Optical manipulation of transition metal dichalcogenide with sub-nanometer metal-insulator-semiconductor cavity

Transition metal dichalcogenides (TMDs) exhibit intriguing optical properties, and integrating them with plasmonic structures offers an effective way to tune the optical response, making TMDs promising for optoelectronic applications. In this work, we report the manipulation of optical properties in WS₂ through the integration into metal-insulator-semiconductor (MIS) structure. In particular, we separated WS₂ from single-crystal Au surface with insulator gaps of sub- to few-nanometers thick. We observed the intensity quenching and frequency shift of static photoluminescence (PL) of WS₂ as a function of MIS geometry, consistent with theoretical models of dielectric screening. An ultrafast pump-probe measurement shows the tuning of WS₂ optical response even with pumping energy lower than the optical gap, suggesting the charge and energy transfers in the MIS structure with the assistance of the excited hot carriers. Our observation is useful for the understanding of PL quenching, charge and energy transfer, and the coupling between TMDs and MIS structure.