1. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
2. Materials Science and Engineering Department, University of California Berkeley, Berkeley, California 94720, United States
3. Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States
4. College of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
5. MESA+ Institute for Nanotochnology, Faculty of Science and Technology University of Twente, Enschede, The Netherlands
6. The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States