1. Center for Technology Innovation, Hitachi Ltd, 7-1-1 Omika, Hitachi, Ibaraki 312-1292, Japan
2. Center for Exploratory Research, Hitachi Ltd, Akanuma 2520, Hatoyama, Saitama 350-0395, Japan
3. Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Fukuoka 819-0395, Japan
4. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
5. The Ultramicroscopy Research Center, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Fukuoka 819-0395, Japan