Optical and dispersion parameters of Ge-Zn-Se glassy films for VIS and FTIR Applications

Abstract

Different ${(GeZn)}_{100-x}S{e}_x\left(9\le x\le 25at\%\right)$ chalcogenide films have been thermally evaporated onto cleaned glass substrates. The film transmission (T) and reflection (R) spectra have been measured over the wavelength spectral range (0.3–2.5 μm). The composition dependence of the optical band gap ( E _g ) has been illustrated and interpreted in the light of the Mott and Davies Model (MDM). The linear correlation between the changes in the optical band gap (ΔE _g) and in the band tail parameter ( $\mathrm{\Delta }\sqrt{B}$ ) confirmed the disorder’s decrease, which explains the observed increase in E _g values with increasing Se concentrations. The dispersion and Sellmeier parameters have been determined and well discussed. A clear blueshift was observed throughout the _observed decrease in values of λ _o and n _o and the observed shift of the absorption edge to the short wavelengths. The GZS films are transparent in the visible, near- and far-infrared, which makes these glasses suitable for VIS and infrared applications.