In this communication, we report the successful transfer of CVD (Chemical Vapor Deposition) grown MoS2 to Au antenna fabricated using electron beam (e-beam) lithography, and we investigate the photoluminescence properties of this hybrid plasmonic-excitonic system. The ultimately thin 2D MoS2 layer has the great advantage of introducing a well controlled local absorber (and emitter) in the plasmonic near-field of the Au antenna. The work is focused on the plasmonic mediated pumping of the MoS2 photoluminescence emission. Off- and in-resonance excitation of the surface plasmons showed drastically different behaviors of the photoluminescence emission from the MoS2. For plasmonically mediated pumping, we found a significant enhancement (~65%) of the photoluminescence intensity, a clear evidence that the optical properties of MoS2 monolayer are strongly influenced by the nano-antenna surface plasmons. In addition, a systematic photoluminescence broadening and red-shift in nano-antenna locations is observed which is interpreted in terms of plasmonic enhanced optical absorption and subsequent heating of the MoS2 monolayers. Using a temperature calibration procedure based on photoluminescence spectral characteristics, we were able to estimate the local temperature changes. We found that the plasmonically induced MoS2 temperature is 4 times larger than the MoS2 reference temperature. Based on Green Dyadic theory simulations of the plasmonic properties of the Au antenna, combined with heat dissipation calculations, we discuss the contribution of the Au antenna heating to the measured temperature increase. We found that the results can be interpreted in terms of efficient light absorption by the plasmonic antenna and its conversion into electron-hole pair excitations of the 2D MoS2 layer thus leading to enhanced excitonic photoluminescence and local heating. This study shines light on the plasmonic-excitonic interaction in the hybrid MoS2/Au semiconductor/metal nano-structures and provides a unique approach for engineering new light-to-current conversion opto-devices such as high sensitivty photodetectors, bio-sensors and plasmonic controlled field-effect transistors.
Centre d'Elaboration de Matiriaux et d'Etudes Structurales-CNRS
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