1. Institute of Physics of the Czech Academy of Science, Cukrovarnicka 10/112, 16200 Prague, Czech Republic
2. Czech Technical University in Prague, Břehová 7, 115 19 Prague, Czech Republic
3. University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague, Czech Republic
4. Department of Materials Science, University of Milano-Bicocca, Via Cozzi 55, 20125 Milano, Italy