1. Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78758, USA
2. NanoMat/Q-Mat/CESAM, and European Theoretical Spectroscopy Facility, Université de Liege (B5), B-4000 Liege, Belgium
3. Research Center for Functional Materials, National Institute of Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
4. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan