Effect of tin addition on the optical parameters of thermally evaporated As–Se–Ge thin films

The aim of this paper is to study the effect of tin (Sn) addition on the optical parameters of (As2Se3)90Ge10 thin films. Thermally evaporated thin films, deposited on the glass substrate, were analyzed for optical parameters viz. optical band gap (Egopt), absorption coefficient (α), and refractive index (n) using transmission spectrum in the spectral range 400–1500 nm. Refractive index has been found to increase with the addition of Sn. Dispersion of refractive index has been studied in terms of Wemple–DiDomenico model. The value of static refractive index has been found to increase with the addition of Sn. Optical band gap has been estimated using Tauc's extrapolation and found to decrease with Sn addition. The change in optical band gap and refractive index Sn addition has been explained on the basis of density of states and increased disorder in the structure respectively.