Atomic Scale Understanding of Intermixing Behavior of Thin Metal Multilayer

We have investigated the atomic scale intermixing behavior of Co-Al system in both theoretical and experimental methods. Asymmetic intermixing was observed by molecular dynamics simulation: severe intermixing occurs when Co was deposited on Al surface resulting in 3 atomic layers of CoAl-B2 compound. In contrast, an atomically sharp interface forms between Al film and Co substrate. The predicted asymmetry in atomic scale intermixing was experimentally confirmed by a coaxial impact collision ion scattering spectroscopy (CAICISS). The adsorbed Al atoms on Co (0001) surface were placed on either fcc or hcp hollow sites with approximately the same probability. On the other hand, the adsorbed 0.5 monolayer (ML) Co ad-atoms were mixed with Al atoms of substrate resulting in the thin surface layer of ordered CoAl-B2 phase. Magneto-optical Kerr effect (MOKE) measurement of Co/Al multilayer also agrees very well with the simulation results in a quantitative manner.