1. Wuhan National Laboratory for Optoelectronics (WNLO)Huazhong University of Science and Technology Luoyu Road 1037 Wuhan 430074 China
2. Shanghai Synchrotron Radiation FacilityShanghai Advanced Research InstituteChinese Academy of Sciences Shanghai 201204 China
3. The State Key Laboratory of Refractories and MetallurgyInstitute of Advanced Materials and NanotechnologyWuhan University of Science and Technology Wuhan 430081 China
4. Department of Physics and Department of Materials Science and EngineeringCity University of Hong Kong Tat Chee Avenue Kowloon Hong Kong 990077 China