[1] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA
[2] Lawrence Berkeley Natl Lab, Mat Sci Div, Berkeley, CA 94720 USA
[3] Univ Calif Berkeley, Kavli Energy NanoSci Inst, Berkeley, CA 94720 USA
[4] Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA
[5] Univ Calif Berkeley, Dept Biochem & Mol Biol, Berkeley, CA 94720 USA
[6] Lawrence Berkeley Natl Lab, Mol Foundry, Berkeley, CA 94720 USA