Influence of Co bilayers and trilayers on the plasmon-driven light emission from Cu(111) in a scanning tunneling microscope

Abstract

Light emission from the gap cavity formed by the tip of a scanning tunneling microscope (STM) and a flat metallic sample allows us to probe the dielectric response of metals at the atomic scale and presents a way to distinguish between different materials. The excitation mechanism of the charge carrier oscillations, which ultimately decay into light, is linked to inelastic electron tunneling as opposed to the mostly semiclassical picture of the electromagnetic resonance of the gap cavity. Thus, the observed light emission does not only reflect the electromagnetic resonance of the cavity but also involves the electronic density of states. In this paper, we compare light emission from Cu(111) and Co nanoislands on Cu(111). We find a strong intensity contrast but almost no alteration of the resonance wavelength except close to step edges. Our results show that the light emission from the STM junction is highly sensitive to a few atomic layers of alien material mostly due to the dielectric properties of the layer.

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

“…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.…”

Measuring fine molecular structures with luminescence signal from an alternating current scanning tunneling microscope

“…To reveal the resonant conditions in the above current, we perform the numerical calculation of the tunneling current with parameters extracted from the experimental setup. In the STML experiments, the metal used for the tip and the substrate is typically chosen as gold (Au) [35][36][37][38][39], silver (Ag) [1,29,30,[40][41][42][43][44][45][46] and copper (Cu) [11,18,47,48]. In our simulation of the STML current, the tip and the substrate are made of silver with Fermi energy μ 0 = − 4.64 eV.…”

Nanoscale Electrically Driven Light Source Based on Hybrid Semiconductor/Metal Nanoantenna

“…Consequently, LDOS in the STM probe-substrate layout is several orders of magnitude greater than the one in a planar MIM system, which makes inelastic electron tunneling much more efficient in a point contact. To date, a great number of publications have been devoted to optical radiation from STM tunnel junctions. − Important advantages of the STM technique as a method for investigation of LEIT phenomenon are the unequaled simplicity in arrangement of a tunnel junction with desired parameters and the possibility to study various emitting structures comparatively, in the same layout and in the course of one experiment. In addition, the STM technique allows for implementation of the indirect method of optical radiation assessment through the analysis of tunneling current–voltage ( I – V ) characteristics …”