Atomic Structure of the Sb-Stabilized GaAs(100)-(2 x 4) Surface.

The microscopic structure of the Sb stabilized GaAs(100)-(2 3 4) surfaces is investigated combining reflectance anisotropy spectroscopy with first-principles total energy minimization and tight-binding calculations of optical properties. We show that the model accepted so far, containing three Sb dimers in the outermost layer, is not a stable surface geometry. Our results reveal a coexistence of Sb and Ga dimers on the Sb-stabilized s2 3 4d surface. [S0031-9007(96)01679-1]