1. Institute
for Advanced Materials and Guangdong Provincial Key Laboratory of
Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China
2. School
of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
3. Department
of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
4. Department
of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
5. Department
of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
6. Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, United States
7. Materials
Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States