INVESTIGATIONS OF HEAT TREATMENT ON STRUCTURAL AND OPTICAL PROPERTIES OF Ge8Se60Te30In2 THIN FILM FOR OPTICAL DATA STORAGE

Chalcogenide glasses of Ge8Se60Te30In2 were synthesized by melt quench process. Thin film of prepared glassy alloy was made by thermal evaporation method. To verify the glassy nature of the prepared sample differential scanning calorimetric (DSC) measurement whereas to investigate the phase transformation X-ray diffraction (XRD) measurement has been done. Annealing induced result on optical constants of prepared film has been explored using UV-Vis Spectrophotometer in the wavelength span 300 to 1100 nm. It is noticed that optical bandgap (E-g) and steepness parameter (sigma) reduces while the absorption coefficient (alpha), extinction coefficient (k) and Urbach energy (E-e) increases with the increase of annealing temperature. It is observed that prepared sample obey the allowed direct transition. The reduction in optical bandgap with annealing temperature has been explained using Mott and Davis model. Due to annealing dependence of the optical constants, the investigated material could be utilized for optical data storage.