form of thin films, nanoparticles and small poly-crystals. It is shown that the laboratory approach suggested could be scaled up for production of tens of kilograms of the germanium-76 isotope in the form of large polycrystals for the in-ternational GERDA and MAYORANA projects dealing with the study of neutrino-less double-beta decay. The results of the experiments on reduction of 98MoF6 in hydrogen plasma resulting in production of 98Мо nanoparticles are discussed. The nanoparticles obtained should be con-verted into radioactive 99Мо isotope and further to metastable 99mТс that is widely used for di-agnostics of various diseases. The particularities of 32SF6 reduction in plasma are discussed as well.


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PC–3

MASS-SPECTROMETRY INVESTIGATION OF PLASMA FOR PARYLENE C DEPOSITION

N. Lukat, E. von Wahl, H. Kersten

Institute for Experimental and Applied Physics, University of Kiel

This work details the results of mass spectrometry in an asymmetric rf-discharge used to deposit parylene C. Parylene is the trade name of a variety of chemical vapor deposited poly(para-xylylene) polymers with a wide range of applications. It is used as a hard coating in medicine because of its biocompatibility and stability, in the car industry to protect metallic surfaces from corrosion, and in the aviation industry to protect electrical circuits. The common conventional method to deposit parylene C is chemical vapour deposition (CVD) with dichloro[2,2]paracyclophane as a precursor. [2,2]paracyclophane is a hydrocarbon which consists of two benzene rings and an aliphatic chain that connects these rings. The prefix dichloro means that one hydrogen atom in each benzene ring has been replaced by a chlorine atom. The CVD of parylene C is a three-step process in which the precursor is sublimated at a temperature of about 150 °C. Afterwards, the precursor is pyrolysed at a temperature of approximately 680 °C to a 1,4-chinondimethan radical. This radical is highly reactive and on surfaces polymerizes to parylene C. To achieve the necessary process conditions, the steps must be spatially separated. Neither the energy consumption nor the complexity of the pyrolysis is a disadvantage during the CVD. However, near the pyrolysis temperature, the aryl-chlorine bond in the precursor readily breaks. For this reason, along with the desired monomer 1,4-chinodimethan, chlorine radicals and [2,2]paracyclophane are also created which polymerize on surfaces to another parylene, namely, parylene N. The above makes clear the importance of chemistry in the deposition processes. In this work, plasma is used for dissociation instead of high temperatures. The feedstock for this plasma is a composition of argon and a small amount of dichloro[2,2]paracyclophane. Due to the use of plasma, the process is called Plasma Enhanced CVD (PECVD . The advantage of this method is that the energy for dissociation is provided by the impact of hot electrons, while the neutral atoms and radicals are nearly at room temperature. The aim of the mass spectrometric investigation is to understand the chemical reactions running in the plasma and how they are affected by changes in the discharge parameters.


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PC–4 INFLUENCE OF THE PREPARATION METHOD ON THE OPTICAL PROPERTIES

OF GeS1.2 – AgI FILMS D. Nicheva1,2, V. Ilcheva2, T.Petkova2, I.N. Mihailescu3, G. Popescu-Pelin3, G. Socol3, C. Ris-

toscu3, P. Petkov1

1Department of Physics, University of Chemical Technology and Metallurgy 8 St. Kliment Ohridski blvd., 1756 Sofia, Bulgaria

2Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences Acad. G. Bonchev bl. 10, 1113 Sofia, Bulgaria

3Laser-Surface-Plasma Interactions Laboratory, National Institute for Lasers, Plasma and Radi-ations Physics, PO Box MG-54, Magurele, RO-77125, Romania

Thin films from the chalcohalide (GeS1,2)1-x(AgI)x system (x = 5, 10 ,15, 20 mol. %) were de-posited by pulsed laser deposition (PLD) and vacuum thermal evaporation (VTE) from the cor-responding bulk materials. Structural, morphological and surface topography studies were per-formed in order to elucidate the effect of the process parameters and preparation method on the films properties. The amorphous character of the films was confirmed by X-ray diffraction analysis. The morphology and topography were investigated by scanning electron microscopy and atomic force microscopy. The transmission spectra of the films were measured within the wavelength range (400 – 2500) nm and the optical band gap was calculated as a function of the films composition and the preparation method. It was found that the values of the optical band gap (Eg) of the films are strongly dependant on the addition of silver iodine to the glassy matrix and the method of preparation. It was assumed that the difference in the Eg values of VTE- and PLD- fabricated films is due to the peculiari-ties of the preparation technique providing differences in the films structure. PC–5

STUDY OF THE MORPHOLOGY OF GE QUANTUM DOTS GROWN BY LIQUID PHASE EPITAXY

I.I. Maronchuk1, D.D. Sankovitch1, H. Nichev2, D. Dimova-Malinovska2

1 Laboratory of Applied Physics and Nanotechnologies for Energy Applications, Sevastopol

National University of Nuclear Energy and Industry, 7 Kurtchatova str. 299033 Sevastopol, The Russian Federation

Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 72 Tsarigradskao Chaussee blvd., 1784 Sofia, Bulgaria

Recently, the study of nano-heterojunctions based on c-Si and Ge quantum dots (QDs) have attracted the interest of many research teams due to their potential for photovoltaic and photothermal application. The theoretical calculation demonstrated that the maximal efficiency of the c-Si/Ge QDs solar cells is 53 %, which is twice as high as the efficiency of commercial c-Si solar cells (22 %). This work reports the results of a study of the process of growing QDs of a narrow-band semiconductor (Ge) in the matrix of a wide-band material (Si) by liquid-phase epitaxy applying


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pulsed cooling of the substrate. The influence was studied of the different technological conditions on the size of the Ge QDs and the density of their distribution. The morphology of the structures was studied by AFM using a CMM-200 type microscope. The results demonstrate that after applying 1 and 3 cooling pulses, the Ge QDs formed are very small with a height of 5 and 10 nm and a width of 20 and 60 nm, respectively, with a 20 % deviation, while their shape cannot be determined accurately. Increasing the number of the pulses to 5 and 10 results in increasing their size, the height being 70 and 150 nm, the width, 190 − 250 nm, respectively, with a 35 % deviation. The Ge QDs have a shape close to the pyramidal one and the density of their distribution on the Si surface is 1 − 2 × 1010 cm-2. However, the samples grown by applying seven pulses have a totally different morphology compared to the samples grown by applying five and ten pulses. Their shape is not well-defined; they look like drops with a width of 150 nm; however their height decreases and is 15 nm. The QDs growth is explained by the Stranski-Krastanoff mechanism and by the authors’ theoretical prediction published previously [1].

