Compositional Dependence of the Optical Properties of Amorphous Semiconducting Glass Se80Ge20-x Cd x (0 aparts per thousandcurrency sign x aparts per thousandcurrency sign 12 at.%) Thin Films

Se80Ge20-x Cd (x) (0 a parts per thousand currency sign x a parts per thousand currency sign 12 at.%) compositions were prepared by a quenching technique. Thin films of the obtained compositions were deposited on dry clean glass substrates by a thermal evaporation technique. The chemical composition of the film samples have been determined by energy dispersive x-ray spectroscopy (EDX). X-ray diffraction measurements showed the amorphous nature of the studied films. The optical constants (n, k) were determined for the studied films using spectrophotometric measurements of transmittance T(lambda) in the wavelength range (350 nm to 2500 nm), and using Swanepoel's method. The values of the dispersion energy E (d), oscillator energy E (o), the lattice dielectric constant epsilon (aL) and the high-frequency dielectric constant epsilon (s) were determined. The optical band gap is estimated for all compositions from the absorption coefficient alpha. The analysis of the optical absorption data revealed the existence of allowed indirect transitions for all compositions. The effect of adding Cd content on the obtained optical parameters was also discussed.