1. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
2. Department of Chemistry, Stanford University, Stanford, California 94305, United States
3. Department of Physics and Materials Science, City University of Hong Kong, Hong Kong, China
4. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States.