1. Center for Physical Sciences and Technology (FTMC), Saulėtekio al. 3, LT-10257 Vilnius, Lithuania
2. Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga, Latvia
3. Institute of Chemistry, Vilnius University, Saulėtekio al. 3, LT-10257 Vilnius, Lithuania