1. Department of Materials Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Japan
2. Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505 Japan
3. Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, 456-8587 Japan
4. Department of Quantum Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Japan
5. Institute of Engineering Innovation, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-8686 Japan.
6. E-mail: ikuhara@sigma.t.u-tokyo.ac.jp.