Investigation on Single-Molecule Junctions Based on Current–Voltage Characteristics

Abstract

The relationship between the current through an electronic device and the voltage across its terminals is a current–voltage characteristic (I–V) that determine basic device performance. Currently, I–V measurement on a single-molecule scale can be performed using break junction technique, where a single molecule junction can be prepared by trapping a single molecule into a nanogap between metal electrodes. The single-molecule I–Vs provide not only the device performance, but also reflect information on energy dispersion of the electronic state and the electron-molecular vibration coupling in the junction. This mini review focuses on recent representative studies on I–Vs of the single molecule junctions that cover investigation on the single-molecule diode property, the molecular vibration, and the electronic structure as a form of transmission probability, and electronic density of states, including the spin state of the single-molecule junctions. In addition, thermoelectronic measurements based on I–Vs and identification of the charged carriers (i.e., electrons or holes) are presented. The analysis in the single-molecule I–Vs provides fundamental and essential information for a better understanding of the single-molecule science, and puts the single molecule junction to more practical use in molecular devices.

Single-molecule quantum-transport phenomena in break junctions

“…Reviews on the experimental features and modelling approaches can be found in ref. 155 and ref. 156 , respectively.…”

Admittance of Atomic and Molecular Junctions and Their Signal Transmission

“…Though this appears a large oversimplification, the model enjoys a wide applicability; by tuning the magnitude of , one can emulate a variety of junctions [ 26 ], from almost insulating molecular junctions with to highly conductive junctions of metal atoms where . The model can also properly describe non-linear I – V characteristics of various molecular junctions [ 4 , 27 ]. These successes of the single-level model come from the fact that, in typical atomic and molecular junctions, only one energy level among many levels of the bridging atom/molecule gives a dominant contribution to electron transmission.…”

“…Another group of experiments using modulated biases is an inelastic transmission spectroscopy [ 27 , 51 ] where the second derivative of the I – V curve is measured with the lock-in detection technique. The modulation frequency is typically a few kHz or lower.…”

“…The theoretical admittance of molecular junctions can be estimated more easily than that of metal contacts because the parameters and in the single-level model can be obtained from experiment by fitting a theoretical I – V curve to an experimental one [ 27 ]. Yamauchi et al [ 64 ] applied this method to Au/BDT(1-4 benzenedihiol)/Au junctions and found that and lie in energy ranges 0.4–1.0 eV and 20–120 meV, respectively.…”

Side-Group Effect on Electron Transport of Single Molecular Junctions

“…Single-molecular junctions have received much attention in recent decades, as they can allow for learning the properties of single molecules, especially the electron transport through single molecules [ 1 , 2 , 3 , 4 ]. Typically, single-molecular junctions are constructed with electrode, molecule, and electrode through scanning tunneling microscopy break junction (STM-BJ) [ 5 , 6 , 7 ] or mechanical controlled break junction (MCBJ) [ 8 , 9 ].…”