1. a Nanotechnology Research Institute (NRI), National Institute of Advanced Industrial Science and Technology (AIST), Central-4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan; Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, S7-5 Ookayama, Meguro, Tokyo 152-8550, Japan
2. b Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, S7-5 Ookayama, Meguro, Tokyo 152-8550, Japan
3. c Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, S7-5 Ookayama, Meguro, Tokyo 152-8550, Japan
4. d Biomaterials Center, National Institute for Materials Science (NIMS), 1-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
5. e Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, S7-5 Ookayama, Meguro, Tokyo 152-8550, Japan
6. f Nanotechnology Research Institute (NRI), National Institute of Advanced Industrial Science and Technology (AIST), Central-4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan, Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, S7-5 Ookayama, Meguro, Tokyo 152-8550, Japan. t.uemura@aist.go.jp
7. g Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, S7-5 Ookayama, Meguro, Tokyo 152-8550, Japan