An investigation was made of adsorbed Si atoms on the Si(111)-7x7 surface deposited from an scanning tunneling microscope tip. In experiments performed at room temperature, 2 types of Si adsorbates were observed on the surface, adsorbate that remained at the same position, and one that was detected as a noise-like feature in scanning tunnelling microscope images. Molecular orbital calculations were performed to distinguish differences in these Si adsorbates. Stable positions, transition states, diffusion barriers and electron density iso-surfaces for extra Si atoms on Si cluster models were obtained. From these results, new assignments for these Si adsorbates were proposed: the fixed and mobile Si adsorbates corresponded to two Si atoms and a single Si atom, respectively.

Difference between Staying and Diffusing Si Adsorbates on the Si(111)7x7 Surface. H.Uchida, S.Watanabe, H.Kuramochi, M.Kishida, J.Kim, K.Nishimura, M.Inoue, M.Aono: Surface Science, 2003, 532-535, 737-45