Quantifying 3D Chemical and Structural Order/Disorder in Thin Film Complex Oxides with Multislice Electron Ptychography

Determining chemical and structural order/disorder within functional oxides is often key to understanding the properties of these materials, for example, relaxor ferroelectrics. Conventional techniques such as X-ray, neutron, or electron diffraction are often used to study these features via diffuse scattering, but only offer insights into the global and average local structure of a sizable material volume. While recent advances in phase contrast imaging techniques in scanning transmission electron microscopy (STEM), such as iDPC, have helped to reveal connections between local polar and chemical order, these approaches are constrained by the ability to capture only a 2D projection of the structure within a thin TEM sample. Consequently, the origins of the exceptional piezoelectric properties of these materials continue to be a subject of debate.<br/><br/>In this presentation, I will explore how multislice electron ptychography can be leveraged to provide nanoscale structural, chemical, and polar variations in functional oxides in 3D. First, I will present the analysis of the reconstructed phase from the thin film paraelectric Pb2MgWO6. I will highlight how the approach provides access to the three-dimensional structure and chemistry of inclined anti-phase boundaries in this material. The comprehensive characterization offers deeper insights into their impact on local polarization, namely stabilizing antiferroelectric distortions at the boundaries. Second, I will discuss our study of the prototypical relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) using ptychography, where structural distortions of the cation and anion sublattices across slices are used to measure polar order in 3D. The results will be compared against conventional HAADF and iDPC imaging from the same region to provide an understanding of the sampling volume of those techniques. Finally, I will discuss how multislice ptychography offers to play a pivotal role in unraveling the intricate relationships between defects, structure, and the influence of intrinsic and extrinsic factors on the behavior exhibited by functional oxides.