Edge-Epitaxial Growth of Graphene on Cu with a Hydrogen-Free Approach

We demonstrate a new concept of edge-epitaxial growth that enables the van der Waals (vdWs) epitaxial graphene growth on different Cu facets. This approach simply entails turning off hydrogen during the nucleation stage of the atmospheric pressure chemical vapor deposition process. Fundamentally, different from conventional vdWs growth, this new type of epitaxial growth benefits from the strong binding between the graphene edge and a metal step in a hydrogen-absent atmosphere. This interaction fixes the orientation of graphene grains in energetically preferable configurations at the early nucleation stage. Specifically, single-crystal graphene grains grown on Cu(111) have irregular shapes with rough edges and are misaligned slightly with respect to the Cu(111) lattice. Graphene grains form with two possible orientations that are rotated by ∼30° on the Cu(100) surface, and grains with three preferred orientations are observed on Cu(110). Density functional theory calculations further prove the enhanced edge-metal step interaction and thus validate the experimental observations of these specific graphene crystal orientations on Cu(100) and Cu(110). Observation of this new type of edge-epitaxial growth helps to clarify many contradictory graphene growth phenomena that have been observed previously and may provide insights that will facilitate an understanding of the growth of other materials using the chemical vapor deposition method.