Structural components of the Pt/Si(111)-(√3 X √3) surface from scanning tunneling microscopy

From topographic inspection of the (root 3 X root 3)-Pt/Si(111) surface by scanning tunneling microscopy, key structural elements are identified. A characteristic triangular building block in each (root 3 X root 3) unit cell, composed of charge maxima at approximately the bulk Pt-Pt distance bond, is observed. The orientation of the trimers is incompatible with the Si(111) substrate symmetry, which becomes obvious at domain-wall boundaries. In consequence, a simple top-layer trimer model is rendered insufficient. Instead, the finding of rotated trimers points at a more complex rearrangement of the surface, which generates the observed symmetry-breaking structural relaxation that leads to a chiral surface.