Amorphous films of Ge34Ga2S64were 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 ℃ 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.