Diamond photoconductors for ionising radiation detection

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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
Antonio De Sio
WUTA 2008
2
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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WUTA 2008
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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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WUTA 2008
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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
Antonio De Sio
WUTA 2008
High Signal
Gain
5
Summary
Diamond detectors
Dark Current
Visible blindness
Sensitivity spectra
Linearity of the response with flux
Response time
Photoconductive Gain
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WUTA 2008
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DETECTORS
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WUTA 2008
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Diamond detectors
MSM structure
Coplanar
geometry
hν
hν
Antonio De Sio
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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WUTA 2008
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Diamond Devices: Single pixel detectors
Interdigitated electrodes
Diamond layer
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WUTA 2008
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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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WUTA 2008
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DARK CURRENT
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WUTA 2008
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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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WUTA 2008
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VISIBLE BLINDNESS
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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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SENSITIVITY SPECTRA
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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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d
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RESPONSE TIME
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WUTA 2008
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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)
Antonio De Sio
WUTA 2008
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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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WUTA 2008
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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)
Antonio De Sio
WUTA 2008
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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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WUTA 2008
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PHOTOCONDUCTIVE GAIN
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WUTA 2008
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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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WUTA 2008
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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)
Antonio De Sio
WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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WUTA 2008
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X-Ray
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WUTA 2008
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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
Antonio
1000
De Sio
Time (s)
2000
WUTA 2008
3000
39
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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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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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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WUTA 2008
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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
Antonio De Sio
WUTA 2008
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