1. School of Materials Science and Engineering, Taizhou University, Taizhou 318000, China
2. Instrumental Analysis Center, Dalian University of Technology, Dalian 116024, China
3. Department of Physics, Taiyuan Normal University, Jinzhong 030619, People’s Republic of China
4. Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China