Atomistic Mechanism of Surfactant-Assisted Epitaxial Growth

Experiments and simulations on the effect of a surfactant on atomic diffusion are presented. Cu adatoms deposited on a Cu(111) surface covered with a monolayer of Pb quickly get buried and diffuse under the Pb layer by exchanging sites with other Cu atoms from the substrate. The surfactant induces layer-by-layer growth by suppressing the hopping mechanism of diffusion over the terraces and promoting atomic exchange, both at the terraces and across the steps. This mechanism may be rather general and has profound implications for the synthesis of artificial materials.