1. Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California 94720, United States
2. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
3. Department of Physics, University of California, Berkeley, Berkeley, California 94720, United States
4. Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, United States
5. Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078, United States
6. Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
7. Kavli Energy Nanosciences Institute, University of California, Berkeley, Berkeley, California 94720, United States