[1] I. E. Maronchuk, T. F. Kulyutina, I. I. Maronchuk, Method of growth epitaxial nano heterojunction structures with quantum dots array. Patent of Ukraine, UA 94699, cl. С 30В 19/00, С 30В 29/00, Н 01L 21/20, 10.06.2011, bulletin. 5. Acknowledgements: The work has been supported by the Bulgarian National Scientific Fund, grant DNTS/Ukraine 01/0005. PC–6 ARENECARBOXIMIDE DERIVATIVES AS DYE-SENSITIZERS APPLIED TO THIN

FILM SOLAR CELLS

H. Nichev2, N. Georgiev1, M. Petrov2, K. Lovchinov2, D. Dimova-Malinovska2, V. Bojinov1

1Department of Organic Synthesis and Fuels, University of Chemical Technology and Metal-

lurgy, 8 St. Kliment Ohridski blvd., 1756 Sofia, Bulgaria 2Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of

Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria Expanding the applications of PV systems requires the development of new, more efficient and less expensive technologies. The dye-sensitized solar cells (DSSCs) are cheap alternatives to silicon solar cells for efficient conversion of solar energy into electrical energy, which is why they have attracted the attention of the scientific community. For the last ten years, increasing efforts have been devoted to the development of organic sensitizers (organic chromophores) for solar cells with high photo-conversion efficiencies. Representatives of these materials are the arenecarboximide (ACI) derivatives, owing their unique chemical, thermal and especially pho-tochemical stability. In this work we report on the preparation of three types of ACI layers by dipping in the solu-tion of glasss substrate covered by SnO2, ITO and ZnO thin films for solar cells formation. The SnO2, ITO and ZnO thin films are used as backside electrodes, and the Ag grid, as front elec-trodes. The current-voltage characteristics of the cells are measured and discussed. Keywords: solar cells, arenecarboximide derivatives.


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PC–7

DEPOSITION OF CARBON NANOSTRUCTURES ON METAL SUBSTRATES AT ATMOSPHERIC PRESSURE

Zh. Dimitrov, M. Nikovski, Zh. Kiss'ovski

Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier blvd., Sofia,

Bulgaria

Plasma-enhanced chemical vapor deposition is the main method of carbon nanostructures synthesis; however, the conditions ensuring fast growth have to be achieved by varying the plasma parameters in the experimental set-up. One of the challenges remains synthesizing such carbon nanostructures by microwave plasma at atmospheric pressure. The microwave discharge produces dense plasma and provides the appearance of reactive species with high concentration needed to ensure the deposition process. Processing the samples at atmospheric pressure allows the deposition period to be shortened and also simplifies the set-up. In this study, we investigated the relation between the substrate temperature and the type of the carbon nanostructures deposited. The process of deposition itself is carried out by an additionally negative DC potential applied to the substrate. The temperature is varied in a wide range using the microwave plasma heating as well as an additional heater [1]. The distance between the substrate and the plasma flame is also varied in order to establish the conditions for efficient deposition process. The deposition process is carried out in specific argon/hydrogen/methane gas mixtures [2]. Optical measurements of the plasma flame spectrum above the microwave discharge tube are conducted to obtain the gas temperature, plasma density and to analyze the existence of reactive species in order to establish their role in the deposition process. The structures deposited on the metal samples are investigated by SEM and the relation of the morphology with the gas-discharge conditions is discussed. [1] Kiss’ovski Zh, Djermanova N, Mitev D and Vachkov V. J. of Physics: Conf. Series 514, 012007 (2014) [2] Y. H. Wu,T. Yu, Z. X. Shen “Two-dimensional carbon nanostructures: Fundamental properties,synthesis, characterization, and potential applications” Journal of Applied Physics 108, 071301 2010 Acknowledgments: This work was supported by Project BG051 PO 001-3.3.06-0057, Opera-tional Program Human Resources Development 2007—2013 PC–8

VACUUM DEPOSITED ORGANIC SOLAR CELL STRUCTURES

G. Georgieva1, D. Dimov2, G. Dobrikov3, M. Vala1, M. Weiter1, and I. Zhivkov1,2 1Faculty of Chemistry, Center for Materials Research, Brno University of Technology, Purky-

nova 118, 612 00 Brno, The Czech Republic 2Acad. J. Malinovski Institute for Optical Materials and Technologies, Bulgarian Academy of

Sciences, Acad. G. Bonchev str., bl. 109, 1113 Sofia, Bulgaria 3Faculty of Electronic Engineering and Technologies, Department of Microelectronics, Tech-

nical University of Sofia, 8 St. Kliment Ochridski blvd., 1756 Sofia, Bulgaria E-mail: [email protected]


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Zinc phthalocyanine (ZnPc) and diphenyl-diketo-pyrrolopyrroles (DPP) thin films were deposited in vacuum on ITO covered substrates. Aluminum top electrodes were also prepared by vacuum evaporation on the organic film (OF). As a result, solar cell structures of the ITO|OF|Al type were produced by an all-dry process that avoids the usage of a solvent. The device parameters were estimated by measuring the current-voltage characteristics in dark and under white light illumination. The light was produced by a solar simulator according to the AM 1.5 standard. The spectral dependence of the photoconductivity was measured and the spectral region for optimal photoelectrical energy conversion was determined. On some of the structures, addi-tional sub- and over-layers were also deposited in vacuum to optimize the device performance. A post-deposition treatment was applied to selected samples to improve the device perfor-mance. It was found that the photovoltaic properties of the samples depend on the conditions for deposition of the top Al electrodes. Increasing the substrate temperature during the electrode deposition worsens the photoelectrical properties. The optimal conditions for electrode deposition were established, which allows reproducible samples to be prepared. Under these conditions, a clear diode dark current characteristics with a diode rectification ratio of 1×105 were obtained. Under light exposure of samples with ZhPc active films, an open-circuit voltage of 0.7 V was observed, while the photocurrent increased by more than five orders of magnitude. It was also found that the post-deposition treatment improves the device parame-ters, especially influencing the solar cell efficiency. Acknowledgements This work was supported by the Czech Science Foundation under project No. 15-05095S; the research infrastructure was supported by project MŠMT No. LO1211. PC–9 MAGNETRON SPUTTERING OF Fe-OXIDE MAGNETIC FILMS ON DIELECTRIC

AND SUPERCONDUCTING SUBSTRATES

T. Nurgaliev1, E. Mateev1, L. Slavov1, 3, B. Blagoev2, 3, G. Gajda3, I. Nedkov1


2Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria

3International Laboratory of High Magnetic Fields and Low Temperatures, 95 Gajowicka Str., 53-421 Wroclaw, Poland

Thin films of iron (Fe) and iron oxides (FexOy) possess unique magnetic and electric properties and are considered suitable candidates for application in sensors, microwave and magnetooptic devices. Magnetic oxides and the ferromagnet/superconductor structures have also been the subject of numerous experimental and computational investigations in view of applications in a very promising area of electronics − spintronics. Magnetron sputtering is one of the main methods used for growing high-quality films of complex oxides. The most challenging problem in growing monophase iron oxide thin films of α-Fe2O3, γ-Fe2O3 and Fe3O4 is the narrow area of transition between phases in the phase diagram of FexOy, so that a precise


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control of the deposition conditions is necessary during the technological process. We report some preliminary results of RF magnetron sputtering of a Fe target in Ar or Ar/O2 atmosphere with the purpose of preparing magnetic FexOy films. The deposition was carried out on Si, Al2O3 substrates at several substrate temperatures. The magnetic properties, the electrical conductivity and the transparency of the films strongly depended on the deposition conditions, especially, on the temperature of the substrate. A FexOy layer was deposited on a surface of a SrTiO3 substrate covered by a high-temperature superconducting YBa2Cu3O7-x film as well. The deposition at lower substrate temperatures did not destroy the superconductivity and the sample exhibited superconducting properties at 77 K. PC–10

INFLUENCE OF THE PULSED LASER DEPOSITION PARAMETERS ON THE PROPERTIES OF EPITAXIAL GST FILMS ON Si(111)

Isom Hilmi, Erik Thelander, Philipp Schumacher, Jürgen W. Gerlach, Bernd Rauschenbach

Leibniz-Institut für Oberflächenmodifizierung e.V., Leipzig 04318, Germany

E-mail: [email protected]

Thin films of Ge2Sb2Te5 (GST) are considered promising candidates for application as phase-change materials with respect to switching speed and stability1. Currently, improved switching characteristics have been shown by tailoring a superlattice-like structure of GeTe and Sb2Te3 layers2, which then gave rise to investigations of higher-order structures of GST materials. One of them has been realized by epitaxial growth of Ge-Sb-Te films in highly-ordered atomic ar-rangement by means of MBE3. However, with this method, there is a severe limitation in terms of the deposition rate which is typically around 0.3 − 0.5 nm per minute4. In this point, pulsed laser deposition (PLD) has been used successfully for deposition of GST5 as it offers signifi-cantly higher GST deposition rates. In this work, epitaxial GST thin films were grown on single crystal Si(111) substrates by means of PLD. The influence of the PLD parameters, namely, laser pulse repetition rate and fluence, on the crystalline quality of the films was investigated by means of X-ray diffraction-based measurements. The film topography was investigated using AFM in tapping mode. The results show that the PLD parameters have a significant impact on the crystal quality of the grown GST. 1. A. V. Kolobov, et. al., Nature Material, Vol. 3, October, 2004. 2. R. E. Simpson et. al., Nat. Nano. 6, 501, 2011. 3. F. Katmis et. al., Cryst. Growth, Des. 11, 4606, 2011. 4. R. Shayduk, et. al., Journal of Crystal Growth, 311, 2215–2219, 2009. 5. H. Lu, et al., Adv. Funct. Mater. 23, 3621–3627, 2013.


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PC–11

MORPHOLOGICAL AND OPTICAL INVESTIGATION OF SOL-GEL ZNO FILMS

T. Ivanova1, A. Harizanova1, A. Petrova2

1 Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee blvd., Sofia, Bulgaria

2 Space Research and Technology Institute, Bulgarian Academy of Sciences, Acad G. Bonchev Str., bl. 1, 1113 Sofia, Bulgaria

Zinc oxide has been widely studied as one of the binary II–VI semiconductor compounds with a hexagonal wurtzite structure possessing an optical band gap of 3,37 eV and a large exciton energy. Other interesting properties of ZnO include its optical, acoustical and electrical properties, high photosensitivity, high optical transparency in the visible region and stability which can be useful in the fields of electronics, optoelectronics and sensors. Some potential applications are as piezoelectric transducers, optical waveguides, acousto-optic media, surface acoustic wave devices, conductive gas sensors, transparent conductive electrodes, solar cell windows, and varistors. This works presents an easy-to-implement sol-gel process for deposition of ZnO films, which is proved to be a very flexible approach to modification of the structural, vibrational and optical properties by simply changing the solvent used in the sol solution. The influence of different thermal treatments is studied. The films microstructure is explored using a NanoScan family scanning nano-hardness measuring device in constant frequency regime, which is based on the atomic force microscopy principle. The surface study revealed that the RMS surface roughness for 985,64×985,64 nm ZnO films increases as the annealing temperature is increased, but the film surface is still uniform and smooth. The results were confirmed by XRD analysis which demonstrated that the crystallite sizes grow from 25 to 36 nm with the thermal treatment. The ZnO films possess high transmittance in the visible spectral range, while the optical band gaps in ZnO films vary from 3.25 eV to 3.52 eV. The optical and morphological properties of ZnO films on Si and quartz substrates thus revealed are very good. The sol-gel approach proposed for deposition of nanostructured ZnO films is promising for applications to optoelectronic devices and solar cells.


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PC–12 SYNTHESIS AND PROPERTIES OF ZnO:Al THIN FILMS PREPARED BY SOL-GEL

METHOD

T. Ivanova1, A. Harizanova1, T. Koutzarova2, B. Vertruyen3

1Central Laboratory of Solar Energy and New Energy Sources,Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., Sofia, Bulgaria

2Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd, Sofia, Bulgaria

3LCIS/SUPRATECS, Institute of Chemistry B6, University of Liege, Sart-Tilman, B-4000 Liege, Belgium

ZnO has been the object of intensive scientific research due to its specific properties, such as a wide band gap (3.37 eV at room temperature) with a large exciton binding energy (60 meV), a high chemical stability, a low dielectric constant, a large electrochemical coupling coefficient, a high thermal conductivity, and binding, antibacterial and UV protection properties. Doping ZnO by different metals leads to modifying its structural, electronic and optical properties. Aluminium-doped ZnO coatings exhibit a high transparency and a low resistivity. The sol-gel technology offers the possibility to produce high-quality homogeneous thin films on large areas with excellent control of the stoichiometry and compositional modification (mixing on a molecular level) via a cost-effective process using inexpensive equipment. This work presents a sol-gel technological process for deposition of thin films of ZnO and ZnO:Al. The effect on their properties of annealing treatments (500, 600, 700 and 800 oC) was studied. The structural evolution with the temperature was investigated by using X-ray diffraction (XRD). Fourier transform infrared (FTIR) and UV-VIS spectrophotometry were applied for characterization of the vibrational and optical properties. The ZnO and ZnO:Al films possessed a polycrystalline structure. The pure ZnO film crystallized in a wurtzite phase with a weak reflection associated to cubic ZnO2. The ZnO:Al spectrum revealed only the XRD lines of wurtzite ZnO without any other crystalline phases. The Al component influenced the crystallization of the films and the crystallite size significantly diminished in comparison with pure ZnO films. The average crystallite size of ZnO was 32.3 nm, and that for ZnO:Al was 20.0 nm. The Al additive affected the shapes and intensity of the IR absorption features without clear indication of bands, which can be associated with Al-O bonds. The FTIR analysis led us to a conclusion in agreement with the XRD study, namely, that the only crystal phase detected was wurtzite ZnO. The films studied were highly transparent in the visible spectral range as the transparency was improved by the aluminium doping. The optical band gap values and haze parameter were also determined. The haze parameter serves as an indicator of diffuse light scattering by the thin films.


