  We demonstrate that the confocal laser scanning microscopy (CLSM) provides a
non-destructive, highly-efficient characterization method for large-area
epitaxial graphene and graphene nanostructures on SiC substrates, which can be
applied in ambient air without sample preparation and is insusceptible to
surface charging or surface contamination. Based on the variation of reflected
intensity from regions covered by interfacial layer, single layer, bilayer, or
few layer graphene, and through the correlation to the results from Raman
spectroscopy and SPM, CLSM images with a high resolution (around 150 nm) reveal
that the intensity contrast has distinct feature for undergrown graphene
(mixing of dense, parallel graphene nanoribbons and interfacial layer),
continuous graphene, and overgrown graphene. Moreover, CLSM has a real
acquisition time hundreds of times faster per unit area than the supplementary
characterization methods. We believe that the confocal laser scanning
microscope will be an indispensable tool for mass-produced epitaxial graphene
or applicable 2D materials.
