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

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ABSTRACT

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.

Significance of the study:

This study highlights the successful fabrication of non-stoichiometric CdSe thin films using the cost-effective Chemical Bath Deposition (CBD) technique. The detailed structural and optical characterization provides valuable insights into the material’s potential for optoelectronic applications, such as photodetectors and solar cells. The findings underscore the impact of deposition parameters on film quality, offering a foundation for further exploration and optimization of CdSe-based materials in advanced technological devices.

Summary of the study:

Cadmium selenide (CdSe) thin films were synthesized using the CBD technique and characterized for their structural and optical properties. XRD confirmed the polycrystalline nature with a cubic structure and (101) orientation. The average crystallite size was 21.53 nm, and the films exhibited a direct band gap of 1.72 eV. Optical and electrical analyses revealed semiconductor-like behavior, making these films promising candidates for optoelectronic applications. The study demonstrates the effectiveness of CBD in producing high-quality CdSe thin films.