OPTICAL CHARACTERIZATION OF AS2S3 AND AS2SE3 SEMICONDUCTING GLASS-FILMS OF NONUNIFORM THICKNESS FROM TRANSMISSION MEASUREMENTS

Based on the interference fringes in transmission spectra at normal in cidence of thin films of As2S3 and As2Se3 semiconducting glass composi tions deposited by thermal evaporation, a method is applied that makes it possible to obtain a parameter indicating the degree of film thick ness uniformity, and to accurately determine the refractive index subs equently used to derive the average film thickness. Thickness measurem ents have been performed with a surface profiling stylus to check the results from the transmission spectra, showing a very good agreement b etween both measurements. The dispersion of n is discussed in terms of the single-oscillator Wemple and DiDomenico model. The optical absorp tion edges are described using the non-direct transition model propose d by Tauc. The optical energy gaps were calculated using Tauc's extrap olation, resulting in values of 2.37 and 1.80 eV respectively. Finally , the optical band gap is interpreted in terms of the bond-strengths o f the chemical bonds present in the glass compositions under study.