Low-frequency tip-enhanced Raman scattering of 2D materials

Two-dimensional materials such as transition metal dichalcogenides have unique optoelectronic properties with broad tunability via doping and stacking, which makes them promising platforms for functional nanodevices. Nanoscale structural characterization of 2D materials provides information about local exciton generation and defects via tip-enhanced photoluminescence (TEPL) and tip-enhanced Raman scattering (TERS). TERS of 2D materials has been previously performed in the high frequency range. However, low-frequency range is advantagous for investigating the interlayer interactions and stacking. Here, we performed low-frequency TERS measurements of twisted 2D spirals of lateral MoSe2-WSe2 heterostructures to understand the correlations between the local structural heterogeneities and nano-optical response. We compared the results with high-frequency TERS and discuss optimizationf of relevant plasmonic processes and enhancement mechanisms.