1. Institute
of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
2. National Institute for Material Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
3. Department
of Electrical Engineering, Keio University, 3-14-1 Hiyoshi Kouhokuku Yokohama 223-8522, Japan
4. Shanghai
Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China