Surface structure of low-coverage Ag on Ge(001) surface using first-principles calculations

The adsorption of Ag on the Ge(001) surface has been studied with first-principles calculations for a range of coverages from an isolated Ag adatom up to a second Ag atom on the surface. Two-dimensional islands of Ag, observed by scanning tunneling microscopy (STM) experiments, consist of the Ag ad-dimers which lie on the trenches between two Ge dimer rows. The Ag ad-dimer is parallel to the underlying Ge dimer direction. We found that the Ag ad-dimers reside stably at the position between Ge dimer rows.