1. Institute of Solid State Physics, University of Latvia, 8 Kengaraga Street, Riga LV-1063, Latvia
2. Advanced Materials Department, Jožef Stefan Institute, Jamova 39, Ljubljana 1000, Slovenia
3. Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, Ljubljana 1001, Slovenia
4. National Institute of Materials Physics, 405A Atomistilor Street, Magurele 077125, Ilfov, Romania