1. Department of Materials Science and Engineering
2. Chonnam National University
3. Gwangju 61186
4. Republic of Korea
5. SBK Materials Co.
6. Department of Physics
7. Faculty of Science
8. Beni-Suef University
9. Beni-Suef 62511
10. Egypt
11. State Key Lab of Artificial Microstructure and Mesoscopic Phisics
12. School of Physics
13. Peking University
14. Beijing 100871
15. China
16. Department of Nanotechnology and Advanced Materials Engineering
17. Sejong University
18. Seoul 05006