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Nov 12th, 2012
Single graphene stripes as electrodes for nanoelectronics
The transport of electrons and thus electrical current is not only of central importance in modern society, but also for scientists in fundamental research where it is of interest for biological processes and for potential applications for future molecular electronics (with single molecules as devices).
A research team at the Fritz Haber Institute Berlin (in collaboration with theoreticians from Toulouse and Singapore) could measure for the first time the electrical current through single molecules at different electrode voltages, thus characterizing various charge transport regimes. Graphene stripes were chosen, due to their interesting electronic properties, and assembled directly on the surface by in-situ polymerization. The central challenge for such measurements is to measure the current through an object at the atomic scale with macroscopic electrodes, ensuring for a well-defined arrangement. In this work, a scanning tunneling microscope was used to pick up single graphene ribbons from a surface, thus realizing the desired geometry. In this way, the decay of the electric current with the molecular length, the key property for charge transport efficiency, can be measured in real time. It is shown that the conductance properties of a single molecule can be correlated with its electronic states. Comparison with calculation reveals that the conductance depends on the precise atomic structure and bending of the molecule in the junction.
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