1. Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
2. Institute of Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
3. Center for Hybrid Nanostructures (CHyN), University of Hamburg, 22761 Hamburg, Germany
4. Karlsruher Nano-Micro-Facility (KNMF), Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany