CVD Diamond Sensors for the
Very Forward Calorimeter of a
Linear Collider Detector
K. Afanaciev,
E. Kouznetsova,
W. Lange,
W. Lohmann
Diamond samples
• Fraunhofer Institute (Freiburg) :
– CVD diamond 12 x 12 mm
– 300 and 200 um thickness
– Different surface treatment :
•
•
•
•
#1 – substrate side polished; 300 um
#2 – substrate removed; 200 um
#3 – growth side polished; 300 um
#4 – both sides polished; 300 um
– Metallization:
•
•
10 nm Ti + 400 nm Au
Area 10 X 10 mm
I(V) dependence – setup
HV
Diamond
Extremely low currents
=>
N2 atmosphere
EM shielding
Keithley 487
Measurements were done with
Keithly 487 picoammeter
•
N2
Usual I(V) curve
Non-ohmic curve

Average resistance
~(1013-1014) Ohm
(ohmic behavior)

3 samples from
different groups
have “non-ohmic”
behavior and lower
resistance
(~1011 Ohm)
Charge Collection Distance (CCD)
Qmeas. = Qcreated x ccd / L
Qcreated(mm) = 36 e-h pairs
Sr90
diam.
The samples haven’t been irradiated
Scint.
PA
before these measurements
PM1
discr
All data was taken 2 minutes after bias
PM2
discr
voltage applied
delay
&
Gate
ADC
CCD measurements results
CCD, mu
Sample#
R(average), Ohm
11
4.60E+13
35
12
3.20E+14
35
43
27
13
8.88E+11
25
33
21
21
5.92E+14
24
22
7.39E+14
9
11
9
10 (700V)
23
3.93E+14
9
12
10
13
31
1.04E+11
28
32
5.12E+13
50
57
50
33
4.63E+13
49
54
52
41
5.12E+11
45 (400 V)
48
42
4.35E+14
43
5.24E+13
54
60
(+500 V)
(+800 V)
(-500 V)
(-800 V)
37
30
17
33 (400V)
58
65
CCD – irradiation studies
 The samples were irradiated with Sr-source with estimated doserate of about 0.45 Gray per hour
 The total absorbed dose for all the samples was at least 5 Gy.
 Bias field was set to 1 V/mm
 Irradiation was homogeneous over the sample area
 Parameters monitored during the irradiation:
- Sr-spectrum peak position
- width of the peak (->noise)
- current in HV-circuit
- test pulse from a generator (-> electronics stability)
CCD – irradiation studies – results
Group #2 (substrate side removed).
HV = 200V
Group #3 (growth side polished).
HV = 300V
CCD – irradiation studies – results
Group #1 (substrate side polished). HV
= 300V
Group #2 (substrate side removed).
HV = 200V
CCD – irradiation studies – results
Group #3 (growth side polished).
= 300V
HV
Group #4 (both sides polished).
HV = 300V
Photoluminescence analysis
-> no nitrogen, no silicon
HeCd Laser
FAP 2_1
LO Phonon
N (575)
N (637)
Si (770)
FAP 4_2
Reference spectra
Raman spectroscopy
Resolution ~ 1 cm-1
Result = S(diam)/S(graphite)*1000
Raman spectroscopy
results
FAP 2_1
FAP 4_1
R_ave
Ccd_Down
500V
Raman
FWHM
Halbw.
Breite
PL
Si.Signal
‘1_1
‘1_2
‘1_3
4.60E13
3.2E14
8.88E11
35
35
25
‘2_1
‘2_2
‘2_3
5.92E14
7.39E14
3.93E14
24
9
9
117.7
4.9568
No
102.0
5.4254
No
‘3_1
‘3_2
‘3_3
1.04E11
5.12E13
4.63E13
28
50
49
329.3
182.4
265.3
4.4672
5.4132
4.4851
No
Removed substrate
 Group#3 – removed substrate (300 mm -> 240 mm)
Results and further studies
 Group#2 in general can work as a detector
 Raman spectroscopy + photoluminescence analysis
-> no nitrogen, no silicon
 Next steps:
- Influence of the substrate side on CCD and stability
- Homogeneity and linearity required for the application
-Test beam (May 2004)