New Model for Reconstructed Si(111) 7 × 7 Surface Superlattices

Abstract

Superlattices of disjoint bilayer atomic microdomains stabilized by epitaxial misfit strain energies are proposed to account for $n\ifmmode\times\else\texttimes\fi{}n$ ($n=5$ at lower $T$, $n=7$ at higher $T$) surface structures of both Si on Si(111) and Sn on Ge(111). The microdomain model accounts well for the relative stability of Si(111) 7\ifmmode\times\else\texttimes\fi{}7 against hydrogenation and chlorination and is energetically more favorable than the original Lander model of 2\ifmmode\times\else\texttimes\fi{}2 building blocks centered on point vacancies.