1. Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA.
2. E. L. Ginzton Laboratory, Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
3. Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
4. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.