Abstract
Bulk glasses of the Se75S23Ag2 and Se75S21Ag4 alloys were prepared by melt quenching technique. Thin films were prepared onto glass substrates by using thermal evaporation technique under a vacuum of 10(-6) Torr. Thin films with thickness 3000 A(0) were thermally annealed for 2 hours at a temperature below their crystallization temperatures. The crystallization temperatures were measured using non-isothermal DSC measurements. Optical band gap and optical constants of thermally annealed films of amorphous Se75S23Ag2 and Se75S21Ag4 alloys have been studied as a function of photon energy in the wave length range region 400-1000 nm. The effect of heat treatment on the optical properties was investigated. The absorption coefficient, optical band gap and extinction coefficient increases with increasing annealing temperatures. The results are interpreted in terms of concentration of localized states.