Microstructure and optical studies of electron beam evaporated ZnSe1-xTex nanocrystalline thin films

Nanocrystalline thin films of ZnSe1-xTex (0.0 <= x <= 1.0) were deposited on glass substrate using electron beam deposition technique. The structure of the prepared films was examined using X-ray diffraction technique and revealed that the deposited films have polycrystalline zinc blend structure with lattice constant, a, increasing linearly from 0.55816 to 0.59989 nm as x varies from 0 to 1. The optical studies of the nanocrystalline ZnSe1-xTex films showed that the refractive index increases and fundamental band gap E-g decreases from 2.58 to 2.21 eV as the tellurium concentration increases from 0 to 1. Furthermore, it was also found that the variation of E-g with composition shows quadratic behavior with bowing parameter equal to 0.105. In addition, the thickness and annealing effects on the structure and optical properties of the deposited films were also investigated. The refractive index dispersion and its dependence on composition were discussed in terms of single oscillator model proposed by Wemple-DiDomenico. (C) 2012 Elsevier B.V. All rights reserved.