Abstract
Thin amorphous films of Cu-x(Ge30Se70)(100-x) (0 < x < 12 at. %) have been prepared onto glass substrates by the well-known thermal evaporation technique. The refractive index (n) of the studied films was obtained using only the transmission spectra, according to Swanepoel's method, within a wavelength range of 0.4-2.5 mu m. Optical dispersion parameters such as the single oscillator energy (E-o) and dispersion energy (E-d) were estimated by applying the Wemple-DiDomenico model. Values of n were used via the Connell and Lewis equation to estimate the absorption coefficient (alpha), which in turn used to evaluate the values of both the extinction coefficient (k) and energy gap (E-g) of the films. It was found that E-g decreases from 2.21 to 1.86 eV with an increase of the Cu content from 0 to 12 at. %. E-g values were used to get the positions of the valence and conduction bands edges of the studied films theoretically. Urbach energy, which is correlated with the structural disorder, increases by increasing the Cu content. In addition, E-o decreases, whereas E-d increases by an increase in the Cu concentration. Using n and k, the optical dielectric constants, then the optical conductivity and the dissipation factor of the studied films have been calculated.