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Combining localized surface plasmons and confined excitons in hybrid metallic/semiconductor nanostructures is a promising route toward the manipulation of the light−matter interaction at the nanoscale and the generation of novel technological applications. In this context, we investigate the interference between plasmonic and excitonic resonances in hybrid MoSe 2 @Au nanostructures consisting of monolayer MoSe 2 supported by Au nanodisks. The optical properties of the nanostructures are probed by means of spatially resolved optical transmission and photoluminescence spectroscopies and interpreted using an analytical model complemented by numerical simulations. A plasmonic−excitonic interaction energy of 42 ± 8 meV is obtained, clearly setting the coupling in the Fano-type regime. On the basis of numerical simulations of the electromagnetic near-field and on calculations of the excitonic transition dipole momentum, we show that the interaction energy is concentrated in the gap region between the disks. The temperature dependence of the plasmonic−excitonic interaction energy is extracted from the optical transmission measurements using a Fano line shape analysis of the observed spectra. We found that the plasmonic−excitonic interaction energy is almost constant in the investigated temperature range. The plasmonic−excitonic interaction revealed in our MoSe 2 @Au nanohybrids is quite stable against temperature variation, which could enable potential applications on thermally driven plasmo-electronic transport or optically induced hyperthermia.

In this work we investigate the interaction between plasmonic and excitonic resonances in hybrid MoSe2@Au nanostructures. The latter were fabricated by combining chemical vapor deposition of MoSe2 atomic layers, Au disk processing by nanosphere lithography and a soft lift-off/transfer technique. The samples were characterized by scanning electron and atomic force microscopy. Their optical properties were investigated experimentally using optical absorption, Raman scattering and photoluminescence spectroscopy. The work is focused on a resonant situation where the surface plasmon resonance is tuned to the excitonic transition. In that case, the near-field interaction between the surface plasmons and the confined excitons leads to interference between the plasmonic and excitonic resonances that manifests in the optical spectra as a transparency dip. The plasmonic-excitonic interaction regime is determined using quantitative analysis of the optical extinction spectra based on an analytical model supported by numerical simulations. We found that the plasmonic-excitonic resonances do interfere thus leading to a typical Fano lineshape of the optical extinction. The near-field nature of the plasmonic-excitonic interaction is pointed out experimentally from the dependence of the optical absorption on the number of monolayer stacks on the Au nanodisks. The results presented in this work contribute to the development of new concepts in the field of hybrid plasmonics.

We report on photo-current generation in freestanding monolayered gold nanoparticle membranes excited by using a focused laser beam. The absence of a substrate leads to a 50% increase of the photo-current at the surface plasmon resonance. This current is attributed to a combination of trap state dynamics and bolometric effects in a nanocomposite medium yielding a temperature rise of 40 K.

We report on the surface enhanced resonant Raman scattering (SERRS) in hybrid MoSe 2 @Au plasmonic-excitonic nanostructures, focusing on the situation where the localized surface plasmon resonance of Au nanodisks is finely tuned to the exciton absorption of monolayer MoSe 2. Using a resonant excitation, we investigate the SERRS in MoSe 2 @Au and the resonant Raman scattering (RRS) in a MoSe 2 @SiO 2 reference. Both optical responses are compared to the non-resonant Raman scattering signal, thus providing an estimate of the relative contributions from the localized surface plasmons and the confined excitons to the Raman scattering enhancement. We determine a SERRS/RRS enhancement factor exceeding one order of magnitude. Furthermore, using numerical simulations, we explore the optical near-field properties of the hybrid MoSe 2 @Au nanostructure and investigate the SERRS efficiency dependence on the nanodisk surface morphology and on the excitation wavelength. We demonstrate that a photothermal effect, due to the resonant plasmonic pumping of electron-hole pairs into the MoSe 2 layer, and the surface roughness of the metallic nanostructures are the main limiting factors of the SERRS efficiency.

Hybridization of plasmonic and excitonic elementary excitations provides an efficient mean of enhancing the optical absorption and emission properties of metal/semiconductor nanostructures and is a key concept for the design of novel efficient optoelectronic devices.Here we investigate the optical properties of 2D MoSe 2 quantum well flakes covered with Au nanoparticles supporting plasmonic resonances. Using spatially resolved confocal spectroscopy, we report the observation of a quenching phenomenon of the Raman scattering and photoluminescence emission of both the MoSe 2 layer and the Au nanoparticles. We found that the quenching of the photoluminescence emission from the Au nanoparticles is partial and measurable unlike the one observed for the Au-covered MoSe 2 layers, which is total. Its dependence on the thickness of the MoSe 2 layer is determined experimentally. Based on electro-dynamics calculations and on the electronic band alignment at the Au/ MoSe 2 interface, the results are interpreted in terms of i) damping of the plasmonic resonance of the Au nanoparticles due to the optical absorption by the MoSe 2 layer ii) a two-pathways charge transfer scheme where the photo-excited electrons leak from the MoSe 2 layer to the Au NPs whereas the photo-excited holes flow in the opposite direction i.e., from the Au NPs to the MoSe 2 layer. The two combined mechanisms account well for the experimental observations and complements the interpretations proposed in the literature for similar metal nanoparticles/transition metal dichalcogenide systems.

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