1. School of Electrical Engineering, Korea University, Seoul 136-713, South Korea
2. National Institute of Advanced Industrial Science and Technology (AIST), and Technology Research Association for Single Wall Carbon Nanotubes (TASC), Tsukuba, Ibaraki 305-8565, Japan
3. Nano Electron-Source Creative Research Center, Creative and Challenging Research Division, Electronics and Telecommunications Research Institute, Daejeon 305-700, South Korea
4. Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
5. Electrical Engineering Division, Department of Engineering, Cambridge University, Cambridge CB3 0FA, United Kingdom