Atom-by-atom chemical coordination effect observed in noncontact AFM topography of Pb/Si(111)-(√3 × √3) mosaic phase

Abstract

Using noncontact atomic force microscopy (NC-AFM), we analyzed the height distribution of individual atoms by atomically resolved topography of Pb/Si(111)-(√3 × √3) mosaic phase surfaces, discriminated Pb, and substituted Si adatoms atom-by-atom. This successfully revealed the atom-by-atom chemical coordination effect in the height distribution of individual atoms. We found that increasing the number of surrounding nearest-neighbor Si adatoms increases the height of Si adatoms but rapidly decreases the height of Pb adatoms. These coordination effects were qualitatively independent of the tip-sample surface distance. This result agreed with previous results on Sn/Si(111)-(√3 × √3) mosaic phase for only Si adatoms. Pb adatoms, however, showed a strong but opposite dependence on the number of surrounding Si adatoms, and the Sn adatom proved independent of the number of surrounding Si adatoms. Such differences in the chemical coordination in NC-AFM height distribution among the fourth period elements of Si, Sn, and Pb atoms will disclose to differences in charge transfer and related phenomena between intermixed heterogeneous atoms, due to differences in electronegativity and/or their metallic nature. © 2008 The Surface Science Society of Japan.