16 × 16 μm
Raman maps collected with a 0.25-μm step size. (a) FLG thickness derived from the normalized integrated intensity of the G band. The thickness is comprised between two and six graphene planes with an average thickness of three planes. (b) Domain size of the graphene crystallites deduced from the I
G ratio. The in-plane size ranges from 20 to 60 nm. (c, d) Raman shift of the G and 2D bands, respectively. The positions of both bands are shifted to higher energies. The G band is around 1610 cm-1 and the 2D band around 2750 cm-1. This high up shift can only be explained by a high in-plane compressive strain of the graphene lattice.