STM tip-induced diffusion of In atoms on the Si(111)$\sqrt{3}$×$\sqrt{3}$-In surface

Scanning tunneling microscopy (STM) tip-induced diffusion of In atoms was observed on the $\mathrm{Si}\left(111\right)\mathrm{}\sqrt{3}\times \sqrt{3}-\mathrm{I}\mathrm{n}$ surface. We found that In migration to the region beneath the tunneling tip results in the In coverage increase and spontaneous $\sqrt{3}\times \sqrt{3}-\mathrm{I}\mathrm{n}\to 2\times 2-\mathrm{I}\mathrm{n}$ structural transformation at negative tip bias voltages. At positive tip bias voltage In diffusion from the region beneath the tunneling tip results in the In coverage decrease and $2\times 2-\mathrm{I}\mathrm{n}\to \sqrt{3}\times \sqrt{3}-\mathrm{I}\mathrm{n}$ structural transformation. Indium adatoms in our experiments show up as being positively charged. STM tip field-induced In-atom migration occurs at room temperature, at bias voltages typical for the STM observations, without additional tip movement toward the surface.