Research On Enhanced Effect Of ZnO Nanowire Arrays Ultraviolet Detection

Due to the properties of high performance, low cost and low power consumption ultra violet (UV) photodetectors based on low-dimensional nanomaterials, have attract extensive attention in the field of nano optoelectronic materials and devices. The UV photodetector of ZnO nanowire arrays have shown a good prospect, for its high responsivity rate and fast response time, moreover, it combined the advantages of nanomaterials and thin films. However, the high crystal quality for ZnO nanowire arrays and reasonable device structure is still the key issues of ZnO nanowire arrays UV detector. In this thesis, we focus on the high performance ZnO nanowires arrays UV detector devices design, preparation and characterization. This paper includes two parts of work, the first part is preparation and control the growth of ZnO nanostructures, such as uniform nanowire arrays, nanobelt and ultra-long nanowires. The second part is Ag nanopaticles (NPs) modified ZnO nanowires for high performance UV detectors, including single nanowire device and nanowire arrays devices. We inverstigated the Ag NPs enhanced the performance of ZnO UV detector by Localized Surface Plasmon Resonance (LSPR) effects. The detail research results shows as following.(1) The ZnO nanowire was synthesised on GaN substrate by solution method and Chemical Vapor Deposition (CVD), respectively. First, the ZnO nanowire arrays were prepared by solution method, the influence of the concentration, reaction temperature, reaction time, the seed layer and the GaN thin film crystal structure were discussed in detail. Furthermore, for better controlling the morphology of ZnO nanowire arrays, the CVD method was adopting. We investigated the effect of Au catalysts thickness, the amount of precursor and the vacuum pressure in the CVD system for ZnO nanowires morphology. In addition, we successful synthetised the ZnO nanobelt by Vapor-Solide growth method.(2) The X-Ray Diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and photoluminescence (PL) spectra and Raman scattering characterization method have been used to analyzes the properties of the ZnO nanowire arrays, the results showed that the preparation of the crystallization of ZnO nanowire arrays. The results show that the ZnO nanowire arrays have high crystal quality, larger specific surface area, and oxygen adsorption on the surface. Two kinds of UV detectors were prepared by difference method, respectively. The performance of two type of UV detectors were tested. The results show that the surface oxygen has important influence on the performance of the UV detectors. One of devices, mark as device A detector, which have the PMMA coated around the ZnO nanowire, and device B detector without PMMA coating. Under the same intensity of 365 nm UV irradiation, device B shows much higher responsivity about 161% increase than device A. The on-off rate of device B was about 29 times large than device A. Also, the response time reduced from 3.8 s to 0.32 s, the recovery time is reduced from 33.72 s to 3.02 s, the result showing that all of indexes of device B are improved significantly than device A.(3) In this work, super-long ZnO nanowires were prepared by CVD method, and the single ZnO nanowire UV detecotr was fabricated. The Ag NPs modified ZnO nanowire single nanowire LSPR effect enhanced UV detectors were investigated. Furthermore, the LSPR enhanced ZnO nanowire arrays UV detector was designed and fabricated. After Ag NPs modified, the responsivity was enhanced from 81.25 A/W to 176.5 A/W, and response timereduced from 320 ms to 80 ms by LSPR effect at 5V bias. In addition, the LSPR enhanced UV detector can work at 1V bias, and show more fast response time. At 1 V bias, the device has the responsivity of 48 mA/W, and response time of 1.13 ms, recovery time of 1.57 ms.The above research showed that the local surface plasmon resonance effect, can significantly improve the responsivity of ZnO UV detector and the key parameters such as response time, which has important potential application prospect.