| Ultraviolet (UV) detection technology is widely used in many fields, such as space communication, pollution monitoring, missile plume detection and even biomedical applications. Compared to commercial photomultiplier and Si basde UV photodetectors, the third generation wide bandgap semiconductor (ZnO, GaN, diamond and SiC) based UV photodetectors have received extensive attention owing to the realization of UV detection function without additional optical filter and cooling system. Among various wide bandgap semiconductor materials, ID ZnO is regarded as one of the most important nanomaterials for UV photodetection, benefiting from its unique characteristics, such as stable physical and chemical properties, strong radiation hardness, large surface area to volume ratio, high electron mobility, process simplicity and environment-friendly. However, the fast recombination rate of photoexcited electron-hole pairs and relatively low UV sensitivity inhibited its practical applications.For the fabrication of UV photodetectors with high UV sensitivity, fast response time and good reliability. In this thesis, materials and structure design are applied to tailor certain properties of ID ZnO based UV photodetectors. Cu-doped ZnO nanofilm array and Sb-doped ZnO nanorod (NR) array were both synthesized by a low temperature hydrothermal method. On this basis, we fabricated Cu-doped ZnO nanofilm array and p-type Sb:ZnO/n-type ZnO NR array based UV photodetectors. Furthermore, we also used a facile photochemical deposition technique to fabricate honeycomb-like NiO/ZnO heterostructures for enhancing UV detector performance. The growth mechanism of NiO nanomaterials and corresponding enhanced UV sensing performance have been investigated in detail.1. A compact Cu-doped ZnO nanofilm array was synthesized by a facile hydrothermal method and post-annealing process. We investigated the influence of Cu doping on the morphology of ZnO NR array and the performance of fabricated UV photodetectors. For Cu-doped ZnO, a much larger flat surface appears and the aspect ratio decreases considerably compared to that of undoped ZnO NRs. The Cu-doped ZnO nanofilm array based UV photodetector exhibits enhanced sensitivity and faster reset time. The enhanced UV sensing properties of the Cu-doped ZnO nanofilm array are mainly attributed to the trapping and de-trapping of electrons by Cu-related defects in ZnO NR.2. A ZnO homojunction UV photodetector based on Sb-doped p-type ZnO NRs and n-type ZnO NRs was fabricated by a low temperature solution method. The XPS and SIMS measurements confirm the incorporation of Sb into ZnO NRs. The fabricated homojunction shows well-defined rectifying characteristics, confirming the p-type conductivity of the Sb-doped ZnO NRs. Moreover, a high UV sensitivity of 3300% and a fast reset time to UV illumination are also achieved.3. Based on our former work, we synthesized honeycomb-like NiO/ZnO heterostructures by a facile photochemical deposition method. Through controlling the various growth conditions we could rationally tailor the morphology of the heterostructured NRs and the UV sensing performance. A reasonable formation mechanism of the honeycomb-like NiO/ZnO NRs is proposed, which is closely related to the production of OH- in the vicinity of ZnO NRs during the photochemical deposition process. The fabricated NiO/ZnO p-n heterojunction shows a well-defined rectifying characteristic with a turn-on voltage of 0.66 V and a negligible leakage current. Moreover, the UV detection performance increases considerably compared to that of bare ZnO NRs, which is attributed to the change of nanostructure and the extended carrier depletion region near p-NiO/n-ZnO junctions. |
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