Edge phonon state of mono- and few-layer graphene nanoribbons observed by surface and interference co-enhanced Raman spectroscopy

Using surface and interference co-enhanced Raman scattering measurements, we detected two well-distinguished Raman bands at 1450 and 1530 cm^-1 from individual mono- and few-layer graphene nanoribbons (GNRs) prepared by chemical exfoliation and mechanical cleavage of graphite. The intensities of these two peaks strongly depend on the width and edge structure of the GNRs. Combining with first-principles calculations, the 1450 and 1530 cm^-1 Raman bands are assigned to the localized vibration of the edge atoms of zigzag and armchair GNRs terminated with H atoms, respectively. In addition, two weak peaks at ∼1140 and 1210 cm^-1 are also observed, which are coupled with 1450 and 1530 cm^-1, respectively. These findings enrich the understanding on the fine structure of mono- and few-layer GNRs by Raman spectroscopy.