MANIPULATION AND DYNAMICS AT THE ATOMIC-SCALE - A DUAL-USE OF THE SCANNING-TUNNELING-MICROSCOPY

Atomic scale modification of surfaces may trigger off dynamical proces ses. This is shown here by using the tip of a scanning tunneling micro scope to extract an individual atom in a controlled manner from a pred efined site of the reconstructed Ge(111)-c(2x8) surface. By thermally activated hopping of neighboring adatoms to the vacant site, the produ ced single-atom vacancy diffuses on the surface. From statistical anal ysis of the adatom configurations observed around the vacancy, we dete rmine tiny (<0.15 eV) differences in free energy between the configura tions. A linear increase of the configuration free energy with the num ber of adatoms located at metastable T-4 sites is reported.