1. Plasma Laboratory; Jozef Stefan Institute; Jamova Cesta 39 1000 Ljubljana Slovenia
2. Jozef Stefan International Postgraduate School; Jamova Cesta 39 1000 Ljubljana Slovenia
3. Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences; POB 49 H-1525 Budapest Hungary
4. Laboratory for Characterization and Processing of Polymers, Faculty of Mechanical Engineering; University of Maribor; Smetanova 17 2000 Maribor Slovenia