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PC–13

INFLUENCE OF THE SURFACE PRETREATMENT OF ALUMINUM ON THE PROCESSES OF FORMATION OF CERIUM OXIDES PROTECTIVE FILMS

R. Andreeva1, E. Stoyanova1, А. Tsanev2, D. Stoychev1

1Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad.

G. Bonchev str., bl. 11, Sofia 1113, Bulgaria

2Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 11, Sofia 1113, Bulgaria

There exists a special interest in the investigating the conversion treatment of aluminum aimed at promoting its corrosion stability, which is focused on electrolytes on the basis of salts of metals belonging to the group of rare-earth elements. Their application is especially attractive, as it enables a successful substitution of the presently applied highly efficient, but at the same time toxic Cr6+-containing electrolytes. The present work presents a study on the influence of the preliminary alkaline activation and acidic de-oxidation of the aluminum surface on the processes of immersion formation of protective cerium oxides films on Al-1050. The results obtained show that their deposition from simple electrolytes (containing only salts of Ce3+ ions) on the Al surface, treated only in an alkaline solution, occurs at a higher rate, which leads to preparing thicker oxide films having a better protective ability. In the cases when the formation of oxide films is realized in a complex electrolyte (containing salts of Ce3+ and Cu2+ ions), better results are obtained with respect to the morphology and protective action of cerium oxides film on samples which have been consecutively activated in an alkaline solution and deoxidized in an acidic solution. Electrochemical investigations were carried out in a model corrosion medium (0.1 M NaCl); it was shown that the cerium protective films deposited by immersion are of a cathodic nature in regard to the aluminum support and inhibit the occurrence of the depolarizing corrosion process – the reaction of oxygen reduction. Key words: aluminum, pretreatment, cerium-containing conversion films, corrosion


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PC–14 TRANSMISSION PHOTOCATHODES BASED ON STAINLESS STEEL MESH AND

QUARTZ GLASS COATED WITH N DOPED DLC THIN FILMS PREPARED BY REACTIVE MAGNETRON SPUTTERING

N.I. Balalykin1, J. Huran2, M.A. Nozdrin1, A.A. Feshchenko1, A.P. Kobzev1, V. Sasinková3

1 Joint Institute for Nuclear Research, 6 Joliot-Curie str., 141980 Dubna,

Moscow Region, Russian Federation 2 Institute of Electrical Engineering, Slovak Academy of Sciences,

Dúbravská cesta 9, 84104 Bratislava, Slovakia 3 Institute of Chemistry, Slovak Academy of Sciences,

Dúbravská cesta 9, 84538 Bratislava, Slovakia

Laser-driven photoelectron sources are widely used in various scientific experiments for the generation of high-quality electron beams. We investigated the influence of the properties of N-doped diamond-like carbon (DLC) films on the quantum efficiency of transmission photoca-thodes. N-doped DLC thin films were deposited on a silicon substrate, a stainless steel mesh and quartz glass (coated with a 5-nm thick Cr adhesion film) with an Al mesh made by the lift-off technique. The films were deposited by reactive magnetron sputtering using a carbon target and an Ar+/N2 gas mixture. The film thickness for the silicon substrate and the stainless steel mesh was about 150 nm, and for the quartz glass, about 25 nm. The elemental concentration in the films was determined by RBS and ERD. Raman spectroscopy of the DLC films was used to determine the D and G peaks intensity ratio (I(D)/I(G)). The G and D peaks were fitted by two Gaussians, while the intensity was calculated as the peaks’ area. The quantum efficiency was calculated from the measured laser energy and the measured cathode charge. The RBS and ERD analyses indicated that the films contained carbon, hydrogen, nitrogen and a small amount of oxygen. The photocathode was placed in a hollow cathode assembly of a DC gun with a Pierce structure. To study the vectorial photoelectric effect, the quartz-type photocath-ode was irradiated by high-power laser pulses (3 − 4 pulses with a power of about 5 MW/cm2) to create micron-sized perforation in the Cr and DLC films by laser ablation. The bunch charge was measured by using a Faraday cup. The quantum efficiency (QE) calculated at a laser ener-gy of 0,4 mJ inreased as the nitrogen concentration in the DLC films was increased, and dra-matically rose up after the micron-sized perforation in the quartz-type photocathodes. The best results achieved for the QE (%) was 0,84×10-3 for the quartz-type transmission photocathode. The Prospectss for implementing N-doped DLC thin films on quartz glass transmission photocathodes for application in the DC gun technology are discussed. This research was executed in the framework of the Topical Plan for JINR Research and Inter-national Cooperation (Project 02-0-1067-2013/2017) and supported by the Slovak Research and Development Agency under contract APVV-0443-12


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PC–15 TRANSFORMATION OF ELECTROMAGNETICALLY INDUCED TRANSPARENCY INTO ABSORPTION IN THERMAL K OPTICAL CELL WITH SPIN-PRESERVING

COATING

S. Gozzini1, A. Lucchesini1, C. Marinelli1,2, L. Marmugi1,4, S. Gateva3, S. Tsvetkov3, S. Cartaleva3

1Istituto Nazionale di Ottica CNR – UOS Pisa, Via Moruzzi 1, 56124 Pisa, Italy

Department of Physical Sciences, Earth and Environment, University of Siena, via Roma 56, 53100 Siena, Italy

3Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

4Department of Physics and Astronomy, University College London, Gower str., London WC1E 6BT, UK

Electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) are coherent phenomena with quickly expanding applications. In a Hanle configuration, the EIA contrast (about 1%) is much worse than the EIT one. To enhance the EIA contrast, the use of a transition with angular momenta of the ground and excited states F = 1 was recently proposed [1]. We report a new experimental approach where an order of magnitude enhancement of EIA re-sonance contrast is obtained (Fig.1b), comparable to that of the EIT (Fig1a). Here, the EIA sig-nal results from the interaction of a weak probe beam with a ground state that has been driven by the pump (counter-propagating) beam. Figure 1 shows double scan probe absorption spectra with the laser frequency slowly detuned over the D1 line of 39K vapor, in a cell with PDMS an-tirelaxation coating. At the same time, a magnetic field orthogonal to the laser beams is tuned at a higher rate across zero. Note that: (i) changing the pump beam polarization from linear to circular reverses the resonance signal from EIT to EIA and (ii) here, in the experimental ab-sorption profile not only the transition with F = 1 is involved, but also two other hyperfine transitions of the D1 line of 39K.

