Crystallinity, Crystallographic Orientation And Enhanced Field Emission Of Au Nanowires

By the development of electronic components and mechanical miniaturization, the research of nano-materials becomes more and more arresting. The physicochemical properties will become very special when its size reduces to nanoscale, which due to small size and quantum size effects. Given the research of controllable preparation of nano-materials and its properties, we hope to create new nanostructures with special functions to meet the requirements of performance and environment. The nano-materials with special properties have broad potential applications in information, environment, energy, chemical, medicine, national defense etc. and bring infinite research opportunities for some subject such as physics, chemistry, life science etc. As two dominant structural properties, crystallinity and crystallographic orientation have been a research focus in nanotechnology.In this thesis, firstly, we briefly introduce the property and application of nano-material, the field emission, the synthesis and characterization of nano-material. Then, using a cyanide-free bath, gold nanowires with controlled crystallinity and preferred crystallographic orientation have been prepared by electrochemical deposition in home-made polycarbonate ion track-etched templates. Next, the influence mechanisms of nanopore diameter, applied voltage, and deposition temperature on structural properties are proposed. Finally, we researched the enhanced field emission of single-crystal nanowires with [100] preferred orientation.According to our research, Single and polycrystal gold nanowires with preferred orientation along [111] and [100] directions have been obtained by selecting fabrication parameters, respectively. While the applied voltage determines the crystal structure in a straightforward manner, the deposition temperature can have either restriction or promotion effect in the final crystal structure depending on the nanopore diameter of the ion track-etched template. We have also found that the growth orientation of the nanowires has a transition from [111] to [100] and the turning point depends on the applied voltage and nanopore diameter. These observations can be well explained by the adsorption of H ions modulated by effective voltage and the nanopore diameter-determined interface energy. Single-crystal wires with [100] preferred orientation shows enhanced field emission which may be attributed to their single-crystal structure and lower work function of loosely packed crystal plane.