Direct Observation of Inner and Outer G' Band Double-resonance Raman Scattering in Free Standing Graphene

TL;DR

This paper reports the direct observation of G' band splitting in free-standing graphene's Raman spectrum, supporting the theory that inner and outer double-resonance processes cause this splitting, influenced by trigonal warping effects.

Contribution

It provides experimental evidence for the coexistence of inner and outer double-resonance processes causing G' band splitting in graphene, confirming theoretical predictions.

Findings

G' band splitting observed in free-standing graphene

Inner and outer processes contribute to G' band features

Trigonal warping affects spectral characteristics

Abstract

In contrary to the widely reported single and symmetric peak feature of G' (or 2D) band in Raman spectrum of graphene, we herein report the observation of splitting in G' band in free standing graphene. Our experimental findings provide a direct and strong support for the previous theoretical prediction that the coexistence of the outer and inner processes in the doubleresonance Raman scattering would cause the splitting of G' mode. Our investigation of the influence of trigonal warping effect on the spectral features of G' subbands further verified the theoretical interpretation established on the anisotropic electronic structure of graphene.