[1] Hubei Univ, Fac Phys & Elect Technol, Wuhan 430062, Peoples R China
[2] Hubei Univ, Nanotechnol Res Ctr, Wuhan 430062, Peoples R China
[3] Chinese Univ Hong Kong, Dept Elect Engn, Hong Kong, Hong Kong, Peoples R China
[4] Chinese Univ Hong Kong, Dept Phys, Hong Kong, Hong Kong, Peoples R China
[5] Huazhong Univ Sci & Technol, Dept Elect Sci & Technol, Wuhan 430074, Peoples R China