1. Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
2. Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75083, United States
3. Applied Materials, Inc., Santa Clara, California 95054, United States
4. Department of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
5. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States