Thermal Annealing Effect on the Single Oscillator Energy and Dispersion Energy of Epitaxial Growth Bilyers of ZnS/ZnSe thin Films

Abstract

ZnS/ZnSe bilyers were preparing by stacking layers deposited on unheated glass substrates by thermal evaporation technique. We have studied the effect of thermal annealing of chalcogenide ZnS/ZnSe thin films on the dispersion parameters of refractive index. The refractive index, spectral dispersion of investigated was determined by Murmann’s exact equation and analyzed. To calculate and discuss the dispersion parameters in the band gap region three different approaches were used (Cauchy, Sellmeier and Wemple–DiDomenico single-oscillator model). The obtained results showed that, the refractive index increased with increasing the annealing temperature and the dielectric properties have weak dependencies of annealing temperature. The average values of oscillator energy, Eo and dispersion energy, Ed, were found to be 3.91 and 19.95eV. Also, the average values of the single resonant frequency ?o was estimated 7.89×1015Hz . Furthermore, the optical parameters such as wavelength of single oscillator ?o, plasma frequency ?p, and dielectric constant ? have been evaluated. Also, a value of carrier concentration based on Drude’s theory was obtained in 1.75x1017cm-3 for the as-deposited film and slight changes with annealing temperatures.