1. School
of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea
2. Department
of Materials Science and Engineering, Yonsei University, Seoul 120-749, Korea
3. Krieger School of Arts & Sciences Advanced Academic Programs, Johns Hopkins University, 1717 Massachusetts Avenue NW, Washington, DC 20036, United States
4. Department
of Materials Science and Engineering, Incheon National University, Incheon 406-772, Korea