performance analysis of poly- and nano-crystalline diamond based photocathodes 6 th international...

Performance Analysis of Poly- and Nano-Crystalline Performance Analysis of Poly- and Nano-Crystalline Diamond based PhotocathodesDiamond based Photocathodes

6th International Workshop on Ring Imaging Cherenkov Counters

(RICH 2007)Stazione Marittima, Trieste, Italy

15 – 20 October 2007

INFN - Sezione di Bari - Via Amendola 173, 70126 Bari (Italy)

M. A. Nitti, M. Colasuonno,

E. Nappi, A. Valentini

RICH 2007 - Trieste - 17th October

Maria Angela Nitti (INFN – Sezione di Bari) 2

Other ContributorsOther Contributors

• Diamond growth: F. Bénédic - Laboratoire d’Ingénierie des Matériaux et des Hautes Pressions, UPR1311 CNRS, Universite´ Paris 13, 99 av. J. B. Clément, 93430 Villetaneuse, France –

• Raman spectroscopy: G. Cicala - Istituto di Metodologie Inorganiche e dei Plasmi (IMIP-CNR) – Sezione di Bari - Via Amendola 122/D, 70126 Bari, Italy -

• Surface hydrogenation treatment: E. Milani, G. Prestopino - Dipartimento di Ingegneria Meccanica, Università di Roma “Tor Vergata”, Via del Politecnico 1, 00133 Roma, Italy -

• Surface morphology analysis: E. Fanizza - Dipartimento di Chimica, Università di Bari, Via Orabona 4, 70124 Bari, Italy -



OutlineOutline

External Quantum Efficiency (QE) results, in the range 150-210 nm, of Poly- and Nano-Crystalline Diamond (PCD and NCD) PCs Informations on the Surface Morphology, Bulk Structure and Crystallinity of PCD and NCD films

Photoemission Model

Surface Hygrogenation Effects on the QE

Ageing due to air exposure

Concluding remarks



Wide Band GapWide Band Gap

Wide Radiation Transparency Wide Radiation Transparency

High Carriers Mobility (> 2000 cmHigh Carriers Mobility (> 2000 cm22VV-1-1ss-1-1 for e for e--))

High Thermal Conductivity High Thermal Conductivity (20 Wcm(20 Wcm-1-1KK-1-1@ @ 20°C)20°C)

High Radiation HardnessHigh Radiation Hardness

Surface activation by hydrogenSurface activation by hydrogen (NEA)(NEA)

Why DIAMOND Why DIAMOND for UV Radiation detectors?for UV Radiation detectors?



Diamond FilmsDiamond Films DEPOSITION PARAMETERSDEPOSITION PARAMETERS

Diamond film

Film Thicknes

s(m)

Input Microwave Power

(W)

Total Gas

Pressure(mbar)

Surface Deposition Temperatu

re (° C)

Gas RatioAr/H2/CH4

(%)

GNCD 2.21 600 200 990 96/3/1

PCD 2.09 1000 50 900 0/98/2

NCD 4.18 600 200 890 96/3/1

PolyPoly and nanonanocrystallinecrystalline diamond films were prepared by MWPECVDMWPECVD, at the LIMHP (Laboratoire d’Ingénierie des Materiaux et des Hautes

Pressions) - CNRS-UPR- Paris.

Substrates = square n-doped silicon

(100) of approximately 1 cm2,

ultrasonically abraded during 1h in a

diamond powder suspension (~ 40 μm

grain size).



External QEExternal QE Comparison with LiteratureComparison with Literature

@ = 150 nm QE(%) < 0.5

LiteratureLiterature

Proceedings SPIE, vol. 4139 San Diego, California (2000)

A.S. Tremsin, O.H.W. Siegmund

&Diamond & Related Materials 14 (2005) 48-53

@ = 150 nm QE(%) = 7

0,01

0,1

1

10

150 160 170 180 190 200 210

GNCDPCDNCD

(nm)

Best photoemission and th

for the

graphitic nanocrystalline diamond film



RAMAN SPECTRA RAMAN SPECTRA of the diamond film photocathodesof the diamond film photocathodes

The PCD film exhibits an intense and narrow diamond peak at 1332 cm-1, and a broad peak at 1550 cm-1 sp3 > sp2

The NCD film exhibits typical peaks at: 1140 and 1470 cm-1 of transpolyacetylene, 1350 and 1580 cm-1 of graphite D and G bands 1332 cm-1 of broad diamond peak sp3 < sp2

The GNCD film presents the typical bulk structure of a graphitic nanocrystalline sample, with peaks at 1350 and 1580 cm-1 of graphite D and G bands, and the low intensity diamond peak at 1332 cm-1 sp3 « sp2

0

5000

1 104

1.5 104

2 104

2.5 104

3 104

3.5 104

4 104

800 1000 1200 1400 1600 1800 2000

GNCD NCD PCD

Raman shift (cm -1) (N. Wada, et al., J.Non Cryst. Solids 35/36 (1980) 543)



50 100 150 200 250 3000

200

400

600

800

Height /nm

PXL

GNCD

hMAX = 150 nm

50 100 150 200 250 3000

200

400

600

800

Height /nm

PXL

PCD

hMAX = 120 nm

Significant difference in their surface texture

Surface morphology & Surface morphology & Quantum Efficiency of Quantum Efficiency of GNCD and PCD PCsGNCD and PCD PCs

The distribution of heights is

centred at a value of about

150 nm for both samples

The QE is comparable, and the GNCD PC presents a higher th with respect to the PCD one

3D AFM surface image

and distribution of heights of

RRaa = 30.3 = 30.3 nmnm

RRaa = 30.5 = 30.5 nmnm

0,01

0,1

1

10

150 160 170 180 190 200 210

GNCDPCD

(nm)



NCD

50 100 150 200 250 3000

200

400

600

800

PXL

Height /nm

hMAX = 90 nm

Surface morphology & Surface morphology & Quantum Efficiency of Quantum Efficiency of GNCD and NCD PCsGNCD and NCD PCs

Very similar morphology

50 100 150 200 250 3000

200

400

600

800

Height /nm

PXL

GNCD



RRaa = 26.4 = 26.4 nmnm The distribution of heights of the

NCD is centred at smaller value, about 90 nm, than that of the

GNCD

The QE of the NCD results

to be lower

RRaa = 30.3 = 30.3 nmnm

0,01

0,1

1

10

150 160 170 180 190 200 210

GNCDNCD

(nm)



hMAX = 150 nm



50 100 150 200 250 3000

200

400

600

800

Height /nm

PXL

GNCD

hMAX = 150 nm

SCD

@ = 150 nm

SCD QE(%) = 2.5

lower than that of

GNCD, PCD and NCD

PCs

RRaa = 1.8 = 1.8 nmnm

0,01

0,1

1

10

150 160 170 180 190 200 210

GNCD

SCD

(nm)

Surface morphology & Surface morphology & Quantum Efficiency of Quantum Efficiency of GNCD and SCD PCsGNCD and SCD PCs

Very different morphology



hMAX = 5 nm

RRaa = 30.4 = 30.4 nmnm



RICH 2004RICH 2004

(a)(a)Film deposited by

thermal evaporationthermal evaporation

(b)(b)Film deposited by

IBSIBS

Electron photoexcitement

regions

FILM

SUBSTRATO

hv hv

FILM

hvhv UV

Photons

SUBSTRATE SUBSTRATE

hv

Photoemission model of CsI PCs grown with

two different deposition techniques

two completely different morphologies

M. A. Nitti et al.

NIM A 553 (2005) 157-164



UVPhotons

Electron photoexcitement

regionsFilm Film

Substrate Substrate

Distribution of heights

(a) (b)

PHOTOEMISSION MODELPHOTOEMISSION MODELfor Diamond Photocathodesfor Diamond Photocathodes

Diamond films which present: (a) a low distribution of heights

(b) a high distribution of heights most of the electron photo-excitement region is located near to the surface, and so many more photoelectrons can escape from the film

a larger portion of the electron photo-excitement regions is far from the film surface; therefore, many photoelectrons have to travel a too long path before escaping

