Transcript Diamond photoconductors for ionising radiation detection

XUV DIAMOND
DETECTORS
Antonio De Sio
Dep. of Astronomy and Space Science
University of Firenze, Italy
XUVLab
Diamond activities

Research design and development of diamond based
photodetectors

Study and Characterization of single crystal and
polycrystalline diamond detectors in VUV spectral range

Study and characterization of polycrystalline and single
crystal diamond detectors in the X-ray
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Collaborations

University of Firenze, Italy


Laboratori Nazionali di Frascati, INFN, Italy


G. Cinque, G. Cibin, N. Tartoni
Italian CNR - GILDA BEAMLINE – ESRF


M. Marinelli, G. Verona-Rinati
Diamond Synchrotron Light Source


A. Marcelli, C. Castellano, D. Hampai
University of Roma “Tor Vergata”


A. De Sio, E. Pace, A. Giannini
F. D’Acapito, S. Mobilio
Fraunhofer Institute – Freiburg

C. Wild, E. Woerner
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Ideal XUV detector
Radiation hardness
REQUESTS
High sensitivity
Very low noise
Large area
Visible blindness
Chemical inertness
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Why diamond
Solar Blindness
Energy Gap 5.5 eV
225nm Cutoff Wavelength
High XUV sensitivity
Few Thermal Carrier
No Cooling
Low Dark Currents (< pA)
Very Low Noise
Low Power Absorption
Chemical inertness
Strong Chemical Bond
Radiation Hardness
Mechanical Robust
Low Capacitance
Low dielectric constant
Electric Properties
Fast response time
High electric charge mobility
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Gain
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Summary
Diamond detectors
Dark Current
Visible blindness
Sensitivity spectra
Linearity of the response with flux
Response time
Photoconductive Gain
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DETECTORS
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Diamond detectors
MSM structure
Coplanar
geometry
hν
hν
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Transverse
geometry
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External quantum efficiency
 Pott    E 
I f   E  WD  qn  E  WD  q   

