Annealing effect on the physical and antibacterial properties of vacuum thermal evaporated Cu-doped ZnO thin films

Cu-doped ZnO thin films were successfully deposited on glass substrates using vacuum thermal evaporation, employing a mixture of ZnO powder and copper grains as source materials. Following deposition, the films were annealed at temperatures of 300°C, 400°C, and 500°C to investigate the influence of thermal treatment on their structural, morphological, optical, electrical, and antibacterial properties.Comprehensive characterization was carried out using X-ray diffraction (XRD) to determine crystal structure, atomic force microscopy (AFM) for surface morphology, UV-Vis spectroscopy and photoluminescence for optical properties, a four-point probe for electrical resistivity, and antibacterial assays to evaluate biological activity. Grain size was estimated using Scherer’s formula based on XRD data.XRD analysis confirmed that all films exhibit a polycrystalline hexagonal Wurtzite structure. Optical measurements revealed that film transmittance increased with annealing temperature up to 400°C, followed by a decrease at 500°C. A gradual decrease in optical band gap energy and an increase in root mean square roughness were observed with higher annealing temperatures. Additionally, grain size was found to increase with increasing annealing temperature. Antibacterial testing demonstrated effective inhibition of Escherichia coli growth on the surface of the Cu-doped ZnO films, confirming their potential for antimicrobial applications.