The observed thousand-fold enhancement in upconverted light emission from plasmonic tunnel junctions under combined electronic and optical excitation stems from intricate hot-carrier dynamics governed by nonradiative plasmon decay and electron-electron interactions. By analyzing the spectral shape and energy dependence of emitted photons, we identify two dominant physical pathways responsible for the synergistic effect: thermally driven hot-carrier recombination and anti-Stokes electronic Raman scattering.
In electrically driven systems, electrons tunnel across a nanoscale gap and inelastically excite localized surface plasmons, which rapidly decay into energetic hot carriers. These carriers thermalize within femtoseconds and subsequently recombine radiatively, emitting photons with energies exceeding the bias voltage threshold—a hallmark of upconversion.Cytokeratin 8 Antibody site The emission spectrum follows a Boltzmann distribution, allowing extraction of an effective temperature (Teff) that scales linearly with applied voltage. This behavior is consistent with viscous heating models where electron-electron collisions mediate energy dissipation in high-current-density regimes.PSMA Antibody Purity
When optical excitation is introduced, the incident laser couples to the LSP mode, further exciting the electron system beyond its equilibrium state.PMID:35025884 The resulting nonradiative decay generates additional heat, raising Teff even at zero bias. This optically induced incoherent temperature T₀ acts as a seed for enhanced carrier populations, leading to a pronounced increase in above-threshold emission. The measured Teff under combined excitation exceeds that of purely electrical driving by over 500 K, explaining the dramatic rise in photon yield.
A key feature of this system is the nonlinear power dependence of Teff: it increases rapidly with laser intensity but saturates at high powers, indicating a balance between excitation rate and relaxation mechanisms. This saturation aligns with theoretical predictions based on plasmon damping and electron-phonon coupling. Furthermore, the fact that the normalized emission spectra collapse onto a single exponential curve—despite different excitation conditions—confirms that the underlying physics remains universal across stimuli.
We also explore the role of anti-Stokes electronic Raman scattering, a process where a photon scatters off an excited electron-hole pair, transferring energy and producing a higher-energy photon. In metallic nanostructures, this process is typically suppressed due to momentum conservation constraints. However, near surfaces and in confined geometries, wavefunction overlap enables finite transition rates, especially when a voltage bias provides access to new energy channels. The resulting emission spectrum matches the observed exponential decay and exhibits similar bias and power dependencies.
While both mechanisms contribute to the total emission, their relative importance remains challenging to disentangle using steady-state measurements alone. Nevertheless, the ability to reproduce the EPL spectrum by scaling the EL spectrum with an elevated Teff strongly suggests that hot-carrier dynamics dominate the response. Future ultrafast spectroscopy experiments may resolve the temporal signatures of each process—prompt Raman scattering versus delayed recombination—providing definitive insight.
These findings highlight the potential of plasmonic tunnel junctions as tunable nanoscale light sources, where the interplay between electronic and photonic excitations can be harnessed for advanced applications in nanophotonics, quantum information, and catalysis.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
