Interpretation of Atomic Resolution Eels Signals at Interfaces

Introduction: Atomically resolved chemical analysis by means of electron energy (core-) loss spectroscopy has been postulated since the technical availability of highly focused sub-nm STEM beams. We study the feasibility of this approach, as compared to the alternative of spatial difference spectra, where interfacial resolution is achieved by subtracting boxes at and apart from the interface. A nanobeam EELS signal is generated by the dynamical propagation of a conical wave through the specimen. This wave acts as 3D-excitation envelope for inelastic scattering and is needed to link the ab-initio calculated atom- and angular-momentum-projected density-of-state (DOS) functions to measurable EELS signals.Projected DOS: For the rhombohedral twin grain boundary in sapphire (FIG 1) as model system, DOS for p states in oxygen have been calculated 4 as described in , for the most stable twin structure obtained by ab-initio calculations.