1. Center for Photonics Information and Energy Materials Shenzhen Institute of Advanced Technology Chinese Academy of Sciences Shenzhen 518055 P. R. China
2. Department of Nano Science and Technology Institute University of Science and Technology of China Suzhou 215123 P. R. China
3. School of Computer and Control Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
4. Shenzhen Institutes of Advanced Electronic Materials Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences Shenzhen 518055 P. R. China
5. School of Electrical and Electronic Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore