Molecular beam growth of graphene nanocrystals on dielectric substrates

We demonstrate the growth of graphene nanocrystals by molecular beam methods that employ a solid carbon source, and that can be used on a diverse class of large area dielectric substrates. Characterization by Raman and near edge X-ray absorption fine structure spectroscopies reveal a sp2 hybridized hexagonal carbon lattice in the nanocrystals. Lower growth rates (below 0.5 Å/min) favor the formation of layered, larger size multi-layer graphene crystallites (up to 22 nm) on all investigated substrates. The surface morphology is determined by the roughness of the underlying substrate (RMS ∼8 Å) and graphitic monolayer steps are observed by ambient scanning tunneling microscopy.