1. Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States
2. Applied Physics Graduate Program, Smalley-Curl Institute, Rice University, 6100 Main Street, Houston, Texas 77005, United States
3. Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States
4. Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, Texas 77005, United States
5. Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, United Kingdom