Cluster models study of Ag bonding, migration and interaction on Si(100)-2 × 1

Abstract

Using cluster models up to 97 atoms, the bonding, migration and interaction of Ag on the Si(100)-2 × 1 surface have been studied by the atom superposition and electron delocalization-molecular obital (ASED-MO) theory. The cave site is determined to be the most stable adsorption site, with the SiAg bond length of 2.93 Å and adsorption height of 1.12 Å. This folding geometry is different from the former experimental suggestion of the linear SiAgSi structure. The migration of Ag on Si(100) is highly anisotropic and the motion is strongly favored in the direction perpendicular to the surface dimer rows. Meanwhile, a strong attractive interaction exists between Ag adatoms. Both the high mobility of Ag adatoms perpendicular to the surface dimer row and the strong AgAg attractive interaction result in the formation of Ag linear chains perpendicular to surface dimer rows.