1. Plasma Processing Laboratory, Lithuanian Energy Institute, Breslaujos Str. 3, 44403 Kaunas, Lithuania
2. Department of Physics, Kaunas University of Technology, Studentu Str. 50, 51368 Kaunas, Lithuania
3. Department of Functional Materials and Electronics, State Research Institute, Center for Physical Sciences and Technology, Savanoriu Ave. 231, 10257 Vilnius, Lithuania