Locally enhanced surface plasmons and modulated "hot-spots" in nanoporous gold patterns on atomically thin MoS2 with a comparison to SiO2 substrate.

Plasmonic phenomena in metals have garnered significant scientific and technological interest in the past decade. Despite many promising applications based on plasmonics, one remaining challenge is to control the surface geometry or morphology of the metallic structures, which can significantly affect the plasmonic properties of nanostructures. Here, we report the morphological modulation of gold (Au) nanopatterns on atomically thin layered molybdenum disulfide (MoS₂), compared to Au nanopatterns grown on SiO₂/Si substrate. We have used electron energy loss spectroscopy in a scanning transmission electron microscope to probe the locally enhanced surface plasmons in nanoporous Au patterns grown on SiO₂/Si substrate as well as on single- and few-layer MoS2 flakes. Thin flakes of MoS₂ as substrates significantly influence the morphology of Au patterns, which locally alters the plasmonic behavior. Features such as nanoscale pores exhibit plasmon localization with strong near fields, akin to "hot spots." Boundary element method simulations demonstrate that the dipolar and breathing modes can be excited at different positions of the nanopatterns. [ABSTRACT FROM AUTHOR]