1. a Institute of Theoretical Physics and Astronomy , A. Gostauto 12, 2600 , Vilnius , Lithuania
2. b Faculty of Physics , Vilnius University , Sauletekio al. 9, III rumai, 2054 , Vilnius , Lithuania
3. c LETI (CEA-Technologies Avancées), DEIN-SPE, Groupe Composants Organiques , Saclay, F-91191 Gif sur Yvette, France