Site-Selection in Single-Molecule Junction for Highly Reproducible Molecular Electronics

Abstract

Adsorption sites of molecules critically determine the electric/photonic properties and the stability of heterogeneous molecule-metal interfaces. Then, selectivity of adsorption site is essential for development of the fields including organic electronics, catalysis, and biology. However, due to current technical limitations, site-selectivity, i.e., precise determination of the molecular adsorption site, remains a major challenge because of difficulty in precise selection of meaningful one among the sites. We have succeeded the single site-selection at a single-molecule junction by performing newly developed hybrid technique: simultaneous characterization of surface enhanced Raman scattering (SERS) and current-voltage (I-V) measurements. The I-V response of 1,4-benzenedithiol junctions reveals the existence of three metastable states arising from different adsorption sites. Notably, correlated SERS measurements show selectivity toward one of the adsorption sites: "bridge sites". This site-selectivity represents an essential step toward the reliable integration of individual molecules on metallic surfaces. Furthermore, the hybrid spectro-electric technique reveals the dependence of the SERS intensity on the strength of the molecule-metal interaction, showing the interdependence between the optical and electronic properties in single-molecule junctions.

Evaluation of the Kinetic Property of Single-Molecule Junctions by Tunneling Current Measurements

“…17 Several values for the single-molecule conductance originated from different binding configurations between the molecule and electrodes were also reported. 18 In contrast, a single conductance value was found in the present I-t measurements. We attributed this observation to the fixed distance between the tip and the substrate.…”

Atomic and Electronic Structures of a Single Oxygen Molecular Junction with Au, Ag, and Cu Electrodes

“…4 Thanks to the development of the measurement techniques, including mechanically controllable break junctions (MCBJ) and scanning tunneling microscopy (STM)-BJ techniques, the electrical conductance of the single atom or molecule can be measured experimentally. [5][6][7][8][9][10][11] Currently, various functionalities have been reported for single atomic and molecular junctions, where a single atom or molecule is bridged between metal electrodes. 10,[12][13][14][15] While there have been enormous studies of the single molecular junctions with a variety of molecules, the atomic and electronic structures of the single molecular junction were not fully characterized with experimental techniques.…”

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

“…In particular, scanning tunneling microscopy shows strong ability to form different types of molecular junctions (tip and substrate can be different materials), which makes it possible to realize new type of functional devices and to observe novel phenomenon . Meanwhile, the effects of molecular anchors, electrode material, and external environment on the properties of single‐molecule junctions have been investigated, which is a large step toward the construction of functional molecular electronic devices. Nonetheless, a number of challenges still need to be overcome before single‐molecule devices can be widely used as commercial products.…”