In-plane geometry of the Si(111)-(√3×√3)Ag surface

Abstract

The technique of impact-collision ion scattering spectrometry was used to determine the in-plane geometry of the Si(111)-(√3×√3)Ag surface. Comparison of experimental data with computer simulation leads to a substitutional trimer model in which Si honeycombs sit on top of Ag trimers occupying substitutional sites. The separation of the Si and Ag layers is 0.7±0.3 Å and the Si–Ag bond length is 2.66±0.3 Å. We also observed type-A and type-B arrangements of the Si and Ag atoms on the surface, with type B being type A rotated 180° about the surface normal. Our results are consistent with reported scanning tunneling microscopy images and also with a missing top layer model proposed from photoemission and x-ray photoelectron diffraction studies.