Studies On The Synthesis And Optical Propertiesof ZnO/ZnS Core-shell Nanowire Arrays

Core-shell nanowires have many unique properties. ZnO/ZnS core-shell nanowires are type-II heterostructures, which is beneficial to separating electrons and holes in the nanowires and increasing the carrier collection. Compared to random nanowires, nanowire arrays can be easily assembled to various devices. Thus, ZnO/ZnS core-shell nanowire arrays have a huge potential application in photodetection.ZnO nanowire arrays have been synthesized on the ITO substrates by hydrothermal method. The morphology of ZnO nanowire arrays can be controlled by the concentration of zinc acetate solution, seed annealing temperature, the time of seed growth, the concentration of growth solution and growth times. ZnO nanowires are of single crystal wurtzite structure and have a growth direction of [002]. In the PL spectrum of ZnO nanowire arrays,there is a strong UV emission peak at 376 nm and a weak visible emission peak at 560 nm, indicating that nanowires have a good quality. ZnO nanowire arrays have been synthesized on the PET film, the Kapton film, the GaN film and the AZO glass. Al-doped ZnO nanowire arrays have been obtained by adding Al3+ into the growth solution.ZnO/ZnS nanowire arrays have been obtained by ion exchange reaction. ZnO core has a single crystal structure and ZnS shell is polycrystalline. The thickness of Zn S shells increase by increasing the concentration of Na2 S solution, reaction time and reaction temperature. Compared to ZnO nanowire assays, UV emissions from ZnO/ZnS core-shell nanowire arrays are weak, which is related to the type-II heterostructure.ZnO/ZnS core-shell nanowire arrays have been embedded in PMMA film and separated from the substrate. The photodetector have been fabricated by making two electrodes on the nanowire arrays. Under the illumination of 365 nm, the current increases 4 orders. On the 365 nm light, the current increases by 10 times in 1s, the current increases 4 orders after 300 s and continues to increase. The photodetector is not sensitive to visible light and room light. The results in the thesis are significant to obtain visible-blind UV photodetector of high sensitivity.