1Department of Material Science and Engineering, Stanford University, Stanford, California 94305, United States
2National Laboratory of Solid-State Microstructures, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
3Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
4School of Material Science and Engineering, Beihang University, Beijing 100191, China
5Department of Applied
Physics, Stanford University, Stanford,
California 94305, United States