Abstract
We present a comprehensive study of graphene grown by chemical vapor deposition on copper single crystals with exposed (100), (110) and (111) faces. Direct examination of the as-grown graphene by Raman spectroscopy using a range of visible excitation energies and microRaman mapping shows distinct strain and doping levels for individual Cu surfaces.
Comparison of results from Raman mapping with X-ray diffraction techniques and atomic force microscopy shows it is neither the crystal quality nor the surface topography responsible for the specific strain and doping values, but it is the Cu lattice orientation itself. We also report an exceptionally narrow Raman 2D band width caused by the interaction between graphene and metallic substrate.
The appearance of this extremely narrow 2D band with full-width-at-half maximum (FWHM) as low as 16 cm(-1) is correlated with flat and undoped regions on the Cu(100) and (110) surfaces. The generally compressed (similar to 0.3% of strain) and n-doped (Fermi level shift of similar to 250 meV) graphene on Cu(111) shows the 2D band FWHM minimum of similar to 20 cm(-1).
In contrast, graphene grown on Cu foil under the same conditions reflects the heterogeneity of the polycrystalline surface and its 2D band is accordingly broader with FWHM >24 cm(-1). (C) 2013 Elsevier Ltd. All rights reserved.