Influence of Replacing Se in Ge10se90 Glassy Alloy by 50 at. % Te on the Optical Parameters

Abstract

The effect of addition of 50 at.% Te by replacing Se in Ge10Se90 glassy alloy on the optical parameters has been studied in the present work. Thin films of Ge10Se90 and Ge10Se40Te50 the glassy alloys were prepared by thermal evaporation technique at a base pressure of ~10-6mbar. Thin films were characterized by X-ray diffraction technique to check the amorphous nature of thin films. Transmission spectra of thin films were taken in the range of 400-1500 nm. The straight forward technique proposed by Swanepoel using transmission spectrum was used to calculate the optical parameters (refractive index and extinction coefficient) of the thin films. The dispersion of refractive index is described in terms of Wemple-DiDomenico single oscillator model. The optical absorption edge is described using non-direct transition model proposed by Tauc and optical band gap ( opt ) g E is calculated by Tauc extrapolation. The optical band gap was found to decrease with 50 at.% addition of Te.