Adatom-promoted graphene growth on nickel: real-time imaging and numerical simulations.

Patera L.L., Bianchini F., Africh C., Dri C., Soldano G.J., Mariscal M.M., Peressi M., Comelli G.

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II - Fisica della materia
Aula 32B-2 - Mercoledì 19 h 09:00 - 13:00
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Single adatoms are expected to participate in many processes occurring at the solid-gas and solid-liquid interfaces, such as the growth of graphene on metal surfaces. We demonstrate, both experimentally and theoretically, the catalytic role played by single metal adatoms during the synthesis at technologically relevant temperatures $(\approx 700$ K) of graphene flakes on Ni(111), mostly characterized by an epitaxial top/hollow-fcc registry with the substrate. Single Ni atoms, diffusing on the metal surface, are temporarily trapped at kink sites along the graphene flake edges and facilitate the incorporation of new C atoms in the graphene network, which thus grows by ordered addition of couples of carbon rows parallel to the edge. Scanning tunneling microscopy (STM) imaging at the millisecond time scale allowed us to identify the edge structure and individual Ni adatoms, directly capturing their catalytic action. Force-field molecular dynamics (MD) and ab-initio density functional theory (DFT) calculations rationalize the experimental observations, giving a complete description of the growth pathways. Our results unveil the mechanism ruling the activity of a single atom catalyst at work.

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