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摘要
We have examined the effect of high-dose x-ray irradiation on electron transport in stabilized amorphous selenium (a-Se) x-ray photoconductive films (of the type used in x-ray image detectors) by measuring the electron lifetime tau(e) through interrupted-field time-of-flight experiments. X-ray induced effects have been examined through two types of experiments. In recovery experiments, the a-Se was preirradiated with and without an applied field (5 V/mu m) during irradiation with sufficient dose (typically similar to 20 Gy at 21 degrees C) to significantly reduce the electron lifetime by similar to 50%, and then the recovery of the lifetime was monitored as a function of time at three different temperatures, 10 degrees C, 21 degrees C, and 35 degrees C. The lifetime recovery kinetics was exponential with a relaxation time tau(r) that is thermally activated with an activation energy of 1.66 eV. tau(r) is a few hours at 21 degrees C and only a few minutes at 35 degrees C. In experiments examining the irradiation induced effects, the a-Se film was repeatedly exposed to x-ray radiation and the changes in the drift mobility and lifetime were monitored as a function of accumulated dose D. There was no observable change in the drift mobility. At 21 degrees C, the concentration of x-ray induced deep traps (or capture centers), N-d, increases linearly with D (N-d similar to D) whereas at 35 degrees C, the recovery process prevents a linear increase in N-d with D, and N-d saturates. In all cases, even under high dose irradiation (similar to 50 Gy), the lifetime was recoverable to its original equilibrium (pre-exposure) value within a few relaxation times.
- 出版日期2013-12-7
