1. Technology Division, Panasonic Holdings Corporation, 3-1-1 Yagumo-naka-machi, Moriguchi City, Osaka 570-8501, Japan
2. Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
3. Nanostructures Research Laboratory, Japan Fine Ceramics Centre, 2−4−1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587, Japan