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Séminaire général

Plasmonics with fast electrons

J. Nelayah

The Physics of surface plasmons is presently at the crossroad of many scientific and industrial interests. For example, many applications such as bio-sensing, cancer therapy and all-optical processing rely on surface-bound optical excitations in metallic nanoparticles. Yet, these excitations are not fully understood as no experimental technique has been capable so far of imaging them with sufficient resolution to reveal their spatial variation over one single nanoparticle. In this talk, I will present a novel method achieving such a resolution by recording maps of plasmons in the near-infrared/visible/UV (NIR-Vis-UV) domain using electron energy loss spectroscopy (EELS) in the context of a scanning transmission electron microscope equipped with a subnanometer electron probe. This method relies on the detection of plasmons as resonance peaks in the energy loss spectra of the electron beam rastered on nanoparticles [1].

After introducing the experimental technique, I will present a detailed study of the optical response, in the NIR-Vis-UV spectral range, of single and coupled triangular silver nanoprisms. Nanometer-scale mapping of their main surface excitations will be shown and discussed with respect to the particle size/shape and as a result of the existence of stationary, quasi-static short range surface plasmons [2].

[1] J. Nelayah et al., Nature Physics, 3, 348-353 (2007)
[2] J. Nelayah et al., Nano Lett., 10 (2010) 902.