[Gong, Li; Duan, Jipeng; Wang, Cheng; Zhang, Junsen] Changsha Univ Sci & Technol, Sch Mat Sci & Engn, Changsha 410114, Peoples R China.
[Wu, Jie; Jiang, Liangxiang] Cent S Univ, Sch Met & Environm, Changsha 410083, Peoples R China.
[Zhou, Conghua; Xie, Haipeng] Cent S Univ, Sch Phys & Elect, Hunan Key Lab Super Microstruct & Ultrafast Proc, Changsha 410083, Peoples R China.
[Gao, Yongli] Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA.
[He, Haiping; Fang, Zhishan; Lu, Jianguo; Lu, Bojing] Zhejiang Univ, Sch Mat Sci & Engn, Hangzhou 310027, Peoples R China.