1. State Key Laboratory of Functional Materials for InformaticsShanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences Shanghai 200050 China
2. University of Chinese Academy of Sciences Beijing 100049 China
3. State Key Laboratory of Surface PhysicsInstitute for Nanoelectronic Devices and Quantum ComputingKey Laboratory of Micro and Nano Photonics Structures (Ministry of Education)Department of PhysicsFudan University Shanghai 200433 China
4. Department of Materials ScienceFudan University Shanghai 200433 China
5. Department of PhysicsDepartment of Materials Science and Engineeringand Department of Biomedical EngineeringCity University of Hong Kong Tat Chee Avenue Kowloon Hong Kong 999077 China