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. Author manuscript; available in PMC: 2013 Sep 25.
Published in final edited form as: ACS Nano. 2012 Aug 24;6(9):8241–8249. doi: 10.1021/nn302918x

Figure 3.

Figure 3

SEM images of monolayer and bilayer graphene on the center of Cu foil synthesized with H2/CH4 ratio of 40 under 1 mbar at 1050 °C for (a) 2 min and (b) 1 hour growth. (c) SEM image shows that the bilayer graphene coverage is increased dramatically by increasing pressure to 5 mbar for 1 hour growth after the first 2 min low pressure nucleation step. (d) SEM image of higher coverage of bilayer graphene obtained after extending the growth duration to 3 hours. Scale bars are 20 μm. (e) Coverage statistics of different layers for the sample shown in (d) demonstrates that ~ 99 % of surface area is covered by bilayer graphene. (f) Representative Raman spectra of the two different stacked bilayer graphene in (d). (g, h) Histograms of the Raman spectrum 2D band FWHMs and I2D/IG ratio of the bilayer graphene. (i) Stacking ratio statistics of the bilayer graphene based on (g, h).