1. Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany
2. Department of Physics, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany
3. Center for Advancing Electronics Dresden & Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, 01069 Dresden, Germany
4. Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany