Plasmonic Pumping of Excitonic Photoluminescence in Hybrid MoS₂–Au Nanostructures

Abstract

We report on the fabrication of monolayer MoS2-coated gold nanoantennas combining chemical vapor deposition, e-beam lithography surface patterning, and a soft lift-off/transfer technique. The optical properties of these hybrid plasmonic-excitonic nanostructures are investigated using spatially resolved photoluminescence spectroscopy. Off- and in-resonance plasmonic pumping of the MoS2 excitonic luminescence showed distinct behaviors. For plasmonically mediated pumping, we found a significant enhancement (∼65%) of the photoluminescence intensity, clear evidence that the optical properties of the MoS2 monolayer are strongly influenced by the nanoantenna surface plasmons. In addition, a systematic photoluminescence broadening and red-shift in nanoantenna 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 increase is nearly four times larger than in the MoS2 reference temperatures. This study shines light on the plasmonic-excitonic interaction in these hybrid metal/semiconductor nanostructures and provides a unique approach for the engineering of optoelectronic devices based on the light-to-current conversion.

Photonic Structure-Integrated Two-Dimensional Material Optoelectronics

“…Either stacking 2D materials on top of those plasmonic nanostructures, or patterning plasmonic nanostructures on top of 2D materials can increase the light absorption at certain wavelengths [93][94][95][96][97]. A significant enhancement~65% of photoluminescence intensity are reported for a monolayer MoS 2 -coated gold nanoantennas system [98]. Similar phenomena are observed for 2D material base optoelectronics.…”

“…First, the introduction of photonic structures into 2D materials can significantly enhance their photoresponsivity [93][94][95][96][97][98][99][100][101][102][103][104][105][106]. On the other hand, by electrostatically tuning the Fermi level of 2D materials, with which photonic structures like waveguides, resonators and cavities are integrated, their modulation performance can be improved [107][108][109][110][111][112][113].…”

Van der Waals Materials for Atomically-Thin Photovoltaics: Promise and Outlook

“…Several strategies have been proposed and preliminary demonstrations have been reported including use of plasmonic metal particles, shells or resonators to enhance photocurrent and photoluminescence. [27][28][29][30][31][32][33][34][35][36][37] More sophisticated and lossless dielectric optical cavities such as photonic crystals and ring resonators have also been used to enhance absorption, mainly aimed at emission applications in monolayer samples. [38][39][40][41] For large area photovoltaic applications, light trapping strategies that involve little or no micro-or nanofabrication and patterning are desirable to improve performance while minimizing cost.…”

Nanoantenna-enhanced light-matter interaction in atomically thin WS2

“…The modification strongly depends on the length of the antenna, which further demonstrates the coupling of exciton and plasmon. The fact that spectral modification of the PL is observed only for emission polarization along the antenna suggests that it originates from an enhanced emission rate, and we can exclude thermal effects 24 as well as morphology changes 23 of the WS 2 monolayers. It should be noted that we have observed robust photoluminescence of the hybrid nanoantenna−monolayer systems over a time period of several months, which allowed us to conduct systematic studies on a single nanostructure.…”

“…Recently, plasmonic nanostructures have been placed above and below MoS 2 monolayers. 20−25 Interesting phenomena such as a reversible structural phase transition in MoS 2 due to hot electron injection 23 or a thermally induced spectral modification of photoluminescence 24 have been observed. However, so far little attention has been paid to the design of the plasmonic nanostructures.…”