Malik Nadeem Ahmed University of Padova, Italy

EXTATIC Welcome Week 2017 CTU, Prague, Czech Republic

22-24th September, 2017

Optical & Structural Properties Measurements of Material(s) in EUV spectral Range

EXTATIC EMJD Detail Name: Nadeem Ahmed Malik Home Institution: UNIPD, Italy Host Institution: UCD, Ireland EXTATIC Cohort: 2016 Lead Supervisor: Prof. Piergiorgio Nicolosi Departement of Enginerring and Information LUXOR-CNR-IFN University of Padova, Italy

Co- Supervisor: Dr. Paola Zuppella CNR - Institute for photonics & nanotechnologies

Host Supervisor: Prof. Gerry O’Sullivan University College Dublin, Dublin, Ireland

• PhD Research Project

• PhD Work Breakdown

• Research Activites – Selection of material & motivation

– Literature review (materials)

– Theoretical modeling/ simulations

– Experimentation and data analysis

• Research Outcomes First Year

• Future Planed Activities

• Acknowlegments

Outline

PhD Research Project

Proposed Research Topic • Topic:

Optical and structural properties measurements of material(s)/compounds in Extreme Ultraviolet Spectral Range

• Abstract:

The aim of the thesis is to characterize the optical properties of element(s)/ compounds, not yet well known in EUV spectral band, applying different diagnostic techniques, based on reflection, absorption and polarimetric measurements, taking into account the polarization of radiation.

Suitable composite structures will be studied in order to emphasize the effect due to the coupling of different materials like stress and interface characteristics.

PhD Breakdown

PhD Breakdown

Breakdown

PHD

Research Work

Host University Home University

Course Work

EXTATIC Requirement

University Requirement

Course Work Progress

• Enrolled in the Doctorate Program for 3 years at Departement of Information Engineering, University of Padova,Italy

As a a fulfilment requirment (20 Credits) for the PhD studies in Padova Univesrity and EXTATIC I have attended following courses during the first year:

1. Foundation Module (EXTATIC+ DEI Program)

2. EUV Optics (EXTATIC + DEI Program)

3. Statistical Methods. (DEI Program)

4. Physics and operation of heterostructure-based electronic and optoelectronic devices. (DEI Program)

5. Italian Language module (EXTATIC)

Course Work Progress

Conferences/ Seminars

• Seminars

– Functional materials for astronomical instrumentation by Dr Andrea Bianco (INAF – Osservatorio Astronomico di Brera)

• International Conferences

– EXTATIC WELCOME WEEK (ICTP, Trieste, Italy)

– Graphene 2017 (March 28-30), Barcelona, Spain

(Largest European Conference on Graphene & 2D Materials)

Research Activities First Year

Research Activities • Scientific background and materials selection

• Modeling and simulation of materials optical throughputs in the EUV spectral range (IMD software).

• Implementation and validation of a table top polarimetric facility for the EUV spectral range EUV ellipsometric studies of SiO2/Si.

• EUV ellipsometric studies of graphene/SiO2/Si monolayer and trilayer. Experiments were performed, the analysis is in process.

• Proposals submission at BEAR beam line (ELETTRA synchrotron) and Bessy II beamline, Berlin for optical characterization of materials of interest in the complete EUV spectral range. Proposal has been accepted as a top ranked proposal and the beam time allotted for experiments in October 2017.

• Research article writing is in process based on the above studies.

Literature Review & Material Selection

Research Activities

• Material Selection 2D MoS2, Graphene and SiO2 has been selected as potential materials for study particularly in EUV spectral band based on the literature review.

• Motivation – To date the optical properties of 2D MoS2 & Graphene in EUV and soft X- ray

region not well known.

– There are some studies related to graphene but only in the framework defects induced by the EUV radiation.

– Knowledge of optical properties of mono/ few layer MoS2, & Graphene in the EUV region many potential applications can be suggested for different technological domains e.g.

• Space optical components

• Lithography masks, pellicles, protective layers etc.

• Enhanced optical elements for free electron lasers & fourth generation light sources.

Literature Review & Material Selection

Properties of Materials Graphene is the best known among the

2D materials with following

• Unique electrical properties, e.g. – high conductivity,

– zero band gap

– semi metallic behavior,

– massless Dirac fermions, ballistic transport

[1, 2],

• Chemically inert

• Thermal & chemical stability in harsh

environments,

• High mechanical strength

• Impermeability to ion diffusion [3, 4].

• Impermeable to gases as small as

Helium [5]

• Oxidation resistance [6].