Fig.1 EIT (a) and EIA (b) resonances observed by means of a double scan: of (i) laser frequency over the absorption profile and (ii) magnetic field varying around zero value; (a) pump and probe beams are of linear polarization; (b) the pump is almost circularly (1:1.4) and the probe is linearly polarized. (a) Wpump = 2.92 mW, Wprobe = 0.98 mW; (b) Wpump = 2.91 mW, Wprobe = 0.57 mW.

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This work was supported by Marie Curie International Research Staff Exchange Scheme Fel-lowship within the 7th European Community Framework Program and by the Italian National Research Council and the Bulgarian Academy of Sciences (Program CNR/BAS 2013-2015). [1] D V Brazhnikov, A V Taichenachev, A M Tumaikin, V I Yudin, Laser Phys. Lett. 11 (2014) 125702. PC–16

STRUCTURAL, OPTICAL AND VIBRATIONAL PROPERTIES OF NANOSTRUCTURED ALUMINUM NITRIDE FILMS SYNTHESIZED BY MULTI-

STAGE PULSED LASER DEPOSITION

L. Duta1, G.E. Stan2, M. Anastasescu3, H. Stroescu3, M. Gartner3, Zs. Fogarassy4, N. Mihailescu1, C. Luculescu1, S. Bakalova5, A. Szekeres*,5, I.N. Mihailescu1

1Lasers Department, National Institute for Lasers, Plasma, and Radiation Physics, P.O. Box

MG-36, 77125 Magurele, Romania; 2National Institute of Materials Physics, 105 bis Atomistilor Street, P.O. Box MG-7, 77125

Magurele, Romania 3 Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy of Sciences, 202 Splaiul

Independentei, 060021 Bucharest, Romania 4Research Institute for Technical Physics and Materials Science, Hungarian Academy of

Sciences, Konkoly Thege Miklos u. 29-33, H-1121 Budapest, Hungary 5Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee

blvd., 1784 Sofia, Bulgaria; *[email protected] Aluminum nitride (AlN) films have great potential for various applications due to their excellent electronic, optical and thermal properties, which can be tailored by varying the deposition methods and the technological conditions. AlN films are finding applications in high-power and high-frequency devices, high-power switches, blue and ultraviolet light-emitting devices and photo-detectors. The successful fabrication of devices based on AlN thin films requires a better understanding of the optical and electronic properties as related to the growth conditions. Our recent studies were focused on pulsed laser multi-stage AlN deposition at different temperatures aiming to obtain nanostructured AlN films at considerably lower de-position temperatures. This report is focused on spectroscopic ellipsometry (SE) studies of the AlN films. In order to support the SE results obtained, SEM, GIXRD and TEM were also applied. The SE measure-ments were performed in a wide region covering the near UV-VIS (193 − 1000 nm) and IR (350 − 5000 cm-1) light spectra. The nanostructured AlN films were synthesized by multi-stage pulsed laser deposition, with the first stage of deposition carried out at 800 °C, which was pre-viously established to be the optimum temperature for AlN crystallization. The second stage, homoepitaxial deposition, was conducted at reduced temperatures (450 °C, 350 °C, RT) at a low nitrogen pressure of 0.1 Pa. The results from the ellipsometric data modeling showed that the refractive index values were lower than those obtained for crystalline AlN, but higher than those for amorphous AlN. This was in accordance with the GIXRD and TEM observations that both crystalline and amorphous phases existed in the films. By increasing the substrate temperature from RT up to 800oC, nanocrystallites appeared in the amorphous matrix (as proved by TEM imaging and GIXRD

mailto:*[email protected]


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analysis), with a tendency of enhancing the crystallization and crystallites’ augmentation. For the AlN films deposited at 350oC and 450oC, the values for the optical constants were close, pointing to similar film structures approaching stoichiometric AlN. For the RT deposition, the TEM imaging showed an amorphous phase, but the corresponding refractive index values were higher revealing an over-stoichiometric AlN structure with excess of Al, as confirmed by the SEM measurements. The band gap energy of AlN increased as the substrate temperature or the laser pulse repetition rate were increased, which we attributed to the increased formation of nanocrystallites of larger sizes, as proved by GIXRD analysis. PC–17

ELECTRICAL PROPERTIES OF p-TYPE In-N CO-DOPED ZnO THIN FILMS DEPOSITED ON DIFFERENT SUBSTRATES

M. Duta1, J. Calderon-Moreno1, S. Preda1, P. Osiceanu1, S. Mihaiu1, M. Zaharescu1, M. Gart-

ner1, S. Simeonov2, D. Spasov2, A. Szekeres2

1 Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy of Sciences 202 Splaiul Independentei, 060021 Bucharest, Romania

2 Institute of Solid State Physics, Bulgarian Academy of Sciences 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

Zinc oxide is a well-known material for opto-electonic applications. Presently, two research directions have been established: depositing n-type thin films with high conductivity on flexi-ble supports for display applications, or obtaining p-type conduction for incorporation in ho-mo- and hetero-junctions. The second aim can be achieved by co-doping the film with donor-acceptor pairs such as In-N, Al-N, B-N, etc. We have deposited In-N co-doped ZnO thin films on four different substrates (glass, alumina, n- and p-Si) through a combined sol-gel and hydrothermal method, followed by annealing at 500 oC for one hour and have investigated the direct or indirect influence of the substrate on their electrical properties. The co-doped nature of the films was confirmed using XPS analysis. The morphology of the films (determined by SEM) showed interconnected, randomly oriented nanorods with a length of a few hundred nanometers. Three of the substrates promoted homo-genous, continuous films, whereas alumina promoted film growth at the Al2O3 grain bounda-ries, leading to non-homogenous films with a lower thickness. The films crystallized in a wurt-zite structure with no evident preferred orientation as indicated by the XRD and the random orientation of the nanorods. Hall Effect (HE) measurements showed high resistivity for the film deposited on alumina, due to the small thickness and the non-homogeneity. The conduction type of the films deposited on n-Si as determined from HE and I-V and C-V measurements dif-ferred, suggesting the presence of a nitrogen gradient or that the conducting substrate contri-butes charges to the film. The presence of donor-type defects in the films was observed with injected carriers trapped at these sites.


