Investigation and use of plasmon losses in energy‐filtering transmission electron microscopy

Abstract

SUMMARY The electron spectroscopic imaging (ESI), diffraction (ESD) and different types of electron energy‐loss spectroscopy (EELS) modes in an energy‐filtering transmission electron microscope can all be used for the investigation and analytical use of plasmon losses. Shifts of plasmon losses caused by differences in composition can be detected with an accuracy of 0.1 eV by parallel‐recorded EELS (PEELS). The dispersion of plasmon losses and the cut‐off angle θc can be observed by angle‐dispersive EELS and by recording spectra at different scattering angles θ. ESD patterns with a selected energy window width of 1 eV enable the dispersion and its anisotropy to be imaged by characteristic intensity distributions between the primary beam and the first Bragg diffracted beams. The ESI mode can be used for the selective imaging of precipitates and for the investigation of the excitation volume of plasmons in small particles.

Interactive electron energy-loss elemental mapping by the "Imaging-Spectrum" method

“…EELS sensitivity has been greatly increased by using multi-channel arrays to detect in parallel the inelastically scattered electrons [3]. This [4] or as a post-column imaging filter behind [5] are commercially available and they are shown in figure 1. Similarly to X-ray mapping using a Scanning Transmission Electron Microscope (STEM) coupled with an Energy Dispersive X-ray Spectrometer (EDXS), some laboratories are performing elemental mapping using STEM coupled with PEELS. The use of a PEELS coupled with a STEM was first introduced by Jeanguillaume and Colliex [7] as the "Spectrum-Imaging" method.…”