The investigation of structural and optical properties of Ge30−xSe70Cdx thin films

Chalcogenide thin film glasses with compositions of Ge30−xSe70Cdx, where x=0 and 16, were prepared and studied in terms of their structures and optical properties. The short range order proposed was obtained by interpretation of the radial distribution function, deduced from the experimental data of X-ray diffraction. The interatomic distances results for the first and second neighbors (2-5 Å) indicate that the structure changes drastically after Cd additive. The optical parameters and the thickness were determined from the extremes of the interference fringes of transmission spectra at normal incidence in the wavelength range of 200-2500 nm using the envelope method. The calculated values of the refractive index were fitted using the two-term Cauchy relation. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple and DiDomenico model. The optical band gap was carried from the absorption coefficient values using Tauc's procedure and the estimated values were 2.05 and 1.86 eV for x=0 and 16, respectively.