In our recent research, we have been able to measure and characterize the impact of intrinsic molecular properties on the conductance of single molecule circuits formed with amine-gold linkages [1-4]. Experiments are carried out by repeatedly forming and breaking a gold point contact in a solution containing the target molecule. This is repeated thousand of times while measuring the junction current at fixed bias resulting in a large number of independent measurements of the conductance for each target molecule. Amine link groups result in a clear conductance signature that we use to study trends with molecule length, conjugation and structure. The hypothesis that the nitrogen atom from the amine group bonds to a coordinatively unsaturated gold atom in the junction through a donor-acceptor mechanism has successfully explained the observed trends. Each molecule has been analyzed using quantum chemistry techniques based on Density Functional Theory, applied to the molecule bonded to a gold fragment to represent each electrode. In this talk, I will review the experiments and the physical picture of the junction based on the calculations. I will then focus on three recent studies: (i) the impact of substituents on the conductance through diaminobenzene ; (ii) the trends in conductance through diaminonaphthalene and diaminoanthracene as a function of the location of the amine link groups ; and (iii) comparison of junctions formed with amine links to those formed with methylthiol and dimethylphosphine links.
Mark S. Hybertsen holds a BA in Physics from Reed College in Portland, OR (1980) and a PhD in Physics from The University of California, Berkeley (1986). His thesis research done under the supervision of Prof. Steven Louie concerned exchange and correlation in semiconductors and insulators. Dr. Hybertsen joined Bell Laboratories in 1986, pursuing a variety of research projects in the theory of the electronic properties of materials (bulk semiconductors, semiconductor surfaces and interfaces, cuprates, porous silicon, optoelectronic device physics). He supervised the Device and Materials Physics Group in the Semiconductor Photonics Research Department for four years. From 2003 to 2006, Dr. Hybertsen was a Senior Research Scientist in the Department of Applied Physics and Applied Mathematics at Columbia University in New York, where he has also been an Adjunct Professor in the Department of Electrical Engineering. In late 2006, Dr. Hybertsen joined the new Center for Functional Nanomaterials at Brookhaven National Laboratory. He also maintains an adjunct appointment at Columbia University. Dr. Hybertsen is a fellow of the American Physical Society and a member of the IEEE.
This work was done in collaboration with Latha Venkataraman, Colin Nuckolls, Michael Steigerwald and Ronald Breslow from the Nanocenter at Columbia University.
Researchers should cite this work as follows: