Deposition of AuN clusters on Au(111) surfaces.: I.: Atomic-scale modeling

The interaction between a monokinetic and mass resolved low-energy gold cluster beam and a gold (111) surface is studied in detail at room temperature by means of molecular dynamics. The model makes use of the classical second moment tight-binding approximation to estimate the interatomic forces. A model is described to account for the electron-phonon coupling. Clusters of the nanometer size are modeled to slow down one after the other on the gold surface until a nanostructured layer about 7 nm thick is formed. The cluster slowing down is studied in detail and the consequences of the diffusionless accumulation of clusters on the surface is investigated. The first impinging clusters undergo pronounced epitaxy with the substrate surface although defects of various kinds can take place in them. The further cluster slowing down stimulates the annihilation of these defects. A pronounced surface roughness indicates no significant coalescence. As the slowing down proceeds further, cluster layers become increasingly defective and highly stressed. This stress field propagates into the first cluster layer, inducing lattice distortions. The memory of the surface orientation is progressively lost as the deposited layer thickness increases. The cluster assembled is characterized by numerous cavities of the nanometer size that may be interconnected and form nanopores. Incident conditions are found to play an important role, which motivates a realistic comparison between simulated and real experiments.