Structural characterization and optical properties of thermally evaporated AgSb0.75In0.25Se2 thin films

Polycrystalline AgSb0.75In0.25Se2 ingot material was prepared by direct fusion of the mixtures of their constituent elements in vacuum-sealed silica tube. The structural characterization of the prepared ingot material was investigated using X-ray diffraction technique. Thin films of the reveiously prepared bulk material were deposited at room temperature using conventional thermal evaporation technique. The structural characterization of the deposited films performed using X-ray diffraction and transmission electron microscope, showed that the as-deposited film has an amorphous phase, whereas those annealed at temperatures Ta≥453K are crystalline. The chemical composition of the deposited films was examined using energy dispersive X-ray analysis. The optical properties of the amorphous and crystalline films have been determined from the transmission spectra using envelope method. The refractive index is adequately described in terms of the single-effective-oscillator model proposed by Wemple-DiDomenico. The optical band gap of the amorphous and crystalline films has been determined from the analysis of the optical absorption coefficient.