1. Institute of Electron Microscopy and Nanoanalysis, Christian Doppler Laboratory for Direct-Write Fabrication of 3D Nano-Probes, Graz University of Technology, Graz Centre of Electron Microscopy, 8010 Graz, Austria
2. Physics Institute, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
3. Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, Graz Centre of Electron Microscopy, 8010 Graz, Austria