1. Institute of Optical and Electronic Materials, Hamburg University of Technology, Eissendorfer Strasse 38, Hamburg D-21073, Germany
2. ITMO University, 49 Kronverkskii Avenue, 197101, St. Petersburg, Russia
3. Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Strasse 1, Geesthacht D-21502, Germany