1. Institute of Chemical Engineering and High Temperature Chemical Processes, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), 265 04 Patras, Greece
2. J. Heyrovsky Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, 182 23 Prague 8, Czech Republic
3. Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin, Germany
4. School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, U.K.
5. Materials Science Department, University of Patras, 265 04 Patras, Greece