Substitution of In for Si adatoms and exchanges between In and Si adatoms on a Si(111)-7×7 surface

Abstract

Substitution of In for Si adatoms and exchanges between In and Si adatoms on a Si(111)-7\ifmmode\times\else\texttimes\fi{}7 surface have been investigated using high-temperature (HT) scanning tunneling microscopy (STM). Indium substitution probability depends on the four different types of adatoms in the 7\ifmmode\times\else\texttimes\fi{}7 reconstruction. Differences in the In substitution energy between different types of adatoms are estimated from the substitution probability. Adatom exchange rates obtained from sequential HT-STM images are also dependent on the combination of In and Si adatoms. Measured activation energies and prefactors for exchanges on Si(111)-7\ifmmode\times\else\texttimes\fi{}7 are comparable to those on Si(111)-$\sqrt{3}$\ifmmode\times\else\texttimes\fi{}$\sqrt{3}$. The adatom exchange is not sensitive to the adatom symmetry. HT-STM results on the adatom exchanges on Si(111) suggest that the motion of the metal adatoms is a rate-limiting step in this process.