Atomic structures on 1*1 Si (111) surface at high temperatur

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Surface atomic structures on Si (111) are investigated. below and above T_c of 7*7 surface reconstruction.Below T_c.the step structure on vicinal Si (111) was studied based on TSK (terrace step kink) model, by using Monte Carlo simulation. The observed step bunching structure induced by 7*7 surface reconstruction was explained by competition between the attractive interaction among 7*7 reconstruction units and the repulsive interaction among steps.Above T_c.the surface atomic structure and the atomic dynamics on 1*1 surface was investigated by using empirical Tersoff-Dodson inter-atomic potential. It is confirmed by the observation of RHEED.LEED and STM.that 1*1 surface is covered by Si adatoms. From the calculation of the surface potential map of a Si adatom. both the surface diffusion coefficient and the evaporation rate of a Si adatom were evaluated. From the Monte Carlo simulation below the bulk melting temperature, it was shown that the surface melting occurd on Si (111) provided the surface was covered by Si adatoms higher than the critical coverage. The number of Si layrs which show the surface melting depends on temperature. Si atoms in the melting layrs are moving about with the diffusion coefficient as large as that of a Si adatom on (111) surafec.