1. MIIT Key Laboratory of Advanced Display Materials and Devices School of Materials Science and Engineering Nanjing University of Science and Technology Nanjing 210094 China
2. CAS Key Laboratory of Standardization and Measurement for Nanotechnology CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology Beijing 100190 China
3. Key Laboratory of Materials Physics of Ministry of Education School of Physics and Microelectronics Zhengzhou University Zhengzhou 450001 China