3D structure mapping using a two-dimensional pixelated STEM detector
Andrew Ross (School of Physics and Astronomy, University of Glasgow, United Kingdom)

In perovskite oxide materials there is a strong coupling between structural and functional properties. Of recent interest are heterostructures, which enable structural coupling over the substrate/thin film interface. A common way of analysing the atomic structure of these heterostructures is using Scanning Transmission Electron Microscopy (STEM) which provide sub-Ångström resolution. Combining Annular Dark Field (ADF) and Annular Bright Field (ABF) imaging it is possible to get precise atom positions for all the atoms, even the light oxygen atom. However, these imaging techniques only reveal the structure orthogonal to the electron beam, yielding atomic structure information about two of the three axes. Normally, two separate TEM-samples thinned on orthogonal zone axis are used to get the 3-D structure. More ideal would be to obtain this information from one sample, such that information about all three axes in the same region can be gathered.

In this work, we have used a fast two-dimensional pixelated electron detector to acquire STEM-diffraction images of a La0.7Sr0.3MnO3/LaFeO3 heterostructure grown epitaxially on a SrTiO3-(111) substrate. One diffraction image has been acquired for every probe position yielding a 4-D-datacube, covering the films and the substrate. By using Higher Order Laue Zones (HOLZ), information about crystal periodicity parallel to the electron beam is extracted. This data is processed using the model based approach, yielding information on both average and variations in lattice size as a function of distance from the interfaces. In co-junction with standard ABF and ADF characterisation a more complete understanding of the structure of these interfaces can be revealed.

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