1. Department of Applied Physics, Stanford University, 348 Via Pueblo, Stanford, California 94305, United States
2. Department of Electrical Engineering, Stanford University, 350 Serra Mall, Stanford, California 94305, United States
3. Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, California 94305, United States
4. Stanford Nano Shared Facilities, Stanford University, 476 Lomita Mall, Stanford, California 94305, United States