Light emission from the slow mode of tunnel junctions on short period diffraction gratings

Abstract

The emission of light from metal-oxide-metal tunnel junctions has been studied as a probe of the interaction of the tunneling current with the surface plasmon polaritons of the tunnel junction structure. The slow mode, with large fields in the oxide layer, is most directly coupled to the tunneling current. In this experiment, diffraction gratings with periods between 70 and 100 nm provide the momentum for the slow mode to radiate. We report the unambiguous measurement of the direct emission from the slow mode showing that it does contribute to the light emission.

Efficient Surface Plasmon Polariton Excitation and Control over Outcoupling Mechanisms in Metal–Insulator–Metal Tunneling Junctions

“…These works are accurate for smooth MIM‐TJs with no roughness but neglect to consider the role of surface roughness and coupling via pathway 2. Their argument cannot explain considerable literature that reports light emission from the MIM‐TJ area,16,21,22,26,30,37,43–46,48,49,60–62 and cannot explain the observations shown in Figure 3.…”

“…Therefore, in order to increase outcoupling efficiencies, momentum‐matching conditions at the metal–dielectric interfaces are required to outcouple the mode to both free space photons and to bound‐SPPs 26,35. Randomly roughened electrodes,17,22,29,30,36–42 gratings,21,43,44 and prisms,45 have been integrated into MIM‐TJs to preferentially outcouple the MIM‐SPP mode or the bound‐SPP mode(s) to photons by reducing this momentum mismatch 17,26,43–46…”

Light at the End of the Tunnel

“…Among these were the roughening of the junction electrodes − and the use of metal nanoparticles, ,,− both of which facilitate mode conversion through random scattering. However, as each scattering event carries the possibility for absorption, outcoupling efficiencies were found to saturate with increasing roughness. ,, In an alternative approach, tunnel junctions were fabricated on top of gratings − in order to “impedance-match” the modes of the tunnel junctions to free-space (cf. Figure a).…”

Antenna-coupled photon emission from hexagonal boron nitride tunnel junctions

“…1, which may subsequently decay into far-field radiation [14]. This effect has since been studied experimentally in macroscopic solid-state tunnel junctions [15,16], and the scanning tunneling microscope (STM) [17][18][19][20][21], as well as theoretically [22][23][24][25][26]. One major appeal of investigating inelastic electron tunneling is its potential speed.…”