Structural, Morphological, and Optical Properties of Chemically Deposited Cd1-xMnxS Thin Films at Varying Temperatures

Abstract

Chemically deposited Cd_1-xMn_xS thin films were synthesized by varying the deposition temperature using the cost-effective and scalable Chemical Bath Deposition (CBD) technique. This work addresses a gap in prior research by optimizing a relatively low-temperature deposition range (60–75 °C), which has been less explored for \(C{d}_{1-x}{Mn}_{x}S\) thin films. This study demonstrates that high-quality crystalline films can be achieved at lower temperatures, making the process more energy-efficient and suitable for large-area and flexible substrate applications. Various structural, optical, and electrical properties were investigated using advanced characterization techniques, including XRD, FESEM, TEM, and UV–Vis spectroscopy. XRD analysis revealed the cubic phase of the \(C{d}_{1-x}{Mn}_{x}S\) thin films, which was further confirmed by TEM analysis. The crystallinity of the film is highly influenced by the deposition temperature within the range of 60–75 °C, with 75 °C identified as the optimal temperature for achieving the best crystalline quality. The FESEM micrographs revealed that the grain size varied between 231 and 415 nm with changes in deposition temperature, exhibiting nanostructured, crack-free, and spherical grains. Additionally, a significant reduction in voids was observed with increasing deposition temperature, indicating improved film density and surface uniformity. The film thickness was determined through FESEM cross-sectional analysis. EDX analysis confirmed the presence of Cd, \(\text{Mn}\), and \(\text{S}\) ions and revealed the variations in the atomic percentages of the metallic constituents with changing deposition temperatures. The optical transmittance of the sample was observed to be approximately 80%, indicating high transparency. Notably, the optical band gap of the deposited \(C{d}_{1-x}{Mn}_{x}S\) thin films gradually decrease from 2.80 eV to 2.75 eV as the deposition temperature increases from 60 °C to 75 °C. The broader band gap makes these films more suitable for UV–visible optoelectronic applications. Overall, the study introduces an improved deposition approach that yields better crystallinity and optical performance at lower thermal budgets, highlighting the material's potential for use in window layers of photovoltaic cells, anti-reflective coatings, and optical waveguides.