1. Regional Centre of Advanced Technologies and Materials Czech Advanced Technology and Research Institute (CATRIN) Palacký University Olomouc 78371 Olomouc Czech Republic
2. Department of Physical Chemistry Faculty of Science Palacký University 78371 Olomouc Czech Republic
3. Institute of Physics Academy of Sciences of the Czech Republic Prague Czech Republic
4. Current address: Department of Physics University of Alberta Edmonton Alberta T6G 2J1 Canada
5. IMDEA Nanociencia, Ciudad Universitaria de Cantoblanco Madrid Spain