Si(111)-( sqrt 3

Abstract

Using the technique of impact-collision ion-scattering spectrometry, we showed that the geometry of the Si(111)-(\ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3 )Ag surface consists of Si honeycomb on top of Ag trimers. The separation of the Si and Ag layers is 0.7\ifmmode\pm\else\textpm\fi{}0.3 A\r{} and the Si-Ag bond length is 2.73\ifmmode\pm\else\textpm\fi{}0.3 A\r{}. We also observed, for the first time, type-A and type-B arrangements of the Si and Ag atoms on the surface, with type B being type A rotated 180\ifmmode^\circ\else\textdegree\fi{} about the surface normal.