1. Fujitsu Research, Fujitsu Limited, 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa, 243-0197, Japan
2. Division of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan
3. Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan