Structural and Optical Characterization of Chemically Deposited Polycrystalline Cadmium Selenide Thin Films

Cadmium selenide (CdSe) thin films were successfully deposited onto glass substrates using the chemical bath deposition (CBD) technique at a controlled temperature of 70 °C. The resulting films were subjected to comprehensive characterization to assess their surface morphology, crystal structure, and optical properties. X-ray diffraction (XRD) analysis confirmed the polycrystalline nature of the films, identifying a predominant cubic structure with a well-defined (111) orientation. The structural parameters, including lattice constants and crystallite size, were systematically calculated, revealing insights into the film’s crystalline quality. Energy-dispersive X-ray analysis (EDAX) confirmed a slight deviation from stoichiometry, suggesting the presence of intrinsic defects within the CdSe lattice. Optical characterization revealed that the films exhibit a direct allowed transition, as evidenced by the absorption coefficient and transmittance measurements. The optical band gap energy was determined, aligning with the expected values for CdSe thin films. The interplay between structural and optical properties is discussed in detail, highlighting the influence of crystallite size and defect states on the optical behavior. Furthermore, the films demonstrated semiconductor-like behavior, as evidenced by high-temperature electrical conductivity measurements. The observed electrical properties are attributed to grain boundary scattering effects, reinforcing the potential application of these films in optoelectronic devices.