1. Department of Chemistry and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, United States
2. Department of Physics, Sogang University, 35 Baekbeom-ro,
Mapo-gu, Seoul 04107, Korea
3. Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
4. Department of Materials Science and Engineering, Pennsylvania State University, State College, Pennsylvania 16802, United States
5. Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States