[1] Changsha Univ Sci & Technol, Coll Phys & Elect Sci, Changsha 410114, Hunan, Peoples R China
[2] Cent S Univ, State Key Lab Powder Met, Changsha 410083, Hunan, Peoples R China
[3] Hunan Univ, Coll Phys & Microelect Sci, Changsha 410082, Hunan, Peoples R China