1. Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
2. Theiss Research Inc., La Jolla, CA 92037, USA.
3. Materials Science and Engineering Division, National Institute of Standards and Technology (NIST), Gaithersburg, MA 20899, USA.
4. Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA.
5. Precourt Institute for Energy, Stanford University, Stanford, CA 94305, USA.