Localization of interlayer excitons in nanoscale wrinkles investigated by nano-PL and nano-Raman spectroscopies

Interlayer excitons (ILE) in TMD-heterostructures have the potential to form complex multiparticle excitonic phases and are of intense recent scientific interest. However, the low photoluminescence quantum yield of ILE’s makes optical investigation of localized ILE's especially challenging, forcing many optical measurements of ILE emission to be done at cryogenic temperatures and with excitation spots >1 um in diameter. Such large probe areas average over local perturbations, complicating analysis. Here, I will show advanced near-field optical characterization of localized ILE’s in a MoSe₂-WSe₂-Au heterostructure. Hyperspectral imaging with few-nm resolution shows a rich variety of ILE states with distinct emission peaks between 850 nm to past 1000 nm that are localized to nanobubble edge regions 1 - 5 nm wide, and have emission intensity that is enhanced by >100x. Using nano-Raman scattering we find that these edge regions have similar vibrational spectra to lattice wrinkles observed to 1L-WSe₂ nanobubbles, suggesting a “double-wrinkle” of the heterolayer as the source. Our results illustrate the potential for strain engineering ILE’s in TMD heterostructures for use in tailoring exciton states for future 2D optoelectronic devices.