1. Department
of Materials Science and Engineering and Inter-university Semiconductor
Research Center, Seoul National University, Seoul 151-742, Republic of Korea
2. Thin
Film Materials Research Center, Korea Research Institute of Chemical Technology, P.O.
Box 107, Yuseong, Daejeon 305-600, Republic of Korea
3. Department
of Physics and Division of Energy Systems Research, Ajou University, Suwon, Gyeonggi-do 443-749, Republic of Korea