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PC–18 IMPACT OF THE ACTIVE LAYER NANOMORPHOLOGY ON THE EFFICIENCY

OF ORGANIC SOLAR CELLS BASED ON A SQUARAINE DYE AS A DONOR

D. Stoyanova1, S. Kitova1, J. Dikova1, M. Kandinska2, A.Vasilev2, I. Zhivkov1,3

A. Kovalenko3

1 Acad. J. Malinovski Institute for Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 109, 1113 Sofia, Bulgaria

2 Faculty of Chemistry and Pharmacy, St. Kliment Ohridski University of Sofia, 1 James Bour-chier blvd., 1164 Sofia, Bulgaria

3 Materials Research Center, Faculty of Chemistry, Brno University of Technology, Purkyňova 118, 612 00 Brno, Czech Republic

E-mail: [email protected] During the past two decades, the organic solar cells (OSCs) have drawn intensive interest due to their light weight and potential of low-cost and simple roll-to-roll production on flexible substrates. In the most successful implementation, a soluble n-type fullerene derivative, (6,6)-phenyl C61 butyric acid methylester (PCBM) as an acceptor, is blended with the donor from conjugated p-type polymers or small molecular weight organic semiconductors to form bulk-heterojunction (BHJ) cells. Although high PCEs of 9 – 10 % have been achieved, the polymer solar cells still suffer from some shortcomings, such as batch-to-batch variation, indefinite molecular weight, polydispersity and impurity. In contrast, small-molecule materials intrinsically do not have such drawbacks. Additionally, the band structure of these materials could be tuned more easily, while they exhibit a higher charge carrier mobility. Even though the highest PCE of 7.38 % has been obtained by solution-processed small- molecule OSCs, it is still lower than that of polymer solar cells owing mainly to the difficulty of controlling the na-nomorphology and phase separation in the active layers, where donor and acceptor components self-assemble to form bicontinuous interpenetrating networks. The latter allows the excitons to diffuse to the donor-acceptor interface and the charge carriers to move to the respective electrodes after separation. Because the photoexcitation/recombination lengths are typically around 10 nm in these disordered materials, the length scale for this self-assembly must be of the order of 10 – 20 nm. In a previous work, we studied the potentiality of our newly synthesized symmetrical n-hexyl substituted squaraine dye, (labeled as Sq1) for use as an electron donating component in BHJ organic solar cells. The results obtained were very encouraging, which gave us reason to con-tinue the investigations. In the present work, the influence is studied of the active layer mor-phology on the efficiency of OSCs based on Sq1 dye as a donor and PCBM as an acceptor. For this purpose, the impact of solvent annealing processing on the nanomorphology and phase se-paration in the Sq1/PCMB blended layers with different donor/acceptor ratios is followed by means of TEM. Further, the optical properties are estimated of the as-deposited and the an-nealed active layers, as well as the efficiency of cells designed on their basis. Thus, the very important relationship was revealed between the Sq1/PCBM blend morphology and the photo-voltaic performance of the organic solar cells studied. On this basis, the possibilities for prac-tical application of the results obtained are discussed. Acknowledgements: This work was supported by the Czech Science Foundation under project No. 15-05095S; the research infrastructure was supported by project MŠMT No. LO1211.



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PC–19

OPTIMIZATION OF THE SERIES RESISTANCE IN BULK HETEROJUNCTION POLYMER SOLAR CELLS

M. Sendova-Vassileva1, G. Popkirov1, P. Vitanov1, G. Grancharov2, V. Gancheva2, H. Dikov1,

E. Lazarova1

1Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria

2Institute of Polymers, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

The series resistance of solar cells is an important parameter which has a decisive influence on their efficiency. The apparent value of the series resistance, Rser, is the sum of contributions of the resistances of the different conducting and semiconducting layers of the solar cell and their respective junctions. Rser cannot be measured directly; thus, a great number of measurements methods have been reported, among which fitting the current-voltage characteristics of the cell to a predefined model seems to be the most commonly used. In this contribution, we present an alternative method, derived from the impedance spectrosco-py, that uses a relatively high-frequency perturbation voltage with a low amplitude applied un-der conditions simulating an open circuit. The method is applied to polymer solar cells (PSCs) of the type ITO/hole transporting layer (HTL)/bulk heterojunction (BHJ)/back contact or in-verted ones of the type ITO/ BHJ/ HTL/back contact. The BHJs deposited by spin coating are either the classic P3HT:PCBM combination or the high open-circuit voltage PCDTBT:PCBM one. The HTL is either spin-coated PEDOT:PSS or an inorganic oxide layer (MoO3, WO3) de-posited by magnetron sputtering. The back contact is sputtered or evaporated silver or alumin-ium. The series resistance measured is compared to the one estimated from the current-voltage characteristics and the observed differences are analyzed. The data obtained concerning the Rser can serve as one of the control parameters in our attempt to improve the PSCs technology. PC–20

OPTICAL AND ELECTRICAL PROPERTIES OF NANOLAMINATE DIELECTRIC STRUCTURES

Ch. Dikov, P. Vitanov, T. Ivanova

Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences,

72 Tsarigradsko Chaussee blvd., 1784 Sofia, Bulgaria The wide application of transparent and conductive oxide (TCO) films to optoelectronics and photovoltaics has promoted the development of low-cost materials and technological processes. Most of the TCO films are binary or ternary compounds containing one or two metallic elements. The combination of conductivity and transparency is impossible to achieve in intrinsic stoichiometric oxides. In order to achieve conductivity in such materials, they should be doped with an appropriate element. The aim of this study is a formation of a conductive area in a nanolaminate dielectric structure. The underlying physical idea is the usage of an electronic conductivity in granular type


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materials. The granules are metallic particles of sizes ranging usually from a few to hundreds of nanometers embedded into an insulating matrix. The nanolayer structure is formed using one or two different dielectrics. The electrical conductivity is modified with planar located metal granules. A magnetron sputtering system with three different targets was used for the deposition of the layers. The advantages of this method are reproducibility of technological parameters, effective process control and a selective formation of conductive areas into the dielectric structure. Our studies reveal that the relation between the sheet resistance and the maximum transparency in the visible spectral range depends on factors such as the dimension of the metal granules ad the thickness of the dielectric layers. Another possibility for engineering the optical and electrical properties of nanolaminate structures is to use different metals and dielectrics layers. We present the results of studying the temperature behavior of resistors with nanolaminate structures. Usually, the TCOs layers have a semiconductor behavior of the conductivity, as a negative temperature coefficient of receptivity (TCR). The nanolaminate structure with metal granulate demonstrates a metallic conductivity, as it reveals a positive TCR. The technological procedure applied to the formation of the transparent conductive coatings makes it possible to predict their optical and electrical properties.


