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(35g) Electric Field Driven Assembly and Temperature Dependent Conduction through Nanoparticle-Molecule-Nanoparticle Structures

Na, J., North Carolina State University
Ayres, J., North Carolina State University
Chandra, K. L., North Carolina State University
Gorman, C. B., North Carolina State University

Understanding conduction mechanisms through a single molecule remains a critical question in molecular electronics. Particular difficulties are related to the instability of metal-molecule contacts and possible interactions between multiple molecules in the junction. Here we report fabrication of unique nanoparticle/molecule/nanoparticle bridge structures consisting of ~40nm gold nanoparticles linked by a phenylacetylene oligomer molecule. We also describe methods to achieve electrical contact to these structures across nanoscale (~70nm) conducting electrodes fabricated by a simple angled metal evaporation method. The assembly of the nanoparticle/molecule structure onto nanoscale electrodes is performed by dielectrophoretic trapping. At the optimum trapping conditions (2VAC, 1MHz, and 60s) a success rate of ~78% is achieved, allowing direct characterization of electrical contact and charge transport. Current versus voltage through the nanoparticle/molecule structure is consistent with a single molecule present between the nanoparticles, and IV results are obtained as a function of temperature and time in ambient. Contacts are observed to be highly stable in vacuum, but conduction is observed to slowly increase by a factor of 10 over time (1-2 weeks) upon exposure to ambient air, consistent with modifications in contact properties. Fitting of the IV data to charge tunneling models will also be presented and discussed.