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Current-Voltage Measurements of Single Peptides and Porphyrin Oligomers

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A.T. Johnson, M. Therien, and W. DeGrado

We use controlled electromigration at 77K to form nanogap electrodes that contact individual molecules.

Experiments to date from other groups have used a very low yield (~2-5%) electromigration process. The work has focused on small molecules consisting of single chemical moeities. The focus has been on single electron charging of individual molecular orbitals and exotic physics such as the Kondo effect.

We form nanogaps using a reproducible, computer-controlled process we first demonstrated (Strachan et al., Appl. Phys. Lett. 2005). The molecules of interest are peptides and porphyrin oligomers that are expected to have high electro-optic functionality.

Conclusions:

  • Molecular circuits have been fabricated at 77K using our new approach. To our knowledge, these are the first samples formed by electromigration that are robust enough for temperature-dependent measurements.
     
  • Single molecule circuits show conductance anomalies that depend on the molecular structure
     
  • Future experiments include temperature-dependent measurements, photoconductivity, and use of electrodes made from refractory metals for improved mechanical stability.

References:
D. Strachan, et al., manuscript in preparation.

 

 

 

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