A non-dispersive Raman D-band activated by well-ordered interlayer interactions in rotationally stacked bi-layer Graphene

TL;DR

This study reveals a non-dispersive D-band in rotationally stacked bilayer graphene caused by well-ordered interlayer interactions, challenging previous understanding of Raman features in sp2 carbons.

Contribution

It introduces a new Raman scattering mechanism in skew-stacked bilayer graphene due to ordered interlayer interactions, with a non-dispersive D-band feature.

Findings

Discovery of a non-dispersive D-band in rotated bilayer graphene.

Identification of a new Raman scattering mechanism linked to interlayer order.

Explanation of the non-dispersive peak via Fourier structure of interlayer potential.

Abstract

Raman measurements on monolayer graphene folded back upon itself as an ordered but skew-stacked bilayer (i.e. with interlayer rotation) presents new mechanism for Raman scattering in sp2 carbons that arises in systems that lack coherent AB interlayer stacking. Although the parent monolayer does not exhibit a D-band, the interior of the skewed bilayer produces a strong two-peak Raman feature near 1350 cm-1; one of these peaks is non-dispersive, unlike all previously observed D-band features in sp2 carbons. Within a double-resonant model of Raman scattering, these unusual features are consistent with a skewed bilayer coupling, wherein one layer imposes a weak but well-ordered perturbation on the other. The discrete Fourier structure of the rotated interlayer interaction potential explains the unusual non-dispersive peak near 1350 cm-1.