1. Materials Science and Engineering Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
2. Department of Electrical and Computer Engineering, George Mason University, 4400 University Drive, Fairfax, Virginia 22030, USA
3. Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742, USA
4. Materials Measurement Science Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
5. Semiconductor and Dimensional Metrology Division, Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
6. Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA