EPITAXIAL ANTIMONY MONOLAYERS ON III-V(110) SURFACES STUDIED BY LOW-ENERGY PHOTOELECTRON DIFFRACTION

Antimony is known to form well ordered epitaxial monolayers on clean c leaved (110) surfaces of III-V semiconductors like InP, GaP, and GaAs. These monolayers provide ideal candidates for photoelectron diffracti on (PED) studies. At low photon energies (40-90 eV) the Sb 4d core lev el emission can be resolved into two chemically shifted spin-orbit spl it doublets indicative of the two distinct adsorption sites on the sur face. The intensity of these two doublets together with that of the In 4d or Ga 3d subtrate emission was monitored as a function of polar an gles and photon energy utilizing an ADES 400 photoelectron spectromete r at the BESSY TGM2 beamline. Strong variation of the intensity ratio of the doublets clearly demonstrates the usefulness of resolving chemi cal shifts. The experimental results are compared to theoretical calcu lations using the multiple-scattering cluster model including spherica l-wave corrections for different adsorption models of the Sb monolayer .