1. Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
2. Kavli Nanoscience Institute, Pasadena, California 91125, United States
3. Materials and Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. Department of Physics, University of California Berkeley, Berkeley, California 94720, United States
5. Department of Applied Physics, Stanford University, Stanford, California 94305, United States
6. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
7. Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
8. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
9. International Center for Materials, Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
10. Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, United States
11. Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, United States