Determination of Optical Constants and Optical Band Gap in Ge40te60-XSBX Thin Films

Abstract

The optical transmission spectra of thin films of Ge 40 Te 60-x Sb x (x = 0, 2, 4, 6 and 10), prepared by vacuum evaporation technique from their corresponding bulk samples, are recorded over the spectral region of 500-2700 nm. A simple straight forward method proposed by Swanepoel has been applied to determine various optical parameters like refractive index (n), extinction coefficient (k), absorption coefficient (α), real and imaginary dielectric constants (ε' & ε") in the measured range of wavelength. The optical band gap (E g ) has also been calculated by Tauc's relation. It has been found that the E g and n decreases with Sb concentration in Ge 40 Te 60-x Sb x system.