Regensburg 2019 – scientific programme
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 6: Focus: Advanced TEM spectroscopy - low energy excitations and chemical composition at high resolution (joint session KFM/HL)
KFM 6.2: Talk
Monday, April 1, 2019, 15:30–15:50, PHY 5.0.20
Spectral Field Mapping of Surface Plasmon Resonances using High Energy Electrons — •Jonas Krehl1, Giulio Guzzinati2, Johannes Schultz1, Pavel Potapov1, Jerome Martin3, Jo Verbeeck2, Bernd Büchner1, and Axel Lubk1 — 1IFW Dresden, Dresden, Deutschland — 2EMAT, Antwerpen, Belgien — 3Institute Charles Delaunay, Troyes, Frankreich
Surface plasmons resonances (SPR) are discrete modes in the response of the electron gas near the surface of a metallic nanoparticle. They contain very strong and localized electric and magnetic fields which enables interesting nanophotonic applications. Conventional electron energy-loss spectroscopy (EELS) is readily used for mapping the loss probablity of these modes with high energy and high spatial resolution.
The energy-loss signal only entails the longitudinal inelastic momentum transfer (IMT), so for a more comprehensive study of the fields of plasmon modes the lateral IMT components are crucial. The associated beam deflection is only a few µ rad so we needed to develop a especially low-angle TEM setup for energy-filtered diffraction. With the energy slit set to a particular mode, the full IMT corresponds to a spectral component of the projected (along the beam trajectory) fields.
We demonstrated this technique in mapping the electric field at the dipole mode of an aluminium nanorod and compared the results with boundary-element-method simulations where we reached reasonable quantitative agreement. We are developing several extensions to this technique which e.g. tackle methodic problems or enable the mapping of magnetic fields.