Influence of thermal treatment on the optical aspects for Ge20In5Se75 films

In this work, the effect of annealing temperature, above room temperature, on the optical constants, optical band gap, dielectric constants and some related optical parameters for Ge20In5Se75 films with thickness range (190-435 nm) has been investigated. The transmittance and reflectance spectrum have been measured at normal incidence of light using spectrophotometric method in the wavelength range 500-2500 nm. The films were annealed at 423, 473 and 523 K for 1 h, then cold slowly. The refractive index n and extinction coefficient k were observed to increase with increasing annealing temperature. Analysis of the absorption coefficient data reveal that the rule of non-direct transition predominates. It has been found that the optical energy gap decreases with increasing annealing temperature, while the width of the tails in the gap have an opposite behavior with annealing temperature. The graphical representation of the other optical parameters, oscillator energy, dispersion energy, the loss factor, the volume and the surface energy loss functions. The dielectric relaxation time and the optical conductivity as a function of annealing temperature are also studied and discussed.