Correlated Diffusion of Adatoms and Islands on the Low Indexed Surfaces of Noble Metals and Alloys

Abstract

The diffusion processes of adatoms and islands on the low indexed noble metal and alloy surfaces were studied by Molecular Dynamics Simulations, based on semi-empirical potential models in analogy to the Tight Binding Theory in the Second Moment Approximation. Several systems were considered, like Cu adatoms and Cu or Au islands/adlayers on the Cu(110) and Cu(111) surface, respectively, and Cu or Au adatoms on the Cu₃Au(001) face. Various diffusion processes, that were monitored and analyzed, were found for these systems. It comes out that collective excitations may play an important role not only in the diffusivity of the adsorbates, but also in the structural and dynamic behavior of the substrate. In addition, it was found that the diffusive behavior of islands is characterized by the high mobility of the peripheral atoms and their different relaxed positions from the other island atoms. The surface and half monolayer island (0.5ML) relaxation were also found to play an important role in the stability and diffusivity of adlayers deposited on the 0.5ML island. Moreover, it was found that the presence of Cu or Au adatoms on the Cu₃Au(001) surface stimulates diffusion processes that can be related to wetting and disordering phenomena occurring at higher temperatures.