[1] Nanjing Univ, Collaborat Innovat Ctr Adv Microstruct, Natl Lab Solid State Microstruct, Nanjing 210093, Jiangsu, Peoples R China
[2] Nanjing Univ, Dept Phys, Nanjing 210093, Jiangsu, Peoples R China
[3] Nanjing Univ, Sch Elect Sci & Engn, Nanjing 210093, Jiangsu, Peoples R China