1. Institute
of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany
2. Laboratory
for Electron Microscopy, Karlsruhe Institute of Technology, Engesserstr.
7, 76131 Karlsruhe, Germany
3. Helmholtz
Institute Ulm, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany