Interface coupling in twisted multilayer graphene by resonant Raman spectroscopy of layer breathing modes

TL;DR

This study demonstrates that resonant Raman spectroscopy can effectively probe interlayer interactions in twisted multilayer graphene, revealing that twisting influences shear modes but not layer breathing modes, thus aiding interface characterization.

Contribution

The paper shows that twisting affects shear modes but not layer breathing modes in multilayer graphene, providing new insights into interlayer coupling via Raman spectroscopy.

Findings

Resonant Raman spectroscopy can measure LBMs at room temperature.

Twisting enhances shear modes but does not affect LBMs.

Interlayer interactions are primarily influenced by shear mode behavior.

Abstract

Raman spectroscopy is the prime non-destructive characterization tool for graphene and related layered materials. The shear (C) and layer breathing modes (LBMs) are due to relative motions of the planes, either perpendicular or parallel to their normal. This allows one to directly probe the interlayer interactions in multilayer samples. Graphene and other two-dimensional (2d) crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientation have different optical and electronic properties. In twisted multilayer graphene samples there is a significant enhancement of the C modes due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. Here we show that this applies also to the LBMs, that can be now directly measured at room temperature. We find that twisting does not affect LBMs, quite different from the case of the C modes. This implies that the periodicity mismatch between two twisted layers mostly affects shear interactions. Our work shows that Raman spectroscopy is an ideal tool to uncover the interface coupling of 2d hybrids and heterostructures.