The surface structure of As-stabilized GaAs(001)-cwas investigated by high-energy X-ray photo-electron diffraction at high angular resolution. Azimuthal-angle scans at several polar angles of both Ga 3d and As 3d intensities were measured and compared to theoretical angular distributions generated by means of single scattering theory. The coordinates of As atoms in the surface layer were systematically varied to simulate both buckled and unbuckled dimer formation in which every fourth dimer was missing. This arrangement of missing dimers led to the basic (2 x 4) surface net that gives rise to c(2 x 8) domains. Optimal agreement between theory and experiment was achieved by modelling unbuckled dimer formation in which an in-plane displacement for surface As atoms of 0.9Å and a vertical inward displacement of 0.1Å were assumed. These displacements lead to bond lengths between dimer atoms and between surface As and second-layer Ga atoms of 2.2 and 2.6Å, respectively. A buckled dimer geometry, such as the one deduced from angle-resolved photoemission and local-density functional calculations for Ge(001)-(2 x 1), did not lead to good agreement with experiment.

Surface Reconstruction Geometry of GaAs(001)-c by High Angular Resolution X-Ray Photoelectron Diffraction. S.A.Chambers: Surface Science, 1992, 261[1-3], 48-56