Tailoring ZnO nanostructure for enhanced capacitive UV response

Abstract

This study explores the effect of zinc oxide (ZnO) nanostructure morphology on the capacitive response of metal–semiconductor–metal (MSM) ultraviolet photodetectors (UVPDs). Different ZnO samples bulk particles, long and short rod-shaped nanoparticles were synthesized and characterized using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and UV-Visible spectroscopy. The results revealed distinct morphological and crystallographic features, with aspect ratios of 1.87, 2.01, and 2.67 for the respective samples. Optical band gaps were calculated to be in the range of 3.18–3.214 eV. The MSM UVPDs were fabricated using interdigitated electrodes (IDEs) coated with ZnO films, and their capacitive responsivity was measured under UV illumination. Bulk ZnO demonstrated higher peak responsivity at 385 nm while nanostructured ZnO exhibited peak responsivity at 376 nm with superior linear response under varying light intensities. The 95% confidence ellipse in intensity variance data also indicates a strong, consistent linear relationship between intensity and capacitance response, with minimal variance orthogonal to the trend. Minimal variation orthogonal to the trend, makes this sensor response highly reliable and ideal for precise measuring applications. These findings highlight the importance of ZnO morphology in optimizing the performance of capacitive UV photodetectors.