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Plasmon mapping of individual ion-shaped nanoparticles

A. Slablab, G. Rizza, P.-E. Coulon

In the last years, ion-shaping technique has been proposed as an innovative and powerful tool to manipulate matter at the nanometer scale [1-5]. Deformation can be indirectly induced by embedding metallic NPs into an ion-deformable amorphous host matrix. With this technique, spherical particles can be transformed into prolate nanorods, nanowires or other original shapes.
Besides the fundamental aspects related to the ion-matter interaction, ion-shaping can also be used to give new insights into the plasmonic properties of metallic NPs. Here, Electron Energy Loss Spectroscopy (EELS) is used to study Localized Surface Plasmon Resonances (LPSR) in ion-shaped metallic nanoparticles with a nanometer-scale spatial resolution. LSPR are generated through electron excitation is a Scanning Transmission Electron Microscope (STEM), equipped with a High Angle Annular Dark Field (HAADF) detector. As the NPs are continuously deformed under irradiation, we investigate the LPSRs dependence on both the geometry and aspect ratio of the nanostructure. Finally, the experimental results are simulated using a specifically developed Auxiliary Differential Equations-Finite Difference Time Domain (ADE-FTDT) code (J. Cardin and al).

individual plasmonic response of a gold nanowire: direct observation of the longitudinal mode (m=0) and its first harmonic modes (m=1, m=2)