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

研究了Si（111）表面的原子结构。在TSK（terrace step kink）模型的基础上，采用Monte Carlo模拟方法，研究了在T_c以下，Si（111）表面的台阶结构。用7 * 7重构单元间的吸引相互作用和台阶间的排斥相互作用的竞争解释了7 * 7重构引起的台阶聚束结构，用经验Tersoff-Dodson原子间势研究了1*1表面的原子动力学和表面结构.通过RHEED、LEED和STM的观察，证实了1 × 1表面被Si原子所覆盖。从Si吸附原子的表面势图计算得到。计算了Si吸附原子的表面扩散系数和蒸发速率。在低于体熔化温度下的MonteCarlo模拟表明，只要Si（111）表面被高于临界覆盖率的Si吸附原子所覆盖，就会发生表面熔化。表明表面熔化的Si层的数目取决于温度。熔化层中的Si原子以与Si原子在（111）表面上的扩散系数相当的扩散系数四处移动。

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.