1. Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095, USA.
2. California NanoSystems Institute (CNSI), University of California, Los Angeles, CA 90095, USA.
3. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
4. Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA.
5. Department of Physics and Center of Integrated Nanomechanical Systems, University of California, Berkeley, CA 94720, USA.
6. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
7. Kavli Energy NanoSciences Institute at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
8. Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA.
9. Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.