2D MoS2 is most promising materials for

flexible, transparent electronic device

components. [7,8].

• Ultrahigh photoresponsivity ~ 6 times that

of graphene,.

• Direct bandgap (sensitive to most of the

visible light.

• Optical Bandgap is tunable by thickness

control [9].

• High mechanical stiffness (Young's modulus

of 270 ± 100 Gpa)

• Breaking stress of 22 ± 4 GPa. [10,11].

• Protective against oxidation and corrosion.

[12] .

Theoretical Modeling

Research Activities

Theoretical Modeling: MoS2 • Following is some comparison of the reflectance spectra of MoS2/SiO2/Si

and SiO2/Si at wavelength 40nm obtained by IMD simulation tool.

0 20 40 60 80 100

0.0

0.2

0.4

0.6

0.8

1.0

0 20 40 60 80 100

0.0

0.2

0.4

0.6

0.8

1.0

1

Rp

Theta (Deg)

Rp MoS2 @ 40 nm

Rp SiO2 @ 40 nm

0 20 40 60 80 100

0.0

0.2

0.4

0.6

0.8

1.0

0 20 40 60 80 100

0.0

0.2

0.4

0.6

0.8

1.0

2

Rs

Theta(Deg)

Rs MoS2 @ 40nm

Rs SiO2 @ 40nm

0 20 40 60 80 100

0.00

0.05

0.10

0.15

0.20

0 20 40 60 80 100

0.00

0.05

0.10

0.15

0.203

RpM

oS

2-R

pS

iO2

Theta (Deg)

Rp MoS2-Rp SiO2

Fig. Reflectance spectra (1) Rp of MoS2/SiO2/Si and SiO2/Si (2) Rs of MoS2/SiO2/Si and SiO2/Si (3) Difference Rp of MoS2/SiO2/Si and SiO2/Si; angle [5, 85°] @40nm.

Theoretical Modeling: MoS2 • Following is some comparison of the reflectance spectra of MoS2(mono,

bi, trilayer )/SiO2/Si and SiO2/Si at angle 70°by IMD simulation tool.

Fig. Reflectance spectra (1) Rp of MoS2 (mono,bi,trilayer)/SiO2/Si (mono, bi, trilayer MoS2)and SiO2/Si (2) Rs of MoS2/SiO2/Si and SiO2/Si (3) Difference Rp of MoS2/SiO2/Si and SiO2/Si; angle [5, 85°] @40nm.

0 5 10 15 20 25 30 35 40 45

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 5 10 15 20 25 30 35 40 45

0.0

0.1

0.2

0.3

0.4

0.5

0.62

Rs @

70

0

Wavelength (nm)

Rs MoS2 0.68@ 70deg

Rs MoS2 2.04@ 70deg

Rs MoS2 3.4@ 70deg

Rs SiO2 @ 70deg

0 5 10 15 20 25 30 35 40 45

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 5 10 15 20 25 30 35 40 45

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

1

Rp

@ 7

00

Wavelength (nm)

Rp MoS2 0.68 @ 70deg

Rp MoS2 2.04 @ 70deg

Rp MoS2 3.4 @ 70deg

Rp SiO2 @ 70deg

0 5 10 15 20 25 30 35 40 45

0.00

0.05

0.10

0.15

0.20

0.25

0 5 10 15 20 25 30 35 40 45

0.00

0.05

0.10

0.15

0.20

0.25

3

Rp

Mo

S2

3.4

-Rp

SiO

2@

70

0

Wavelength (nm)

RpMoS2 3.4-RpSiO2

Theoretical Modeling: Carbon/graphene

• Following is some comparison of the reflectance spectra of C/SiO2/Si at different wavelength 40, 30, 13.5nm obtained by IMD simulation tool.

Fig. Reflectance spectra (left) R of C/SiO2/Si at fixed wavelength (right) Difference Rp of C/SiO2/Si and SiO2/Si; angle [5, 85°] @40nm.

0 20 40 60 80 100

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 20 40 60 80 100

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Re

fle

cta

nce

Theta (Deg)

RC @ 40nm

RC @ 30nm

RC @13.5nm

0 20 40 60 80 100

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0 20 40 60 80 100

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

RC

p-R

pS

iO2

@4

0n

m

Theta (Deg)

RCp-RpSiO2 @40nm

Experimental Setup for Reflectometry & Polarimetric Measurement at IFN, Padova

Research Activities

Setup for Reflectometry and Polarimetric studies

Experimental Setup

Real view of the FUV and EUV normal incidence reflectometer at CNR-IFN Padova.

