UV sensitivity enhancement in ZnO:Cu films through simple post-annealing treatment

Influence of post-annealing temperature on structural, morphological, optical, and electrical properties of ZnO:Cu films was investigated. The films were deposited using the ultrafast spray pyrolysis technique for 10 s. Post-annealing treatment was then conducted at a temperature range of 400–600 °C under ambient pressures. Structural, morphological, electrical, and optical properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), current–voltage (I–V) curve, and UV–Vis spectroscopy, respectively. By increasing the annealing temperature, SEM images show morphology modification from rods to spherical grain due to atomic rearrangement. XRD patterns show significant improvement in crystallinity. From I–V curves, the sensitivity of UV detection is also increased. The increase of annealing temperature provokes both the dark current and photocurrent enhancement. UV–Vis spectroscopy analysis shows the decrease of bandgap by increasing the annealing temperature. Our study is essential to improve the functionality of ZnO:Cu film and realizes mass-scale fabrication with low cost.