Abstract
Development of new chalcogenide glasses in the form of bulk as well thin-film having a great interest in the field of optoelectronic devices. Nano sized thin films of Ge10Se60Te30 (GSTS- 0), Ge8Se60Te30Sb2
(GSTS-2), Ge6Se60Te30Sb4 (GSTS-4), Ge4Se60Te30Sb6 (GSTS-6) have been deposited by the thermal evaporation process. Characteristic temperatures of bulk samples have been investigated using the DSC. The DSC
demonstrates one glass transition peak and one melting point. The XRD is used to examine the structural properties. The X-ray analysis showed that the as-deposited film has an amorphous nature whereas annealing the as-deposited films at different temperatures showed amorphous to crystalline
phase transition. In this study, we used a double beam spectrophotometer to determine optical constants for fresh deposited and thermally annealed thin films between 373 to 403 K. It has been found that thermal annealing is followed by structural effects, which in turn lead to changes in the
optical parameters. It's confirmed that the optical absorption process follows the direct allowed transition. The value of optical band gap for fresh deposited and annealed films have been evaluated using Tauc's relation from the optical transmission spectra. It has been found
that optical band gap decreases with increase of annealing temperature. The findings obtained for amorphous and crystalline materials were described in terms of the Mott and Davis model.