EFFECT OF GAMMA-IRRADIATION ON OPTICAL AND ELECTRICAL-PROPERTIES OF SE1-XTEX

The effect of gamma-irradiation on optical and electrical properties o f amorphous and polycrystalline Se1-xTex (0.211 < x < 0.802) thin film s of thickness 180 nm were investigated. The analysis of the absorptio n coefficient data revealed the existence of indirect transition both before and after irradiating. It was observed that the value of the op tical energy gap depends on the value of x, decreasing as x increases. It was found also that the optical energy gap decreases with an incre ase of gamma-doses for all compositions. The obtained results for all Se1-xTex, films have been interpreted in terms of density of states mo del of Mott and Davis. From the experiment of electrical conductivity sigma at various temperatures, it was observed that Se1-xTex. films ex hibited ln sigma versus T-1 relationships at high temperatures and ln sigma(T)(1/2) versus T-1/4 hopping conductivity behaviour at low tempe ratures. It was found that the thermal activation energies Delta E dec rease with increasing Te content and increases with decreasing gamma-d oses. X-ray diffraction patterns for the as-deposited Se1-xTex, show t hat polycrystalline films start to appear for x > 0.407. (C) 1998 Else vier Science Ltd. All rights reserved.