1. Chair for Photonics and Optoelectronics; Department of Physics and Center for NanoScience (CeNS); Ludwig-Maximilians-Universität; Amalienstrasse 54 80799 Munich Germany
2. Nanosystems Initiative Munich (NIM); Schellingstrasse 4 80799 Munich Germany
3. EMAT; University of Antwerp; Groenenborgerlaan 171 B-2020 Antwerp Belgium
4. Department of Chemistry and Center for NanoScience (CeNS); Ludwig-Maximilians-Universität (LMU); Butenandtstrasse 5-13 81377 Munich Germany
5. Department of Materials Science and Metallurgy; University of Cambridge; 27 Charles Babbage Rd Cambridge CB3 0FS UK