Experimental studies of an In/Pb binary surface alloy on Ge(111)

In this study, we present a binary In/Pb surface alloy on Ge(111) formed by evaporating In on the Pb/Ge(111)3×3 β phase. A well-defined 3×3 periodicity is formed after annealing, as verified by both low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Overview STM images show a clear 3×3 periodicity. Detailed STM images reveal protrusions corresponding to atomic sized features with a local hexagonal arrangement. Each 3×3 unit cell contains nine such features indicating a structure with 9 atoms per 3×3 cell in the topmost layer. Based on angle resolved photoelectron spectroscopy (ARPES) data, we have identified five surface bands within the bulk band gap. Four of them cross the Fermi level leading to a metallic character of the surface. The dispersions of these bands have been mapped in detail along two high symmetry directions of the surface Brillouin zone. Constant energy contours, mapped in two dimensional k-space, show interesting features. In particular, the occurrence of two differently rotated hexagon-like contours is presented.