1. Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Department of Functional Materials, Na Slovance 2, 182 21 Prague 8, Czech Republic
2. J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, CZ-18223 Prague 8, Czech Republic
3. Department of Condensed Matter Physics, Faculty of Mathematic and Physics, Charles University in Prague, Ke Karlovu 5, 121 19 Prague 2, Czech Republic
4. Institut für Synchrotronstrahlung (ISS), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein, Leopoldshafen, Germany