Optical properties of amorphous Ge28-xSe72Sbx thin films

Bulk glasses of formal composition Ge28−xSe72Sbx 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 Ge28−xSe72Sbx 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 Ee 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 E0 (single-oscillator energy), Ed (dispersive energy) and M−1, M−3 (moments) were discussed in terms of the single-oscillator Wemple–DiDomenico model.