INFLUENCE OF THERMAL ANNEALING ON STRUCTURAL AND OPTICAL PROPERTIES OF Se70Te15Sb15 THIN FILMS

The effect of thermal annealing on the structural and optical properties of Se70Te15 Sb-15 thin films was investigated. X-ray diffraction (XRD) patterns revealed that the as deposited films were amorphous in nature. Analyzing the XRD patterns and the morphology of the scanning electron microscopy (SEM) of the annealed films show improved crystallinity with increasing annealing temperature. Particle size and crystallinity increased but the dislocation density and strain decreased with increasing annealing temperature. The indirect optical energy gap decreased with increasing the annealing temperature. The refractive index, n, and the extinction coefficient, k(ex), increased with increasing the annealing temperature. Dispersion of refractive index was described using Wemple-Didomenico (WDD) single oscillator model. The dispersion parameters, the high frequency dielectric constant and the ratio of the free carrier concentration to its effective mass N/m* are sensitive to the annealing temperature. These results are discussed and correlated in terms of amorphous-crystalline transformation.