(Color online) (a) Contrast-stretched optical micrograph of CVD graphene transferred to 309 nm SiO2 substrate under λ = 600 nm illumination. Inset shows a reference sample of two mechanically exfoliated graphene flakes on a background of 306 nm SiO2. (b) Histograms of reflected light intensity from the marked regions of (a) normalized to equal intensity for the SiO2 substrate. Dashed lines show theoretical peak positions for 0–4 layer graphene for the corresponding substrate thickness (see main text).
(Color online) Representative micro-Raman spectra of CVD graphene at points 1 and 2 in Fig. 1 with low (∼12–13%, point 1) and high (∼19%, point 2) contrast, along with comparative spectra of a mechanically exfoliated bilayer graphene (MEBLG) sample, all normalized to equal G peak height. Solid curves show Lorentzian fitting peaks, while dashed lines show Raman background.
(Color online) (a) 2 D peak positions, (b) 2 D peak widths, and (c) relative intensity of 2 D peaks for 514 nm (left) and 633 nm (right) Raman spectra on the CVD graphene sample shown in Fig. 1 (points 1–5) and an additional sample (points 6–9; see supplemental material). Blue circles indicate points of lower (∼12-13%) optical contrast, while red triangles indicate points of higher (∼19%) contrast. Shaded bands indicate ranges for each peak parameter, grouped by contrast. (Note: 633 nm Raman spectra were not measured for point 7.)
(Color online) (a) Tapping-mode ambient AFM topography image around the edge of a piece of CVD graphene transferred from copper to nominal 300 nm SiO2. (b) Line profile of sample height (in nm) along the length of the dashed box in (a), averaged across its width. A step from the SiO2 substrate to the graphene is visible, followed by a second step indicating one or more monolayers of graphene on top of the first. The arrow in (a) indicates another such step visible nearby on this sample. Crosses in (a) and dashed vertical lines in (b) indicate edges of the first step from SiO2 to graphene.
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