Effect of vacuum thermal annealing on optical properties of amorphous (Se80Te20)94Ag6 chalcogenide thin films prepared by thermal evaporation technique

Abstract

Abstract Amorphous (Se80Te20)94Ag6 thin films are prepared at room temperature by using thermal evaporation technique. The as-prepared thin films are annealed both at higher and lower temperatures than glass transition temperature Tg. X-ray diffraction of annealed film above Tg confirms the presence of different phases. The glass transition temperature of as-prepared glass is evaluated with the help of DSC measurement. Transmittance measurements are used to find the value of optical parameters and optical band gap Eg. Refractive index and extinction coefficient increases with increase in annealing temperature. The band gap show an increase for the annealing temperature less than Tg and decrease for the temperature greater than Tg. Mott and Davis Model forms the basis for the explanation of change in optical band gap.