1. Engineering Research Center of Electronic Information Materials and Devices, Ministry of Education, Guangxi Key Laboratory of Information Material, Guilin University of Electronic Technology, Guilin 541004, P. R. China
2. School of Physics and Electronic & Electrical Engineering, and Jiangsu Key Laboratory of Modern Measurement Technology and Intelligent Systems, Huaiyin Normal University, Huai’an 223300, P. R. China
3. School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen 518055, P.R. China
4. Department of Materials Science and Engineering, SIT Research Laboratories, Innovative Global Program, Faculty of Engineering, Shibaura Institute of Technology, Tokyo 135-8548, Japan