1. School of Materials and Chemical Technology, Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama 226-8502, Japan
2. Research Center for Functional Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan
3. Tosoh Corporation, 2743-1 Hayakawa, Ayase, Kanagawa 252-1123, Japan
4. Laboratory for Materials and Structures, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan