Coverage-dependent geometries of nanowires on Ge(0 0 1)-Au surfaces: modification of trenches

Despite intense research the microscopic atomic structure of Au-induced nanowires on Ge(0 0 1) substrates is still under discussion. We analyse a variety of structural models for Au-induced nanowires on the Ge(0 0 1) surface using first-principles calculations. Here we focus on subridge modifications at higher Au coverages and study geometries based on the giant missing row model with Ge-Ge dimers in the grooves between the nanowires due to replacing them by Ge-Au heterodimers or Au-Au homodimers. Stable geometries are predicted for higher Au coverages, which however have only a minor influence on the electronic structure. The findings are interpreted that the Au coverage and the actual geometry may vary in the various experiments according to the preparation conditions.