1. Graz Centre for Electron Microscopy, Steyrergasse 17, 8010 Graz, Austria
2. Institute
of Electron Microscopy and Nanoanalysis, Graz University of Technology, Steyrergasse 17, 8010 Graz, Austria
3. Institute
of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria