Molecular junctions for nanoelectronics : electron transport through Zn-porphyrin

Saha, Swatilekha
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Lewis, Kim M.
Wang, G.-C. (Gwo-Ching), 1946-
Nayak, Saroj K.
Ramanath, G. (Ganpati)
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To gain insight to the mechanism of switching behavior and understand how the electrode metal-molecule coupling affects the transport behavior, we completed inelastic electron tunneling spectroscopy (IETS). IETS is a powerful technique that probes the vibrational modes of the molecule at temperatures <10 K in molecular junctions. From the spectra, we were able to identify vibrational mode excited by the metal-molecule interface (Au-S bond) for each molecule. This unambiguously proved that we were successful in creating molecular junctions and all the measured transport characteristics are due to ZnP in the junction. We also identified vibrational modes intrinsic to the porphyrin molecule by comparing the peaks in the IET spectra to infra-red (IR) and Raman spectra. Additionally, by correlating peaks in the IET spectra to switching, we were able to recognize that switching is a result of inelastic electron tunneling and believe that the energy lost by the electron is used to switch the molecule to a different conformation state. We expect that our results will enable fundamental understanding of metal-molecule-metal junction behavior and impact the design of molecular based electronics that can use porphyrins as switches.
August 2013
School of Science
Dept. of Physics, Applied Physics, and Astronomy
Rensselaer Polytechnic Institute, Troy, NY
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