DYNAMIC MONTE-CARLO SIMULATION FOR THE ION-BEAM-INDUCED ATOMIC TRANSPORT IN BILAYER SYSTEMS

A dynamic Monte-Carlo simulation (MCS) program, containing not only co llisional mixing but also sputtering effects, has been developed to el ucidate the dynamic mixing processes and the atomic transport of const ituents in Al-Pd bilayer systems. MCS results reveal that the preferen tial inward displacement of the top-layer element dominates and that t here is an enhancement of the inward displacement when the heavier ele ment is in the top layer. Also we develop an analytical model to inter pret this MCS result. The inward displacement is controlled by both of an anisotropic and an isotropic atomic transport. The anisotropic ter m is caused by the primary recoil of atoms, which has a characteristic phi (ion dose) dependence, and the isotropic term is associated with the random cascade motion, which has a square-root phi dependence. How ever, the outward displacement is governed by only the isotropic motio n; thus, the inward displacement always dominates over the outward mot ion, which leads to a preferential displacement of the top-layer eleme nt to the bottom layer.