Inelastic electron scattering at large angles: the phonon polariton contribution

We explore the inelastic electron scattering in SrTiO3, PbTiO3, and SiC intheir phonon energy range, challenging the assumption that phonon polaritonsare excluded at large angles in high-resolution transmission electronenergy-loss spectroscopy. We demonstrate that through multiple scattering, theelectron beam can excite both phonons and phonon polaritons, and the relativeproportion of each varies depending on the structure factor and scatteringangle. Integrating dielectric theory, density functional theory, andmulti-slice simulations, we provide a comprehensive framework for understandingthese interactions in materials with polar optical phonons.