1. Department of Innovative and Engineered Material, Tokyo Institute of Technology, Yokohama 226-8503, Japan
2. NTT Device Technology Laboratories, Nippon Telegraph and Telephone, 3-1, Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan
3. Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
4. PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
5. National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8564, Japan