Reliable Formation of Single Molecule Junctions with Air-Stable Diphenylphosphine Linkers
We measure the conductance of single Au-molecule-Au junctions with a series of air-stable diphenylphosphine-terminated molecules using the scanning tunneling microscope-based break junction technique. Thousands of conductance versus displacement traces collected for each molecule are used to statistically analyze junction conductance and evolution upon elongation. Measured conductances for a series of alkane-based molecules exhibit an exponential decrease with increasing length, as expected for saturated molecules, with a tunneling decay constant of 0.98 {+-} 0.04. Measurements of junction elongation indicate strong metal-molecule binding, with a length that increases with the number of methylene groups in the backbone. Measured conductance histograms for four molecules with short, unsaturated backbones (e.g., benzene) are much broader with less well-defined peaks. These measurements are supported by density function theory calculations. The phosphine binds selectively to under-coordinated gold atoms through a donor-acceptor bond with a binding energy of about 1 eV. The calculated tunnel coupling correlates very well with experiment.
- Research Organization:
- Brookhaven National Laboratory (BNL) Center For Functional Nanomaterials
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 985533
- Report Number(s):
- BNL--93711-2010-JA; KC020401H
- Journal Information:
- Journal of Physical Chemistry Letters, Journal Name: Journal of Physical Chemistry Letters Journal Issue: 14 Vol. 1; ISSN 1948-7185
- Country of Publication:
- United States
- Language:
- English
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