Wrinkling and crumpling in twisted few and multilayer CVD graphene: High density of edge modes influencing Raman spectra

TL;DR

This study reveals how crumpling in twisted few and multilayer CVD graphene affects Raman spectra, highlighting enhanced G band intensity, surface defects, and new edge mode resonances, providing insights into stacking and defect characterization.

Contribution

It demonstrates that crumples in graphene significantly influence Raman spectra, introducing new edge modes and refining defect analysis methods.

Findings

Crumples enhance G band intensity similar to twisted bilayer graphene.

Identification of 23 new resonant bands at 633 nm linked to edge modes.

Raman spectral features provide qualitative insights into layer stacking.

Abstract

Richness and complexity of Raman spectra related to graphene materials is established from years to decades, with, among others: the well-known G, D, 2D,... bands plus a plethora of weaker bands related to disorder behavior, doping, stress, crystal orientation or stacking information. Herein, we report on how to detect crumpling effects in Raman spectra, using a large variety of few and multilayer graphene. The main finding is that these crumples enhance the G band intensity like it does with twisted bi layer graphene. We updated the D over G band intensity ratio versus G band width plot, which is generally used to disentangle point and linear defects origin, by reporting surface defects created by crumples. Moreover, we report for the first time on the existence 23 resonant additional bands at 633 nm. We attribute them to edge modes formed by high density of crumples. We use Raman plots (2D bands versus G band positions and widths) to gain qualitative information about the way layers are stacked.