| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1994: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1993: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
Monte Carlo simulations have been performed for the silicon (100) surfaces with adsorbed alkali metal atoms, gold atom adsorbed silicon (111) surfaces and the reconstructed silicon (100) surface with some defects like steps, dimer vacancies and chemisorbed atoms. In the following, the main results are summarized.
Alkali metal atom, particularly potassium and sodium, adsorbed silicon (100) surfaces are well known because of controversy on their structures. We adopt the so called double layr model, which we believe true. There are the first principles theory on their structures and the experimental results of thermal desorption of the adsorbates. Taking the lattice gas model for the adsorbates, we estimates the site energies and interaction constants from the results of the first principles theory. Using monte Carlo simulations for adsorbate structures at temperatures from 400K--900K and the rate equation of desorption for interacting system, we obtain desorption spectra to be compared wi
… More
th the experimental ones. Reasonable and suggestive results are obtained.
Gold atom adsorbed silicon (111) surface shows the 5 by 2 structure with streaks in LEED and RHEED intensities. These streaks suggest anisotropic short range order on this surface system. A linear chain lattice model had been proposed to explain the streaks. Recently, scanning tunneling microscopy (STM) measurement has been made and a new model has been proposed including again a linear lattice model by Dr.T.Hasegawa. From ten sheets of the STM images supplied kindly by him, which contain about 4300 adsorbed Au atoms for 32000 adsorption sites, for we extract the experimental positional correlation function of the adsorbed Au atoms. On the basis of this observation, we construct a linear chain lattice model with repulsive interaction and irregularity. We obtain almost perfect fitting of theoretical correlation function to the experimental one by the standard Monte Carlo simulation which gives reasonable parameters. This is one of the typical example of anisotropic short range order on solid surfaces. Before this work, we worked out another example of this type, Li adsorbed Cu (100) reconstructed surface, though substrate is metal.
From about 30 STM images of alkali metal atom adsorbed silicon (100) reconstructed surfaces again kindly supplied by Professor Sakurai, we have made quantitative analyzes of irregularities of step edges and positional correlation functions of alkali metal adsorbates and dimer defects. Theoretical analyzes of these data are our future problems. Less
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