Dispersive optical constants of amorphous Se1−xTex films

Optical constants of amorphous Se1−xTex films have been measured for 0⩽x⩽0.45 at wavelengths from 0.35 to 2 μm using both an ellipsometer and a spectrophotometer. The results show that the optical transmission cutoff wavelength, the refractive index, and the extinction coefficient vary linearly with x (the Te content). The optical constants are dispersive. The dispersion is attributed to the optical transition of electrons from the valence band to the conduction band. All results can be consistently explained on this basis. The substitution of Te atoms for Se atoms in Se1−xTex films increases the density and enhances the tailing of the localized states into the mobility gap, thus resulting in the change of optical constants with x in Se1−xTex films.