Preparation And Field Emission Properties Of ZnO One-dimensional Structures

Due to novel applications of semiconductor oxide in optical, opto-electronic, catalyst and piezoelectric area, the oxide-based one-dimensional material attract worldwide attention more than ever before. ZnO is an important â…¡-â…£ semiconductor, with wide direct band gap, which has a broad range of applications in short-wave opto-electronic devices. ZnO one-dimensional nanostructure is a perfect combination of nanomaterials and semiconductor oxide. Several kinds of ZnO one-dimensional nanostructures have already been reported. Investigation on fabrication, properties, growth mechanisms and applications of ZnO one-dimensional nanostructures plays an important role in both fundamental research and technological applications.Our research focused on growth of ZnO one-dimensional nanostructures. We have successfully fabricated many kinds of ZnO one-dimensional nanostructures with novel morphology by thermal evaporation and MOCVD method. Based upon that, effect of growth parameters on morphology, compositional, structural, optical and field emission properties have been investigated. The growth mechanism of as-grown nanostructures has also been proposed.We fabricated pure ZnO nanocomb with high uniformity and excellent crystallinity by thermal evaporation on silicon substrate, the point diameters of which are around 25nm and lengths range between 800 and 1500nm. Rod-like, tower-like, pencil-like and dumbbell-like ZnO nanostructures have also been synthesized via same method, all of which are well oriented along c axis. It is found that the position of substrate, growth temperature and grow time are key points to the morphology. The theory of low-temperature nucleation and high-temperature growth could explain the growth process. All measurement demonstrated that the growth of ZnO one-dimensional nanostructures is controllable in some degree.We fabricated pure ZnO nanowires, which are well oriented and even distributed using a two-step metal organic chemical vapor deposition (MOCVD) technique. The diameters of ZnO nanowires range from 30 to 60 nm and lengths range from 200 to 400 nm. Only one peak in ultraviolet wave band showed on photoluminescence spectrum, which indicating that the as-grown ZnO nanowires have good crystal quality and few oxide vacancies.The test result of field emission properties of different kinds of ZnO one-dimensional nanostructures was quite approving, showing that the turn-on field of ZnO nanocomb and ZnO nanoarray was around 2 V/ u m and the threshold field was between 5 V/ p m and 8 V/pm. Furthermore the field emission current was steady and E-J curve is well consistent with the F-N mechanism. We also analyzed the effect of morphology on field emission properties.