1. MOE Key Laboratory of Materials Modification by Beams and School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
2. School of Information Science and Engineering, Dalian Polytechnic University, Dalian 116034, China
3. Department of Physics, Harbin Institute of Technology, Harbin 150001, China
4. State Key Laboratory of Nuclear Physics and Technology and School of Physics, Peking University, Beijing 100871, China