1. Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
2. Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K.
3. Department of Chemistry, School of Science, Tokyo Institute of Technology, Tokyo 152-8551, Japan
4. Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047, Japan
5. Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan