Structure analysis of the Si(111)√3 × √3R30°-Ag surface

The structure of the Si(111){}3 ×{} {}3 R30^∘{}-Ag surface has been analyzed with a novel form of low-energy ion-scattering spectroscopy and energy-minimization calculations. The topmost layer of the surface is formed by Ag atoms with a honeycomb-chained-trimer arrangement in which the intratrimer Ag-Ag distance is 5.1±{}0.2 {}. At 0.75±{}0.07 {} below the Ag layer there exists a Si layer with three Si atoms per surface unit cell. The lower layer of the subsequent bulklike Si double layers is split into a honeycomb and a {}3 ×{} {}3 layer with a large interlayer distance of about 0.6 {}.