Zinc oxide nanostructures and nanoengineering

ZnO is a large band-gap (3.37 eV) semiconductor, a potentially important material for numerous optoelectronic applications. Nanostructures, by definition are the structures having at least one dimension between 1--100 nm. In this thesis we will investigate a brief account of the strategies to grow ZnO nanostructures. Since invariably nanomaterial properties tend to change significantly during scale-up from development on limited volume equipment. Goal of this study is to demonstrate a practical technique which is able to synthesize large quantities of nanowires while keeping the unique properties of nano-sized materials. Using ZnO as an example, we discussed a strategy to produce nanowires in gram quantity.; Ability to define position, size, and density of nanostructures on surfaces enable detailed studies of the properties of individual sites as well as collective properties of the assembly. These periodic structures are usually manufactured using electron beam lithography, photolithography, or x-ray lithography techniques. These methods allow fabrication of nanostructures and provide highly reproducible results. However, they are mostly not scalable to large areas, and are limited by a multistage, time-consuming, and expensive preparation procedure. We described an unique technique combining nanosphere self-assembly lithography and vapor-liquid-solid (VLS) approach of fabricating periodic array of catalyst dots in various geometry and subsequently grow vertically aligned ZnO nanowires in a large area hoping to achieve enhanced ultraviolet lasing and many other photonic devices.; ZnO being a transparent conducting oxide, the fabrication of ZnO field emitters can be easily integrated with ITO and ZnO thin film fabrication process. Thus a low cost solution for fabrication of field emission display can be realized using ZnO nanowires as field emitters. There have been several demonstrations of using ZnO nanowires as field emitters. However no significant improvement in terms of field enhancement factor or turn on voltage has been achieved. Most of these nanowires were grown on smooth substrate. We will discuss effect of substrate geometry on field emission properties of nanostructures. We choose carbon cloth as an example, where the woven cloth geometry combined with the high aspect ratio of the nanowires significantly improved the field emission property.