1. School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
2. School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230029, P.R. China
3. Institute of Physical Science and Information Technology, Anhui University, Hefei 230029, P.R. China
4. Computer, Electrical, and Mathematical Sciences, and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
5. Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109, United States
6. Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR 999077, P.R. China