1. Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, U.S.A.
2. Applied Physics Graduate Program, Smalley-Curl Institute, Rice University, Houston, TX 77005, U.S.A.
3. Smalley-Curl Institute, Rice University, Houston, TX 77005, U.S.A.
4. Department of Physics and Astronomy, Rice University, Houston, TX 77005, U.S.A.
5. Department of Materials Science and NanoEngineering, Rice University, Houston, TX 77005, U.S.A.