[1] Univ Sci & Technol China, Dept Mat Sci & Engn, Hefei 230026, Anhui, Peoples R China
[2] Chinese Acad Sci, Beijing Lab Electron Microscopy, Inst Phys, Beijing 100190, Peoples R China
[3] Florida Int Univ, Dept Mech & Mat Engn, Miami, FL 33174 USA
[4] Max Planck Inst Solid State Res, D-70569 Stuttgart, Germany