Effect of thermal-bleaching on the structure and optical properties of thermally evaporated Ge ₃₄Ga ₂S ₆₄ film

Amorphous films of Ge ₃₄Ga ₂S ₆₄ were deposited on quartz substrates by using thermal evaporation method. The optical parameters of as-deposited and annealed films are calculated using the Swanepoel method and Tauc law from the optical transmission spectra. After the heat treatment of as-deposited films at 375°C for 2 h, the thermal-bleaching effects are observed, which are related to the reduction of clusters and fragments, as well as the density of homopolar bonds confirmed by the Raman spectra. As a result, the absorption spectra are blue shifted, the optical band gap of the studied films is increased by 0.118 eV, and the surface roughness is decreased by 0.515 nm.