Spectral dependence of light output from LEIT devices on electrode morphology

Abstract

The light output from Al-I-Au tunnel junctions is observed to depend on the morphology of the Au film electrode. Films deposited quickly (2 nm s-1) give out less light, especially towards the blue end of the spectrum, than those deposited slowly (0.03 nm s-1). An explanations is offered in terms of elastic scattering of surface plasmon polaritons in the Au film. The scattering increases the chance of plasmon decay by internal electromagnetic absorption at the expanse of photon emission. A model, of more general applicability, has been developed which can explain the results. SEM has been used to determine the grain size in the Au films and STM to measure the surface roughness.

Interplay of CaF2

“…The explanation is that SPPs are elastically scattered at the grain boundaries and are thus less frequently incident on the surface roughness features that promote radiation . A similar result was observed earlier in light emitting tunnel junctions [24] . On nominally smooth films this effect is not prominent because of the longer SPP mean free path before radiative emission [24] .…”

“…A similar result was observed earlier in light emitting tunnel junctions [24] . On nominally smooth films this effect is not prominent because of the longer SPP mean free path before radiative emission [24] .…”

Light emission from gold and silver thin films in a scanning tunneling microscope: role of contamination and interpretation of grain structure in photon maps

“…This is additional evidence for partial grain isolation. That SPP scattering at grain boundaries is significant was demonstrated [43] some time ago. So, if grains are regarded as sufficiently isolated to define a local tip induced plasmon oscillation with at most moderate disturbance from neighbouring grains, we have a plausible explanation of the observed light emission pattern.…”

Electrically Excited Plasmonic Nanoruler for Biomolecule Detection

“…As described in the theory, it is visible that the major portion of the emitted light goes to the silicon substrate, and a small portion is emitted into the free space above the junction in the form of spherical waves, which was observed by Lambe and other authors. − A third portion is propagating along the metal boundary in the form of surface pSP, which do not radiate into the free space due to the large k-vector. To increase the light emission efficiency of the LETJ structures, several methods such as implementation of artificial surface roughness by interlayers, ,− gratings, − multiple-tunneling barriers, prism coupling, , and annealing of the surface to form nanoagglomerates − were studied, which should enhance the conversion of pSP into free space radiation.…”