1. Nanomaterials Research Institute, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
2. Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
3. Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan