[1] Univ Calif Los Angeles, Dept Mat Sci & Engn, Los Angeles, CA 90095 USA
[2] Univ Calif Los Angeles, Calif NanoSyst Inst CNSI, Los Angeles, CA 90095 USA
[3] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[4] Univ Calif Los Angeles, Dept Chem & Biochem, Los Angeles, CA 90095 USA
[5] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA
[6] Univ Calif Berkeley, Ctr Integrated Nanomech Syst, Berkeley, CA 94720 USA
[7] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA
[8] Univ Calif Berkeley, Kavli Energy NanoSci Inst, Berkeley, CA 94720 USA
[9] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA
[10] Lawrence Livermore Natl Lab, Phys & Life Sci Directorate, Livermore, CA 94550 USA
[11] Johns Hopkins Univ, Dept Mat Sci & Engn, Baltimore, MD 21218 USA