Identification of graphite with perfect rhombohedral stacking by electronic Raman scattering

TL;DR

This paper introduces a simple optical Raman scattering method to accurately identify perfect rhombohedral stacking in few-layer graphite, overcoming limitations of previous techniques especially in thicker samples.

Contribution

It demonstrates that electronic Raman scattering can distinguish flawless rhombohedral graphite from defective structures in 3 to 12 layers using standard Raman equipment.

Findings

Distinctive ERS peak positions for perfect RG

Method applicable at room temperature with visible light

Overcomes previous stacking identification limitations

Abstract

Rhombohedral graphite (RG) shows strong correlations in its topological flat band and is pivotal for exploring emergent, correlated electronic phenomena. One key advantage is the enhancement of electronic interactions with the increase in the number of rhombohedrally stacked graphene layers. Increasing thickness also leads to an exponential increase in the number of stacking faults, necessitating a precise method to identify flawless rhombohedral stacking. Overcoming this challenge is difficult because the established technique for stacking sequence identification, based on the Raman 2D peak, fails in thick RG samples. We demonstrate that the strong layer dependence of the band structure can be harnessed to identify RG without stacking faults, or alternatively, to detect their presence. For thicknesses ranging from 3 to 12 layers, we show that each perfect RG structure presents distinctive peak positions in electronic Raman scattering (ERS). This measurement can be carried out using a conventional confocal Raman spectrometer at room temperature, using visible excitation wavelengths. Consequently, this overcomes the identification challenge by providing a simple and fast optical measurement technique, thereby helping to establish RG as a platform for studying strong correlations in one of the simplest crystals possible.