1. Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States
2. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
3. Division of Electronics and Electrical Engineering, Dongguk University, Seoul 04620, South Korea
4. Department of Electrical and Computer Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, South Korea