In-situ fabrication of CuO/ZnO heterojunctions at room temperature for a self-powered UV sensor

Abstract

This work presents a novel, low-cost, wet chemical fabrication technique to develop a self-powered photonic sensor. Thin films of zinc and copper were DC-sputtered on an ITO-coated glass slide, followed by an in-situ one-step oxidation of copper and zinc to form CuO (copper oxide) and ZnO (zinc oxide) heterojunctions at room temperature. The surface morphologies and chemical compositions characterized by a scanning electron microscope (SEM), X-ray diffraction (XRD), and an X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of heterojunctions between p-type CuO nanowires and n-type ZnO nanoparticles. The material's light absorbance was measured using ultraviolet-visible (UV–vis) spectroscopy. The fabricated device works in a photovoltaic mode; as photons strike the substrate, the built-in potential separates excitons, resulting in an electrical current without an external bias. The current-voltage characteristics of the device studied using a 365 nm centered laser radiation revealed an ideal p-n junction behavior. The sensor demonstrated stable and reproducible responsivity and photosensitivity of 0.108 A/W and 114, respectively, under a periodic UV radiation condition.