Analysis of low-energy electron diffraction and angle-resolved photoemission from InP(110)-p(1 × 1)-Sb (1 ML)

Abstract

The deposition of Sb on InP(110) at room temperature produces a stable, ordered, saturated adsorbate structure at a coverage of approximately one monolayer (1 ML, i.e., one Sb for each In and P surface species). An analysis of the atomic geometry of this InP(110)-p(1 × 1)-Sb(1 ML) overlayer system was performed by the comparison of dynamical calculations of elastic low-energy electron diffraction (ELEED) intensities with those measured at T = 110 K. A relativistic model embodying energy-dependent Hara exchange was utilized to calculate the electron scattering from the In, Sb and P ion cores because both relativistic effects and energy-dependent exchange have been found previously to be important in the analysis of ELEED intensity data from In and Sb containing compounds. On the basis of prior results for GaAs(110)-p(1 × 1)-Sb and of total-energy minimization calculations the structural search was confined to models in which the Sb adsorbates occupy inequivalent sites corresponding to the top layer In and P species on nearly unreconstructed InP(110). The quality of the description of the measured ELEED intensities by the model geometries was evaluated using the X-ray ( R X) and integrated intensity ( R I ) R-factors. Two comparable minimal R X structures are found corresponding to perpendicular displacements of Δ 1,⊥ = 0.25 A ̊ and 0.75 A ̊ , respectively, of the two inequivalent surface Sb species. In both structures the SbSb bond lengths are at nearly the value characteristic of bulk Sb (i.e., 2.87 Å) but the SbP bond length is anomalously small (i.e., 2.1 Å) for the Δ 1,⊥ = 0.75 A ̊ structure. Utilization of these structures to calculate the surface state eigenvalue spectrum reveals that both of them provide a satisfactory description of the surface states extracted from angle-resolved valence-electron photoemission.