1. Nanoscale Device Characterization Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
2. Department of Electrical & Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
3. Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
4. Theiss Research, La Jolla, California 92037, United States
5. Department of Electrical & Computer Engineering, Duke University, Durham, North Carolina 27708, United States
6. Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
7. Department of Chemistry, Duke University, Durham, North Carolina 27708, United States