[1] Chinese Acad Sci, Key Lab Ion Beam Bioengn, Inst Plasma Phys, Hefei 230031, Peoples R China
[2] City Univ Hong Kong, Dept Phys & Mat Sci, Kowloon, Hong Kong, Peoples R China
[3] Wuhan Univ Sci & Technol, Hubei Prov Key Lab Ceram & Refractories, Coll Mat & Met, Wuhan 430081, Peoples R China