| The silicon surface could be protected by silicon dioxide, which adapt to insulate different circuit components and come into being capacitor. Furthermore, SiO2/Si interface have great stabilization and controllable electrical properties. However, silicon surface could be oxidized into silicon dioxide, which has influenced physical properties of some silicon-based equipment. Lots of studies about sample preparation, basic properties, formation mechanism and chemical component of the oxidation of silicon surface have been investigated widely. Recently, a great many researchers'work mainly focus on configuration structures, surface atom, electronic properties, application researches and dinamics of the oxidation structure on silicon surface. But the precise microstructure of the oxidized surface and the idiographic process of adsorption and diffusion have not yet realized distinctly. The interface structure and property of the oxidation structure on silicon surface are very complex, and relate to different environment.It is difficult to obtain accurate microstructure of the oxidation structure on silicon surface by experimental technique. Theoretical calculation had been successfully applied to investigate the surface atom and electronic properties, and it has become an important method to investigate the oxidation of silicon surface.In this paper, we have performed the first-principles method based on density functional theory to analyze the geometric structure and the electronic property of silicon oxide clusters, and we also investigated the adsorption and diffusion process on silicon surfaces in the atomic scale. The main research works and results are as follows:Firstly, we calculated novel adsorption models (2×1) of oxygen molecule on Si(001) surface structure. The adsorption process, the system energy, dynamic track and the diffusion coefficient are investigated.The results indicate that the adsorption process can be divided into four stages, the physical adsorption, the chemical adsorption early stage, the chemical adsorption late stage and the superficial stable state. The Si=O structure, the Si-O-Si surface oxygen-bridge structure and the Si-O-Si oxygen-bridge structure which oxygen atom inserted into the backbonds between the surface and the second layer silicon atoms in the stable adsorption structures, were beneficial to the formation of the silica tetrahedral structure. The difference of the orientation and the position of oxygen molecule on Si(001) surface during the physical adsorption stage lead to different diffusion paths, which formative two stable adsorption structure are coexist in the early process of silicon surface oxidation.Secondly, the possible models of the silicon oxide clusters on Si(001) surface, including the regular symmetric structure(A), the periodic asymmetric structure (B), the periodic asymmetric structure (C) and the irregular structure (D), have been fully optimized using the first-principles general gradient approximation method based on density-functional theory. The results show that all the optimized surface structures are amorphous. The optimized surface structures of the B, C and D models have the similar geometric character to the tetrahedron structure of SiO2. Furthermore, the coalescent between the Si and O atoms of the silicon oxide clusters includes significant ionic bond and certain covalent bond by employing the Mulliken population analysis and the graphics of electron localization function(ELF).Finally, the band structure and density of state of the silicon oxide clusters have been calculated based on the density funcional theory. The clean structure of Si(001) 2×2 surface have been optimized and we also have calculated band structure and density of state of the structure of Si(001) after optimization. The result shows that the peaks of surface states of silicon oxide clusters is lower than that of Si(001) 2×2 surface. It means that the surface activity the silicon oxide clusters have decreased greatly.
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