1. California NanoSystems Institute, University of California, Santa Barbara, CA 93106, USA.
2. Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095, USA.
3. California NanoSystems Institute, University of California, Los Angeles, CA 90095, USA.
4. Advanced Institute for Materials Research at Tohoku University, a World Premier International Research Centers (WPI) Initiative Program (WPI-AIMR) and joint center with the California NanoSystems Institute, University of California, Santa Barbara, CA 93106, USA.
5. Department of Materials, University of California, Santa Barbara, CA 93106, USA.
6. Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA.