1. Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
2. Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
3. Department of Civil and Environmental Engineering, Institute of Critical Technology and Applied Science Sustainable Nanotechnology Center, Virginia Tech, Blacksburg, Virginia 24061, United States
4. Institute for Research in Electronics and Applied Physics and Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, United States