Optical and other physical characteristics of amorphous Ge15Te85−xCux alloys

Abstract

Composition dependencies of the optical properties of as- deposited amorphous Ge15Te85−xCux (x = 2, 3, 4, 5 and 6 at %) prepared by thermal evaporation have been studied. The optical transmission and reflection spectra are measured in the wavelength range (200–1200 nm). The optical absorption coefficient are studied for as- deposited samples. The optical absorption edge shift to higher energy range, as the copper content, x, increases in the film. Tauc's relation for the allowed direct transition is successfully describing the mechanism of the optical absorption. The refractive index, n has been determined from the transmission spectra measured at normal incidence. The absorption coefficient, α, therefore extinction coefficient, k, have been determined from the transmission spectra at the strong absorption region. The dispersion of refractive index is discussed in terms of the Single-oscillator Wimple–DiDomenico model. The optical dielectric constant is also estimated. The average heat of atomization and related parameters such as the average coordination number were also calculated from the heat of atomization and coordination number of the used elements. These obtained results were discussed in terms of chemically ordered network model and constraints theory.