Atomic geometry of GaSb(110): Determination via elastic low-energy electron diffraction intensity analysis

Elastic low-energy electron diffraction (ELEED) intensities from GaSb(110) of normally incident electrons with energies 30E 210 eV were measured at T=125 K. Intensity versus incident-energy profiles were recorded for 14 diffracted beams. The surfaces were prepared by a chemical-polishion-bombardanneal cycle. The stoichiometry of the surfaces and reproducibility of the data from one sample to another were verified explicitly. Comparison of these measured intensities with dynamical ELEED intensity calculations indicates that the dimensions of the surface unit cell are identical to those of truncated bulk GaSb, but that the atomic geometry within that cell is reconstructed. The best-fit structure consists of a bond-length conserving rotation by 1=(30±2) of species in the uppermost atomic layer with the Sb relaxing outward and the Ga inward. No displacements of the second-layer species are indicated by the analysis. The structure resembles those of ZnTe(110) and GaP(110), but is quite distinct from those of GaAs(110), InSb(110), and CdTe(110). This result reveals that ionicity alone is an inadequate index of the surface atomic geometries of compound semiconductors, independent of the definition chosen for the ionicity.