Effect of thermal annealing on the structural and optical properties of amorphous Se75−xTe25Sbx thin films by thermal evaporation method

Se75−xTe25Sbx (x = 0, 3, 6, and 9) bulk glasses were obtained using conventional melt quenching technique. Thin films of these glasses were prepared by vacuum evaporation technique at a base pressure of 10−6 Torr on to well cleaned glass substrates. a-Se75−xTe25Sbx thin films were annealed at different temperatures below their crystallization temperatures for 2 h. The structure of as prepared and annealed films has been studied by X-ray diffraction. The X-ray pattern indicates that the as-prepared films are amorphous in nature but it shows some polycrystalline structure in amorphous phase after annealing. The optical band gap of as prepared and annealed films as a function of photon energy in the wavelength range 400-1100 nm has been studied. It is found that the optical band gap decreases with increasing annealing temperatures in the present glassy system.