1. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark
2. Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
3. Belarussian State University, Praspyekt Nyezalyezhnastsi 4, 220030 Minsk, Belarus