1. Department of Solid State Physics, Faculty of Sciences and Technology, University of Debrecen, P.O. Box 400, H-4002 Debrecen, Hungary
2. Doctoral School of Physics, University of Debrecen, Egyetem sqr. 1, 4032 Debrecen, Hungary
3. Department of Physics, Faculty of Education, Ain Shams University, Roxy, 11341 Cairo, Egypt
4. IB Group, Department of EP Application, EP Business Unit, JEOL Ltd., 196-8558 Tokyo, Japan
5. Department of EM Application, EM Business Unit, JEOL Ltd., 196-8558 Tokyo, Japan