Optical characterization and theoretical investigations of (Ge2S8)100-xTex chalcogenide system for the IR applications

Abstract

The present research reports the optical and theoretical studies for (Ge2S8)100-xTex (0 ≤ x ≤ 12) amorphous chalcogenide thin films. The glassy samples have been prepared from the traditional melt quenching technique. The thermal evaporation process has been involved in depositing the thin films on clean glass substrates under a vacuum of 10−5 mbar and at room temperature. The X-ray diffraction patterns affirm the amorphous nature of the samples under investigation. The absorbance spectra have been utilized to estimate the absorption parameters, optical band gap (Eg) and tailing parameter of the Ge-S-Te system. The value of Eg and the energy of the absorption edge decrease; however, band tail-width energy values increase when the Te ratio is enhanced in the binary Ge–S system. The physical parameters viz. density (ρth), compactness (δ), and molar volume (Vm) have also been evaluated for the current system. Conduction band and valence band positions have also been estimated, and a correlation between the refractive index (n) and Eg has been set up. Results indicate that Ge-S-Te system samples are appropriate for various optical applications.