[1] Nanyang Technol Univ, Sch Elect & Elect Engn, Ion Beam Proc Lab, Singapore 639798, Singapore
[2] Huazhong Univ Sci & Technol, Sch Mat Sci & Engn, State Key Lab Die & Mould Technol, Wuhan 430074, Hubei, Peoples R China
[3] Wuhan Univ, Ctr Res & Anal Mat, Wuhan 430072, Hubei, Peoples R China
[4] Wuhan Univ Technol, Ctr Res & Anal Mat, Wuhan 430072, Hubei, Peoples R China