1. Stanford
Nano Shared Facilities, Stanford University, Stanford, California 94305, United States
2. Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
3. Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
4. Department
of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States