Molecular Junctions for Nanoelectronics: Electron Transport through Porphyrin Molecules

Tuesday, September 17, 2013 - 3:15pm - 4:30pm
Regents 109
Kim Michelle Lewis
Rensselaer Polytechnic Institute

Our research focuses on electron transport in nanoscale junctions for molecular electronic applications. We have demonstrated two-state conductance and rectification (i.e. unidirectional flow of current) in molecular junctions, and believe that understanding these fundamental processes may enable us to identify the origin of the electronic transport characteristics. In this presentation, electron transport measurements from various zinc porphyrin structures in molecular junctions formed from electromigrated nanogaps will be discussed. These measurements show asymmetric current-voltage (I-V) behaviors in contrast to measurements from an empty nanogap without a molecule, which display symmetric I-V characteristics. Gate dependence measurements were completed for one form of the zinc porphyrin structure, which showed that current is suppressed as gate voltage is increased indicating highest occupied molecular orbital (HOMO) mediated tunneling. For a different structure of zinc porphyrin in the nanogap, “switch-like” behavior was observed at 4.2 K. Currently, our strategy is to gain insight into vibrational energies in these nanoscale devices by investigating the inelastic electron tunneling spectra (IETS) from the molecular junctions. IETS experimental results are presented and future experiments are proposed that may provide key insights into the two-state conductance observed in porphyrin molecules; and connect the existence of molecular conductance to redox states and vibration modes that exist in the molecules.

Biosketch: Dr. Kim Michelle Lewis graduated from the University of Michigan in Ann Arbor with a Ph.D. in Applied Physics in 2004 and an M.S. in Electrical Engineering. After completing her graduate studies she earned a Ford Postdoctoral Fellowship to work at Louisiana State University (LSU) in Baton Rouge to study molecular electronics. In 2006 Dr. Lewis joined the Rensselaer physics faculty. Since accepting her position she has received a 2012 NSF Career Award, Woodrow Wilson Career Fellowship, National Faculty Role Models Award, and a Rensselaer School of Science Outstanding Early Research Award for her work on molecular electronics. Currently, she is completing her sabbatical at Howard Nanoscale Science and Engineering Facility in Washington, DC. At Howard University she is studying the binding and electrophysiology of tumor cells and human adult stems cells using scanning probe microscopy.

REFRESHMENTS AT 3:00 PM IN REGENTS HALL 109

Host: Paola Barbara
Discussion Leader: Paola Barbara