1. Department
of Physics, University of California, Berkeley, California 94720, United States
2. Materials
Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
3. Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. Department of Physics & Astronomy, California State University Long Beach, Long Beach, California 90840, United States
5. Department
of Chemical Engineering, Stanford University, Stanford, California 94305, United States
6. School
of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, United Kingdom
7. School
of Chemistry and Chemical Engineering, Queen’s University Belfast, Belfast BT7 1NN, United Kingdom
8. Graduate
Group in Applied Science and Technology, University of California, Berkeley, California 94720, United States
9. Advanced
Materials Laboratory, National Institute for Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305-0044, Japan