1. Lehrstuhl für Experimentalphysik 1, Institut für Physik and Augsburg Centre for Innovative Technologies (ACIT), Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany
2. Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 München, Germany
3. School of Science and Engineering, Reykjavik University, Menntavegur 1, 101 Reykjavik, Iceland
4. Department of Theoretical Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland
5. Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
6. Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13(E), 81377 München, Germany