1. Department of Chemistry University of California Berkeley 699 Tan Hall Berkeley CA 94720 U.S.A.
2. Department of Physics University of California Berkeley 345 Birge Hall Berkeley CA 94720 United States
3. Materials Science Division Lawrence Berkeley National Laboratory Berkeley CA 94720 United States
4. Kavli Energy NanoSciences Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory Berkeley CA 94720 United States