Linearly Polarized Electroluminescence from MoS₂ Monolayers Deposited on Metal Nanoparticles: Toward Tunable Room‐Temperature Single‐Photon Sources

Abstract

Break junctions in noble‐metal films can exhibit electroluminescence (EL) through inelastic electron tunneling. The EL spectrum can be tuned by depositing a single‐layer crystal of a transition‐metal dichalcogenide (TMDC) on top. Whereas the emission from the gaps between silver or gold nanoparticles formed in the break junction is spectrally broad, the hybrid metal/TMDC structure shows distinct luminescence from the TMDC material. The EL from individual hotspots is found to be linearly polarized, with a polarization axis apparently oriented randomly. Surprisingly, the degree of polarization is retained in the EL from the TMDC monolayer at room temperature. In analogy to polarized photoluminescence experiments, such polarized EL can be interpreted as a signature of valley‐selective transitions, suggesting that spin‐flip transitions and dephasing for excitons in the K valleys are of limited importance. However, polarized EL may also originate from the metal nanoparticles formed under electromigration which constitute optical antenna structures. Such antennae can apparently change over time since jumps in the polarization are observed in bare silver‐nanoparticle films. Remarkably, photon‐correlation spectroscopy reveals that gold‐nanoparticle films exhibit signatures of deterministic single‐photon emission in the EL, suggesting a route to designing room‐temperature polarized single‐photon sources with tunable photon energy through the choice of TMDC overlayer.

Bright and Efficient Light‐Emitting Devices Based on 2D Transition Metal Dichalcogenides

“…[ 332–338 ] Light emission from monolayer TMDCs using the AC voltage‐assisted carrier injection has also been reported. [ 208,339–342 ] One of the typical reports on AC‐driven light emission from monolayer semiconductors demonstrates devices consisting of a SiO 2 /Si substrate, a 2D TMDC‐based active layer, and a metal source. [ 208 ] A bipolar square wave signal is fed to the device through the metal contact that enables the injection of electrons and holes into the TMDC layer during voltage transitions.…”

The Luminescence Hypothesis of Olfaction

“…A common method utilized to electrically excite photons via in elastic electron tunneling is metal–insulator–metal tunnel junctions [ 42 ]. Noble-metal films can also exhibit electroluminescence through inelastic electron tunneling [ 43 ]. The optical properties of IET tunnel junctions have been controlled by changing the shape or the material of the electrodes with the aim to improve photon emission efficiencies [ 44 ].…”

“…In addition, the resonant peak of emitted photons from IET can be spectrally tuned [ 45 ]. Interestingly, electroluminescence following IET has been found to be linearly polarized [ 43 ].…”

Enhanced Visible-Light Response of Ultrathin Er-Doped MoS2 Nanosheets through a Wet-Chemical Method

“…Recently, transition metal dichalcogenide (TMD) nanomaterials, especially mono- and few-layer nanosheets, have received extensive research interest for their peculiar properties and promising applications in transistors, catalysis, photodetectors, electroluminescent devices, and photothermal conversions . To date, the preparation methods of mono- or few-layer TMD nanomaterials have been developed by top-down and bottom-up synthesis strategies .…”