1. Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
2. Department of Applied Physics, Stanford University, Stanford, California 94305, United States
3. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
4. Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
5. Thesis Research, Inc., La Jolla, California 92037, United States
6. Research Center for Functional Materials, National Institute of Materials Science, Tsukuba 305-044, Japan
7. International Center for Materials, Nanoarchitectonics, National Institute of Materials Science, Tsukuba 305-044, Japan
8. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
9. Kavli Nanoscience Institute, Pasadena, California 91125, United States