1. Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
2. School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
3. Department of NanoEngineering, University of California, San Diego, La Jolla, California 92093, United States
4. School of Natural Sciences, University of California, Merced, California 95343, United States