Structural and Optical Properties of Znse1−Xtex Nanocrystalline Thin Films in Terms of Optical Spectroscopic Ellipsometry

Abstract

Polycrystalline 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. The optical constants and film thicknesses of nanocrystalline ZnSe1−xTex films were obtained by fitting the spectroscopic ellipsometric data (ψ, Δ) using a three-layer model system in the wavelength range from 400 to 1100 nm. The refractive index was observed to increase with increasing Te concentration. This increase in the refractive index with increasing Te content may be attributed to the increase in the polarizability due to
the large ionic radius of Te compared to the ionic radius of Zn. The optical studies of the polycrystalline ZnSe1−xTex films showed that the refractive index increases and fundamental band gap opt g E 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 optical band gap with composition
shows quadratic behavior.

Keywords: ZnSe1−xTex thin film, nanocrystalline, Spectroscopic ellipsometry, bandgap.