1. Department of Nanoscience and Nanoengineering, Waseda University, Tokyo 169-8555, Japan
2. Technology Research Association for Single Wall Carbon Nanotube (TASC), 1-1-1 Higashi, Tsukuba 305-8565, Japan
3. Kagami Memorial Research Institute for Material Science and Technology, Shinjuku-ku, Tokyo 169-0051, Japan