performance analysis of poly- and nano-crystalline diamond based photocathodes 6 th international...
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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 -
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 3
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 4
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?
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 5
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).
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 6
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 7
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)
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 8
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)
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 9
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
3D AFM surface image
and distribution of heights of
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)
3D AFM surface image
and distribution of heights of
hMAX = 150 nm
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 10
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
3D AFM surface image
and distribution of heights of
hMAX = 5 nm
RRaa = 30.4 = 30.4 nmnm
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 11
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 12
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 13
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 14
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)
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 15
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 16
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)
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 17
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 18
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 19
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
RICH 2007 - Trieste - 17th October
Maria Angela Nitti (INFN – Sezione di Bari) 20
Thank You
for Your Kind Attention !!!
Maria Angela Nitti
- mariangela.nitti@ba.infn.it -
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