CONDUCTIVITY EFFECTS IN HYDROGENATED AMORPHOUS-SILICON INDUCED BY GAMMA-RAY IRRADIATION

Hydrogenated amorphous silicon films 0.45 and 1.12 mu m thick, grown b y RF glow discharge plasma PECVD on Coming-7059 glass, were irradiated by a Co-60 source (activity 2.8 x 10(15) Bq) in the dose range 10-450 kGy at different dose rates. The dark current of the samples, under 1 00 V applied voltage, was measured before, during and af:er gamma irra diation. When the irradiation starts, the dark current increases up to a level linearly dependent on the dose rate. When the irradiation is switched off, the dark current returns close to the initial value in a few days. Such behaviour suggests a possible application of hydrogena ted amorphous silicon films in dosimetry and as gamma ray sensors. Mor eover, the film optical constants were computed from the transmittance spectra measured in the range 500-2500 nm, before and after irradiati on. After irradiation, the film optical absorption is slightly increas ed and the energy gap is substantially unchanged.