Gap Size-Dependent Plasmonic Enhancement in Electroluminescent Tunnel Junctions

Abstract

Nanoscale plasmonic structures have been primarily characterized through scattering studies, but electroluminescence offers an exciting alternative from a technological standpoint by removing the need for optical excitation. In sub-nanometer biased junctions, electronic tunneling can serve as the excitation source for plasmon-coupled electroluminescence, but the gap size dependence to this plasmonic enhancement has not been characterized. Here, we simultaneously probe the electroluminescence and conductance of Au tunnel junctions. We find that plasmonic enhancement increases as the gap size is reduced for junctions biased between 1.4 and 1.8 V, consistent with the behavior of charge transfer plasmons. At biases above 1.9 V, we see decreasing plasmonic enhancement with the decreasing gap, showing quenching due to tunneling in remarkable agreement with the trends observed for high energy plasmons in scattering experiments. Critically, we find that plasmonic enhancement of electroluminescence is gap size-dependent and, furthermore, is in agreement with the nature of modes excited by scattering.

Tuning Light Emission Crossovers in Atomic-Scale Aluminum Plasmonic Tunnel Junctions

“…The 1e and 2e labels indicate different order tunneling processes. Due to the low conductance here, contributions from higher-order processes are negligible compared to U 1e ( V b ,ℏω) where S I (ℏω) corresponds to the current shot noise spectral density (eq S2 in the Supporting Information). ,,,, …”

“…Due to the low conductance here, contributions from higher order processes are negligible compared to 𝑈 1𝑒 (𝑉 𝑏 , ℏ𝜔), 𝑈 1𝑒 (𝑉 𝑏 , ℏ𝜔) = 𝜌(ℏ𝜔)𝑆 𝐼 (ℏ𝜔) (1) where the 𝑆 𝐼 (ℏ𝜔) corresponds to the current shot noise spectral density (Eq. (S2) in the SI) 2,3,13,16,32 .…”

Resonant transport in a highly conducting single molecular junction via metal–metal covalent bond

“…The central motivation of molecular electronics is to reduce the size of the conventional electronic components by taking advantage of the quantum mechanical phenomena at the atomic scale, along with the structural versatility of molecules. By adopting the revolutionary idea proposed by Aviram and Ratner, 1 various experimental techniques 2–19 were developed to create single-molecule junctions, allowing access to electrical, 20–24 chemical, 25–29 mechanical, 30–32 magnetic, 33 thermal, 34–38 and optical 39,40 properties. Typically, various anchoring groups, such as thiol ( –SH ), 11,41,42 amine ( –NH 2 ), 43,44 pyridyl ( –PY ), 11 nitrile ( –CN ), 45 isonitrile ( –NC ), 46,47 carboxylic acid ( –COOH ), 48 nitro ( –NO 2 ), 49 trimethyl-tin ( –SnMe 3 ), 50 and fullerene ( C60 ), 51,52 are used to connect organic molecules to the metal electrodes to achieve a physically stable structure with reliable electronic coupling at the interface.…”

“…The central motivation of molecular electronics is to reduce the size of the conventional electronic components by taking advantage of the quantum mechanical phenomena at the atomic scale, along with the structural versatility of molecules. By adopting the revolutionary idea proposed by Aviram and Ratner, 1 various experimental techniques [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] were developed to create single-molecule junctions, allowing access to electrical, [20][21][22][23][24] chemical, [25][26][27][28][29] mechanical, [30][31][32] magnetic, 33 thermal, [34][35][36][37][38] and optical 39,40 properties. Typically, various anchoring groups, such as thiol (-SH), 11,41,42 amine (-NH 2 ), 43,44 pyridyl (-PY), 11 nitrile (-CN),…”

Femtosecond Laser-Printed Gold Nanoantennas for Electrically Driven and Bias-Tuned Nanoscale Light Sources Operating in Visible and Infrared Spectral Ranges

“…The prevailing explanation for tunneling electroluminescence implies the existence of optical levels in the gap between two conductors or semiconductors. A tunneling electron can transfer a part of its energy to excite the optical states (so-called gap plasmon), which eventually results in generation of free-space photons (see Figure a) , or plasmons . Visible and near-infrared (NIR) light sources based on the LEIT principle possess exceptional characteristics, such as subnanometer dimensions, radiation wavelength electrically tuned by gap bias voltage, , and ultrafast response times of several femtoseconds limited only by the RC constant of the supply circuit. , However, practical implementation of nanosized LEIT photon sources had long been hampered by insufficient quantum efficiency traditionally shown by such devices.…”