Temperature-Dependent Tunneling in Furan Oligomer Single-Molecule Junctions.

Two commonly observed charge transport mechanisms in single-molecule junctions are coherent tunneling and incoherent hopping. It has been generally believed that tunneling processes yield temperature-independent conductance behavior and hopping processes exhibit increasing conductance with increasing temperature. However, it has recently been proposed that tunneling can also yield temperature-dependent transport due to the thermal broadening of the Fermi energy of the contacts.

Controlling Contact Configuration of Carboxylic Acid-Based Molecular Junctions Through Side Group.

In this paper, the contact configuration of single molecular junction is controlled through side group, which is explored by electrochemical jump-to-contact STM break junction. The conductance values of 2-methoxy-1,3-benzenedicarboxylic acid (2-M-1,3-BDC) is around 10 G, which is different from that of 5-methoxy-1,3-benzenedicarboxylic acid (5-M-1,3-BDC) with 10 G. Interestingly, the conductance value of 2-M-1,3-BDC is the same as that of 1,3-benzenedicarboxaldehyde (1,3-BDCA), while single molecular junctions of 5-M-1,3-BDC and 1,3-benzenedicarboxylic acid (1,3-BDC) give out similar conductance value.

Controlling and Observing Sharp-Valleyed Quantum Interference Effect in Single Molecular Junctions.

The ability to control over the quantum interference (QI) effect in single molecular junctions is attractive in the application of molecular electronics. Herein we report that the QI effect of meta-benzene based molecule with dihydrobenzo[ b]thiophene as the anchoring group ( meta-BT) can be controlled by manipulating the electrode potential of the junctions in electrolyte while the redox state of the molecule does not change. More than 2 orders of magnitude conductance change is observed for meta-BT ranging from <10 to 10 G with varying the electrode potential, while the upper value is even larger than the conductance of para-BT ( para-benzene based molecule with anchoring group of dihydrobenzo[ b]thiophene).

Low Tunneling Decay of Iodine-Terminated Alkane Single-Molecule Junctions.

One key issue for the development of molecular electronic devices is to understand the electron transport of single-molecule junctions. In this work, we explore the electron transport of iodine-terminated alkane single molecular junctions using the scanning tunneling microscope-based break junction approach. The result shows that the conductance decreases exponentially with the increase of molecular length with a decay constant β = 0.

Detecting Electron Transport of Amino Acids by Using Conductance Measurement.

The single molecular conductance of amino acids was measured by a scanning tunneling microscope (STM) break junction. Conductance measurement of alanine gives out two conductance values at 10 G₀ (1095 nS) and 10 G₀ (15.5 nS), while similar conductance values are also observed for aspartic acid and glutamic acid, which have one more carboxylic acid group compared with alanine.

Comparative Study on Single-Molecule Junctions of Alkane- and Benzene-Based Molecules with Carboxylic Acid/Aldehyde as the Anchoring Groups.

We have measured the alkane and benzene-based molecules with aldehyde and carboxylic acid as anchoring groups by using the electrochemical jump-to-contact scanning tunneling microscopy break junction (ECSTM-BJ) approach. The results show that molecule with benzene backbone has better peak shape and intensity than those with alkane backbone. Typically, high junction formation probability for same anchoring group (aldehyde and carboxylic acid) with benzene backbone is found, which contributes to the stronger attractive interaction between Cu and molecules with benzene backbone.