MISSING DIMER VACANCIES ORDERING ON THE SI(100) SURFACE

We have used the Stillinger-Weber potential to calculate the interacti on energy between pairs of missing dimer vacancies (MDVs) on the Si(11 0) surface. We have found that there is a long-range repulsion between two MDVs located in the same dimer row, and a slight attraction betwe en MDVs in adjacent rows. The results have been used to model the coll ective equilibrium properties of ensembles of vacancies. At low temper ature and high concentration the vacancies self-organize into long wav y lines perpendicular to the dimer rows. When heated, these lines brea k up to form a ''gas'' of short nearly linear aggregates consisting of several vacancies. At an even higher temperature the vacancies tend t o form pairs which serve as nuclei for the formation of ''vacancy isla nds''.