1. Department
of Materials Science
and Engineering, Research Institute of Advanced Materials, Seoul National University, 599 Gwanak-ro, Gwanak-gu,
Seoul 151-742, Republic of Korea
2. Korea Atomic Energy Research Institute, P.O. Box 105, Yuseong-gu, Daejeon
305-600, Republic of Korea
3. Department of Physics, Kookmin University, Seoul 136-702, Republic of Korea
4. Department of Materials Science
and Engineering, KAIST, 291 Daehak-ro,
Yuseong-gu, Daejeon 305-600, Republic of Korea