1. Department of Materials Engineering Science; Graduate School of Engineering Science; Osaka University; 1-3 Machikaneyama, Toyonaka Osaka 560-8531 Japan
2. Research Center for Ultra-High Voltage Electron Microscopy; Osaka University; 7-1, Mihogaoka, Ibaraki Osaka 567-0047 Japan
3. Research Center for Solar Energy Chemistry; Osaka University; 1-3, Machikaneyama, Toyonaka Osaka 560-8531 Japan