Manipulation of single Si adatoms and observation of fast diffusion of Si dimers on a Pb-covered Si(111) surface

The authors demonstrate lateral manipulation of individual Si adatoms on the Si(111) ( 7×3)-Pb surface at ∼125 K using the tip of a scanning tunneling microscope (STM). At this sample temperature, Si adatoms are not mobile. However, a Si adatom could be moved along, or across, the surface trimer row through a vertical movement of the tip toward the surface at certain positions near the Si adatom. The repulsive interaction between the tip and the Si adatom pushed the adatom toward a neighboring adsorption site. Through this manipulation, the authors also moved a Si adatom to meet another Si adatom. When a Si dimer was formed, it diffused rapidly on the Pb-covered surface until it was trapped by a defect site. This work demonstrates the potential to use atomic manipulation methods to reveal the surface dynamic processes that cannot be observed with scanning tunneling microscopy alone. In addition, the manipulation revealed the true atomic positions of Si adatoms on the surface, which solves a common problem...