▎ 摘　　要

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 sp(2) hybridized hexagonal carbon lattice in the nanocrystals. Lower growth rates (below 0.5 angstrom/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 similar to 8 angstrom) and graphitic monolayer steps are observed by ambient scanning tunneling microscopy. (C) 2012 Elsevier Ltd. All rights reserved.