Rapid infrared imaging of rhombohedral graphene

The extrinsic stacking sequence based on intrinsic crystal symmetry in multilayer two-dimensional materials plays a significant role in determining their electronic and optical properties. Compared with Bernal-stacked (ABA) multilayer graphene, rhombohedral (ABC) multilayer graphene hosts stronger electron-electron interaction due to its unique dispersion at low-energy excitations and has been utilized as a unique platform to explore strongly correlated physics. However, discerning the stacking sequence via scanning mapping methods has always been a fairly time-consuming process. Here, we report a rapid recognition method for ABC-stacked graphene with high accuracy by infrared imaging based on the distinct optical responses in the infrared range. The optical contrast of the image between ABC- and ABA-stacked graphene is strikingly clear, and the discernibility is comparable to traditional optical Raman microscopy but with higher consistency and throughput. We demonstrate that the infrared imaging technique can be integrated with dry transfer techniques commonly used in the literature. This rapid and convenient infrared imaging technique will significantly improve the sorting efficiency for differently stacked multilayer graphene, thereby accelerating the exploration of the novel emergent correlated phenomena in ABC-stacked graphene.