1. Department of Materials Science & Engineering, University of Maryland, College Park, Maryland 20742, United States
2. U.S. Naval Research Laboratory, Washington, DC 20375, United States
3. College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, New York 12203, United States
4. Department of Physics, SUNY Brockport, Brockport, New York 14420, United States