Regensburg 2007 – scientific programme

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 7: Single Molecule Contacts

SYOE 7.2: Talk

Tuesday, March 27, 2007, 17:15–17:30, H32

Ultrathin contacts for single molecules: Ag nanostructures on Si(100) — •Gernot Gardinowski, Jendrzej Schmeidel, Herbert Pfnür, Jörg Meyer, and Christoph Tegenkamp — Institut für Festkörperphysik, Leibniz-Universität Hannover, 30167 Hannover, Germany

The fabrication and characterization of metallic nanometer–sized(nm) gaps suitable for conductivity measurements of single molecules has been investigated systematically. First results of conductivity measurements of single molecules and of their direct observation by STM are presented. Epitaxially grown Ag structures with a thickness down to 10 monolayers on Si(100) were used for a controlled gap formation by electromigration (EM). The gaps obtained range from several nm down to sub–nm, as revealed by lateral conductivity measurements and by scanning tunneling microscopy done under ultra high vacuum conditions. Annealing to 300 K closes the gap by surface diffusion of Ag and a new cycle of opening by EM at low temperature(77K) can be performed. The functionality of the contacts is demonstrated by adsorption of single ferrocenedithiol molecules. The zero bias resistance is around 40kOhm. In addition, the dI/dV curve shows clearly molecular contributions in the range of 50meV and 150meV, which can be attributed to ferrocene induced states near the Fermi edge, as revealed by DFT calculations.