1. Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
2. Department of Electrical and Computer Engineering, The University of Texas at Dallas, Richardson, Texas 75080-3021, United States
3. Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
4. Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan