diamond sensors laboratory 3d micro-structuring of diamond for radiation detector applications...
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Diamond Sensors Laboratory
3D micro-structuring of diamond for radiation detector applications
B.Caylar, M.Pomorski, P.BergonzoDiamond Sensors Laboratory CEA-LIST, Gif-Sur-Yvette, France
José AlvarezLaboratoire de génie électrique de Paris (LGEP), Gif-sur-Yvette, France
Alexander OhUniversity of Manchester, School of Physics and Astronomy, Manchester, United Kingdom
Thorsten WenglerCERN, Geneva, Switzerland
Diamond Sensors Laboratory
Advantages1: Higher electric field for a given applied bias voltage Shorter drift path thus drift time Lower probability of trapping
2
Context – Why using 3D electrodes?
[1] J.Morse, C.J. Kenney, E.M. Westbrook et al. / Nuclear Instruments and Methods in Physics Research Section A, 524 (2004) 236.
2DElectrodes
3DElectrodes
Ionizing particle
Diamond Sensors Laboratory
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Context – Why using 3D electrodes?
Planar 3D
0 2 4 6 80.0
3.0x10-6
6.0x10-6
9.0x10-6
1.2x10-5
1.5x10-5
Perfect cristal
= 250ns
= 2ns
Cur
rent
(A
)
Time (ns)0 2 4 6 8
0.0
3.0x10-6
6.0x10-6
9.0x10-6
1.2x10-5
1.5x10-5
Perfect Cristal
= 250ns
= 2ns
Cur
rent
(A
)Time (ns)
Analytically calculated currents generated by a MIP
Diamond Sensors Laboratory
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NIEL induces bulk defects
When flux increases :
Defects number increases Carrier lifetime reduction CCE decreases
[2] Michal Pomorski – PhD debate, Frankfurt University 07/08/2008
0 5 10 15 20 250
1
Nor
mal
ized
cou
nts
Collected charge [ke]
before irradiation after 1.2 x 1014 20MeV n.cm-2
after 1.97 x 1014 20MeV n.cm-2
Signal decrease
Context – Why using 3D electrodes?
Diamond Sensors Laboratory
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3D geometry is faster : 8ns vs 208ps. 3D geometry makes the detector more radiation hard
0 2 4 6 80.0
0.5
1.0
1.5
2.0
2.5
3.0
99.99%
Col
lect
ed c
harg
e (f
C)
Time (ns)
Perfect cristal
= 250ns
= 2ns
95%
0 2 4 6 80.0
0.5
1.0
1.5
2.0
2.5
3.0
Perfect cristal
= 250ns
= 2ns
Col
lect
ed c
harg
e (f
C)
Time (ns)
47%
99.6%
Context – Why using 3D electrodes?
Planar 3D
Diamond Sensors Laboratory
• Burried electrodes Laser setup & Fabrication Structural characterization Electrical characterization
• pc-CVD Detector (e6 detector grade) Electrical characterization Characterization under alpha particles
• sc-CVD Detector (e6 electronic grade) Optical characterization Electrical characterization Transient current measurements
• Conclusion
6
Outline
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Burried electrodes – Laser setup
Tunable parameters Scan velocity 1-1000 µm/s Laser power 0-160µJ/pulse Repetition rate 1-30 Hz
Sample holder
Nitrogen laser λ = 337nm
τ = 3ns
XYZMotorized stage
Webcam
20x Lens
Diamond Sensors Laboratory
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Burried electrodes – Fabrication
997000 997500 998000 998500 9990000.00020
0.00021
0.00022
0.00023
0.00024
0.00025
0.00026
Am
plitu
de (
V)
Time (ms)
XYZMotorized stage
Photoluminescence during laser processing
Translation
Graphitization
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Clean surface (Where graphitization starts)
Cracked Surface (Where graphitization ends)
Tilted sample
150 µm
Optical grade sc-CVD sample
Structural characterization – Optical microscopy
10µm diameter
20-100 µm diameter
700µm depth
Diamond Sensors Laboratory
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Structural characterization – 2D Raman mapping
2D Raman depth mapping obtained by integrating diamond peak
No micro-channel Micro-channel with cracks
1000 CCD cts
0 CCD cts
1000 CCD cts
0 CCD cts10µm 10µm
Depth
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Structural characterization – SEM imaging
Channel’s clean side after laser processing
Channel’s clean side after H2 plasma
H2
Plasma
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Electrical characterization – I(V) measurements
Graphite’s channel resitivity
[3] T.Ohana, T.Nakamura, A.Goto et al. / Diamond and Related Materials, 12 (2003) 2011
ρ(average) = 5.7x10-1 Ω.cm
R(500µm) ~ 2kΩ
-2 0 2 4 6 8 10-1
0
1
2
3
4
5
6
Voltage (V)
Cur
rent
(m
A)
Match with nanocrystalline graphite given in literature3
A
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PC-CVD DETECTORELECTRICAL CHARACTERIZATION
E6 detector grade10 x 10 x 0.7 mm3
Sample courtesy Alexander Oh
Diamond Sensors Laboratory
0 200 400 6001E-14
1E-13
1E-12
1E-11
Cu
rre
nt (
A)
Voltage (V)
17
Electrical characterization – Device leakage current
0 200 400 6001E-14
1E-13
1E-12
1E-11
Planar 3D
Cur
rent
(A
)
Voltage (V)
A
Comparison between planar and 3D geometry
Planar 3D
Diamond Sensors Laboratory
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α
Al front contact
Al backcontact
Am-241 Source5.486MeV
R
Vbias = ±500V
Characterization under alpha particles – Experimental setup
FCSA
Fast Charge Sensitive Amplifier M.Ciobanu, GSI, Germany
Signal
Scope
Collimator
Diamond Sensors Laboratory
0 200 400 600 800 10000
20
40
60
