[1] Chinese Acad Sci, Ningbo Inst Mat Technol & Engn, Ningbo 315201, Zhejiang, Peoples R China
[2] Hunan Univ, Key Lab Micronano Optoelect Devices, Minist Educ, Changsha 410082, Hunan, Peoples R China
[3] Chinese Acad Sci, Ningbo Inst Mat Technol & Engn, Ningbo 315201, Zhejiang, Peoples R China