The compositional dependence of the structural and optical properties of amorphous As20Se80−xTlx films

Thermal evaporation technique was used to deposit various samples of As20Se80−xTlx on a glass substrate where (5⩽x⩽35 at%). The XRD studies were carried out for thin films of As20Se80−xTlx, where the results confirm the amorphous nature for the as-deposited films. Chemical compositions of thin films analysis were done using EDS. The optical energy gap Egopt of the as-deposited films was determined from transmission and reflection spectra. The decrease of Egopt , with increasing Tl content was attributed to the effect of localized states. The optical constants n, k could be determined and were found to increase with the increasing of Tl-content. The dielectric constants (ε∞ and εL) were increasing with the increasing of Tl-content. Dispersion parameters were determined according to Wemple-DiDomenico relationship.