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POST DEADLINE CONTRIBUTION PA–27

THEORETICAL STUDY OF SURFACE-WAVE-DISCHARGES IN VACUUM–

PLASMA AND DIELECTRIC–PLASMA CONFIGURATIONS

K. Ivanov, T. Bogdanov, E. Benova

St. Kliment Ohridski University of Sofia, Sofia, Bulgaria

Electromagnetic wave travelling along the dielectric-gas interface can produce plasma. These gas discharges called surface-wave-discharges (SWDs) exist in various geometries: pla-nar, spherical, cylindrical, coaxial, and around dielectric cylinder. The typical coaxial surface-wave-sustained discharge (CSWD) is produced outside the dielectric tube when a metal rod is arranged at the tube axis. The CSWD is studied intensively both theoretically and experimen-tally since 1998. The experimental investigations show that in some conditions the plasma can be produced outside the dielectric cylinder even when there is not any metal antenna at the di-electric axis [1].

In order to find out theoretically these conditions and the plasma characteristics we have built one-dimensional fluid model for vacuum–plasma and dielectric–plasma configura-tions. The basic relations in our model are the local dispersion relation describing the wave propagation and the wave energy balance equation, both obtained from Maxwell’s equations. Analyzing the phase diagrams, the axial profile of dimensionless plasma density and the 3D distribution of electric and magnetic field components, one can obtain information about the ability of the electromagnetic wave to sustain plasma at given discharge conditions.

The purpose of this work is to investigate theoretically the behaviour of wave phase diagrams and axial profiles at various discharge conditions and to find out the values of plasma parameters at which plasma can be sustained in vacuum–plasma and dielectric–plasma con-figurations. Reference: 1. Liang R., Nie Z., Liang B., Liang Y., Chang X., He L., Li Z. MICROWAVE DISCHARGES: Fun-

damental and Applications, Ed. M. Kando and M. Nagatsu, Japan: 2009, 95. Acknowledgements: This work has been supported by the Fund for Scientific Research at the University of Sofia under Grant No 187/2015.


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AUTHOR`S INDEX

A Adamek J. 29 Aftanas М. 71 Alexandrov M.T. 88 Alexandrova S. 97 Alexiou G. 52 Alipieva E. 78 Amanatides E. 52, 54 Anastasescu M. 122 Anda G. 30 Andreeva R. 119 Angelov Ch. 104 Angelov V. 100 Arsova D. 106 Asenova I. 74 Atanasov P. A. 85, 88, 89, 90 Atanasova G. B. 86, 87 Atanasova M. 48 Aumayr F. 109 Avdeev G.V. 87

Ayrapetov A.A. 55 B Balabanova E. 72, 73 Balalykin N.I. 120 Bakalova S. 122 Bankova A. 66, 95, 104 Barton D. 73 Begrambekov L.B. 55 Beletskii A. 68 Belmonte T. 32 van den Bekerom D.C.M. 41 Beňačka Š. 84 Benčurová A. 98 Bencze A. 30 Benova E. 47, 48, 127

Berberova N. 99 Berden G. 41 Berova M. 101, 102 Berta M. 30 Biederman H. 50 Bilkova P. 29, 71 Bineva I. 106 Bischoff L. 101, 102 Blagoev A. 61 Blagoev B. 53, 83, 85, 115 Blagoev K. 62 Blagoeva B. 99 Bogdanov T. 47, 127 Bohm P. 71 Bojinov V. 113 Bongers W. A. 41 Bornoldt S. 26 Borodkov A.S. 92 Boyadjiev S. 57 Bozhinova I. 61 C Cahyna P. 29 de la Cal E. 67 Calderon-Moreno J. 123 Cartaleva S. 121 Chechkin V. 68 Chernogorova T. P. 64 Chirita V. 36 Chromik S. 83, 84, 85 Clyne T.W. 32 Costea S. 69 Cruz J. 83


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D Damyanova M. 72, 73 Dankov P. 72 Daskalova A. 91 Dechev D. 101 Dejarnac R. 29, 69, 70, 71 Dias F. 69 Dikov Ch. 125 Dikov H. 125 Dikova J. 124 Dikovska A. O. 87 Dimitrov D. 103 Dimitrov D. Z. 53 Dimitrov Zh. 114 Dimitrova M. 29, 69, 70, 71 Dimov D. 114 Dimova-Malinovska D. 112, 113 Dinescu A. 106 Dinescu G. 34 Dmitriev S. N. 104 Dobrikov G. 114 Dobruchowska E. 93 Dokládalová L. 51 Donchev V. 96 Donkov N.Y. 92, 93, 94 Dubrava T. 94 Dunai D. 30 Duta L. 122, 123 Dzharov V. 74 E Ehiasarian A. P. 37 Engeln R. 41 Evsin A.E. 55 F Facsko S. 109 Fedchenko Yu. I. 65 Fekete L. 51 Feshchenko A.A. 120 Fogarassy Zs. 122 Fukata N. 85

G Gadjov I. 103 Gajda G. 115 Gál N. 84 Ganchev M. 103 Gancheva V. 125 Gartner M. 122, 123 Gateva S. 121 Gaži Š. 84 Georgiev A. 61 Georgiev N. 113 Georgieva G. 114 Georgieva V. 57 Georgieva V.B. 92 Gerlach J. W. 22, 85, 116 Ghafoor N. 35 Ghanbaja J. 39 Gleeson M.A. 40 Goltsev A. 94 Golubev S. V. 110 Goncharov I. 94 Gordeev A.A. 55 Gozzinia S. 121 Grancharov G. 125 Graswinckel M.F. 41 Grechnikov A. 92 Grigor’eva L. 68 Grozeva M. 49, 62, 63 Gruber E. 109 Grunin A.V. 55 Guaitella O. 42 Guerra V. 24 Gunn J. P. 31 Gyergyek T. 79 H Hacek P. 29, 30 Halova E. 97 Hanus J. 50 den Harder N. 41 Harizanova A. 117, 118 Hasan E. 70 Havlicek J. 29, 69 Heller R. 109 Henrion G. 32 Hilmi I. 116

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Hirsch D. 85 Hohm U. 73 Honova J. 51 Horáková P. 51 Horwat D. 39 Hovsepian P. Eh. 37 Hristova-Vasileva T. 106 Hrkut P. 98 Hron М. 29, 71 Huran J. 120 Husinsky W. 91 I Ignatova V. 43 Ilcheva V. 112 Imrisek M. 29 Iordanova E. 49 Iordanova S. 61 Ivanov I.G. 96 Ivanov K. 127 Ivanov N. 101 Ivanov O. 62 Ivanova P. 70, 71 Ivanova T. 117, 118, 125 J Jones B.J. 105 Junek P. 70, 71 K Kalachev A.M. 55 Kalampounias A. 52 Kandinska M. 124 Karashanova D.B. 88, 90, 101 Karatodorov S. 49, 62 Kardjiev M. 74 Kaschieva S. 104 Kasilov A. 68 Kersten H. 26, 111 Khvedchyn I. 56 Kiss’ovski Zh. 78, 114 Kitova S. 124 Kleyn A.W. 40

