Structure determination of a Sb monolayer on Ge(111) from first-principles calculations.

Abstract

We have performed first-principles calculations to determine the surface atomic structure of a monolayer of Sb on the Ge(111) surface. Experimental structural information about this structure has recently become available. However, different models have been proposed for this surface: a (2\ifmmode\times\else\texttimes\fi{}1) structure with the Sb atoms located at on-top positions and forming zig-zag chains was used to explain x-ray diffraction experiments, while a (1\ifmmode\times\else\texttimes\fi{}1) substitutional geometry was favored by a low energy electron-diffraction study. Our results, based on local-density functional theory, find that the (2\ifmmode\times\else\texttimes\fi{}1) structure is energetically more favorable than the (1\ifmmode\times\else\texttimes\fi{}1). However the difference in the surface formation energy of these two structures is so small that the coexistence of both is possible. \textcopyright{} 1995 The American Physical Society.