Optimal temperature of the sol–gel solution used to fabricate high-quality ZnO thin films via the dip-coating method for highly sensitive UV photodetectors

Abstract

We used a ZnO sol–gel solution to deposit ZnO thin films at various temperatures via a dip-coating method and investigated their structural, optical, and photoresponse properties. All the deposited ZnO thin films exhibited a fibrous structure, and the average thickness of the films increased from 0.04 to 0.52 μm with decreasing temperature of the sol–gel solution. From the X-ray diffraction results, we found three distinct diffraction peaks corresponding to the (100), (002), and (101) planes of wurtzite ZnO, without any preferred orientation. With decreasing temperature of the sol–gel solution, the intensity of the diffraction peaks increased. In the photoluminescence analysis, a sharp ultraviolet and a broad orange emission were exhibited in all ZnO thin films, and the intensity of the both emissions increased with decreasing temperature of the sol–gel solution. However, the highest photocurrent and photosensitivity were achieved from a ZnO thin film deposited using the sol–gel solution at 60 °C.