Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 42: Methods: Scanning Probe Techniques III
O 42.1: Talk
Wednesday, March 28, 2007, 15:45–16:00, H41
Infrared Nanofocus Maps Sub-10 nm Particles — •Antonija Cvitkovic1, Nenad Ocelic1, Javier Aizpurua2, Reinhard Guckenberger1, and Rainer Hillenbrand1 — 1Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany — 2Donostia International Physics Center, Paseo Manuel Lardizabal 4, 20018 Donostia San Sebastian, Spain
Infrared spectroscopy is a powerful tool for material identification based on molecular vibrational fingerprints. However, due to extremely weak scattering cross sections at infrared wavelengths, far-field analysis of individual nanoparticles has not been possible so far.
We demonstrate nanoscale resolved infrared imaging of sub-10 nm gold particles by scattering-type scanning near-field microscopy (s-SNOM). Our s-SNOM is basically an AFM, with the metallized probing tip additionally illuminated by IR light (λ=10 μm). Due to an optical antenna-effect, light is concentrated at the apex of the tip forming a wavelength-independent nanoscale focus. In order to make a detection of sub-10 nm particles possible, we use highly reflecting or polariton resonant materials as sample carriers. That way a strong tip-substrate near-field interaction intensifies the nanofocus illuminating the particles, resulting in the enhanced optical contrasts [1].
Our results already promise a wide application potential in high resolution imaging of nanoscale objects (e.g. gold biolabeling). Combined with spectroscopic mapping, our method opens the door to label-free chemical identification of individual nanocrystals or biomolecules.
[1] A. Cvitkovic et al, Phys. Rev. Lett. 97, 060801 (2006)