Improving Performance of ZnO Nanorods Photodetectors with the Use of Au Nanoparticles

In this research, we try to improve the performance of ultraviolet (UV) photodetector based on ZnO nanorods through decoration with Au nanoparticles. One-dimensional ZnO nanorods were grown on the quartz substrates by the vapor phase transport (VPT) method. Then, Au nanoparticles by depositing a thin nanometric Au layer with thicknesses 3, 6, 9, and 12 nm via sputtering technique and a heating process were coated on the ZnO nanorods. The morphology and structure of the samples were characterized by using a Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD). The results showed formation of rather aligned ZnO nanorods with wurtzite hexagonal crystalline structure and preferred orientation along the c-axis which are coated with Au nanoparticles. The obtained data from measuring ultraviolet photoresponse shows that the decorated sample with 9 nm thick Au film possesses a higher on/off ratio (6.5), responsivity (568 ± 33 mA/W), and faster rise and decay times. In addition, with presence of Au nanoparticles, responsivity in the visible region (λ= 520 nm) increased from 6 ±0.5 mA/W to 19±1 mA/W. This improved detecting behavior results from Localized Surface Plasmons (LSPs) of the Au nanoparticles and the formation of localized Schottky barriers between Au nanoparticles and ZnO.