1. School of Physics and Optoelectronic Engineering, Guangdong University of Technology, WaiHuan Xi Road, No. 100, Guangzhou 510006, China
2. School of Electronics and Communications, Guangdong Mechanical & Electrical Polytechnic, Guangzhou 510515, China
3. School of Applied Physics and Materials, Wuyi University, Jiangmen 529020, China
4. Guangdong Provincial Key Laboratory of Rare Earth Development and Application, Institute of Resources Utilization and Rare Earth Development, Guangdong Academy of Sciences, Guangzhou 510651, China
5. College of Physics Science & Technology, Hebei University, Baoding 071002, China
6. Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, China