Comparison of Raman spectra and vibrational density of states between graphene nanoribbons with different edges

TL;DR

This study compares vibrational properties of graphene nanoribbons with different edges, revealing how reconstructed zigzag edges influence vibrational modes and Raman spectra, and showing their similarity to armchair edges.

Contribution

It demonstrates that reconstructed zigzag edges can be identified via vibrational modes and Raman spectra, highlighting differences from traditional zigzag edges.

Findings

Reconstructed zigzag edges show high-energy vibrational modes due to triple bonds.

Vibrational density of states of reconstructed zigzag edges resemble armchair edges.

Reconstructed zigzag edges exhibit increased rigidity.

Abstract

Vibrational properties of graphene nanoribbons are examined with density functional based tight-binding method and non-resonant bond polarization theory. We show that the recently discovered reconstructed zigzag edge can be identified from the emergence of high-energy vibrational mode due to strong triple bonds at the edges. This mode is visible also in the Raman spectrum. Total vibrational density of states of the reconstructed zigzag edge is observed to resemble the vibrational density of states of armchair, rather than zigzag, graphene nanoribbon. Edge-related vibrational states increase in energy which corroborates increased ridigity of the reconstructed zigzag edge.