1. Key Laboratory of Standardization and Measurement for Nanotechnology of Chinese Academy of Sciences, National Center for Nanoscience and Technology, Beijing 100190, People’s Republic of China
2. Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China
3. Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, Republic of China
4. Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan