1. College of Physics and Electronic EngineeringSichuan Normal University Chengdu 610101 China
2. Division of Interfacial Water and Key Laboratory of Interfacial Physics and TechnologyShanghai Institute of Applied PhysicsChinese Academy of Sciences Shanghai 201800 China
3. Center of Electron Microscopy and State Key Laboratory of Silicon MaterialsSchool of Materials Science and EngineeringZhejiang University Hangzhou 310027 China