Stacking-induced Second Harmonic Generation in Graphene Trilayers

Van der Waals stacking of layered two-dimensional crystals, such as few-layer graphene, can lead to profound effects on electronic, optical and mechanic properties. It has been reported that the Bernal (ABA) and rhombohedral (ABC) stacking graphene trilayers have dramatically different electronic, transport and optical properties. So it is crucial to develop an effective method to identify the stacking order and domain of graphene trilayers. Previously, Raman scattering and infrared absorption spectroscopies have been employed to investigate the stacking order of graphene few-layers. However, all these techniques have either low imaging throughput or poor spatial resolution. In this talk, we report the use of second harmonic generation (SHG) microscopy to image the ABA and ABC stacking order of graphene trilayers due to their distinct structural symmetry. We found that the stacking-induced SHG response from ABA stacked trilayer is surprisingly strong, comparable to other non-centrosymmetric layered materials. Furthermore, the crystalline orientation of ABA trilayer could be unambiguously determined by polarization-resolved SHG measurement. Therefore, our work is expected to expedite the exploration of stacking dependent physics in graphene.