1. Institute of Solid State Physics and Chemistry, Uzhhorod National University, Pidhirna Str., 46, 88000 Uzhhorod, Ukraine
2. Wigner Research Centre for Physics, Hungarian Academy of Sciences, 1121 Budapest, Hungary
3. Institute for Nuclear Research, Hungarian Academy of Sciences, H-4001 Debrecen, Hungary
4. Pavol Jozef Šafárik University in Košice, Park Angelinum 9, Košice, Slovak Republic
5. Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Prague 8, Czech Republic
6. Institute of Physics, Academy of Science of the Czech Republic, Na Slovance 2, CZ-182 21 Prague 8, Czech Republic
7. Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, in Area Science Park, 34149 Basovizza, Trieste, Italy
8. Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, 34149 Basovizza, Trieste, Italy