Scanning-tunneling-microscope study of the α and β phases of the GaAs (001)-(2×4) reconstruction

Abstract

Atomic-resolution scanning-tunneling-microscope (STM) images of the GaAs (2\ifmmode\times\else\texttimes\fi{}4) reconstructed surface are presented which show details of the atomic geometry of two distinct surface structural phases. Interpreted within the presently accepted dimer vacancy model, these structures correspond to the previously suggested \ensuremath{\alpha} and \ensuremath{\beta} phases identified by reflection high-energy-electron-diffraction experiments and from total-energy calculations. Images of the \ensuremath{\alpha} phase show the position of localized As dimer nonbonding charge density relative to an underlying structure not previously observed in STM studies of this surface. Resolution of the As dimers of the \ensuremath{\beta} phase has allowed accurate measurement of the relative spacing of the local charge density associated with the dimer bonds of this surface.