1. School
of Electrical Engineering, Kookmin University, Seoul 136-702, Republic of Korea
2. Department of Materials
Science and Engineering, KAIST, Daejeon 305-338, Republic of Korea
3. School of Electrical and
Electronic Engineering, Yonsei University, Seoul 120-749, Republic of Korea
4. Department of Materials Science
and Engineering, Chungnam National University, Daejeon 305-764, Republic of Korea