Confocal Sputtered ZnO Thin Films: The Role of RF Sputtering Power and Annealing in Enhancing Structural and Optoelectronic Properties

This research investigates the deposition of ZnO thin films on glass substrates at ambient temperature using radio-frequency (RF) magnetron sputtering, with RF power levels between 50 and 300 W. The films were subsequently annealed in air at 300 °C for 60 min. Characterization of the films focused on how RF power and annealing affect their microstructure, morphology, and optoelectronic properties. X-ray diffraction analysis revealed that all films crystallized in the hexagonal wurtzite phase, with increased RF power leading to stronger (002) peak intensity, indicating better c -axis growth. Annealing enhanced the crystallinity of the ZnO thin films, leading to a more uniform and well-defined crystalline structure. Field emission scanning electron microscopy images demonstrated the influence of RF power and annealing on surface features like grain size and morphology. UV–Visible spectroscopy showed that RF power influences the average transmittance and bandgap of the films, with both properties improving after annealing, which indicate enhanced optical characteristics. Photoluminescence measurements revealed that the UV-violet emission of the samples is affected by RF power. However, annealing at 300 °C enhances UV emission and suppresses green emission. Higher sputtering power deteriorates electrical performance, while annealing at 300 °C enhances it.