 h   L 
I f h
E
EQE 

 G
L
Pott q
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Diamond Devices: Single pixel detectors
Interdigitated electrodes
Diamond layer
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Diamond Devices: Single pixel detectors
Electrodes
Diamond layer
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Pixel array detectors
Lift-off photolitographic technique
Al contacts (blocking)
20 m interelectrode spacing
70 m pitch
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DARK CURRENT
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Photodetectors dark current
-13
4.0x10
-13
Dark Current (A)
3.0x10
-14
1,25x10
-13
2.0x10
-13
1.0x10
-14
1,00x10
0.0
-15
7,50x10
0
2
4
6
Electric Field ( V / m )
-15
5,00x10
-15
0,00
-15
-15
4.00x10
-15
3.75x10
-15
3.50x10
-2,50x10
-15
-5,00x10
-15
-7,50x10
Current (A)
Current (A)
2,50x10
-14
-1,00x10
-14
-1,25x10
-2,5
-2,0
-1,5
-1,0
-0,5
0,0
0,5
1,0
Electric field (V / m)
1,5
2,0
2,5
-15
3.25x10
-15
3.00x10
-15
2.75x10
-15
2.50x10
-15
2.25x10
0
1
2
3
4
5
Electric Field (V / m)
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VISIBLE BLINDNESS
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Visible blindness
E. Pace et al., Diam. Rel. Mater. (2000)
External quantum efficiency
100
10
E = 2.8 V/m
1
UV / VIS > 108
0,1
0,01
1E-3
1E-4
1E-5
1E-6
1E-7
1E-8
200
400
600
800
1000
Wavelength (nm)
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UV Pulsed mode measurements
Normalized Photoresponse (a.u.)
 Responsivity
lower
than
our
detection limit at >1300 nm
 Substrate contribution at >225 nm
(Nitrogen impurities in the Ib
substrate)
 Stable and highly reproducible
detector response
 Undesirable memory effects as well
as pumping ARE NOT OBSERVED
1
10
-1
10
-2
10
-3
10
-4
10
-5
10
-6
200
400
600
800
1000
1200
Wavelength (nm)
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SENSITIVITY SPECTRA
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EUV detection capabilities
Sample: SCD 8
0,2
He-Ne
0,6
Current (pA)
30.4 nm
0,6
0,4
0,7
58.4 nm
He
25.6 nm
Current (pA)
0,8
Sample: SCD 31
0,8
0,5
0,4
0,3
0,2
0,1
0,0
20
30
40
50
Wavelength (nm)
60
0,0
20
30
40
50
60
70
80
90
Wavelength (nm)
Emission spectrum of a DC discharge He and He-Ne lamp
HeII 25.6 nm and 30.4 nm HeI as well 58.4 nm emission lines clearly detected
Good detection capability of the device even in this extreme UV spectral region
High signal to noise ratio, in spite of the pA range of the output photocurrent
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EUV electro-optical performance
SCD 8 - 30.4 nm
0.45
0.40
0.30
SCD 8 - 58.4 nm
0.25
0.20
0.8
0.15
0.7
0.10
0.6
0.05
0.00
0
10
20
30
Time (s)
40
50
60
Current (pA)
Current (pA)
0.35
0.5
0.4
0.3
0.2
0.1
0.0
0
10
20
30
40
50
60
Tim e (s)
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EQE (Electrons/Photon)
DUV electro-optical performance
0.1
0.01
1E-3
140
160
180
220
200
240
260
Wavelength (nm)
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LINEARITY
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Normalized response (a.u.)
UV Pulsed mode measurements
 215 nm illumination
 Linearity test by systematically varying
1.0
the optical diffuser to diamond detector
distance
0.8
 Detector response as a function of the
0.6
calculated incident energy
 Good linear behaviour
0.4
0.2
0.0
0.0
0.2
0.4
0.6
0.8
1.0
Normalized intensity (a.u.)
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Linearity
0
Diamond sc-HPHT
Coplanar contacts
Gold Contacts
Photocurrent (pA)
-20
-40
200 nm
210 nm
-60
-80
-100
-120
λ
EQEm
EQEc
Diff.
-140
10
8.0x10
11
1.0x10
11
1.2x10
11
1.4x10
11
1.6x10
11
1.8x10
11
2.0x10
11
2.2x10
200
0.0129
0.0135
4.5%
210
0.00863
0.00813
6%
Photon Flux (Ph/s)
I mesured I dark I ph I dark qF o
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RESPONSE TIME
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Time response and PPC
Photocurrent Transient
8
@160nm (Flux=10  /s)
-12
3,5x10
-12
3,0x10
-12
Photocurrent (A)
2,5x10
-12
2,0x10
-12
1,5x10
-12
1,0x10
-13
5,0x10
0,0
-13
-5,0x10
0
100
200
300
400
500
600
700
800
900
1000 1100 1200
Time (s)
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Time response and PPC
-12
2,0x10
Photocurrent (A)
-12
1,5x10
-12
1,0x10
-13
5,0x10
0,0
0
100
200
300
400
500
600
Time (s)
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Photocurrent (A)
Time response and PPC
3,0x10
-13
2,5x10
-13
2,0x10
-13
1,5x10
-13
1,0x10
-13
5,0x10
-14
0,0
0
100
200
300
400
500
600
Time (s)
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Time response and PPC
@160 nm
 sc-HPHT
1 V/μm
Photocurrent (A)
1E-12
1E-13
1E-14
0
200
400
600
800
1000
Time (s)
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PHOTOCONDUCTIVE GAIN
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Photoconductive Gain
Diamond sc-CVD
Coplanar contacts
EQE(electrons/photon)
Gold contacts
100
10
1
5.0 V/m
1.0 V/m
0.1
0.01
120
140
160
180
200
220
240
260
Wavelength(nm)
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Photoconductive Gain
De Sio et al. Appl. Phys. Lett. 2005
Single pixel device
Material from LIMHP-CNRS
Device built and tested in Firenze
Single crystal CVD diamond
EQE ( electrons / photon )
100
10
1
Free standing
0.1
Mechanically
0.01
Au electric contacts on both
Coplanar 1V/um
Coplanar 5 V/um
Transverse 1V/um
Transverse 2V/um
1E-3
1E-4
140
polished
160
180
200
surfaces
220
240
260
Wavelength (nm)
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DUV electro-optical performance
EQE (electons/photons)
0,1
0,01
1E-3
140
160
180
200
220
240
260
Wavelength (nm)
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Pixel array: cross talk
0.50
*
Pixel n.1
Pixel n.1
Pixel n.1
 Pixel array characterization with 5 ns
Photocurrent (a.u.)
0.25
laser pulses at 215 nm (preliminary)
0.00
0.50
Pixel n.2
*
Pixel n.2
Pixel n.2
0.25
 Three adjacent pixels of the array
 Focusing of the laser beam on the pixel
marked with *
0.00
Pixel n.3
Pixel n.3
0.50
*
Pixel n.3
0.25
0.00
0 10 20 30 40 0 10 20 30 40 0 10 20 30 40 50
t (ns)
 Good spatial resolution (negligible cross-talk) and fast response times
 Good sample homogeneity
 Very good stability and reproducibility
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Conclusion
 Single crystal and polycrystalline diamond based UV
single pixel and pixels array devices can be fabricated

