1. Department of Environmental Science and Technology, Faculty of Engineering, Shinshu University, Nagano 380‐8553, Japan, Fax: +81‐26‐269‐5550
2. Faculty of Engineering, Shinshu University, Nagano 380‐8553, Japan
3. Institute for Materials Research, Tohoku University, Sendai 980‐8577, Japan
4. Institute of Carbon Science and Technology, Shinshu University, Nagano 380‐8553, Japan
5. Department of Electrical and Electronic Engineering, Faculty of Engineering, Shinshu University, Nagano 380‐8553, Japan