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 nm Au Area 10 X 10 mm

Average resistance ~( ) Ohm (ohmic behavior) 3 samples from different groups have “non-ohmic” behavior and lower resistance (~10 11 Ohm) I(V) dependence – setup Extremely low currents =>N 2 atmosphere EM shielding Measurements were done with Keithly 487 picoammeter Usual I(V) curve Diamond Keithley 487 HV N2N2 Non-ohmic curve

Charge Collection Distance (CCD) Q meas. = Q created x ccd / L Q created(  m) = 36 e-h pairs The samples haven’t been irradiated before these measurements All data was taken 2 minutes after bias voltage applied & Gate PA discr delay ADC Sr 90 PM1 PM2 diam. Scint.

CCD measurements results Sample#R(average), Ohm CCD,  u (+500 V)(+800 V)(-500 V)(-800 V) E E E E E (700V) E E (400V) E E E+1145 (400 V) E E

CCD – irradiation studies The samples were irradiated with Sr-source with estimated dose- rate 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/  m 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). HV = 300V Group #4 (both sides polished). HV = 300V

Photoluminescence analysis -> no nitrogen, no silicon Reference spectra N (575) N (637) LO Phonon Si (770) FAP 2_1 FAP 4_2 HeCd Laser

Raman spectroscopy Resolution ~ 1 cm -1 Result = S(diam)/S(graphite)*1000 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_14.60E1335 ‘1_23.2E1435 ‘1_38.88E1125 ‘2_15.92E No ‘2_27.39E149 ‘2_33.93E No ‘3_11.04E ‘3_25.12E No ‘3_34.63E ‘4_15.12E1145 (400V) Small ‘4_24.35E Small ‘4_35.24E No

Removed substrate Group#3 – removed substrate (300  m -> 240  m)

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)