Scanning Tunneling Microscopy-Induced Light Emission and I(V) Study of Optical Near-Field Properties of Single Plasmonic Nanoantennas

Abstract

Electrically driven plasmonic nanoantennas can be integrated as a local source of the optical signal of advanced photonic schemes for on-chip data processing. The inelastic electron tunneling provides the photon generation or launch of surface plasmon waves. This process can be enhanced by the local density of optical states of nanoantennas. In this paper, we used scanning tunnel microscopy-induced light emission to probe the local optoelectronic properties of single gold nanodiscs. The electromagnetic field distribution in the vicinity of plasmonic structures was investigated with high spatial resolution. The obtained photon maps reveal the nonuniform distribution of electromagnetic near-fields, which is consistent with nanoantenna optical modes. Also, the analysis of derived I(V) curves showed a direct correlation between the nanoantenna optical states and the appearance of features on current–voltage characteristics.

Femtosecond Laser-Printed Gold Nanoantennas for Electrically Driven and Bias-Tuned Nanoscale Light Sources Operating in Visible and Infrared Spectral Ranges

“…As shown previously, this approach provides a powerful tool for visualization of the LDOS distribution with a spatial resolution of the order of several tens of nanometers. 17,18 Moreover, the STM-LE method enables the light source position identification with a subdiffraction resolution, which exceeds the capabilities of modern optical methods, such as aperture scanning near-field optical microscopy (SNOM), 34 etc. As can be seen from Figure 3d, the tunnel gap luminosity decreases at voltages above 2.5 V, which can be explained in several ways.…”

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

“…In addition, in our previous work, we studied the LEIT on a nanoantenna in the form of a gold disk. 37 We also evaluated the efficiency of this process at the level of 3.9 × 10 −6 . Thus, we can suggest that the formed hybrid Si/Au nanoantennas have a higher quantum efficiency than both pure gold film and gold nanoantennas (see Table 1).…”

“…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 …”

“…We modeled the electromagnetic problem of the layered system (see the Supporting Information). For 3D numerical modeling, we employed the finite-element method in the frequency domain, implemented in Comsol Multiphysics Software with the procedure described in refs , , and . The Purcell factor was calculated as a ratio of the power emitted by an optical dipole in the considered tunnel gap, , to the power emitted by a dipole in free space in vacuum, , provided that the dipole moments are equal. , …”

“…Our studies showed that at a bias voltage of 2.5 V, the EQE for a pure gold surface is 9.0 × 10 –7 , while on a hybrid nanoantenna the EQE increases to 1.2 × 10 –5 . In addition, in our previous work, we studied the LEIT on a nanoantenna in the form of a gold disk . We also evaluated the efficiency of this process at the level of 3.9 × 10 –6 .…”