Four Reflection Polarizer

Fig. (a) Design of four reflecting mirrors polarizer (b) all mirrors consisting of

200 nm layer of Au on Si substrate (c) Overall shape of four reflection

polarizer attached to the rotation stage. (courtesy of AHMED)

Brief Theoretical Background

Theoretical Background

Light Beam can be characterized in terms of the Stokes parameters that are the components of the

Stokes vector S= (S0 S1 S2 S3). The effect of simple and complex optical elements can be described

by the Mueller matrix M(4x4) associated to the system.

M.SS'

Muller matrix of four reflection polarizer is 8 88 8

s p s p

8 88 8

s p s p

FRP

44

s p

r r r r 0 0

2 2

r r r r 0 0M

2 2

0 0 r r 0

0

44

s p

0 0 r r

rs2 and rp

2 are the electric field amplitude of the reflection of gold mirror.

Mathematical representation of rotated polarizer 8 8 88 8 8

s p s p s p

8 88 8

s p s p 2 4 4 2

r r r r r r cos2 sin 2 0

2 2 2

r r r rcos 2 cos 2 sin 2

2 2s pr r

88

s p 4 4 2

8 8 88 8 8

s p s p s p4 4 2 4 4 2

r r cos2 .sin 2 sin 2 .cos2 0

2

r r r r r rsin 2 sin 2 .cos2 - cos2 .sin2 sin 2 cos 2 0

2 2 2

0

s p

s p s p

r r

r r r r

4 4 0 0 s pr r

Theoretical Background

Then the output intensity of the beam impinging the sample and passing through the analyzer S'=R(-Ѳ)×M(FRP)×R(Ѳ)×M(WR)×S

8 2 8 28 2 8 2

0

8 2 8 28 2 8 2

1

8 88 8

2 3

cos 2

1' cos 2

4

2 cos sin 2 2 sin sin 2

s p s p s p s pR RR R

s p s p s p s pR RR R

R R R R

s p s P s p s P

r r r r r r r r S

S r r r r r r r r S

r r r r S r r r r S

Output of the light beam at the detector after reflecting from the sample and passing through the

analyzer.

Ellipsometric Parameters:

relative phase change

relative amplitude change

Experimental Results

Research Activities

Polarimetric Results: SiO2

0 50 100 150 200 250

-500

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

0 50 100 150 200 250

-500

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

Co

un

ts (

Arb

itra

ry U

nits)

Analyzer Angle (Degree)

50 Degree @121.6nm

60 Degree @121.6nm

65 Degree @121.6nm

70 Degree @121.6nm

75 Degree @121.6nm

80 Degree @121.6nm

Reflectometry Data: SiO2

0 20 40 60 80 100

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.90 20 40 60 80 100

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Re

fle

cta

nce

(A

rbitra

ry u

nits)

Incidence angle (Degrees)

RsSiO

2/Si

RpSiO

2/Si

-10 0 10 20 30 40 50 60 70 80 90 100

0.2

0.4

0.6

0.8

1.0

-10 0 10 20 30 40 50 60 70 80 90 100

0.2

0.4

0.6

0.8

1.0

Ra

tio

=r p

/rs=

(S

qrt

(R

p/R

s))

Incidence angle (Degrees)

Ratio SiO2/Si

Polarimetric Results: SiO2

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

0.0

0.2

0.4

0.6

0.8

1.0

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity (

a.u

.)

Rotation angle (Radian)

Exp Data 50

Fitted 50

Direct at 45

50 55 60 65 70 75

0

20

40

60

80

100

120

140

50 55 60 65 70 75

0

20

40

60

80

100

120

140

Ph

ase

Diff (0

)

Incidence angle [degree]

Phase Diff Matlab

Phase Diff IMD @122nm

Fig. Phase difference retrieved by using a Matlab code based

on the experimental data (black) and phase difference by IMD

simulations (red).

Fig : Polarization measurements: experimental (black) and fitted

(red) data against the incidence angle (blue) shows direct signal

acquired without the sample and by rotating the polarizer.

Experimental Data SiO2

Fig. Ratio with error bars: experimental ratio (black+), Matlab fitted ratio (green+) and IMD based modeling ratio

(blue+) against the incidence angle (50°- 80°).

