1. Department of Materials Science and EngineeringCollege of EngineeringPeking University Beijing 100871 China
2. MIIT Key Laboratory of Flexible Electronics (KLoFE)Xi'an Institute of Flexible ElectronicsNorthwestern Polytechnical University Xi'an 710072 Shaanxi China
3. CAS Key Laboratory of Standardization and Measurement for NanotechnologyCAS Center for Excellence in NanoscienceNational Center for Nanoscience and Technology Beijing 100190 China
4. Joint Key Laboratory of the Ministry of EducationInstitute of Applied Physics and Materials EngineeringUniversity of MacauAvenida da Universidade Taipa 999078 Macao, SAR China