Nano-Raman Spectral Imaging of Localized Vibrations in Two-Dimensional Systems

Here we report graphene systems' nano-Raman hyperspectral imaging based on tip-enhanced Raman scattering (TERS). The vibrational and electronic structures are modulated within the graphene-related materials, leading to nano-scale changes in the behavior of electrons and phonons that can be used for spectral imaging. Furthermore, we utilize a He-focused ion beam to do nanolithography on graphene. We then show that the tiny features on graphene made by the He-focused ion beam can only be visualized under nanometer-scaled spectroscopy imaging. We have also imaged low-angle reconstructed twisted bilayer graphene, and our observations highlight the relevance of solitons and topological points for the structures' vibrational and electronic properties, relevant in the context of twistronics.