Shaping the Atomic‐Scale Geometries of Electrodes to Control Optical and Electrical Performance of Molecular Devices

Abstract

A straightforward method to generate both atomic-scale sharp and atomic-scale planar electrodes is reported. The atomic-scale sharp electrodes are generated by precisely stretching a suspended nanowire, while the atomic-scale planar electrodes are obtained via mechanically controllable interelectrodes compression followed by a thermal-driven atom migration process. Notably, the gap size between the electrodes can be precisely controlled at subangstrom accuracy with this method. These two types of electrodes are subsequently employed to investigate the properties of single molecular junctions. It is found, for the first time, that the conductance of the amine-linked molecular junctions can be enhanced ≈50% as the atomic-scale sharp electrodes are used. However, the atomic-scale planar electrodes show great advantages to enhance the sensitivity of Raman scattering upon the variation of nanogap size. The underlying mechanisms for these two interesting observations are clarified with the help of density functional theory calculation and finite-element method simulation. These findings not only provide a strategy to control the electron transport through the molecule junction, but also pave a way to modulate the optical response as well as to improve the stability of single molecular devices via the rational design of electrodes geometries.

Atomic switches of metallic point contacts by plasmonic heating

“…There is no need for special optical set-ups or high-power laser sources in the experiments. To fabricate the nanocontacts, a commercially available gold wire with a constriction in the middle is fixed on a spring steel substrate 19 . The constriction can be precisely stretched by bending the substrate using a mechanically controllable break junction (MCBJ) setup 24–27 , as shown in Fig.…”

“…The metallic atomic-scale contact was obtained utilizing the mechanically controllable break junction technique by precisely stretching a metal wire 18,19 . When the cross-section of a metal wire is reduced to few nanometers or a few atoms, the contact diameter becomes comparable to the Fermi wavelength of the electrons, then quantum-mechanical effects will strongly influence the electron transport properties 14 .…”

Plasmonic Nanogaps: From Fabrications to Optical Applications

“…Another method to form nanoscale gaps is the mechanically controllable break junction (MCBJ) technique, which has been used for decades to form molecular junctions; a schematic drawing of the sample mounting of the MCBJ technique is presented in Figure . Its principle is as follows: a metallic wire is positioned on top of an elastic substrate, which serves as the bending beam.…”

“…The results demonstrated that the role of SPPs for optically controlling the transport in metallic nanostructures and are important for designing opto‐nanoelectronic devices. Recently, Xiang and co‐workers reported an atomic‐scale sharp and atomic‐scale planar electrodes . The gap size can be precisely controlled at subangstrom accuracy by precisely stretching a suspended nanowire, and the atomic‐scale planar electrodes are obtained via mechanically controllable interelectrode compression followed by a thermal‐driven atom migration process.…”

Study of the surface structure of Fe quantum wire prepared by electrochemical method in solution

“…Although the metal quantum wires have received much attention for the last decades due to their potential applications in nanoelectronics and chemical sensing [7][8][9], few studies have been reported on the surface microstructures of this novel nanostructured material, especially in aqueous solution. Because the cross section of a metal junction is composed of only a few atoms and most atoms are located on the surface of the junction, distinctive characteristics unlike those of bulk form can be expected.…”