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Scientific highlights

Tailored nanoscale plasmon-enhanced vibrational electron spectroscopy

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Atomic vibrations and phonons are an excellent source of information on nanomaterials that we can access through a variety of methods including Raman Scattering, infrared spectroscopy, and electron energy-loss spectroscopy (EELS). In the presence of a plasmon local field, vibrations are strongly modified, and in particular, their dipolar strengths are highly enhanced, thus rendering Raman scattering and infrared spectroscopy extremely sensitive techniques. Here, we experimentally demonstrate that the interacion between a relativistic electron and vibrational modes in nanostructures is fundamentally modified in the presence of plasmons. We finely tune the energy of surface plasmons in metallic nanowires in the vicinity of hexagonal boron nitride, making it possible to monitor and disentangle both strong phonon-plasmon coupling and plasmon-driven phonon enhancement at the nanometer scale. Due to the near-field character of the electron beam-phonon interaction, optically-inactive phonon modes are also observed. Read more »

Optical gap and optically active intragap defects in cubic BN

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Studies on the optical properties of cubic BN are generally hindered by the very high density of crystal defects. Thus, the precise value of its optical gap is still debated, with large discrepancies between reported theoretical and experimental estimated values. In this study we addressed open questions of the cubic BN optics by employing high spatially resolved spectroscopy techniques to the highest-quality samples available and combining these observations with state-of-the-art quasiparticle calculations.

Phys. Rev. B 98, 094106 (2018)

Publications

Kociak, M., Galvão Tizei, L.H., Meuret, S., Lourenço-Martins, H. & Stephan, O. Spectromicroscopies électroniques : sonder les propriétés optiques de nanomatériaux avec des électrons rapides. Photoniques 39 - 43 (2020).doi:10.1051/photon/202010239  Download: photon2020102p39.pdf (386.08 KB)
Paulauskas, T., et al. Atomic-Resolution EDX, HAADF, and EELS Study of GaAs1-xBix Alloys. Nanoscale Research Letters 15918, (2020).
Tizei, L.H.G., et al. Tailored nanoscale plasmon-enhanced vibrational electron spectroscopy. Nano Letters (2020).doi:10.1021/acs.nanolett.9b04659
Li, X., et al. Plasmonic Oligomers with Tunable Conductive NanojunctionsPlasmonic Oligomers with Tunable Conductive Nanojunctions. The Journal of Physical Chemistry Letters 10, 7093 - 7099 (2019).
Saito, H., et al. Emergence of point defect states in a plasmonic crystal. Physical Review B 100, (2019).
Tararan, A., et al. Optical gap and optically active intragap defects in cubic BN. Physical Review B 982121, (2018). Download: PhysRevB.98.094106.pdf (2.16 MB)
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