Surface structure of GaP(110): Ion scattering and density functional theory study

The structure of the GaP(110) surface has been investigated using coaxial impact collision ion scattering spectroscopy (CAICISS) and density functional theory (DFT). CAICISS simulations based on structural parameter values of the well known buckled dimer model obtained in quantitative low energy electron diffraction studies in the 1980s were found to fit well with experimental data measured in the [1̄10] azimuth, but offered a relatively poor fit in all other incident geometries. A new surface structure derived from DFT calculations, involving small changes to bond angles and interlayer spacings, was optimized during the analysis of CAICISS data, until good fits of the data were obtained for all three azimuths ([1̄10], [001], and [1̄11]). The key feature of the new structure found to be required for this improved agreement with experiment is the inclusion of relaxations both parallel and perpendicular to the surface between the second and third layers.