Ag-Induced Si(100) Reconstruction: Si(100)-(2 Root 2 X 2 Root 2)R45 Degrees-Ag

A type of Ag-induced Si(100) reconstruction described as Si(100)-(2 root 2 x 2 root 2)R45 degrees-Ag has been fabricated by breaking Si dimers and forcing Ag atoms to bond directly to these Si atoms. High-resolution scanning tunneling microscopy images and density functional theory calculations reveal that the basic unit of the reconstruction contains two Ag atoms bonded to Si dimers and two Ag atoms located at the grooves between neighboring dimer rows. These four Ag atoms constitute an elongated ring-shaped feature and are distributed on one or two neighboring dimer rows to form two types of reconstruction with the same reconstruction label. Such reconstructions are semiconducting, and the band gaps vary from 0.12 eV for two-row reconstruction to 0.26 eV for one-row reconstruction.