1. Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research , Stuttgart , Germany
2. University of Vienna, Faculty of Physics , Vienna , Austria
3. Institute of Materials Chemistry, Vienna University of Technology (TU Wien) , Vienna , Austria
4. Institute for Applied Physics, University of Tübingen , Tübingen , Germany
5. Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and Bio-Engineering Research Centre (AMBER) , Dublin , Ireland
6. School of Chemistry, Trinity College Dublin, The University of Dublin , Dublin , Ireland