Theoretical study of the role of surface defects on the dimer dynamics on Si(0 0 1)

We have performed high temperature tight-binding molecular dynamics simulations as well as 0 K calculations to study the motion of the surface dimers near different types of steps. We compare these results with the corresponding results for dimers in a clean terrace, far from any defect. We have found that the dimers in step A edge flip slower than those in a clean surface, in agreement with STM observations, while those in rebounded step B edge flip faster. These differences in the energy barriers are reflected in the electronic structures, in particular in the local density of states (LDOS) near the energy gap. temperature and 0 K calculations predict the same relevant flipping barriers for dimers near step A edge, but the agreement is not as good for dimers close to rebounded step B edge, where correlated flipping events are important. In this case, finite temperature molecular dynamics simulations are more efficient to estimate the effective barrier. imilarities in the dynamics are found between dimers close to single dimer vacancies (SDV), steps, and steps with kinks. First neighbours of an SDV, upper step B edge dimers, and dimers close to kinks in step A have similar local environment. Therefore all tend to flip faster, and spend most of the time symmetric. On the other hand, second neighbours of an SDV, upper step A edge dimers, and dimers close to kinks in step B tend to flip slower.