Growth and Morphology of Zinc Oxide Thin Films: A Comparative Analysis of Solution-Based Deposition Methods

Zinc oxide (ZnO) has emerged as a promising material for applications in photocatalysis, energy devices, gas sensors, healthcare, and environmental technologies due to its unique physicochemical properties. The performance of ZnO thin films is strongly dependent on the fabrication technique, which governs morphology, surface reactivity, and functional characteristics. This comparative study highlights three solution-based deposition techniques, namely electrospinning, drop-casting, and spin-coating, for the ZnO thin film preparation, followed by hydrothermal treatment to improve crystallinity. Optimized precursor concentrations of 50 mg/mL polyvinyl alcohol and 100 mg/mL Zn(Ac)₂ were used for electrospinning, while drop-casting enabled the study of varying hydrothermal conditions. Surface morphology and topography were analyzed using scanning electron microscopy and optical profilometry. Results revealed that spin-coating at 4000 rpm produced highly uniform, thin films with flower-like nanostructures, reduced roughness, and controlled thickness. In contrast, drop-casting resulted in elongated nanorod assemblies with non-uniform distribution, while electrospinning generated disordered, fibrous morphologies with significant irregularities. Fourier-transform infrared spectroscopy confirmed ZnO growth. Overall, spin-coating demonstrated superior control over film morphology and quality, establishing it as the most effective deposition method for ZnO thin films in sensor fabrication.