1. Hakodate National College of Technology, 14-1 Tokura-cho, Hakodate, Hokkaido 042-8501
2. Nanoelectronics Research Institute, AIST, Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568
3. Institue of Materials Structure Science, KEK, Tsukuba, Ibaraki 305-0801