Molecular dynamics simulations of film-substrate interface mixing in the energetic deposition of fcc metals

Embedded-atom-method molecular dynamic simulations have been performed to examine the interface mixing produced by deposition of fee metals on fee metal substrates. Atom arrival energies of 0.1, 10, 20, and 10 eV have been studied. The interface mixing initiated by atom impacts on the substrate surface was found to increase significantly with increasingly negative heats of solution of film atoms in the substrate lattice. As expected. both the total amount of interface mixing and the depth over which it occurred increased with increasing atom deposition energy. Comparison of the interface mixing results for two different temperature-control algorithms led to the conclusion that the interface mixing was very sensitive to short-lived localized substrate lattice excitations in the vicinity of atom impacts. This concept of interface mixing has some similarities to the concept of a thermal spike in bulk ion mixing, but does not involve any localized melting of the lattice. For a simulation of 0.1 eV Ni deposition on a Au substrate, a thermally-activated interface mixing process with a low activation energy was observed, driven by the difference between the surface energies of Ni and Au.