MISSING DIMER VACANCIES ORDERING ON THE SI(100) SURFACE

We have used the Stillinger-Weber potential to calculate the interaction energy between pairs of missing dimer vacancies (MDVs) on the Si(110) surface. We have found that there is a long-range repulsion between two MDVs located in the same dimer row, and a slight attraction between MDVs in adjacent rows. The results have been used to model the collective equilibrium properties of ensembles of vacancies. At low temperature and high concentration the vacancies self-organize into long wavy lines perpendicular to the dimer rows. When heated, these lines break up to form a ''gas'' of short nearly linear aggregates consisting of several vacancies. At an even higher temperature the vacancies tend to form pairs which serve as nuclei for the formation of ''vacancy islands''.