1. The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
2. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
3. Center for Nanotechnology Innovation @ NEST, Instituto Italiano di Tecnologia, 56127 Pisa, Italy
4. Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.
5. Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
6. Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, United States
7. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0047, Japan
8. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0047, Japan