Effect of Sn addition on the optical gap and far-infrared reflectivity spectra of amorphous Sb–Se films

This paper reports the spectroscopic studies on the thermally evaporated SnxSb20Se80 − x (2 ≤ x ≤ 8) films. Optical gap and band tailing parameter decreases except for x = 8, where it increases. The red shift in peak reflectivity spectrum in the interband transition region (200–800 nm) has been observed. The position and shape of the reflectivity bands (80–378 cm− 1) indicate the change in the local structure of the films. The Kramer–Kronig transformations have been used to evaluate the dielectric constants from the far-infrared reflectivity spectrum. Splitting of the longitudinal optic and transverse optic mode characterizes the partial ionic character for Sn–Sb–Se system. The relationship between the optical properties and structure has been revealed.