1. Department of Chemistry Stanford University Stanford CA 94305 USA
2. Stanford Institute for Materials and Energy Sciences SLAC National Accelerator Laboratory Menlo Park CA 94025 USA
3. Department of Geological Sciences Stanford University Stanford CA 94305 USA
4. Department of Physics Stanford University Stanford CA 94305 USA
5. Department of Applied Physics Stanford University Stanford CA 94305 USA
6. Department of Physics University of Illinois at Chicago Chicago IL 60607 USA
7. MESA+ Institute for Nanotechnology University of Twente 7500 AE Enschede The Netherlands