The High Miller Index Surface Of Metals And Semiconductors: Surface Energy And Electronic Structure

The properties of high miller index surface, both metals and semiconductors, are important topic and need to further studies in surface science. At present, the studies on this are mainly focus on the surface geometry structure. Little is payed for the electronic structure. In this dissertation, the surface properties of high miller index surface of metals and semiconductors were studies by using the molecular dynamics method, the scattering theoretical method and the ab initio quantum mechanical molecular dynamics simulations. The main conclusions are the following:1. The calculation of surface energy of metals Al, Cu and NiBy using the molecular dynamics combining the EAM potential, we calculated the surface energy of some high miller index surfaces belong to the (001) to (111) and (001) to (110) in Al, Cu and Ni. We also develop an experiential formulation based on structural unit model for high-index surfaces and that can give an estimate of the energies of the high-index surfaces, given the value of surface energy of (001), (110) or (111). The calculation result shows that the surface energies of the closest surfaces are the lowest and that the surface energies of the closest surfaces and the closer surfaces are the extremum of the surface energies function of orientation angle. The theory simulation result,formulation calculation result and experiment data are well corresponded each other. In addition, we calculated the surface energy of Al and Cu at different temperatures.2. The Studies of Surface Electronic States of High miller index of GaAs:In this section, we have carried out theoretical investigation on the electronicstructure of some high miller index surface of GaAs, such as (112), (113), (114) and (2 5 11). The bulk electronic properties of GaAs have been described both by the second-neighbour tight-binding formalism for (112), (113) (114) surface and nearest neighbour tight-binding sp3s* for (2 5 11) surface. In each case, we present the surface band structure together with the projected bulk band of both ideal and reconstruction surface respectively, the number of the surface states is determined, and the localized surface features and orbital properties of this surface states along the high symmetry lines in the 2D SBZ are discussed. For the GaAs(113)(l XI) surface, we have tested two possible models, i.e., "the bridge site" and "the hollow site" models. In comparison with the APUPS, the results have shown that the surface states of the hollow site are in good agreement with the experiment. So we concluded that the hollow site model is favourable for the GaAs(113)(l XI) surface and the bridge site model should be excluded. 3. Other worksBeside this, we also carried out the studies of the properties of some materials, such as me surface geometry stmcture and electronic stmctiire of PbTe^ PbSeandPbS (001) surface, the oxygen properties of YBCO superconductor, and the Ti and Ni adsorption and diffusion on the diamond surface. Some results are interesting, for example, in our calculation, there are no reconstruction in the cleaned PbTe> PbSe> PbS (001) surface. But there are different rumple occurs. Unlike the III-V and II-VI semiconductors, there are no surface states in the fundamental gaps.