1. Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
2. Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124, USA
3. Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA
4. Department of Physics, Arizona State University, Tempe, Arizona 85281, USA
5. Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA