Ordering dynamics of anisotropic missing dimer clusters on Si(001) surfaces

Two types of anisotropic missing dimer cluster have been observed on (2×1) Si(001) surfaces: a missing dimer line parallel to the dimer direction and a missing dimer row parallel to the dimer row. The appearance condition of each type of cluster and their formation dynamics were studied using kinetic Monte Carlo simulations of the lattice gas model of missing dimers with interaction calculated by the Stillinger–Weber potential. A missing dimer row cluster exerts on a single missing dimer in the same dimer row an attractive interaction in the non-rebonded side and a repulsive interaction in the rebonded side. The dominant types of cluster formed by annealing of random missing dimers changes with increasing missing dimer concentrations from missing dimer line clusters to missing dimer row clusters. As the annealing temperature increases the average size of missing dimer line clusters reduces, while that of missing dimer row clusters increases.