Atomic motion induced by a scanning tunneling microscope tip on the Si(111) surface

Using scanning tunneling microscopy (STM), we have observed the STM-tip-induced atomic motion of the Si adatoms in the Si(111)?(7 × 7) surface structure near out-of-phase boundaries in the structure. In order to excite the motion of Si adatoms, the tip was fixed at a certain height at every pixel in the lateral scan and the sample bias was changed stepwise. Although the motion of Si adatoms occurs in a complicated manner, analysis shows that its elemental process is quite simple. Namely, the Si adatom jumps from an occupied T₄ site to an unoccupied T₄ site.