Surface plasmon polariton–enhanced photoluminescence of monolayer MoS₂ on suspended periodic metallic structures

Abstract

Plasmonic nanostructures have garnered tremendous interest in enhanced light–matter interaction because of their unique capability of extreme field confinement in nanoscale, especially beneficial for boosting the photoluminescence (PL) signals of weak light–matter interaction materials such as transition metal dichalcogenides atomic crystals. Here we report the surface plasmon polariton (SPP)-assisted PL enhancement of MoS2 monolayer via a suspended periodic metallic (SPM) structure. Without involving metallic nanoparticle–based plasmonic geometries, the SPM structure can enable more than two orders of magnitude PL enhancement. Systematic analysis unravels the underlying physics of the pronounced enhancement to two primary plasmonic effects: concentrated local field of SPP enabled excitation rate increment (45.2) as well as the quantum yield amplification (5.4 times) by the SPM nanostructure, overwhelming most of the nanoparticle-based geometries reported thus far. Our results provide a powerful way to boost two-dimensional exciton emission by plasmonic effects which may shed light on the on-chip photonic integration of 2D materials.

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS2/Au Nanocavity

“…In most cases, the scattering spectrum of a nanoparticle coupled with a two-dimensional material, for example, metallic nanoparticles used in previous studies and Si nanoparticles used in this work, is employed to characterize plasmon–exciton coupling because only the excitons coupled with the nanoparticle can radiate into far field. In comparison, the PL spectrum of the two-dimensional material is seldom used to examine the plasmon–exciton coupling. , When the excitons in the WS 2 monolayer couple weakly with the plasmons supported by the nanocavity, one can expect an enhanced PL because of the existence of the hot spots (i.e., the Purcell effect). − However, the enhancement factor for the PL may not be large because the size of the hot spots (∼8.8 nm) is much smaller than that of the laser spot (∼1.2 μm) (see Figure S4a). When the plasmon–exciton coupling enters into the strong coupling regime, however, a reduction in the PL is anticipated because the excitons located at the hot spots may transfer their energies to the nanocavity and decay in the form of scattering …”

Excitation and emission distinguished photoluminescence enhancement in a plasmon–exciton intermediate coupling system

“…PL enhancement of monolayer TMDCs has been reported in several coupling systems, such as Au nanorods and WS 2 , 24,25 Ag nanocubes on Au film and MoS 2 or WSe 2 , 26–29 Ag NWs on Au film and MoSe 2 , 30 Au nanospheres or nanosphere dimers on Au film and MoS 2 , 31,32 and metal nanostructure arrays and MoS 2 or WSe 2 . 33–36 Among a variety of plasmonic nanostructures, the coupled structure of a metal nanoparticle and a metal film is widely used, which is usually called nanoparticle-on-mirror (NPOM), due to its easy fabrication, ultrasmall mode volume, and readily tailored optical resonance over a wide spectral range. 37 In addition to PL enhancement, strong or intermediate coupling of the plasmon mode with one exciton state has been demonstrated in the coupled systems of NPOMs and monolayer TMDCs.…”

Unconventional Enhancement of Photoluminescence in Multilayer MoS2 within MoS2/MoO2 Heterostructures: Implication for Optoelectronic Devices

“…One effective strategy is the incorporation of plasmonic nanostructures due to their unique capability of electromagnetic field confinement at nanoscale. As the emission quantum yield is associated with the plasmon-enhanced local field intensity, PL enhancement can be achieved when the transition-metal chalcogenides (TMD) is in the vicinity of a plasmonic nanostructure. − However, plasmonic nanostructures often require complex nanofabrication procedures, and the choice of plasmonic materials is mainly restricted to noble metals such as gold and silver. − Therefore, the discovery of alternative PL enhancement platforms based on new materials would be beneficial for optoelectronic applications of multilayer TMDs.…”