Linear and nonlinear optical studies of thermally evaporated chalcogenide a-Pb-Se-Ge thin films

Abstract

Abstract This article is dedicated to studying optical characteristics of thermally evaporated Pb10Se90-xGex (0.0≤x\u202f≤\u202f10.0\u202fat.%) thin films. These films were deposited on pre-cleaned high-quality glass substrates under a vacuum about 5\u202f×\u202f10−4\u202fPa. The amorphous nature of films was affirmed by X-ray diffractograms. Elemental analysis was done by Energy-dispersive X-ray spectroscopy. Optical properties of Pb–Se-Ge films were studied and investigated using the transmission spectra. Thickness of the films and refractive index were computed utilizing Swanepoel envelope method. Wemple-Di-Domenico model was applied to get dispersion energies and oscillator parameters. Absorption coefficient values of films were estimated and found to be of the order of 10−4cm−1. The electronic transitions of a-Pb10Se90-xGex thin films were resulted from allowed indirect transitions and the optical band gap was found to decrease from 1.623eV to 1.538eV with increasing Ge-ratio while Urbach energy was found to increase from 61\u202fmeV to 86\u202fmeV. All discussed parameters strongly depend on the Ge-concentration.