1. Institute for Semiconductor and Solid State Physics; Johannes Kepler Universität; Altenberger Str. 69 4040 Linz Austria
2. National Technical University “Kharkiv Polytechnic Institute”; Frunze Str. 21 61002 Kharkiv Ukraine
3. Helmholtz-Zentrum Berlin für Materialien und Energie; Albert-Einstein Str. 15, 12489 Berlin Germany
4. Institute of Physics; Polish Academy of Sciences; Aleja Lotników 32/46 PL-02-668 Warszawa Poland
5. Department of Condensed Matter Physics; Masaryk University; Kotlárˇská 2 61137 Brno Czech Republic
6. Consiglio Nazionale delle Ricerche CNR-SPIN; Via dei Vestini 31 66100 Chieti Italy
7. Institut für Physik und Astrophysik; Universität Würzburg; Am Hubland Campus Süd Würzburg 97074 Germany