1. School of Electronic Engineering, Xi’an University of Posts and Telecommunications, Xi’an 710121, China
2. Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
3. Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
4. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States