UC Berkeley

We study the nucleation and growth of epitaxial graphene on Pt(111) surfaces at the atomic level using scanning tunneling microscopy (STM). Graphene nucleation occurs both near Pt step edges and on Pt terraces, producing hexagonally shaped islands with atomically sharp zigzag edges. Graphene interacts strongly with Pt substrate during growth, by etching and replacement of Pt atoms from step edges, which results in faceting of the Pt steps. The favorable lattice orientations of graphene islands are found to be parallel to those of the Pt substrate, but other orientations are still possible. Grain boundaries are formed when two graphene islands merge with different lattice orientations. Improved growth conditions such as smaller nucleation density and higher growth rate can produce high quality graphene film with larger grain sizes.