Abstract
AbstractIn crystalline materials, the presence of surfaces or interfaces gives rise to crystal truncation rods (CTRs) in their X‐ray diffraction patterns. While structural properties related to the bulk of a crystal are contained in the intensity and position of Bragg peaks in X‐ray diffraction, CTRs carry detailed information about the atomic structure at the interface. Developments in synchrotron X‐ray sources, instrumentation, and analysis procedures have made CTR measurements into extremely powerful tools to study atomic reconstructions and relaxations occurring in a wide variety of interfacial systems, with relevance to chemical and electronic functionalities. In this review, an overview of the use of CTRs in the study of atomic structure at interfaces is provided. The basic theory, measurement, and analysis of CTRs are covered and applications from the literature are highlighted. Illustrative examples include studies of complex oxide thin films and multilayers.
Highlights
In crystalline materials, the presence of surfaces or interfaces gives rise to a heterostructure; consider, for instance, crystal truncation rods (CTRs) in their X-ray diffraction patterns
New ways to exploit CTRs and new applications for CTR-based techniques are in constant development
We first summarize and draw attention to overarching themes related to the use of CTRs in contemporary research on surfaces, interfaces, thin films, and heterostructures
Summary
The toolbox of structural characterization techniques for physicists, materials scientists, and chemists is overflowing. In terms of spatial resolution of atomic positions, highquality CTR data sets measured at synchrotron X-ray sources routinely provide layer-resolved atomic positions with precisions in the range of 1–10 pm in the surface normal direction Experimental factors such as instrumental resolution, crystalline quality, and the reliability of phase retrieval and/or structural refinement procedures influence the uncertainty in extracted structural parameters.[29] High-resolution STEM and TEM analysis using new image processing techniques can approach this level of precision,[30] providing real-space information which can complement CTR-derived parameters. The high X-ray brightness available at synchrotron sources is needed to resolve structural features related to ultrathin layers with sufficient contrast Another relevant aspect of the technique is that it provides spatially averaged information within the probe volume of the X-rays, which can be regarded as either an advantage or disadvantage. Using CTR scattering and STEM imaging in concert, researchers have revealed new and interesting structural features, such as polarization in metallic systems[31] and the transfer of octahedral rotations across interfaces.[32,33]
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