CLUSTER-MODELS STUDY OF AG BONDING, MIGRATION AND INTERACTION ON SI(100)-2X1

Using cluster models up to 97 atoms, the bonding, migration and intera ction of Ag on the Si(100)-2 x 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 s ite, with the Si-Ag bond length of 2.93 angstrom and adsorption height of 1.12 angstrom. This folding geometry is different from the former experimental suggestion of the linear Si-Ag-Si structure. The migratio n of Ag on Si(100) is highly anisotropic and the motion is strongly fa vored in the direction perpendicular to the surface dimer rows. Meanwh ile, a strong attractive interaction exists between Ag adatoms. Both t he 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.