Influence of Sb addition on the structural and optical characteristics of thermally vacuum evaporated Se85SbxS15-x thin films

•Se85SbxS15-x(1, 3, 7 and 9 at.%) alloy film films were successfully prepared by thermal evaporation technique.•Structural characteristics of the films were investigated by XRD, TEM and SEM.•Dispersion parameters were obtained and their compositional dependence was analyzed.•Optical band gap was found to be indirect and increase with increasing Sb-content.

Films of Se85SbxS15 − x (x = 1, 3, 7 and 9 at.%) were prepared by conventional thermal evaporation under vacuum of 10− 3 Pa. The structural characteristics confirm that the prepared films are amorphous in nature. Optical properties were estimated using spectrophotometric measurements of transmittance and reflectance in a wide wavelength range (200–2500 nm). The optical constants were extracted from the interference maxima and minima using the Swanepole method. The refractive index dispersion was analyzed on the basis of the single oscillator model, expressed by Wemple–Didomenico. The oscillator energy, the dispersion energy, the high frequency dielectric constant and the lattice dielectric constant are found to be Sb content dependent. The type of electronic transition of the films was found to be indirect allowed transition with energy gaps varies with the addition of Sb content. The energy gap was found to increase while urbach energy decreases with increasing Sb content.