ALD prepared silver nanowire/ZnO thin film for ultraviolet detectors

Abstract

Ultraviolet (UV) detectors have played an important role in military communication, natural disaster warning, biomedical detection and other fields. In the ultraviolet region, ZnO has the advantages of a wide band gap, high exciton binding energy and intrinsic response band, which is an excellent semiconductor material for ultraviolet detectors. However, to improve the performance of ZnO-based UV detectors, it requires the control of their oxygen vacancy defects by keeping the free carrier concentration at a low level, which can be depleted to achieve the cutoff state of the detector. Therefore, it is necessary to modify the ZnO thin film material to reduce defects and improve crystallinity. In this paper, ZnO films with optical advantages nonpolar structure, AgNW/ZnO enhanced UV detectors and silver nanowires/ZnO (AgNW/ZnO) electrodes were prepared by atomic layer deposition (ALD) and heat treatment. The XPS analysis shows that the crystallinity and oxygen vacancy of ZnO films are improved after heat treatment at 600 ℃. The surface resistance of ZnO films reaches the level of MΩ per centimetre. In the comparison of the properties of the detectors after heat treatment at 500–800 ℃, the detector obtained the best comprehensive performance after heat treatment at 600 ℃. The light responsiveness (5 V, 365 nm) can reach 120.4 A/W, with a light-to-dark current ratio of 6686 times, and a light detection value of 3.4 × 1011 Jones. It is found that the number of deposition cycles has little effect on the transmittance of AgNW/ZnO electrodes in the visible range (380–780 nm), and AgNW/ZnO electrodes for 500 times have excellent thermal stability, which the square resistance is only increased by 1.9 times when heated at 400 ℃ for 180 min.