Metallic III-V (001) Surfaces: Violations of the Electron Counting Model

Abstract

We describe Sb-rich reconstructions of nearly lattice-matched AlSb and GaSb (001) surfaces using scanning tunneling microscopy/spectroscopy and first-principles electronic structure calculations. Whereas AlSb reconstructs to an insulating $c\left(4\ifmmode\times\else\texttimes\fi{}4\right)$ surface like that of other III-V compounds, GaSb forms $c\left(2\ifmmode\times\else\texttimes\fi{}10\right)$ and $\left(2\ifmmode\times\else\texttimes\fi{}10\right)$ surfaces that are weakly metallic and violate the electron counting model. We attribute the differences to a competition between the energy gain from Sb-Sb bond formation and the cost from the increased surface stress (which depends on the elastic properties of the substrate).