1. Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, Torun 87-100, Poland
2. Sieć Badawcza Łukasiewicz-Instytut Technologii Elektronowej, Al. Lotnikow 32/46, Warsaw 02-668, Poland
3. Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska St., Kiev 01601, Ukraine
4. Faculty of Physics, Warsaw University of Technology, 75 Koszykowa Str., Warsaw 00-662, Poland