Single molecule bridging between metal electrodes

Abstract

Single molecular junctions, in which a single molecule bridges between metal electrodes, have attracted wide attention as novel properties can appear due to their peculiar geometrical and electronic characters. The single molecular junction has also attracted attention due to its potential application in ultrasmall single molecular electronic devices, where single molecules are utilized as active electronic components. Thus, fabrication of single molecular junctions as well as understanding and controlling their properties (e.g. conductance, optical and magnetic properties) have become long-standing goals of scientists and engineers. This review article focuses on the experimental aspects of single molecular junctions, with primary focus on the electron transport mechanism.

A quantum circuit rule for interference effects in single-molecule electrical junctions

“…Owing to their small size (on the scale of Angstroms) and the large energy gaps (on the scale of eV), transport through single molecules can remain phase coherent even at room temperature, and constructive or destructive quantum interference (QI) can be utilized to manipulate their room temperature electrical [10][11][12][13] and thermoelectrical 14,15 properties. In previous studies, it was reported theoretically and experimentally that the conductance of a phenyl ring with meta (m) connectivity is lower than the isomer with para (p) connectivity by several orders of magnitude [16][17][18][19][20][21][22][23][24][25] . This arises because partial de Broglie waves traversing different paths through the ring are perfectly out of phase leading to destructive QI in the case of meta coupling, while for para or ortho coupling they are perfectly in phase and exhibit constructive QI.…”

“…The basic unit for studying QI in single molecules is the phenyl ring, with thiol 17,21 , methyl thioether 27 , amine 17 or cyanide 19 anchors directly connecting the aromatic ring to gold electrodes. Recently, Arroyo et al 28,29 studied the effect of QI in a central phenyl ring by varying the coupling to various anchor groups, including two variants of thienyl anchors.…”

Electron transport through polyene junctions in between carbon nanotubes: An ab initio realization

“…Parallel to the thread of conventional metal electrodes [1][2][3] in the studies of single molecule junctions, where the fabrication for the delicate metal-molecule links is still a challenging task to overcome, single-walled carbon nanotubes (SWCNTs) provide a better controlled alternative for the electrodes, especially when p-conjugated molecules are considered for the junction bridge. It is well-known that in graphene [4], the planar sp 2 hybridization forms a strong r-bond hexagonal network, giving energy bands sitting far away from the Fermi energy (E F ), while the ðpppÞ bands locate close to or cross the E F .…”

Interface electronic structures of reversible double-docking self-assembled monolayers on an Au(111) surface

“…Section 4 provides the conclusions of this study. We choose -SH (thiol), -Pyr (pyridyl) and -CN (cyano) as the docking groups, all of which have been experimentally used as anchoring groups to create single molecular junctions [25,31].…”