OPTICAL CHANGES INDUCED BY LASER–IRRADIATION ON THIN FILMS OF Se75S15Ag10 CHALCOGENIDE

摘要

Chalcogenide thin films of Se75S15Ag10 have been prepared by using thermal evaporation technique with thickness of 3000 .. Optical constants (absorption coefficient, optical band gap, refractive index and extinction coefficient) of as evaporated and laser irradiated thin films of Se75S15Ag10 has been studied as a function of photon energy in the wavelength region 400-900 nm. Analysis of the optical absorption data shows that the rule of in-direct transitions predominates. It has been found that the absorption coefficient and optical band gap increases with increasing time of laser-irradiation. This change in the optical band gap may be due to the increase in the grain size and the reduction in the disorder of the system. The values of refractive index and extinction coefficient decrease by increasing time of laser-irradiation. The results are interpreted in terms of the change in concentration of localized states due to the shift in Fermi level