硅高指数面上纳米线和纳米点结构的研究

Nanodots and nanowires are building block for the fabrication of nanoelectronic devices. The synthesis, stabilities, and structural and electronic properties of nanodots and nanowires are fundamental for fabricating high performance nanoelectronic devices based on these nanomaterials. Ideal structures of the high index surface of Si are composed of low index terraces separated by periodic monolayer steps. Because of the high density of steps, high index surfaces were considered as ideal templates for the self-organized growth of nanowires and nanodots. The research on the growth of nanowires and nanodots on the high index surfaces of Si is just beginning and it shows more and more importance as the feature size of the current electronic devices based on Si goes deep into nanometer scales.The atomic structures, electronic structures and stabilities of the substrate surface are important factors that affect the self-organized growth of nanowires and nanodots on the substrate. The aim of this project is to look for the suitable high index surface of Si, study on its atomic structures, electronic structures and the stability of the surface, and determine the suitable surface structures and processing methods for the self-organized growth of nanowires and nanodots. Then metallic nanowires and nanodots will be fabricated on the suitable high index surface of Si by self-organized method, the electronic properties and transport properties of these nanostructures will be characterized to explore the new concepts and methods for fabricating nanoelectronic devices based on nanowires and nanodots. According to the recent advance of the research of nanomaterials, the project also carried out the research on the synthesis, structural and electronic properties of some new nanomaterials, e.g., carbon nanotubes, chains of Au nanoclusters and Au nanowires synthesized with organic templates. The following are the main results of the project: ①The reconstructions and structural stabilities of Si(337) surface were studied with STM and found that Si(337) surface was not a stable high index surface. The reconstruction surface of Si(337) is mainly consisted of more stable Si(5512) units and exists long and short periods. Various metastable reconstructions of Si(111) surface were investigated and found that the atom densities were the key factor for the formation of metastable reconstructions. Two kinds of ring-like structures were observed at domain boundaries of different reconstructions. Ag/Si(111) and Ag/Si(111)3′1 reconstructions were observed in the investigation of Ag deposited on the Si(111) surface. ② Au nanoclusters, chains of Au nanoclusters and Au nanowires were fabricated on the HOPG surface. Quasi-ordered, stripe-like nanometer-scale structures were spontaneously created on surfaces of high-purity aluminum by electropolishing and stabilities of the structures were studied. Arrays of Au nanowires were synthesized by electrodedeposition on polycarbonate membrane template. The I-V characteristics of individual nanowire revealed metallic characteristics with a conductive AFM. ③Single-walled carbon nanotubes (SWCNT) were synthesized using CVD method and the growth conditions were investigated. It was found that an optimal temperature existed for the growth of SWCNT by CVD method. Nanotube-Onion-Nanotube composite carbon structures were synthesized by carefully controlling the growth conditions. Controllable manipulation of SWCNTs on the surface of HOPG was realized with an AFM. Individual nanotubes was successfully separated from nanotube bundles using an AFM tip for the first time. The results achieved by the project are important for the research on the synthesis of nanodots, nanowires and their arrays. These results will be very helpful for the fabrication of new nanoelectronic devices based on nanodots and nanawires.

选择适当的高指数硅表面，以其为基底利用自组织现像研究金属纳米线和纳米点的制备工艺进而研究金属纳米线和纳米点及其阵列的电学和光学特性。此项研究的目的是探讨减小硅电子、光电子器件的尺寸，提高其性能的途径。