Optical investigation of vacuum evaporated Se80−xTe20Sbx (x = 0, 6, 12) amorphous thin films

Abstract

Amorphous thin films of Se80−xTe20Sbx (x=0, 6, 12) chalcogenide glasses has been deposited onto pre-cleaned glass substrate using thermal evaporation technique under a vacuum of 10−5Torr. The absorption and transmission spectra of these thin films have been recorded using UV spectrophotometer in the spectral range 400–2500nm at room temperature. Swanepoel envelope method has been employed to obtain film thickness and optical constants such as refractive index, extinction coefficient and dielectric constant. The optical band gap of the samples has been calculated using Tauc relation. The study reveals that optical band gap decreases on increase in Sb content. This is due to decrease in average single bond energy calculated using chemical bond approach. The values of urbach energy has also been computed to support the above observation. Variation of refractive index has also been studies in terms of wavelength and energy using WDD model and values of single oscillator energy and dispersion energy has been obtained.