Probing gap mode plasmonic enhanced optical properties in the oxidized edge of WSe₂ monolayer

Driven by the recent investigations in quantum engineering on tuning the electrical and optical density of states of the Transition Dichalcogenide Metal (TMD) monolayer in nanoscale, this work focuses on taking nanoscale spectroscopic imaging of the WSe₂ monolayer by the scanning near-field optical microscope (SNOM). For the results in this talk, the near-field enhancement was based on the strong plasmonic resonance within the few-nanometer size gap between the Gold coated sharp tip and the gold substrate surface. In order to have the gap plasmonic mode, we deposited the TMD monolayer on the top of an ultra-flat gold thin film. The near-field photoluminescence (PL) images and correlated topographic images reveal that the optical resolutions of the nano PL mappings are consistent with sizes of the near-field tips. Through spectral and nano-auger analysis, we also identified the oxidized feature along the sample edge.