I have seen the "universal" curve of inelastic mean free path (MFP) of electrons in many places (both experimental data, and just sketches of the curve) e.g. enter image description here https://en.wikipedia.org/wiki/Inelastic_mean_free_path

  1. Why does the MFP rise at low energy? I think this is because there are no scattering mechanisms at low energy - but don't have any good details or resources to back up that claim.
  2. If the MFP is very large at low energy, then why do TEM's require large energies for imaging? Perhaps it is the technical trouble of being able to detect ~1-10 eV electrons above the noise level (?)
  • $\begingroup$ Samples for TEM are thicker than 2nm... $\endgroup$ – Jon Custer Dec 26 '18 at 16:44
  • $\begingroup$ If you have access to this (experimental) article there are some materials which have 10-1000nm MFP in that range: onlinelibrary.wiley.com/doi/abs/10.1002/sia.740010103 $\endgroup$ – nortcele Dec 26 '18 at 16:47
  • $\begingroup$ The fact that there may be some materials with longer scattering lengths does not invalidate my comment. Then add in a desire to use diffraction. Mix well. Higher energy electrons are more useful in TEM (to a limit - MeV class machines have disappeared). $\endgroup$ – Jon Custer Dec 27 '18 at 19:44
  • $\begingroup$ Yes, I think this addresses point 2 of my question. $\endgroup$ – nortcele Jan 2 '19 at 16:20

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