1. National Laboratory of Solid
State Microstructures, Ecomaterials and Renewable Energy Research
Center (ERERC), and Department of Physics, Nanjing University, Nanjing 210093, People’s Republic of China
2. School of Materials Science
and Engineering, Kunming University of Science and Technology, Kunming 650093, People’s Republic of China
3. Department of Materials Science
and Engineering, Nanjing University, Nanjing
210093, People’s Republic of China