Surface electronic structures of Au-induced reconstructions on the Ag/Ge(1 1 1)√3×√3 surface

A small amount of Au atoms deposited at room temperature transforms the Ag/Ge(1 1 1)√3×√3 surface into a √39×√39 surface. The presence of the Au atoms leads to downward shifts and modifications of the surface state bands compared to the initial √3×√3 surface. Further deposition of Au on the √39×√39 surface changes it into a 6 × 6 periodicity. At the same time the surface electronic structure changes from a metallic to a semiconducting phase with a gap of around 0.2 eV with respect to the Fermi-level. Finally, the 6 × 6 phase transforms into a new 2√3×2√3 phase when more Au is added, and the surface switches back to a metallic state.