A Comprehensive Study of the Optical, Structural, and Morphological Properties of Chemically Deposited ZnO Thin Films

Zinc oxide (ZnO) is a wide bandgap semiconductor with optoelectronic and photocatalytic properties, which depend on its optical, structural, and morphological characteristics. In this study, we synthesized ZnO thin films by chemical bath deposition (CBD) and then thermally annealed them at 400 °C and 600 °C to evaluate the effect of thermal treatments. We characterized their structural, optical, morphological, and chemical properties using X-ray diffraction (XRD), UV–Vis spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The optical bandgap values were 3.20 eV for the as-grown thin films, and 3.23 eV and 3.21 eV after annealing at 400 °C and 600 °C, respectively. SEM micrographs revealed a change from elongated agglomerates in the as-grown thin films to uniform flower-like structures after annealing at 600 °C. XPS analysis confirmed ZnO formation in all samples, and we detected residual precursor species only in the as-grown thin films, which were completely removed by annealing at 600 °C. These results demonstrate that the CBD synthesis of ZnO can tune its optical and morphological properties through thermal annealing, making it suitable for optoelectronic, sensing, and photocatalytic applications.