1. Walter Schottky Institute, TUM School of Natural Sciences, Technical University of Munich, 85748 Garching bei München, Germany
2. Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
3. Paul-Drude-Institute for Solid State Electronics, Leibniz-Institut Im Forschungsverbund Berlin e.V., 10117 Berlin, Germany