Optical properties of amorphous Ge 28 -xSe 72Sb x thin films

Abstract

Bulk glasses of formal composition Ge 28− x Se 72Sb x with 0≤ x≤28 were prepared by applying the quench technique. The optical transmission spectra—using a melt were measured in the range from 200 to 1200 nm for Ge 28− x Se 72Sb x films which are prepared by thermal evaporation technique. A simple, straightforward procedure suggested by Swanepoel, which is based on the use of interference fringes, has been applied to calculate the film thickness. On other hand the driving absorption coefficient ( α), consequently the band tail width E e and the optical band gap have been estimated. The real ( ε′) and imaginary parts ( ε″) of the dielectric constant have been determined and the optical band gap can also be calculated as a function of imaginary part ( ε″). The dispersion parameters such as E 0 (single-oscillator energy), E d (dispersive energy) and M −1, M −3 (moments) were discussed in terms of the single-oscillator Wemple–DiDomenico model.