FI-STM STUDY OF ALKALI-METAL ADSORPTION ON SI SURFACES

Alkali metal (Cs/K) adsorption on the Si(111)7 x 7 and Si(100)2 x 1 surfaces was investigated with the FI-STM. At the initial coverage on the Si(111)7 x 7 surface, Cs(K) atoms adsorb at the on-top site of the center adatoms and are almost completely ionized. When heated at 300-degrees-C, a new 1 x 3 phase with misfit defects is formed. On the Si(100)2 x 1 surface, Cs atoms occupy the off-centered valley bridge site at the initial coverage. These results, together with Li/K adsorption, can be well understood based on the strong interaction between the directional Si dangling bonds and active alkali metal atoms.