1. Institute of Multidisciplinary Research for Advanced
Materials, Tohoku University, Aobaku, Sendai 980-8577, Japan
2. Department of Advanced Materials Science
and Nanotechnology, University of Science and Technology of Hanoi, 18 Hoang Quoc Viet, Hanoi 100000, Vietnam
3. Field Solution Division, JEOL Ltd., 1156 Nakagami, Akishima, Tokyo 196-0022, Japan