1. Department of Solid State Engineering, University of Chemistry and Technology, Prague 166 28, Czech Republic
2. Central Laboratories, University of Chemistry and Technology, Prague 166 28, Czech Republic
3. Faculty of Mathematics and Physics, Charles University, Prague 12116, Czech Republic
4. New Technologies−Research Centre, University of West Bohemia, Univerzitní 8, Plzeň 30614, Czech Republic
5. CENAB, Faculty of Science, J. E. Purkyne University, Usti nad Labem 40096, Czech Republic