INTERFACE MIXING OF ENERGETIC METALS DEPOSITED ONTO METALS

Experimental studies of ion beam mixing have indicated that the extent of mixing is sensitive to the heat of mixing of the two atom types. A nalytical studies of this phenomenon have utilized an initial short ti me random ballistic mixing combined with a longer time diffusional pro cess that is a function of the heat of mixing. We have utilized molecu lar dynamics simulation with potentials of the embedded atom method to study low energy (0.1 to 40 eV per atom) deposition of metals onto me tal substrates. We have observed that even the short term ballistic mi xing process is sensitive to the heat of solution. For example, Pt and Au have similar masses as do Ni and Cu, and the heat of solution for the potentials we utilized are -0.54 eV per Pt atom into Cu and +0.30 eV per Au atom into Ni. For 1 monolayer (200 atoms) of Pt deposited on to Cu with 10 eV kinetic energy per Pt atom, we observed that 85 of th e Pt atoms mixed into the Cu substrate during a simulation of 200 hs. Under the same conditions 28 Au atoms mixed into the Ni substrate. Det ailed study of individual mixing events shows that most of the mixing occurs during the ballistic part of the deposition process. We report on the deposition as a function of incident atom energy, substrate tem perature, heat of solution of the atom pairs, and relative mass of the pairs. We discuss the relationship of these results to theoretical an alysis of energetic atom mixing at very low energies.