In experiments of Si deposition onto the Si(111)-(7x7) surface using scanning tunneling microscopy, so-called diffusing Si adsorbates were observed which were detected as a noise-shaped pattern in addition to the previously reported so-called stationary ones that remained at the same positions. The stable positions and diffusion energy barriers of Si atoms on the surface were obtained using molecular-orbital calculations. For one Si atom, the diffusion barrier was only several tenths of eV, while it exceeds 1eV for two Si atoms. The so-called stationary adsorbate was attributed to the two Si atoms and the so-called diffusing one to the single Si atom.

Adsorbed Si on the Si(111)-(7x7) Surface Studied by Scanning Tunneling Microscopic and Molecular-Orbital Approaches - Stationary and Diffusing Si Adsorbates. H.Uchida, S.Watanabe, H.Kuramochi, J.Kim, K.Nishimura, M.Inoue, M.Aono: Physical Review B, 2002, 66[16], 161316 (4pp)