Stabilization mechanism of Si(111) 7 x 7 domain growth: important role of shared corner-holes

We analyze the stabilization mechanism in the dimer-adatom-stacking-fault (DAS) structure formation on Si(I 1 1). A single faulted (F) half of the unit cell of the DAS structure grows into a small DAS domain, as previously observed by scanning tunneling microscopy. New F-halves are created from a corner-hole of an existing F-half at the edge of the DAS domain. Atom-ic-structure modeling of the formation process of a new F-half implies that a corner-hole shared by two F-halves reduces the number of dangling bonds. We calculated the surface free energy during the 7 x 7 DAS domain growth using an established cell model to deduce the critical size. The critical size of the DAS domain consists of two F-halves sharing one corner-hole at 653 K, which is in good agreement with our experimental results. We conclude that the shared corner-hole has a strong stabilizing effect on the DAS domain. (C) 2001 Elsevier Science B.V. All rights reserved.