1. Institute of Materials Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria
2. Department of Interface Science, Fritz-Haber-Institut der Max-Planck Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
3. University Service Center for Transmission Electron Microscopy, TU Wien, Wiedner Hauptstraße 8-10, 1040 Vienna, Austria