1. CAS Center for Excellence in NanoscienceCAS Key Laboratory of Nanosystem and Hierarchical FabricationNational Center for Nanoscience and Technology Beijing 100190 China
2. State Key Laboratory of Electronic Thin Films and Integrated DevicesUniversity of Electronic Science and Technology of China Chengdu 610054 China
3. Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of Science Beijing 100049 China