Giant missing row reconstruction of Au on Ge(001)

We report on a giant missing row reconstruction emerging upon the adsorption and subsequent annealing of (sub)monolayer amounts of Au on Ge(001). The emerging microfacets are of (111) type and reminiscent of those in the well-known (2×1) missing row reconstruction of the clean (110) surfaces of the fcc transition metals Au, Ir, and Pt. The (111) microfacets are aligned along the [110] directions and decorated with Au atoms. The periodicity perpendicular to the ridges amounts to 1.6 nm. Surprisingly the corrugation of these Au-induced facets is found to be not less than 0.6 nm. The facets exhibit a (√3×√3)R30° reconstruction similar to the Au-induced reconstruction of Ge(111). Scanning tunneling microscopy and spectroscopy measurements reveal that the top ridges consist of buckled Ge-dimer rows.