1. School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan, Prism Technology, Inc., 804 Hakyeonsan Research Center, Chungbuk National University, Cheongju, Chungbuk 361-763, Korea, School of Electrical and Computer Engineering, Chungbuk National University, Cheongju, Chungbuk, 361-763, Korea, and Department of Polymer Science and Engineering, Pusan National University, Pusan, 609-735, Korea