Determination of the Crystallographic Orientation of Graphene by Raman Spectroscopy

We present a systematic study of the Raman spectra of the G band in graphene monolayers under tunable uniaxial tensile stress. The G band splits into two distinct sub-bands (G$^{+}$, G$^{-})$ because of the strain-induced symmetry breaking. Raman scattering from the G$^{+}$ and G$^{-}$ bands shows a distinctive polarization dependence that reflects the angle between the axis of the stress and the underlying graphene crystal axes. Polarized Raman spectroscopy therefore constitutes a purely optical method for the determination of the crystallographic orientation of graphene.