Summary of polarimetric data SiO2

Incidence

angle

Ratio

(Matlab

code)

Ratio

(exp)

Ratio

(IMD)

@121.6nm

Phase

(Matlab

code)

Phase

(IMD)

50 0.46 0.45 0.51 13 14

60 0.25 0.27 0.32 28 29

65 0.16 0.18 0.23 45 48

70 0.14 0.18 0.18 91 87

75 0.24 0.27 0.24 136 134

80 0.41 0.43 0.40 147 157

Polarimetric Data: Graphene

0 50 100 150 200 250

-500

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

0 50 100 150 200 250

-500

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Co

un

ts (

Arb

itra

ry U

nits)

Analyzer Angle (Degree)

50 Degree @121.6nm

60 Degree @121.6nm

65 Degree @121.6nm

70 Degree @121.6nm

75 Degree @121.6nm

80 Degree @121.6nm

Reflectometry Data Graphene

0 10 20 30 40 50 60 70 80 90

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20 30 40 50 60 70 80 90

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Re

fle

cta

nce

Incidence Angle (Degree)

Rs

Rp

0 10 20 30 40 50 60 70 80 90

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50 60 70 80 90

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Ra

tio

= r

p/r

s

Incidence Angle (Degree)

Ratio= rp/r

s=Sqrt (R

down/R

up)

Research outcome_first year • Successful execution of planned activities

• Validation and successful Implementation of a table top polarimetric facility for EUV ellipsometric studies of SiO2/Si and Graphene/ SiO2/Si.

• Research article writing is in process based on the above studies.

• Experimental proposal for beam time at Elettra synchrotron facility is accepted as a top ranked proposal and beam time allotted for experiments in October 2017.

• Poster Presentation accepted at the PTB's 304. Seminar "VUV and EUV Metrology". October 19, 2017.

• Publications:

– 02 conference publications (SPIE)

– 01 article is submitted in an international journal

Future Planed Activity • Continue writing of manuscript(s) based on the data collected

first year.

• Experimentation for data collection at Elettra synchrotron facility

• Sample preparation/ acquisition for future possible experiments at synchrotron facilities at Berlin and Trieste.

• Data analysis and possible research publication (s)

• Remaining EXTATIC modules of courses will be taken

• Mobility will be planned

References

1. K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, M. I. Katsnelson, I. V. Grigorieva, S. V. Dubonos, and A. A. Firsov, Nature 438(7065), 197–200 (2005).

2. Y. B. Zhang, Y. W. Tan, H. L. Stormer, and P. Kim, Nature 438(7065), 201–204 (2005).

3. W.A. de Heer, C. Berger, X. Wu, P.N. First, E.H. Conrad, X. Li, T. Li, M. Sprinkle, J. Hass, M.L. Sadowski, M. Potemski, and G. Martinez, Solid State Commun. 143(1–2), 92 (2007).

4. S. Shivaraman, M. Chandrashekhar, J. Boeckl, and M. Spencer, J. Elec. Materi. 38 (6), 725 (2009).

5. M. Bruna, and S Borini, App. Phys. Lett. 94, 031901 (2009).

6. S. Chen, L. Brown, M. Levendorf, W. Cai, S.-Y. Ju, J. Edgeworth, X. Li, C.W. Magnuson, A. Velamakanni, R.D. Piner, J. Kang, J. Park, and R.S. Ruoff, ACS Nano. 5 (2), 1321 (2011).

7. Arkamita Bandyopadhyay and Swapan K Pati. Materials Research Express, Volume 2, Number 8, (2015).

8. Intek Song, Chibeom Park and Hee Cheul Choi. The Royal Society of Chemistry 2015,5, 7495–7514.

9. H. S. Lee, S.-W. Min, Y.-G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu and S. Im, Nano Lett., 2012, 12, 3695–3700.

10. A. Castellanos-Gomez, M. Poot, G. a. Steele, H. S. J. van der Zant, N. Agra ¨ıt and G. Rubio-Bollinger, Adv. Mater., 2012, 24, 772–775.

11. S. Bertolazzi, J. Brivio and A. Kis, ACS Nano, 2011, 5, 9703–9709.

12. H. Sener Sen, H. Sahin, F. M. Peeters, and E. Durgun, journal of applied physics 116, 083508 (2014).

Acknowledgment I would like to express my sincere thanks and gratitude to:

• The Education, Audiovisual and Culture Executive Agency (EACEA) Erasmus Mundus Joint Doctorate Program and EXTATIC management.

• I would like to express my deepest gratitude to Prof. Piergiorgio

Nicolosi and Dr. Paola Zuppella for their guidance, and great cooperation.

THANK YOU FOR YOUR ATTENTION