Promoted localized defect-bound exciton emission of MoS2 over wide temperature range via plasmonic nanocavity chain

Noble metal nanostructures offer an exciting opportunity to modulate photoluminescence (PL) in two-dimensional (2D) transition metal dichalcogenides materials, showing promising prospects for optoelectronic devices. However, achieving a low-cost, designable, and residue-free nanofabrication method remains challenging. Herein, we present a one-step ultrafast laser nanofabrication approach for creating large-area periodic nanocavity chain substrate, which can be engineered as a localized surface plasmon resonance substrate via coating with a Au film by magnetron sputtering. Subsequently, a hybrid system is formed through mechanical exfoliation and transfer of monolayer molybdenum disulfide (MoS₂). A three-fold PL enhancement is achieved in the MoS₂ on plasmonic nanocavity chains, which can be attributed to nanoscale confinement of incident laser and exciton-trion interconversion induced by hot electron transfer. Even more attractively, a prominent localized defect-bound exciton appears on the hybrid in the low-energy region at low temperature, exhibiting significant intensity enhancement compared to MoS₂ on Au film deposited over unprocessed regions. Remarkably, the localized defect-bound exciton on plasmonic nanocavity chains demonstrates considerably maintained substantial intensity over a wide temperature range from 4 to 200 K. These results unlock opportunities for applying defect-bound exciton emission in nanophotonic devices based on 2D material/plasmonic hybrid.