Photoresponse and decay mechanism of an individual ZnO nanowire UV sensor

UV sensor based on an individual ZnO nanowire (NW) was fabricated by micro-grid template method. The photo-electric properties of the sensor were investigated under the illumination of He–Cd laser (325 nm). The current–voltage (I–V) characteristics are linear and the resistivity of the ZnO NWs is calculated to be 1.7 Ω cm in dark and 0.2 Ω cm under UV illumination. The decay process, after the illumination is off, exhibits a third-order exponential decay function, with time constants of τ1 = 0.2 s, τ2 = 8.5 s and τ3 = 86.6 s. It can be attributed to the electron–hole recombination, and the readsorption of vaporized water and oxygen molecules.