Preparation of CdSe thin films: annealing effects on structure and optical properties
摘要
In this work, we prepared well−crystallized CdSe thin films onto glass substrates using vacuum thermal evaporation method (VTE). The CdSe thin film was deposited on the substrate for 10 min in a vacuum chamber where the pressure was maintained at 5⋅10-5 Torr. To further increase the crystallinity, the as-deposited CdSe films were next thermally annealed in the air at annealing temperatures between 200 and 400 °C. The CdSe films were then investigated for phase composition, morphology, and optical properties. X-ray diffraction (XRD) examinations demonstrated a hexagonal phase of CdSe with preferential orientation along the (002) direction. The morphology analysis showed a homogeneous morphology with an average grain of approximately 65.55–90.25 nm in size. Chemical analysis confirmed the stoichiometric presence of Cd and Se. In addition, the optical band gap, determined from Tauc’s plot, using UV-Vis spectroscopic data, was found to be in the range of 1.66–1.69 eV. An annealing temperature of 300 °C resulted in the most favorable condition with the lowest optical band gap value of 1.66 eV, indicating a narrower band gap in the annealed CdSe thin film. The high deposition rate of VTE presents a significant advantage for this technique, potentially facilitating its use in creating optoelectronics and solar cells that are highly efficient and cost-effective.