1. Department of Chemistry and Physics of Materials, University of Salzburg, Jakob-Haringer-Strasse 2a, 5020 Salzburg, Austria
2. Central European Institute of Technology, Brno University of Technology, Purkynova 123, 612 00 Brno, Czech Republic
3. University Service Centre for Transmission Electron Microscopy, Technische Universität Wien, 1040 Vienna, Austria