1. Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
2. Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, United States
3. Kavli Energy NanoSciences Institute at the University of California at Berkeley, Berkeley, California 94720, United States
4. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
5. National Center for Electron Microscopy, The Molecular Foundry, One Cyclotron Road, Berkeley, California 94720 United States