Statistics of lateral atom manipulation by atomic force microscopy at room temperature

We perform vacancy-mediated lateral manipulations of Si adatoms on the Si(111)-(7x7) surface by atomic force microscopy at room temperature. A variety of line profiles associated with different atom hopping processes is observed in successive topographic line scans for the atom manipulations. Atom manipulation statistics show stochastic behavior in atom movements. The probability of atom movement increases with a decrease in the tip-surface distance. Moreover, it depends on the scan direction, even with crystallographic equivalence, because of tip apex asymmetry. In addition, the hopping rate reflects the difference in stability of the adsorption sites of the manipulated atoms.