1. School
of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
2. State
Key Laboratory of Silicon Materials and School of Materials Science
and Engineering, Zhejiang University, Hangzhou 310027, People’s Republic of China
3. Chu
Kochen Honors College, Zhejiang University, Hangzhou 310058, People’s Republic of China
4. Department
of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
5. School
of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University, Gwanak-gu, Seoul 151-747, Republic of Korea
6. Center
for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea
7. Department
of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-747, Republic of Korea
8. Department
of Physics, Harvard University, Cambridge, Massachusetts 02138, United States