1. Department
of Physics and Oxide Research Centre, Hankuk University of Foreign Studies, Yongin 449-791, Korea
2. Division
of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-791, Korea
3. Department
of Physics and Department
of Energy Systems Research, Ajou University, Suwon 443-749, Korea
4. Department
of Physics, Ewha Womans University, Seoul 120-750, Korea
5. Department
of Material Science and Engineering, Seoul National University, Seoul 151-747, Korea
6. Department
of Material Science and Engineering and Inter-University Semiconductor
Research Center, Seoul National University, Seoul 151-744, Korea
7. Department
of Physics Education, Seoul National University, Seoul 151-748, Korea