Visualization of Raman spectroscopy for stacking orders: distinguishing Bernal and rhombohedral graphite

Abstract

Raman spectroscopy is a powerful tool to investigate the properties of materials. In particular, the ability to analyze the crystallinity, the number of layers, defects, and electronic properties of two-dimensional materials (2DMs). 2DMs make it a valuable analytical tool in numerous fields. Among 2DMs, rhombohedral stacking graphite, which has ABC-stacked layers, has a different band structure that shows peculiar electronic properties compared to Bernal stacking graphite, which has ABA-stacked layers, and exhibits the characteristics of a topological insulator, making it a unique material. Using Raman spectroscopy, Bernal and rhombohedral stacking can be easily distinguished at room temperature. In multi-layer graphene (MLG), the stacking order can be distinguished by various bands generated from Raman scattering. Additionally, changes in the excitation energy of the laser result in shifts in the Raman peaks and changes in the line shape. In this study, 633 nm and 514 nm lasers were utilized to compare the Raman bands of MLG in Bernal and rhombohedral stacking order. The 2D band, which is a second-order overtone of different in-plane vibrations, was fitted with three Lorentzian peaks to investigate how each Lorentzian peak changes according to the stacking order. Subsequently, the D + Dʺ, N, and M bands, which are weak combination bands with double resonant Raman modes, were investigated to see how they change in Bernal and rhombohedral stacking MLG with increasing laser energy. Conclusively, we present an easy method to distinguish Bernal and rhombohedral stacking in MLG at room temperature using Raman spectroscopy.