Role of Convergence and Collection Angles in the Excitation of Long- and Short-Wavelength Phonons with Vibrational Electron Energy-Loss Spectroscopy

@article{Venkatraman2021RoleOC,
  title={Role of Convergence and Collection Angles in the Excitation of Long- and Short-Wavelength Phonons with Vibrational Electron Energy-Loss Spectroscopy},
  author={Kartik Venkatraman and Peter A. Crozier},
  journal={Microscopy and Microanalysis},
  year={2021},
  volume={27},
  pages={1069 - 1077}
}
Abstract Current generation electron monochromators employed as attachments to scanning transmission electron microscopes (STEM) offer the ability to obtain vibrational information from materials using electron energy-loss spectroscopy (EELS). We show here that in crystals, long- and short-wavelength phonon modes can be probed simultaneously with on-axis vibrational STEM EELS. The long-wavelength phonons are probed via dipole scattering, while the short-wavelength modes are probed via impact… 
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References

SHOWING 1-10 OF 36 REFERENCES
Position and momentum mapping of vibrations in graphene nanostructures
TLDR
A new pathway is provided to determine phonon dispersions down to the scale of an individual free-standing graphene monolayer by mapping the distinct vibrational modes for a large momentum transfer.
Lattice resolution of vibrational modes in the electron microscope.
Vibrational-loss EELS and the avoidance of radiation damage.
Mapping vibrational surface and bulk modes in a single nanocube
TLDR
By demonstrating the excitation of both bulk and surface vibrational modes using a single probe, this work represents advances in the detection and visualization of spatially confined surface and bulk phonons in nanostructures.
Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope
TLDR
A classical response theory is developed that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported.
Vibrational spectroscopy at atomic resolution with electron impact scattering
Atomic vibrations control all thermally activated processes in materials, including diffusion, heat transport, phase transformations and surface chemistry. Recent developments in scanning
Nanoscale momentum-resolved vibrational spectroscopy
TLDR
A widely applicable method for accessing phonon dispersions of materials at high spatial resolution is demonstrated and should allow for direct correlation of nanoscale vibrational mode dispersions with atomic-scale structure and chemistry.
Vibrational spectroscopy in the electron microscope
TLDR
It is demonstrated that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can been used for analysis carried out with the beam positioned just outside the sample—that is, for ‘aloof’ spectroscopy that largely avoids radiation damage.
Phonon Spectroscopy at Atomic Resolution.
TLDR
It is demonstrated that phonon spectral mapping of atomic structure is possible and it is confirmed that Z-contrast imaging is based on inelastic scattering associated with phonon excitation.
The influence of surfaces and interfaces on high spatial resolution vibrational EELS from SiO2.
TLDR
It is shown that nanometer resolution is possible when selecting theSiO2/Si interface signal which is at a different energy position than the bulk signal, and that, at 60 kV, the signal in the SiO2 can be treated non-relativistically (no retardation) while the signalIn the Si, not surprisingly, is dominated by relativistic effects.
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