Effect of Anchoring Groups on Single-Molecule Conductance:  Comparative Study of Thiol-, Amine-, and Carboxylic-Acid-Terminated Molecules

We studied the effect of anchoring groups on the conductance of single molecules using alkanes terminated with dithiol, diamine, and dicarboxylic-acid groups as a model system. We created a large number of molecular junctions mechanically and analyzed the statistical distributions of the conductance values of the molecular junctions. Multiple sets of conductance values were found in each case. The I-V characteristics, temperature independence, and exponential decay of the conductance with the molecular length all indicate tunneling as the conduction mechanism for these molecules. The prefactor of the exponential decay function, which reflects the contact resistance, is highly sensitive to the anchoring group,…

• NS
  National Science Foundation
• UD
  U.S. Department of Energy
• DO
  Division of Chemistry