1. Department of Electrical and Computer Engineering, University of California, Los Angeles, Los Angeles 90095, California, United States
2. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley 94720, California, United States
3. Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley 94720, California, United States
4. Department of Electricity and Electronics, University of the Basque Country, Leioa 48940, Spain
5. Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles 90095, California, United States
6. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley 94720, California, United States
7. California NanoSystems Institute, Los Angeles 90095, California, United States