1. Solid State Physics & Material Research Laboratory, School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
2. Research Center for Advanced Information Materials (CAIM), Huangpu Research and Graduate School of Guangzhou University, Guangzhou 510555, China
3. School of Physics, Guangdong Province Key Laboratory of Display Material and Technology, Sun Yat-sen University, Guangzhou 510275, China