1. Department of Physics, The University of Texas, Austin, Texas 78712, United States
2. Department of Electrical and Computer Engineering, The University of Texas, Austin, Texas 78712, United States
3. Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
4. The Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
5. Mitsubishi Electric Research Laboratories, Cambridge, Massachusetts 02139, United States