Step structure of vicinal Ge (001) surfaces

The microscopic details of the step morphology of vicinal Ge(001 ) surfaces are analyzed on an atomic level using scanning tunnelling microscopy. Despite the strong correspondence to vicinal Si (001) surfaces, the step structure of the vicinal Ge(001) surface exhibits some significant differences. Rebonded, as well as nonbonded SB step edges, are observed and, related to the occurrence of both configurations, kinks with a minimum length of a0( ≈ 4 Å) do occur. Kinks in SB rebonded step edges can be regarded as independent excitations whereas for kinks in SB nonbonded step edges this is definitely not the case. Occasionally dimers are found at the SB steps, which are located just in between two dimer rows of the upper terrace. Finally, for the first time a ferromagnetic-like coupling between buckled dimers in the same row is observed close to step edges.