1. Department of Physics; Kyiv National Taras Shevchenko University; 64 Volodymyrska Str. 03310 Kyiv Ukraine
2. Department of Chemistry; Kyiv National Taras Shevchenko University; 64 Volodymyrska Str. 03310 Kyiv Ukraine
3. Institut d'Électronique du Solideet des Systèmes; 23, rue Du Loess, BP 20 CR 67037 Strasbourg, Cedex 2 France
4. Department of Physics; Ben-Gurion University of the Negev; Be'er-Sheva Israel