Determination of the complex refractive inner of thermally evaporated thinfilms of binary chalcogenide glasses by reflectance measurements

The optical constants of thermally evaporated binary chalcogenide glass thi n films of chemical compositions As25S75 and Ge33Se67 were obtained in the 400-2200 nm spectral region using a method proposed by Minkov based on the maxima and minima envelopes of the reflection spectrum. The real and imagin ary parts of the complex refractive inner, n and k respectively and the fil m thickness, d, were derived from the experimental spectra and the results were cross checked by using a surface profiling stylus to measure the film thickness. Dispersion of n is discussed in terms of the single oscillator W emple-DiDomenico model and optical band gaps are determined front absorptio n coefficients using Tauc's procedure.