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

摘要

Different compositions of amorphous Sn_x (GeSe)_(100-x) (0.0 ≤ x ≤ 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 (α_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 x~((3)) was calculated with the help of E_0 and E_d values. The obtained values of x~((3)) are too high, indicating that the films under study are interesting materials for nonlinear optical devices.