1. Molecular Electronics, Technische Universität München, Theresienstr. 90, 80333 München, Germany
2. Physik Department, Walter Schottky Institut and Center for Nanotechnology and Nanomaterials, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
3. Faculty of Science and Technology, Free University of Bozen-Bolzano, 39100 Bolzano, Italy
4. Fraunhofer Research Institution for Microsystems and Solid State Technologies (EMFT), Hansastrasse 27d, 80686 Munich, Germany
5. Center for NanoScience (CeNS), Ludwig-Maximilians-University, Geschwister-Scholl Platz 1, 80539 Munich, Germany