1. Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
2. Department of Engineering, University of Cambridge, Cambridge CB2 1TN, United Kingdom
3. IBM T.J. Watson Research Center, Yorktown
Heights, New York 10598, United States
4. Center for Individual Nanoparticle Functionality, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark