Electronic Temperature and Two-Electron Processes in Overbias Plasmonic Emission from Tunnel Junctions

Abstract

The accurate determination of electronic temperatures in metallic nanostructures is essential for many technological applications, like plasmon-enhanced catalysis or lithographic nanofabrication procedures. In this Letter, we demonstrate that the electronic temperature can be accurately measured by the shape of the tunnel electroluminescence emission edge in tunnel plasmonic nanocavities, which follows a universal thermal distribution with the bias voltage as the chemical potential of the photon population. A significant deviation between electronic and lattice temperatures is found below 30 K for tunnel currents larger than 15 nA. This deviation is rationalized as the result of a two-electron process in which the second electron excites plasmon modes with an energy distribution that reflects the higher temperature following the first tunneling event. These results dispel a long-standing controversy on the nature of overbias emission in tunnel junctions and adds a new method for the determination of electronic temperatures and quasiparticle dynamics.

Evidence of exciton-libron coupling in chirally adsorbed single molecules

“…3c, d ) which are in accord with the values estimated from the calculations (see Supplementary Table 2 for comparison). The effective temperature above 50 K resulting from the fitting indicates that the excess energy of inelastic tunnelling electrons of a few eV can excite high librational states and create a transient initial state population above the zero-level libron state 39 .…”

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

“…This has been verified, as including the calculated 2e contribution results in a better match with the measured data, which is plotted in the inset in Figure 2a. Moreover, the electron temperature in the Boltzmann factor within the 1e shot noise spectrum can be estimated via the shape of the spectrum's bias threshold in a way similar to that of Martin-Jimenez et al, 4 with T = 45 K leading to acceptable fitting results (the detailed fitting process is documented in section 3 in the Supporting Information). This analysis assumes that the electronic distribution in the source and drain is of the Fermi−Dirac form, with a characteristic electronic temperature.…”

“…An electrically biased light-emitting tunnel junction provides a feasible platform to investigate light–matter interactions at the atomic scale, particularly the role of plasmonic excitations with deep subwavelength confinement. In the low current limit, electrons may inelastically tunnel through the barrier, exciting a localized surface plasmon (LSP) individually which then with some probability radiatively decays to emit a photon, with the upper photon energy threshold set by the applied voltage bias (ℏω ≤ eV b ). − In the high current limit, however, photon emission above the voltage threshold (ℏω > eV b ) has been observed. The underlying physics of the above-threshold photon emission remains an open question.…”

Tunable directional emission from electrically driven nano-strip metal–insulator–metal tunnel junctions

“…16 A number of pioneering experiments have also reported above-threshold light emission in planar MIM tunnel junctions [23][24][25] mediated by hot electrons. Though the mechanism responsible for abovethreshold light emission is still being debated, 26,27 hot electron generation from electrically driven tunnel junctions can be promising for applications such as photochemistry, 28 photodetection, 29 and sensing. 30 Theoretically, the efficiency for the excitation of gap plasmons due to IET can reach up to 10%, 31 and the highest reported experimental external quantum efficiencies (EQE) from MIM tunnel junctions are in the range of $2% 32,33 for below-threshold light emission.…”