Practical Electron Microscopy and Database

In TEM, incoherent electron scattering (not in phase) can be induced in uncorrelated scattering events from different scattering centers, for instance high-angle (also called large-angle) elastic scattering or the inelastic scatterings. However, high-angle scattering of high-energy electrons is mainly elastic and happens when the electron passes close to an atomic nucleus. In this scattering the shielding effects of the atomic electrons are negligible.

In HAADF STEM, the "high-angle" means beyond the angle at which diffraction maxima (spots) can be found. High-angle scattered electrons are few in number of elections and are mostly induced by Rutherford scattering. Due to absence of diffraction intensity, the key advantage of HAADF for imaging and analysis is that they are usually insensitive to crystalline structure and orientation but strongly dependant on atomic number (see Z-contrast), meaning that the collected electrons strongly depends on chemical composition.