1. School of Electronic Science and Applied Physics and Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices, Hefei University of Technology, Hefei 230009, PR China
2. Department of Applied Physics and Materials Research Center, Hong Kong Polytechnic University, Hung
Hom, Kowloon, Hong Kong 99077, PR China
3. School of Materials Science and Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China