1. Lehrstuhl für Experimentalphysik 1 and Augsburg Centre for Innovative Technologies, Universität Augsburg, Universitätsstr. 1, 86179 Augsburg, Germany
2. Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80339 Munich, Germany
3. Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universität München, Königinstr. 10, 80539 Munich, Germany
4. Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, 80539 Munich, Germany
5. Nanospectroscopy Group, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universität München, Königinstr. 10, 80539 Munich, Germany