1. Materials
Science and Engineering Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
2. Department
of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-2115, United States
3. N5 Sensors Inc., Rockville, Maryland 20852, United States
4. Institute
for Research in Electronics and Applied Physics, University of Maryland, College
Park, Maryland 20742, United States
5. Department
of Physics, Seton Hall University, South Orange, New Jersey 07079, United States