TAILORING THE STRUCTURAL AND OPTICAL PROPERTIES OF CdZnS THIN FILMS BY VACUUM ANNEALING

Effect of vacuum annealing on structural and optical properties of CdZnS thin films is reported. Nano-crystalline CdZnS films have been deposited through sublimation technique and subsequently vacuum annealed at 300 degrees C and 400 degrees C for two hours. The samples have been characterized through X-ray diffraction, Scanning Electron Microscopy, Raman Scattering, UV-Visible spectroscopy and Photoluminescence. New diffraction peaks along (002) and (103) planes have been observed after vacuum annealing the polycrystalline thin films. Sample annealed at 400 degrees C revealed that large grains were made up of uniformly distributed tinier grains. Raman spectroscopy confirmed the existence of ZnS along with CdZnS and a decrease in substitution disorder due to Zn diffusion in the crystal structure with vacuum annealing. The band gap energy increased from 2.56 eV to 2.70 eV with a decrease in CdS enriched phase. Photoluminescence peaks exhibited a blue shift and Stoke's shift energy increased from 160 meV to 230 meV as a result of the vacuum annealing process.