Event Information

David Cahen, Head of Optoelectronic Materials Group (Weizmann Institute of Science, Rehovat, Israel)
Electronic Charge Transport Across Molecules: From Simple Alkyls to Proteins
Abstract:

In molecular electronics data and models abound and it is rare that some fit cannot be found. This however, does not really help us in constructing reliable models with predictive power. Such models will require data sets that are sufficiently robust so that any model will have to be tested against them, rather than only those that the experimenter/ theoretician chooses…..

We have over the past few years set ourselves as goal to provide such data sets. This requires high quality, reproducible systems. We found semiconductor/alkyl chain monolayers/metal structures, with the molecules directly chemically bound to the semiconductor (Si, GaAs) and/or the metal (Hg, Au, Pd) to give the required reproducible and reliable data, as underscored by our recent finding that we can actually controllably dope those layers. The importance here is that doping is possible only if the residual defects do not anymore dominate the electrical transport, a characteristic of monolayers that we found by far to be the most sensitive of all the ones that we explored.

Combining our transport results with those from photoemission and electronic structure calculations led us to question some “conventional wisdoms”:
* To what extent should we use the simple HOMO/LUMO concept for these systems?
* How relevant is the concept of a transport barrier with a well-defined energy & width?
* How important is molecule-electrode chemical bonding for transport? and, more trivial(?)
* Do we actually know what are the contact areas in molecular electronics? In spite of these uncertainties, our work with these simple systems showed a way to work with much more complicated biological ones. I’ll illustrate the latter briefly with results on bacteriorhodopsin. While much more work is needed, results already hold some surprises.
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* Work done with A. Salomon, O. Seitz, H. Shpaisman, G. Nesher, A. Vilan, I. Ron, T. He, Y.-D. Jin (Weizmann Inst.), T. Boecking & J. Gooding, UNSW, Sydney, Australia and with the groups of Antoine Kahn, Princeton Un., Eberhard Umbach, Würzburg Un., Germany, Nobuo Ueno, Chiba Un., Japan , L. Kronik, R. Naaman and M. Sheves at the Weizmann Institute.

Host: Ravindra Venkatramani of the Beratan group

Monday, October 15, 2007, 10:30am
Theory Seminar