1. Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
2. Department of Mechanical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
3. Materials Science & Technology Division, Naval Research Laboratory, Washington, D.C. 20375, United States
4. Department of Physics, University of California, Berkeley, Berkeley, California 94720, United States
5. Laboratory for Physical Sciences, College Park, Maryland 20740, United States
6. National Institute for Materials Science, Tsukuba 305-0047, Japan
7. Department of Chemistry, Columbia University, New York, New York 10027, United States
8. Department of Physics, Columbia University, New York, New York 10027, United States