Thursday, 10 August, 2006
Infrared Imaging of Single Nanoparticles via Strong Field Enhancement in a Scanning Nanogap
A. Cvitkovic, N. Ocelic, J. Aizpurua, R. Guckenberger, and R. Hillenbrand -
Phys. Rev. Lett. 97, 060801 (2006)
We demonstrate nanoscale resolved infrared imaging of single nanoparticles employing near-field coupling in the nanoscopic gap between the metal tip of a scattering-type near-field optical microscope and the substrate supporting the particles. Experimental and theoretical evidence is provided that highly reflecting or polariton-resonant substrates strongly enhance the near-field optical particle contrast. Using Si substrates we succeeded in detecting Au particles as small as 8 nm (>lambda/1000) at midinfrared wavelengths of about lambda=10 µm. Our results open the door to infrared spectroscopy of individual nanoparticles, nanocrystals, or macromolecules.