1. Center for Physical Sciences and Technology, Semiconductor Physics Institute, Saulėtekio Ave. 3, LT-10257 Vilnius, Lithuania
2. Vilnius Gediminas Technical University, Naugarduko 41, LT-03227 Vilnius, Lithuania
3. Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania