1. Institute of microelectronics, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, China
2. Beijing Graphene Institute, Beijing 100095, China
3. Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
4. Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Peking University, Beijing 100871, China