1. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
2. Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
3. Department of Physics, Vanderbilt University, Nashville, Tennessee, 37240 United States
4. Department of Materials Science and Engineering, University of California, Berkeley, California, 94720 United States
5. Institute for Problems of Materials Science
6. Institute of Semiconductor Physics