LOW-ENERGY PHOTOELECTRON DIFFRACTION STUDY OF EPITAXIAL SB MONOLAYERS ON GAAS(110)

The photoelectron diffraction technique has been applied to investigate the geometrical structure of an epitaxial Sb monolayer (ML) on GaAs(110) using low photon energies. Ultra-high surface sensitivity is combined with high experimental resolution (less than or equal to 200 meV) providing additional information about chemically shifted components. The ordered Sb monolayer was prepared by depositing 3-4 ML onto a UHV-cleaved GaAs(110) surface and subsequent annealing up to 620 K. Photoelectron spectra of the Sb 4d and Ga 3d core level emission lines were recorded as a function of polar angles. The Sb 4d core level emission line clearly exhibits two chemically shifted components which are due to the distinct bonding sites of the Sb atoms. The two corresponding diffraction patterns with marked modulations are compared with calculated ones using a multiple scattering cluster model for various adsorption geometries of Sb. These results are in good agreement to previous LEED and total-energy-minimization studies and demonstrate the potential of this technique. In addition, a clear assignment of the two chemically shifted components of the Sb 4d core level to the two distinct adsorption sites is achieved.