Zno Field Emission Properties

Nanomaterials and nanostructures have received great interests due to their peculiar and fascinating properties, superior to their bulk counterparts for applications. The cold cathode is one of the focus of the nanomaterials study even the whole nanotechology research, and the high aspect ratio and large length/radius ratio makes them genuine candidates of election field emission. Zinc oxide (ZnO) is a promising wide band gap semiconductor material for field emission, because of its remarkable physical and chemical properties. It was necessary to evaluate the field emission properties of ZnO systematically. This thesis conducted an elementary study on ZnO field emission property. ZnO hexagonal microtubes and nanowires array were obtained by hydrothermal method and chemical vapor deposition　respectively. The microstructures of products were characterized. The field emission properties were measured to research field enhancement factor, stability and affect of vacuum. It was found that ZnO nanowires have excellent field emission properties with the low turn on field of 5-6 V/μm , threshold field of 6.5-8 V/μm. ZnO microtubes also have good field emission properties with the low turn on field of 12-15 V/μm, threshold field of 15-19 V/μm. The influence of heat treatment and working pressure on the field emission properties on ZnO microtubes was discussed in the thesis. The emission characteristics of ZnO film and nanowires array have been analyzed theoretically. The carrier concentration-dependence of field emission was theoretically investigated by calculating the conduction band contribution to emission current. The calculated field emission current densities were found to increase with increasing concentration even higher interface barrier were existed under the same applied field. It was found that there are always optimum densities that correspond their best emission current density. and the smaller the radius of nanowire, the larger the field enhancement factor. In the ZnO film, the larger carrier concentration, the larger field emission current was obtained.