Optical Constants of The Thermally Evaporated a-Se70Ge30 Thin Films

Abstract

Thermal evaporation technique was used to prepare a-Ge70Se30 thin films onto glass substrates of thicknesses range (108–717 nm). Transmittance measurements in the wavelength range (400-2500nm) were used to calculate the refractive index n and the extinction coefficient k using Swanepole’s method. The calculated parameters such as optical band gap optg E , the width of the tail of localized states in the band gap e E , optical conductivity opt σ , complex dielectric constant, relaxation time τ and dissipation factor tanδ were determined. The analysis of the optical absorption data revealed that the optical band gap optg E was indirect transitions. The optical dispersion parameters o E and d E were determined according to Wemple - DiDomenico method.