On the study of the optical constants for different compositions of Sn x (GeSe)100-x thin films in terms of the electronic polarizability, electronegativity and bulk modulus

Different compositions of amorphous Sn (x) (GeSe)(100-x) (0.0 a parts per thousand currency sign x a parts per thousand currency sign 0.12 at.%) thin films were deposited onto glass substrates by the thermal evaporation technique. The optical constants (n and k) and film thicknesses of Sn (x) (GeSe)(100-x) thin films were obtained based only on their measured reflectance spectra in the wavelength range 300-2500 nm. It was found that the refractive index (n) increased while the optical energy gap (E (g)) decreased with increasing tin content. The possible optical transition in these films obeys the allowed non-direct transitions. The obtained results were discussed in terms of the electronic polarizability (alpha (e)). The dispersion parameters [the single-oscillator energy (E (0)) and the dispersion energy (E (d))] were obtained by fitting the refractive index according to Wemple and Di-Domenico model. The third-order nonlinear optical susceptibility chi ((3)) was calculated with the help of E (0) and E (d) values. The obtained values of chi ((3)) are too high, indicating that the films under study are interesting materials for nonlinear optical devices.