Effect of annealing process in tuning of defects in ZnO nanorods and their application in UV photodetectors

ZnO nanorod (NR) arrays were grown by a simple two-step chemical bath deposition method. The as deposited NRs were then annealed at different temperatures (300,400 and 500 degrees C) for two time durations (1 and 5 h). The NRs were studied by scanning electron microscopy, photoluminescence spectroscopy, Xray diffraction and two-point electrical test. Finally, ultraviolet (UV) detection properties of samples as an active layer in UV photodetector devices were evaluated. The structural results showed that the sample annealed at 400 degrees C had the best crystallinity. Furthermore, it was seen that the optical transparency and band gap of NRs increased with increase of the annealing temperature up to 400 degrees C and then decreased at 500 degrees C. The electrical resistance decreases with increment of the annealing temperature due to intensive desorption of oxygen molecules from the surface of ZnO NRs. The UV detection results proved a meaningful relevance of UV detection properties with the density of defects and quantity of oxygen molecules absorbed on the surface. ZnO NRs annealed at 300 degrees C for 1 h had the highest photosensitivity of 300 and photoresponsivity of 2.067 A/W which make it suitable for the practical applications. (C) 2016 Elsevier GmbH. All rights reserved.