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

The interaction between a monokinetic and mass resolved low-energy gold clu ster 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 secon d 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 gol d surface until a nanostructured layer about 7 nm thick is formed. The clus ter slowing down is studied in detail and the consequences of the diffusion less accumulation of clusters on the surface is investigated. The first imp inging clusters undergo pronounced epitaxy with the substrate surface altho ugh defects of various kinds can take place in them. The further cluster sl owing down stimulates the annihilation of these defects. A pronounced surfa ce roughness indicates no significant coalescence. As the slowing down proc eeds further, cluster layers become increasingly defective and highly stres sed. This stress field propagates into the first cluster layer, inducing la ttice distortions. The memory of the surface orientation is progressively l ost as the deposited layer thickness increases. The cluster assembled is ch aracterized by numerous cavities of the nanometer size that may be intercon nected and form nanopores. Incident conditions are found to play an importa nt role, which motivates a realistic comparison between simulated and real experiments.