1. Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
2. Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
3. Walter-Schottky-Institut and Physik-Department, Technical University of Munich, Garching 85748, Germany
4. Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 7610001, Israel
5. Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
6. Radboud University of Nijmegen, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
7. Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, E-28049, Madrid, Spain
8. Department of Physics, Montana State University, Bozeman, Montana 59717, United States
9. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
10. Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, United States