1. Key Laboratory of Advanced Materials (MOE) School of Materials Science and Engineering Tsinghua University Beijing 100084 China
2. School of Instrumentation Science and Opto‐electronics Engineering Beihang University Beijing 100191 China
3. Department of Materials Science and Engineering The Pennsylvania State University University Park PA 16802 USA
4. Department of Chemistry Department of Physics and Center for 2‐Dimensional and Layered Materials The Pennsylvania State University University Park PA 16802 USA
5. Institute of Carbon Science and Technology Shinshu University Wakasato 4‐17‐1 Nagano 380‐853 Japan