The Synthesis And Characteristics Of Different ZnO Nanostructures

ZnO is an important wide band semiconductor with a band gap of 3.37 eV and exciton binding energy of 60 meV, which makes it a promising material for electronic and optical devices. Nano-ZnO has some different properties which are different from the bulk materials in electricity, magnetics, optics and chemistry, so the research on it becomes one of the most important works. In this article, we introduce the synthesis and characterization of different ZnO nanostructures, at the same time, the photoluminescence and field emission properties of them are also been studied. Main concludes and results are as follows:1. ZnO nanowires with excellent photoluminescence and field emission properties were synthesized by a two-step method. Compared with those that were fabricated by a thermal evaporation method, the ZnO nanowires here shows better UV luminous property and there is a 5nm blue-shift. The turn on field and the threshold field of the immersed ZnO nanowires are much lower. Other morphologies of ZnO nanostructures are also changed by immersing them into TU solution. We also found that if we immerse these nanostructures into too high concentration solution or for too long time, the quantities of the ZnO nanostructures will decrease or even all of the nanostructures disappear.2. By changing the experimental conditions, we firstly fabricated nanocherries, nanocentipedes, nanospindles and long nanorods ZnO structures with the thermal evaporation method. XRD and SEM are used to study the morphologies and structures of these ZnO nanostructures. We found the nanostructures are closely relative to the growth conditions. And we found that the ZnO nanostructures can affect the photoluminescence and field emission properties. At last, we obtained other ZnO structures by changing the growth temperature and analyzed the growth mechanisms of these ZnO nanostructures.3. We successfully synthesized centimeter-long nanocombs and nanobelts structures for the first time by using sources that are distinct from the reported before. The yield of these microscopical structures is great and the growth of them can be repeated. The length of these nanostructures is from millimeter to centimeter andthe longest one of them is about 2cm, so we use a one-off needle tubing easily separate one nanocomb or a nanobelt from the samples and test some characteristics of them. The SEM images of them show that the branches of the nanocombes structures are about 100nm-350nm; the width of the nanobelts is 20μm and the thickness of them is about 50nm. Then the PL characteristics of the ultra-long nanocombs and nanobelts were studied and we found that there were no differences of the PL characteristics between the ultra-long nanostructures and the nano/meter-long structures. We also investigated the TEM and optical interference of the centimeter-long nanocombs and found that the thickness of them is well-proportioned and the distance between the branches is also even. SAED indicates that these ultra-long nancombs are single crystal. In the end, we discussed the growth mechanism of the ultra-long nanocombs and nanobelts.