Low dark current values

High XUV sensitivity was observed

Good response times

No persistent photoconductivity

No pumping effects

Negligible cross-talk in pixel arrays
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X-Ray
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X-Ray detection
X-ray detection
1.6
30 mA
1.4
25 mA
Fast response time (less than 0.2 s)
Good reproducibility
No persistent photocurrent
No memory effects
No Pumping effect
Good stability
20 mA
1.0
15 mA
0.8
0.6
10 mA
0.4
5 mA
0.2
2 mA
0.0
0
50
100
150
200
250
300
350
t (s)
1.2
30 kV , 20 mA , Vb= 20 V
1.0
Current (nA)
Current (nA)
1.2
Cu X-ray source 30kV
0.8
0.6
0.4
0.2
0.0
0
50
100
150
200
250
300
350
t (s)
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8.00E-009
14
7.00E-009
12
6.00E-009
10
8
4.00E-009
6
3.00E-009
IC (a.u.)
5.00E-009
4
2.00E-009
2
1.00E-009
50
mins
of
simultaneous
measurements with IC and diamond
detector at 10 KeV. Differences are
below 0.4% during the whole
measurement.
0
0.00E+000
-2
-1.00E-009
0
500
1000
1500
2000
2500
3000
Time (s)
0.4
Differences (%)
Diamond Current (A)
Response stability
0.2
0.0
-0.2
-0.4
0
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De Sio
Time (s)
2000
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Linearity with X ray intensity
HPHT - SRS
Loosen correlation between IC
and diamond response
Poly N doped - Stanford
1
1
0.1
0.1
1
10
IC current (A)
100
Signal Diam.Detec. (a.u.)
Diamond Current (nA)
10
0.1
0.01
1
10
100
Signal IC (a.u.)
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Linearity with X ray intensity
Ionization Chamber
Ionization Chamber
Diamond 18V Bias
Diamond 72V Bias
8 KeV
1
7.5
0
0.0
0.2
0.4
0.6
Normalized Flux (a.u.)
0.8
1.0
-log(PhCurr/(NormIRing*NFlux)) (A.U.)
Signal (a.u.)
2
7.4
7.3
Ionization Chamber
Ionization Chamber
Diamond 18V Bias
Diamond 72V Bias
7.2
7.1
7.0
6.9
6.8
6.7
6.6
-50
0
50
100
150
200
250
300
350
400
Al Foils (um)
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K edge Fe Absorption
HPHT 1b Diamond
Polycrystalline Diamond N doped
 (E)
1.2
2.6
Ionization chamber
Diamond Detector
0.6
2.4
2.2
2.0
7200
7500
Energy (eV)
7800
 (E)
1.8
0.0
1.6
1.4
1.2
1.0
Ionization Chamber
Diamond Detector
0.8
0.6
0.4
7200
7500
7800
Energy (eV)
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EXAFS Signal
Polycrystalline Diamond N doped
HPHT 1b Diamond
1.6
2.0
ion_chamber
diamond
1.8
1.6
1.4
1.2
1.4
1.0
1.2
0.8
1.0
k(k)
k(k)
0.8
0.6
Diamond
0.6
0.4
0.4
0.2
0.2
0.0
0.0
IC
-0.2
-0.2
-0.4
-0.6
-0.4
-0.8
-0.6
2
-1.0
4
6
8
10
12
14
16
18
-1
0
2
4
6
8
10
12
14
k (A )
16
-1
k(A )
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Fourier Analysis Vs Theoretical
Polycrystalline Diamond N doped
HPHT 1b Diamond
1.2
experimental
theoretical
1.5
experimental
theoretical
1.0
0.8
1.0
k(k)
Diamond
0.6
k(k)
diamond
0.4
0.5
0.2
0.0
0.0
ion chamber
IC
-0.2
-0.5
-0.4
4
6
8
10
12
14
4
6
8
-1
10
12
14
16
k (A )
-1
k(Å )
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EXAFS Results
HPHT - 1b
Poly N doped
Ion Chamber
N1
: 8.0 ± 0.0
SIG1^2 : 4.53E-03
R1
: 2.48 ± 0.01
Ion Chamber
N1
: 8.0 ± 0.0
SIG1^2 : 5.19E-03
R1
: 2.49 ± 0.01
N2
: 6.0 ± 0.0
SIG2^2 : 6.6E-03
R2
: 2.89 ± 0.01
N2
: 6.0 ± 0.0
SIG2^2 : 1.11E-2
R2
: 2.895 ± 0.01
Residual =
Residual =
1.19E-02
1.20E-02
Diamond
N1
: 8.0 ± 0.0
SIG1^2 : 4.3E-03
R1
: 2.48336 ± 0.01
Diamond
N1
: 8.0 ± 0.0
SIG1^2 : 4.53E-03
R1
: 2.48 ± 0.01
N2
: 6.0 ± 0.0
SIG2^2 : 6.5E-03
R2
: 2.89894 ± 0.01
N2
: 6.0 ± 0.0
SIG2^2 : 8.88E-03
R2
: 2.905 ± 0.01
Residual =
Residual =
1.12E-02
Good agreement
between IC and
Diamond detector
and
with
the
theoretical data
1.25E-02
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