1. State Key Laboratory of Integrated OptoelectronicsCollege of Electronic Science and EngineeringJilin University Changchun 130012 China
2. Key Laboratory of Polar Materials and DevicesDepartment of Electronic ScienceSchool of Physics and Electronic ScienceEast China Normal University Shanghai 200241 China
3. Center for Excellence in Nanoscience (CAS)Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS)National Center for Nanoscience and Technology Beijing 100190 China