1. National Creative Research Initiative Center for Oxide Nanocrystalline Materials and School of Chemical Engineering, Seoul National University, Seoul 151-744, Korea, New Materials Evaluation Center, Korea Research Institute of Standards and Science, Taeduk Science Town, P.O. Box 102, Taejon 305-600, Korea, and AE Center, Samsung Advanced Institute of Technology (SAIT), P.O. Box 111, Suwon 440-600, Korea