1. Max‐Planck‐Institut für Metallforschung, Heisenbergstrasse 3, D‐70569 Stuttgart (Germany)
2. Beijing Laboratory of Electron Microscopy, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)
3. State Key Laboratory for Superhard Materials, Jilin University, Changchun 130023 (China)
4. Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)