1. Department of Materials Science, Chiba University, Chiba 263-8522, Japan
2. Department of Physics, Chiba University, Chiba 263-8522, Japan
3. School of Electronic and Electrical Engineering and Sungkyunkwan Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University (SKKU), Suwon 16419, South Korea
4. International Centre for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
5. Research Centre for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
6. Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA
7. School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706, USA