1. Department of Physics, Engineering and Astronomy Austin Peay State University 601 College St. Clarksville TN 37044 USA
2. Department of Semiconductor Electronics Lviv Polytechnic National University 12, Bandera str. Lviv UA-79013 Ukraine
3. Faculty of Science and Technology Jan Dlugosz University in Czestochowa 13/15, al. Armii Krajowej Czestochowa 42200 Poland