Nano-Raman and photoluminescence imaging of moiré domains in twisted TMDs

When monolayer transition metal dichalcogenides are vertically stacked, lattice mismatch and non-zero lead to the formation of moiré superlattices. This imposed periodic potential modifies the optoelectronic landscape, leading to the formation of novel phononic and excitonic states. For twisted TMDs, visualization of the moiré domains has typically been done with scanning probe imaging techniques such as atomic force or scanning tunneling microscopy, or electron microscopy, each of which reveal substantial heterogeneity in low twist angle homo and hetero-bilayers due to intrinsic strain and lattice reconstruction. However, because of the diffraction limit, this variation can cofound experimental comparisons with optical probes. In the presentation I will show nano-Raman and nano-photoluminescence imaging of reconstructed twisted TMD bilayers. Our results so a strong optical intensity in the Raman and PL signals from the moiré domain walls. Comparing with AFM imaging, our results show exact agreement of with boundaries of the moiré cells. Further, nano-Raman spectroscopy of the domain walls provides a direct optical of the relative strain.