1. Transmission Electron Microscopy Station, National Institute for Materials Science,1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
2. Center for Functional Sensor & Actuator, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
3. Toray Research Center Inc., 3-3-7 Sonoyama, Otsu, Shiga 520-8567, Japan