Electron Energy Loss Spectroscopy (EELS) At the Magic Angle

Abstract Electron loss near edge structure (ELNES) reflects transitions of inner shell electrons to site- and symmetry-projected unoccupied electronic states, which in a solid lie above the Fermi level and may be calculated using advanced electronic structure calculations. The direction of momentum transfer, q, imparted during the inelastic scattering process is dependent on the angle over which the scattered electrons are collected. It is usual to resolve the momentum transfer, into components parallel and perpendicular to the incident beam direction (q∥and q⊥). in a specimen region which is crystallographically anisotropic, the exact direction of the momentum transfer and hence energy states available to the excited electron will depend on the specimen orientation with respect to the incident electron beam. Practically, this can present problems where quantitative comparisons and/or modelling of electronic structure between different specimen regions at different orientations, or within a polycrystalline material, or even between different samples are required.