A new Si tetramer structure on Si (001)

摘要

Interactions between Si ad-dimers on Si (001) have been studied by molecular dynamics simulations using the Stillinger-Weber potential. The interactions determine the formation of clusters from diffusing dimers. We show different pathways for the formation of multiple-dimer clusters and propose a new tetramer (T_(CC)) structure formation by two diffusing dimers interacting. This tetramer structure has been found to be energetically stable with respect to isolated ad-dimers. Moreover, their local bonding configuration is very similar to the B-type step edge which is known to be the favoured adsorption site for epitaxial growth. The proposed tetramer may play a crucial role as the nucleus of the new epitaxial layer on Si (001).