Polarized Nonresonant Raman Spectra of Graphene Nanoribbons

We study the nonresonant Raman scattering of armchair and zigzag graphene nanoribbons (GNRs) using density functional perturbation theory. We find that, in both GNR types, the Raman spectrum is extremely polarized along the ribbon axis direction with the scattering intensity being over 10(2) times greater than those of the other polarizations because of the geometrical confinement. Along the dominant polarization direction, the scattering intensity and frequency oscillate strongly with the ribbon width in the armchair GNRs, while the scattering intensity initially increases and then decreases with the ribbon width and the frequency monotonically changes with the ribbon width in the zigzag GNRs. Such a difference is closely associated with the different width dependences of band structure between the two types of GNRs.