Raman Radial Mode Revealed from Curved Graphene

One of the unsolved fundamental issues of graphene is establishing an appropriate way to discern layers of graphene structures. We report a simple methodology to analyze graphene structures using Raman signals in the range of ∼100 to ∼500 cm^-1 comprising clear 118 or 175 cm^-1 peaks. We demonstrate that the low-energy signals on Raman spectra of plasma-seeded grown graphene sheets originated from nanocurvature (c) of mono- (175 and 325-500 cm^-1 signals) (c - 1 nm) and bilayer (118 cm^-1 peak) (c -2 nm) graphene with Raman simulations, based on Raman radial mode (RM) Eigen vectors. Our RM model provides a standard way of identifying and evaluating graphene structures.