[1] Univ Sci & Technol China, Natl Synchrotron Radiat Lab, CAS Key Lab Mech Behav & Design Mat,Dept Chem, Div Nanomat & Chem,Hefei Natl Lab Phys Sci Micros, Hefei 230026, Peoples R China
[2] Univ Sci & Technol China, Engn & Mat Sci Expt Ctr, Hefei 230026, Peoples R China
[3] E China Normal Univ, Lab Polar Mat & Devices, Shanghai 200241, Peoples R China
[4] Chinese Acad Sci, Inst Phys, Beijing Natl Lab Condensed Matter Phys, Beijing 100190, Peoples R China