1. Surface Physics and Structure Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan
2. Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan
3. Transmission Electron Microscopy Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan
4. Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
5. Department of Materials Science and Technology, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548, Japan