Study of radiation damage in silicon detectors for high ... - F9

82 5. Dose Rate DependenceSample V 0 FD [V] T eq [n/cm 2 s] eq [n/cm 2 ] bias [V]SA1 12 -10 C + 2:2 10 8 1:3 10 14 0SA2 12 -10 C + 2:2 10 8 1:3 10 14 150 K3 6 5 C 1:9 10 9 1: 10 14 200K1 32 5 C 3:7 10 11 1: 10 14 200K0 32 5 C 1:6 10 12 1: 10 14 200P0A 8 -5 C + 5 10 15 1:1 10 14 0 P0B 8 -5 C + 5 10 15 1:1 10 14 200 Table 5.1: List of diodes used in the study of dose rate inuence. Full depletion voltage beforeirradiation, irradiation/storage temperature, irradiation ux and uence normalised to 1 MeVneutrons and bias voltage are given for each sample. Thickness of samples was 3005 m.+ Sample was heated to 20 C several times for a few hour periods to repair brokenbias/measurement lines. Biasing of SA2 was lost several times during the rst 6 months due to lost contact. Whenheating to 60 C started, 200 V bias was used. Sample P0A was biased to 350 V for about rst 30 min, then the contact was lost. Sample P0B was not biased for the rst few days.were kept at -10 C and -5 C, respectively, as indicated in table 5.1 37 .Development ofN eff and reverse current of samples was compared to observe possibledierences due to a dose rate eect. Results of the study are presented in the followingsections.5.2 Results on NeffTime development ofN eff for samples listed in table 5.1 after start of heating to 60 Cisshown in gure 5.1. The second order ansatz 4.7 was used in the t. The second orderparametrisation was chosen because it describes the late stage of reverse annealing betterthan the rst order one. The uence dependence of the time constant, that is the maindierence between the two models, was not important in this case, because all samples,used for the study of the ux eect, were irradiated to similar uences (table 5.1). Resultsof the ts are given in table 5.2 and compared in gures 5.2 to 5.4.Neither plots of N eff time development during reverse annealing nor t resultsshow any systematic variations that could be correlated with ux. Discrepancies betweendierent samples can be attributed to dierent biasing conditions (see chapter 6) and37In this time samples were not yet fully annealed and thus storage had negligible inuence on studyof reverse annealing.