Kobzev A.P. 120 Kolev S. 90 Koleva E. 74, 75, 98 Koleva L. 75 Koleva M. E. 89 Kolesnikov D. 94 Komm M. 29 Komsalova L. 103 Konečníková A. 98 Kornev R. A. 110 Kostadinova D. 99 Kostič I. 98 Koujuharova N. 97 Koutzarova T. 90, 118 Kovacheva D. 90 Kovačič J. 79 Kovalenko A. 51, 124 Kozulya M. 68 Kratochvílová L. 51 Krbec J. 30 Kubáč L. 51 Kudryavtsev A. 63 Kuzminova A. 50 Kylian O. 50 L Lazarova E. 125 Leclercq J. B. 53 Lemieux J. 96 Levchuk I.P. 76, 77 Lilova D. 103 López-Bruna D. 67, 71 Lovchinov K. 80, 113 Lozin A. 68 Lucchesinia A. 121 Luculescu C. 122 Lukat N. 111 Luňák S. 51 M Malcheva G. 62, 63 Maletić D. 33 Malinov P. 72 Malović G. 33. 69 Marinellia C. 121 Marinov S. 69


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Marinova P. 48 Marinova V. 99 Markovic T. 29 Marmugi L. 121 Maronchuk I.I. 112 Martin J. 32 Maslov V.I. 76, 77 Mataras D. 52, 54 Mateev E. 115 Mateev G. 99 Matejicek J. 69 Mehandzhiev V. B. 53 Michailova D. 61 Mihailescu I. N. 112, 122 Mihailescu N. 122 Mihailov V. 49, 62 Mihaiu S. 123 Milanova M. 96 Minea T. 41 Mironov Y. 68 Mitov M. 66, 95 Mladenov G. 74, 75, 98 Mozetič M. 21 Mücklich F. 39 Muhl S. 83 Murzynski D. 93 N Nakajima Y. 89 Nathala C. 91 Nazarova D. 99 Nedelchev L. 99 Nedkov I. 115 Nedyalkov N. N. 85, 88, 89, 90 Nemec P. 98 Nesheva D. 106 Nichev H. 80, 112, 113 Nicheva D. 112 Nickolov R. 86 Nikolov A.S. 88, 90 Nikov R.G. 88, 90 Nikov Ru. 85, 89, 90 Nikovski M. 78, 114 Nominé A. 32 Nominé A.V. 32 Nozdrin M.A. 120 Nurgaliev T. 83, 85, 115

O Öncel S. 34 Onishchenko I.N. 76, 77 Ormanova M. 100 Osiceanu P. 123 P Panek R. 29, 30, 69, 70, 71 Pashov A. 61 Pavlichenko R. 68 Pavlov E.L. 88 Pejova B. 106 Peneva P. 90 Pento A.V. 92 Peterka M. 29 Petkov P. 112 Petkova T. 112 Petrov I. 23 Petrov M. 80, 113 Petrov P. 100, 101 Petrova A. 117 Petrović Z. Lj. 33, 69 Pierson J.F. 39 Pirovska A. 63 Pisarčík M. 84 Popescu-Pelin G. 112 Popkirov G. 103, 125 Popov K.T. 105 Popov Tsv. K. 66, 67, 69, 70, 71 Pramatarov P. 63 Preda S. 123 Puac N. 33, 69 R Rauschenbach B. 85, 116 Raykov K. 66, 95, 104 Restrepo J. 83 Ristoscu C. 112 van Rooij G.J. 41 Rossokha I. 94

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S Sabchevski S. 72 Sadovskiy Ya.A. 55 Safonov V. 93, 94 Saifutdinov A. 63 Salgueiriño V. 99 Sandulov M. 101, 102 Sankovitch D.D. 112 van de Sanden M.C.M. 40, 41 Sasinková V. 120 Sauchyn V. 56 Schmool D. 99 Schneider V. 26 Schumacher Ph. 116 Sears V.G. 105 Selaković N. 33 Seidl J. 29 Sendova-Vassileva M. 103, 125 Shelemin A. 50 Shigin P.A. 55 Shtinkov N. 96 Sennikov P. G. 110 Simeonov S. 123 Slaveeva S. I. 64, 65 Slavov L. 115 Slikboer E.T. 42 Šmatko V. 84 Sobota A. 42 Socol G. 112 Soldera F. 39 Sojkova M. 83, 84, 85 Španková M. 84, 85 Spasic K. 69 Spasov D. 123 Spassova I. 86 Spethmann A. 26 Stan G.E. 122 Stankova N.E. 85, 90 Stefanova M. 63 Stöckel J. 29, 69, 70 71 Stoeva N. 86 Stoyanchov T. R. 85 Stoyanova D. 124 Stoyanova E. 119 Stoychev D. 119 Stoykova E. 99

Škoro N. 69 Štrbík V. 83, 84, 85 Stroescu H. 122 Sveshtarov P. K. 53 Szekeres A. 97, 122, 123 Szilágyi I. M. 57 T Takami A. 89 Tankova V. 62, 63 Taskova E. 78 Tatarova E. 78 Temelkov K. A. 64, 65 Terakawa M. 89 Thelander E. 116 Todorov D. 75 Todorov G. 78 Trottenberg T. 26 Troughton S.C. 32 Tsanev A. 119 Tsigaras G. 52 Tsvetkov S. 121 Tsvetkova T. 101, 102 Tyutyundzhiev N. 80 Tzaneva B. 95 U Ürgen M. 34 V Vala M. 51, 114 Valcheva E. 74 Valkov S. 101 Vasilev A. 124 Vasileva E. 70, 72 Veres G. 30 Vertruyen B. 118 Videkov V. 66, 95, 104 Vitanov P. 103, 125 Voitsenya V. 68 Vondráček P. 29, 71 Vrakatseli V.E. 54 Vutova K. 98


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W v. Wahl E. 111 Walkowicz J. 93 Weinzettl V. 29, 69 Weiter M. 51, 114 Wilhelm R.A. 109 Wong Y. 39 Y Yakovin S. 93, 94 Yankov G. 49 Yegorov A.M. 76 Yordanov O. 38 Yordanov Tc.A. 92 Yordanova D. 63 Yuferov V.B. 76 Z Zaharescu M. 123 Zahria T. 40 Zakharov A.M. 55 Zamanov N. 68 Zapryanov St. 61 Zavaleyev V. 93 Zhelyazkov I. 72 Zhivkov I. 114, 124 Zoethout E. 41 Zoletnik S. 30 Zykova A. 93, 94


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sixteenth international summer school on vacuum, electron and ion

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