Ag deposited onto the (100) surface in silicon studied by Density Functional Theory and Classical Molecular Dynamics

Numerous theoretical studies have been dedicated to Ag deposited on Si(111) and the properties of this system are now well assessed. On the contrary, the interface Ag/Si(100) is more elusive and several problems of this system have not been satisfactorily solved yet. In this work the Density Functional theory with GGA corrections and Molecular Dynamics simulations with classical interatomic potentials have been applied to the evaluation of adsorption of Ag on Si(100). Small clusters representing a fragment of the exposed surface are used in GGA calculations to study the chemistry of Ag/Si bonds in dependence of the shape, bulk-terminated or dimerized, of the Si(100) surface. Isothermal molecular dynamics simulations describe the motions of the diffusing adatoms in a temperature range from T=10 to 1000 K. The results indicate that the Ag atoms are adsorbed in a cave site among surface atoms, a feature consistent with experimental observations. Furthermore it is shown that, though there are no contradiction between the two methods, the difference between the stationary GGA and the dynamical MD evaluation is noticeable. This result has both practical and conceptual relevance.