Indirect Detection of the Light Emission in the Local Tunnel Junction

Abstract

Herein, I(V) characteristics of the tunnel junction between the scanning tunneling microscopy (STM) Pt/Ir probe and atomically flat Au film on mica using ultrahigh vacuum STM is investigated. To ensure cleanness and flatness of the Au films, optimization of the substrate annealing and Ar plasma treatment are performed. The obtained technological parameters allow to drastically improve the reproducibility of I(V) measurements. The analysis of I(V), d2I/dV2 (V), and Fowler–Nordheim plots is conducted, and the presence of the features in the bias region near 1.8 V in the form of peak and minimum, peak and anomalous extra minimum, respectively is demonstrated. The direct optical measurements confirm that the features on I(V) curves are associated with the generation of photons from the STM probe‐sample gap, governed by inelastic tunneling processes. The proposed I(V) analysis approach is used for indirect sensing and investigation of the light emission in the tunnel junction offering a powerful tool for the studies of the photonic sources with deeply subwavelength dimensions.

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

“…As shown in our recent paper, the STM-LE should be reflected on tunnel contact I ( V ) dependences. Typical I ( V ) curve and the corresponding current second derivative d 2 I /d V 2 dependence in the (0; 2.5) V bias range for both polarities obtained at the edge of a nanodisc are presented in Figure a and b.…”

“…By swiping the bias voltage applied to the tunnel junction, LDES mapping can be performed, revealing the energies of occupied and unoccupied electronic states. , In the case of inelastic electron tunneling spectroscopy, the analysis of acquired I ( V ) curves can also provide information on LDOS . As shown in our recent paper, features on I ( V ) curves reveal the inelastic tunneling processes, associated with the generation of photons and plasmons.…”

“…Thus, the minima near (1.6; 1.8) V and (2.1; 2.3) V cannot be associated with the features of LDES of studied metals, but instead they correspond to the processes governed by inelastic electron tunneling . The results of optical spectral measurements are presented in the Supporting Information.…”

“…The thin 50 nm gold layer was thermally evaporated on mica and then was annealed in an ultrahigh (UHV) vacuum condition to form a close-to single-crystal gold surface. More details on the importance of annealing and substrate preparation are provided in ref . The precisely cut Pt/Ir wire (DPT10, Bruker, USA) was used as an STM tip.…”

“…The LDES of Pt has no features in the studied regions. Thus, the obtained features should correspond to the system LDOS and inelastic electron tunneling process rather than the LDES of the metal …”