1. Research Center for Ultra-High Voltage Electron Microscopy, Osaka University , 7-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
2. Research & Development Group, Hitachi, Ltd. , 1-280, Higashi-koigakubo Kokubunji-shi, Tokyo 185-8601, Japan
3. Department of Electrical and Electronic Engineering, Fukui University of Technology , 3-6-1, Gakuen, Fukui City, Fukui 910-8505, Japan
4. Institute of Applied Physics, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan
5. Institute of Materials and Systems for Sustainability, Nagoya University , Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan