Optical reflection and transmission spectra, at normal incidence, of
amorphous Ge15 Se85-x Agx (x = 0, 10, 20) chalcogenide glass thin films, have
been obtained in the range 400-2400 nm. Investigated films have been
deposited by thermal evaporation. The optical constants of the films were
determined using the method proposed by Swanepoel. The method allows
determination of both the real (n) and imaginary (k) parts of the complex
refractive index, and the film thickness (d). The optical energy gap has been
estimated from the absorption coefficient values using Tauc's procedure. It is
found that, the films exhibit indirect gap, which decreases with increasing Ag
content. The dispersion of (n) is discussed in terms of the single–oscillator
Wemple- DiDomenico model.