Tunnelling and field-emitted electrons from the tip of a scanning tunnelling microscope were used to displace, in a reversible manner, Si adatoms on (111)-7 x 7 surfaces at between 30 and 175K. The displacement rates were determined as a function of current, sample bias voltage, and lateral distance from the tip. The displacement was found to be site-specific, with a strong preference for centre Si adatoms in the faulted half of the unit cell. The Si adatoms returned to their normal site via the same method, or during annealing at above 155K, with an activation energy of 0.49eV and attempt frequency of about 1.6 x 1012/s.

Site-Specific Displacement of Si Ad-Atoms on Si(111)- (7 x 7). B.C.Stipe, M.A.Rezaei, W.Ho: Physical Review Letters, 1997, 79[22], 4397-400