Lower QE

Higher QE



Dependence ofDependence of the QE on the distribution of heigths the QE on the distribution of heigths

GNCD

th = 203 nm

PCD

th = 195 nm NCD

th = 189 nm SCD

th = 189 nm

0

2

4

6

8

10

150 120 90 5h

MAX (nm)

GNCD

50 100 150 200 250 3000

200

400

600

800

Height /nm

PXL hMAX = 150 nm

PCD

50 100 150 200 250 3000

200

400

600

800

Height /nm

PXL hMAX = 120 nm

NCD

50 100 150 200 250 3000

200

400

600

800

PXL

Height /nm

hMAX = 90 nm

hMAX = 5 nm

SCD



0

500

1000

1500

2000

40 50 60 70 80 90 100 110 120

SiNCD

2(°)

0

500

1000

1500

2000

40 50 60 70 80 90 100 110 120

SiPCD

2 (°)

Crystalline structure (XRD)Crystalline structure (XRD)

0

500

1000

1500

2000

40 50 60 70 80 90 100 110 120

SiGNCD

2 (°)

(111)

(220)

(111)

(111)

(400)

0

2 105

4 105

6 105

8 105

1 106

1,2 106

1,4 106

118 118,5 119 119,5 120 120,5 121 121,5 122

SCD

2 (°)

High LOCAL crystalline quality

0

500

1000

1500

2000

40 50 60 70 80 90 100 110 120

Si

2°)

(400)

(442)



Hydrogenation effect on the QEHydrogenation effect on the QE

SURFACE effect reduction in the photoemission threshold ENERGY Eth

NEA properties

0,01

0,1

1

10

100

150 160 170 180 190 200 210

GNCD untreatedGNCD HYDROGENATED

(nm)

QE enhancement @ each

QE (%) @ 150 nm = 13



Sample stability against ageing Sample stability against ageing due to air exposuredue to air exposure

Comparison between the of:

a CsI PC

the hydrogenated GNCD PC

depositedas

airhumidinhafter

QE

QERQE 24

After 24h air exposure: RQECsI < RQE hydrogenated GNCD

the hydrogenated GNCD PC is more stablestable than the CsI one

0,35

0,4

0,45

0,5

0,55

0,6

0,65

158 162 166 170 174 178

GNCD HYDROGENATEDCsI

(nm)



I HYDROGEN-treatment: - photoemission enhancement @ each

- reduction in the photoemission threshold energy Eth (SURFACE effect)

II HYDROGEN-treatment, after 24h AIR exposure:

- complete recovery of the QE (%) and Eth at the same values of the I

HYDROGENATION

Repeated HRepeated H22 plasma treatments: plasma treatments: effects on the QE effects on the QE

0,01

0,1

1

10

100

150 160 170 180 190 200 210

GNCD HYDROGENATED - fresh -GNCD HYDROGENATED - after 24h AIR exposure -GNCD RE-HYDROGENATED

(nm)

QE (%) @ 150 nm = 18

QE (%) @ 150 nm = 3



Concluding remarks NCD PCs, that generally show a lower QE with respect to PCD ones, enhance

their photoemission if a graphitic component is present in the film Not closed dependence of QE and grain size

A possible explanation for the observed higher QE has been described

in the light of a photoemission model correlated to the distribution of heights QE of Diamond based PCs QE of CsI PCs

The hydrogenated diamond PC evidences:

- the enhancement of the photoemission with respect to the untreated

sample, and the lowering of the photoemission energy threshold

- a stability in air better than the CsI one

- the recovery of the initial QE value after air exposure, if the

H2 plasma treatment is repeated multiple times



Outlook

Work is in progress in order to:

better understand the role of the graphite and crystalline defects contribution to the photoemission

study doped diamond film PCs

implement an innovative diamond deposition

technique, and a new surface treatment



Thank You

for Your Kind Attention !!!

Maria Angela Nitti

- [email protected] -

performance analysis of poly- and nano-crystalline diamond based photocathodes 6 th international...

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