1. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
2. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
3. Department of Applied Physics, Stanford University, Stanford, California 94305, USA
4. IBM Watson Research Center, Yorktown Heights, New York 10598, USA
5. OcteVue, Hadley, Massachusetts 01035, USA