A Novel Nano-Electroplating based Plasmonic Platform for Emission Engineering of Monolayer MoS₂

Two-dimensional semiconductors, like monolayer MoS₂, have garnered significant interest due to their remarkable electronic and optical properties. Nevertheless, their practical utility has been hindered by limited light absorption stemming from their atomically thin thickness and low quantum yield. To address these challenges and manipulate the optical properties effectively, integrating subwavelength plasmonic nanostructures with monolayer MoS₂ is an effective method. In our previous work, we reported the easy fabrication of flat-topped gold nanodisc (AuND) array using EBL and nano-electroplating [1]. In this study, monolayer MoS₂ transferred on top of the gold nanodisc (AuND) array exhibited an impressive photoluminescence enhancement of up to 150-fold compared to monolayer MoS₂ transferred on Au film [2]. The obtained enhancement factor is without normalising the area of plasmonic hotspots. To understand the mechanism behind this enhancement, we conducted FDTD simulations. The demonstrated fabrication of AuND using electroplating will give a flat-topped surface, which is helpful for the delicate wet transfer of monolayer MoS₂ from as-grown sapphire. We investigated the effect of using a dielectric spacer between monolayer MoS₂ and AuND. We also discussed the exciton-trion dynamics in PL of monolayer MoS₂ on AuND, Au film, and as-grown sapphire. Our findings shed light on exploring the nano electroplating technique to tailor the optical properties of monolayer semiconductors.