Nov 6, 2013
Measuring the conductance through molecular junctions made from non-gold electrodes
Researchers from Zhejiang Normal University in China have developed an electrochemical jump-to-contact scanning tunnelling microscopy break junction (ECSTM-BJ) that allows them to make conductance measurements on single molecule junctions made from different metallic electrodes. Various metal electrodes with well-defined structures can be measured using this approach.
Understanding how charge travels through molecular electrode contacts is crucial for fabricating efficient nanoelectronics devices. There are two ways to optimize electrode contacts: find suitable anchoring groups for molecules and find good electrode materials. While the former has received the most attention, there are few reports on electrode materials other than those made of gold.
By using the ECSTM-BJ approach, the researchers succeeded in measuring the conductance of pyridyl-based single molecule junctions made from copper electrodes. The values measured are smaller than those for molecules contacting to gold electrodes – something that can be attributed to the different electronic coupling efficiencies between the molecules and the electrodes. In addition, the consistent conductance values of pyridyl-based molecules in acidic and neutral solutions show that the protonated pyridyl group might be contacting to the electrode through its deprotonated form.
The results show that electrode materials play an important role in electron transport through molecular junctions. Most importantly, the ECSTM-BJ approach can also be extended to investigate other metal-molecule-metal junctions, and even single molecule spintronics junctions.
More information can be found in the journal Nanotechnology.
• Molecular tunnel junctions configured with palladium electrodes (Oct 2012)
• Conductance screening tool rapidly measures single molecule conductance (Jun 2008)
• Understanding current transport in molecular junctions (May 2011)
About the author
This work was carried out in Dr. Xiao-Shun Zhou’s group at the Institute of Physical Chemistry, Zhejiang Normal University, China. The group’s current research interests focus on charge transport through metal quantum wires and single molecule junctions.