1. Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong
2. Shenzhen Research Institute, City University of Hong Kong, Shenzhen, People’s Republic of China
3. Cultivation Base for State Key Laboratory, Qingdao University, No. 308 Ningxia Road, Qingdao, People’s Republic of China
4. Department of Materials Science and Engineering, National Tsing Hua University, No. 101 Sec. 2 Kuang-Fu Road, Hsinchu 30013, Taiwan