1. Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstrasse 3-3A, D-30167 Hannover, Germany
2. Institute of Condensed Matter Physics, Braunschweig University of Technology, Mendelssohnstrasse 3, D-38106 Braunschweig, Germany
3. Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
4. Institute for Applied Materials, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
5. Physics Department, State University of Maringá, Av. Colombo 5790, 87020−900 Maringá, Brazil
6. Institute of Physical and Theoretical Chemistry, Braunschweig University of Technology, Hans-Sommer-Strasse 10, D-38106 Braunschweig, Germany