Enhanced Light-Matter Interactions in Self-Assembled Plasmonic Nanoparticles on 2D Semiconductors.

Two-dimensional (2D) transition-metal dichalcogenide (TMD) monolayers of versatile material library are spotlighted for numerous unexplored research fields. While monolayer TMDs exhibit an efficient excitonic emission, the weak light absorption arising from their low dimensionality limits potential applications. To enhance the light-matter interactions of TMDs, while various plasmonic hybridization methods have been intensively studied, controlling plasmonic nanostructures via self-assembly processes remains challenging. Herein, strong light-matter interactions are reported in plasmonic Ag nanoparticles (NPs) hybridized on TMDs via an aging-based self-assembly process at room temperature. This hybridization is implemented by transferring MoS monolayers grown via chemical vapor deposition onto thin-spacer-covered Ag films. After a few weeks of aging in a vacuum desiccator, the Ag atoms in the heterolayered film diffuse to the MoS layers through a SiO spacer and self-cluster onto MoS point defects, resulting in the formation of Ag-NPs with an estimated diameter of ≈50 nm. The photoluminescence intensities for the Ag-NP/MoS hybrids are enhanced up to 35-fold compared with bare MoS owing to the local field enhancement near the plasmonic Ag-NPs. The localized surface plasmon resonances modes of this hybrid are systematically investigated via numerical simulations and dark-field scattering microscopy.