StripeSTEM, a technique for the isochronous acquisition of high angle annular dark-field images and monolayer resolved electron energy loss spectra

Abstract

A technique capable of producing monolayer resolved electron energy loss (EEL) spectroscopy data along one direction in crystal structures is introduced. Unambiguous assignment of EEL spectra to atomic planes is possible via the execution of high angle annular dark-field (HAADF) imaging and EEL spectrum acquisition in parallel. The recording of instrumental instabilities in the HAADF image during the measurement enables a proper quantification by virtue of post-acquisition correction. Compared to the conventional line profile technique a dose reduction by several orders of magnitude can be achieved. The technique is applied to bulk SrTiO3 and ZnO:In2O3 in order to explore its capabilities and limits. Monolayer resolution was achieved for the Ti–L23 and In–M45 core-losses. Multislice calculations were carried out for the purpose of assessing the residual delocalisation of the inelastic signal. Fundamental limits to the resolution are imposed by dynamical dispersion of the electron wave in the crystal combined with the extension of the inelastic potential. In the present case, owing to the requirement of a high beam current, the geometrical probe size cannot be neglected when compared to the width of an inelastic scattering potential.