Heteroepitaxial growth of Co Cu(001): An accelerated molecular dynamics simulation study

We employ static energy calculations and accelerated molecular dynamics (MD) simulations to study atomistic processes involved in the growth of Co on Cu(001) surfaces. The system is modeled with an empirical tight-binding (second-moment approximation) potential. Our accelerated MD algorithm, which detects, on the fly, groups of states connected by small barriers and consolidates them into larger states, allows us to reach time scales of seconds close to room temperature. These capabilities enable direct comparison to kinetic Monte Carlo and experimental studies of the initial stages of Co Cu(001) growth. We observe upward interlayer transport mechanisms that contribute to bilayer island formation at low surface temperatures. At high temperatures the mixing of Co into the surface produces qualitative changes in the island structure, leading to the reversal of the low-temperature transport mechanisms and resulting in monolayer growth. We find that small Co islands can be as mobile as single adatoms and that they significantly affect the low-coverage morphology.