Figure 6

(a) A white-light reflection image of graphene on Si/SiO₂ (285 nm). Slight contrast changes indicate areas where multiple layers of graphene are present. Raman spectra taken at these points (right) confirm that the number of graphene layers changes due to a decrease in the 2D/G ratio and a broadening of the 2D peak. Adapted from Ref. 10 (© 2009 AAAS). (b) Confocal Raman maps of the G-band intensity of ¹³C (left) and ¹²C (right) in CVD graphene grown on copper, where ¹³C and ¹²C sources were alternated during graphene growth. The G-band peaks position of ¹²C and ¹³C are different because the heavier nucleus red-shifts the G-band phonon mode slightly, allowing the two sources to be differentiated. These images can be used to map growth vs time and to study the growth mechanism of CVD graphene on various substrates. Adapted from Ref. 17 (© 2009 ACS).