Raman spectra were collected with a Renishaw inVia confocal Raman microscope. Typical excitation laser (l = 514.5 nm) power was ~ 1 mW with a ~ 0.7 µm spot size; 1800/mm gratings were used. During spectral acquisition, the characteristic Si vibrational mode at ~ 520 cm -1 was used for calibration. Analysis of Raman spectra was performed using the following routine in MATLAB: 1) background subtraction was performed using a linear approximation, 2) fitting of the 1050 cm -1 to 1750 cm -1 region of the spectra using five Raman bands (three of these bands, i.e. D-, G-and D´-bands for graphene, have standard peak positions and widths), and 3) we fit the 2600 cm -1 to 2800 cm -1 region of the spectra using a single Raman band corresponding to the 2D-band for graphene. This fitting enabled estimation of the ID/IG, I2D/IG, ID/ID´, ωD, ГD, ωG, ГG, ωD´, ГD, ω2D, and Г2D parameters.