1. Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8370, United States
2. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
3. Faculty of Engineering, The Chinese University of Hong Kong, Hong Kong
4. Department of Electronics Engineering, The Chinese University of Hong Kong, Hong Kong
5. G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States