Optical, dielectric and opto-electrical study of Se-Te-Ge glassy thin films

Addition of germanium to the Se-Te alloy causes change in the optical, dielectric and henceforth the opto-electrical and physical properties of Se-Te-Ge alloys. Se80Te15Ge5, Se80Te13Ge7 and Se80Te10Ge10 amorphous thin films have been prepared from corresponding glasses on the microscopic glass slides via vacuum resistive heating. The optical band gap of these thin films has been resolved from the transmission spectra and found to increase from 1.54 eV to 1.62 eV. Dielectric constant (epsilon) has been determined from the values of refractive index (n), extinction coefficient (k) calculated using Swanepoel approach and found to decrease with the addition of Ge content. Some theoretical parameters have also been calculated. The changes in optical parameters with composition of the thin films have been interpreted on the basis of the theoretical parameters i.e. lone-pair electrons, coordination number, glass forming ability, deviation of stoichiometry and electronegativity. The variation of the greater part of the specified parameters is due to the change in covalent characters of the films under investigation.