1. Institute for Physical Chemistry, Heidelberg University, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany
2. Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4, 85748 Garching by Munich, Germany
3. School of Physics, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
4. Applied Physical Chemistry, Heidelberg University, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
5. Electrical Engineering Division, University of Cambridge, 9 JJ Thomson Ave, Cambridge CB3 0FA, United Kingdom
6. Department of Inorganic Chemistry, Faculty of Chemical Technology, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic
7. Physical Chemistry of Nanomaterials, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany