[1] Chinese Acad Sci, Inst Solid State Phys, Hefei Inst Phys Sci, Key Lab Mat Phys, Hefei 230031, Peoples R China
[2] Chinese Acad Sci, Inst Solid State Phys, Hefei Inst Phys Sci, Anhui Key Lab Nanomat & Nanotechnol, Hefei 230031, Peoples R China
[3] Univ Sci & Technol China, Dept Mat Sci & Engn, Hefei 230026, Peoples R China
[4] Univ Delaware, Dept Mech Engn, Newark, DE 19716 USA