Pentamers with interstitial atoms as the building blocks of the Ge(331)-5 × 1 surface

Abstract High-index Si and Ge surfaces are used for growth of low defect density epitaxial layers and for nanostructure growth. In this work an atomic structure model of the high-index Ge(3 3 1)-5 × 1 surface is developed on the basis of the Si(3 3 1)-12 × 1 building block, consisting of a pentamer with an interstitial atom. Based on first-principles density functional calculations, it is shown that the proposed surface model leads to very low surface energy and good agreement with scanning tunneling microscopy images of the Ge(3 3 1)-5 × 1 surface available in the literature. Thus, we demonstrate that the Ge(3 3 1)-5 × 1 belongs to a family of surfaces, whose members are stabilized by pentamers with interstitial atoms, namely Si(3 3 1), Si(1 1 3), Ge(1 1 3), Si(1 1 0), Ge(1 1 0).