Selenium-based chalcogenides are useful in telecommunication devices like infrared optics and threshold switching devices. The investigated system of Ge5Se95-xZnx (0.0 ≤ x ≤ 4 at.%) has been prepared from high purity constituent elements. Thin films from the bulk material were deposited by vacuum thermal evaporation. Optical absorbance measurements have been performed on the as-deposited thin films using transmission spectra. The allowed optical transition was found to be indirect and the corresponding band gap energy determined. The variation of optical band gap energy with the average coordination number has also been investigated based on the chemical bonding between the constituents and the rigidity behaviour of the system’s network.

Chalcogenide glasses are very important in the modern technology especially selenium-based. These glasses are sensitive to electromagnetic radiation useful in the infrared optics. The study investigated the effect of substrate temperature on the as-deposited selenium-bismuth thin films in addition to bismuth content. The films were deposited by flash evaporation method. Thickness of the films was measured on a surface profiler and confirmed through calculation based on the Swanepoel method. The spectral range of study was between 200 -3000 nm. It is found that the effect of increasing bismuth content on the as-deposited films led to increased absorption coefficient, reflectance, refractive index and extinction coefficient while transmittance and optical band gap energy decreased. On the other hand, reflectance, absorption coefficient, extinction coefficient, refractive index, real and imaginary parts of dielectric constant increased with increase in substrate temperature but transmittance and optical band gap energy decreased.