1. Department of Materials Science & Engineering, Seoul National University, San 56-1, Shillim-Dong, Kwanak-Gu, Seoul 151-744, Korea, Pyungtaek R&D Center, Dongwoo FineChem Co., Ltd., 1177, Pyungtaek-Si, Kyunggi-Do, 451-764, Korea, and The Center for Ultrafast Optical Characteristics Control and Department of Chemistry, Yonsei University, Seoul 120-749, Korea