1. National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California , United States
2. Department of Materials Science and Engineering, University of California , Berkeley, California , United States
3. Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts , United States
4. Center for Integrated Nanotechnologies, Los Alamos National Laboratory , Albuquerque, New Mexico , United States
5. School of Natural Sciences, Technical University of Munich , Munich , Germany