Structure and electronic properties of ultrathin gold films on vicinal silicon (111)

The surface of vicinal Si(111) with a misorientation of 10° towards the azimuthal 112 direction is investigated by scanning tunneling microscopy and spectroscopy before and after submonolayer deposition of Au. For 0.2 and 0.4 ML coverage, the surface structure shows domains corresponding to Si(557) facets with chain-like protrusions and rows extending along the step edges. Tunneling spectra taken above the protrusions clearly reveal different electronic properties of Si(557):Au in contrast to the bare Si(111)-(7×7) surface. In particular, for tunneling voltages {\textbar}U{\textbar}\>0.5 V the spectra do not show any distinct features which suggests the presence of electronic bands with a smooth dispersion. The temperature dependence of the surface conductance indicates a non-metallic behavior for the bare Si(111)-(7×7) surface and for Si(557):Au-0.2 ML. For 0.4 ML an anisotropic conductance is measured which depends on the direction of the current with regard to the step edges.