Cluster formation of Li on the Si(111)7×7 surface

Using a field ion-scanning tunneling microscope (FI-STM), the adsorption process of Li on the Si(111)7×7 surface has been studied. At the initial stage, trimers are formed preferentially in the faulted half of the 7×7 unit cell. At higher coverages, these trimers coalesce to form six-atom and nine-atom clusters across the interface between the faulted and unfaulted halves. It is suggested, based on the careful study of the adsorption sites, that the Si adatoms of the dimer–adatom-stacking fault (DAS) model may be removed upon the Li adsorption.