80
100
Single hit Trend
Hit number
CC
E (%
)
0 200 400 600 800 10000
10
20
30
40
50
60
70
80
90
100
Single hit Trend
CC
E (%
)
Hit number
20
Characterization under alpha particles - Results
Polarization study – Holes drift (pc-CVD sample)
Planar 3D
Diamond Sensors Laboratory
0 500 1000 1500 20000
10
20
30
40
50
60
70
80
90
100
Single hit Trend
CC
E (%
)
Hit number0 500 1000 1500 2000
0
10
20
30
40
50
60
70
80
90
100
Single hit Trend
CC
E (%
)
Hit number
21
Characterization under alpha particles - Results
Polarization study – Electrons drift (pc-CVD sample)
Planar 3D
Diamond Sensors Laboratory
0 20 40 60 80 1001
10
100
Cou
nts
CCE (%)
Planar 3D
0 20 40 60 80 1001
10
100
Cou
nts
CCE (%)
Planar 3D
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Characterization under alpha particles - Results
Holes drift (pc-CVD sample)
αα
Amplitude has been normalized with the signal of a sc-CVD « e6 electronic grade » diamond
Diamond Sensors Laboratory
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Characterization under alpha particles - Results
Electrons drift (pc-CVD sample)
0 20 40 60 80 1001
10
100
Cou
nts
CEE (%)
Planar 3D
0 20 40 60 80 1001
10
100
Cou
nts
CCE (%)
Planar 3D
αα
Amplitude has been normalized with the signal of a sc-CVD « e6 electronic grade » diamond
Diamond Sensors Laboratory
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Characterization under alpha particles - Analysis
α
α
Low CCE
High CCE
Electric field simulation 3D Geometry but pseudo–3D detector
700µm
200µm
HV +500V
V/µm5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
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SC-CVD DETECTOR
E6 electronic grade - <100> oriented3 x 3 x 0.3 mm3
Sample courtesy Eleni Berdermann
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Bulk strain mapping after graphitization
Micro structured sc-CVD diamond observed with crossed polarizers
Test areas
Detector area
Detector’s optical characterization – Optical microscopy
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Detector’s optical characterization – Optical microscopy
Detector after metallization
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Electrical characterization – Device leakage current
sc-CVD sample after plasma O2 etching
HV on cracked surface HV on clean surface
-200 -100 0 100 2001E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4 Increasing Voltage Decreasing Voltage
Cur
rent
(A
)Voltage (V)
-200 -100 0 100 2001E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4 Increasing Voltage Decreasing Voltage
Cur
rent
(A
)
Voltage (V)
Diamond Sensors Laboratory
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2D Zone
HV +100V
ELECTRICAL CHARACTERIZATION – SETUP AND METHODS
2D Zone
Signal
ScopeAmpli
Transient current measurements
300µm
Ultra-Fast 40 dB, 2 GHz Broadband Amplifier
Diamond Sensors Laboratory
Signal 3D~500mV
Electrons drift
Mixed e/h drift
Signal 2D~100mV
Signal 2D~80mV
Holes drift
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TRANSIENT CURRENT MEASUREMENTS - RESULTS
Without collimator
Alphas’ injection on cracked side Alphas’ injection on clean side
1 ns
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TRANSIENT CURRENT MEASUREMENTS - RESULTS
With collimator
1 nsMixed e/h drift
Alphas’ injection on cracked side
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V/µm
35
TRANSIENT CURRENT MEASUREMENTS - ANALYSIS
Electric field simulation
3
2.5
2
1.5
1
0.5
0
300µm
+100 Vα
α
Planar+3D signal
Planar signal only
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TRANSIENT CURRENT MEASUREMENTS - RESULTS
Experimental results
-2 0 2 4 6 8 100.0
0.1
0.2
0.3
0.4
0.5
0.6
Planar 3D
Sig
nal a
mpl
itude
(V
)
Time (ns) Selection of relevant events
Amplitude ratio = 6
Diamond Sensors Laboratory
-2 0 2 4 6 8 100,0
5,0x10-5
1,0x10-4
1,5x10-4
2,0x10-4
2,5x10-4
Ana
lytic
ally
cal
ulat
ed s
igna
ls (
A)
Time (ns)
Planar 3D
Amplitude ratio = 23.8
2GHz low pass filter
37
TRANSIENT CURRENT MEASUREMENTS - RESULTS
Analytically calculated signals
-2 0 2 4 6 8 100,0
5,0x10-5
1,0x10-4
1,5x10-4
2,0x10-4
2,5x10-4
An
aly
tica
lly c
alu
late
d s
ign
als
(A
)
Time (ns)
Planar 3D
Theoritical response
Amplitude ratio = 22
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Amplitude’s ratio = 6.2
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TRANSIENT CURRENT MEASUREMENTS - RESULTS
Analytically calculated signals
350 MHz low pass filter
Ampli + device bandwith ~350MHz
Rdevice ~ 520Ω
12 channels connected
Rchannel ~ 6 kΩ
-2 0 2 4 6 8 100,0
5,0x10-5
1,0x10-4
1,5x10-4
2,0x10-4
2,5x10-4
Ana
lytic
ally
cal
ulat
ed s
igna
ls (
A)
Time (ns)
Planar 3D
Diamond Sensors Laboratory
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Conclusion
• Conductive graphitic structures has been achieved on both pc- and sc-CVD sample
• These structures are suitable for detectors applications
• Two dectetors using 3D-geometry electrodes has been produced
• A real improvement between planar and 3D geometry has ben observed Higher signal Faster response « Polarization effect » decrease on pc-CVD detector
But real 3D detector hasn’t been achieved yet…