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.