In Situ MEMS-Based Cryo/Heating STEM for Probing Dislocation Dynamics and Domain Evolution in Single-Crystal BaTiO₃

Domain engineering at the nanoscale in ferroelectric materials holds great promise for improving their overall functional properties, particularly in electromechanics and electronics. This method involves creating topological defects in functional materials to enhance their performance^[¹^]. However, progress in developing these ferroelectric functional materials is hindered by our limited grasp of how defects behave and interplay at varying temperatures and how these defects affect domain nucleation and domain wall motion. Bridging this knowledge gap is essential to fully exploit the potential of nanoscale domain wall engineering.<br/> <br/>In this work, we introduced well-aligned {100}&lt;100&gt;-type and {101}&lt;101&gt;-type dislocations through high-temperature uniaxial compression along [110] and [001] directions^[2]. Using MEMS-based <i>in situ</i> heating and cryogenic scanning transmission electron microscopy (STEM) technology^[3], we directly probed the temperature-induced structural evolution of the dislocation dipole at the atomic scale over an extensive temperature range spanning from -175°C to 200°C, covering all possible phases of BaTiO₃. We investigated the charged dislocation cores by electron energy loss spectroscopy (EELS) at various temperatures. Geometric phase analysis (GPA) was implemented for generating strain maps around dislocation core regions. These comprehensive approaches allowed us to study both the dislocation-enhanced local polarization and the total energy density of ferroelectric BaTiO₃ in terms of different degrees of freedom (DOFs), namely the charge, elastic lattice, and strain gradient.<br/> <br/>Our research, by revealing the atomic-scale evolution of local lattice structures, not only advances the field of domain wall engineering in ferroelectric materials but also introduces a novel approach for understanding and manipulating nanoelectronics across a broad temperature range. This atomic-level insight provides a foundation for developing advanced functional materials with precisely tailored properties.<br/> <br/><b>References</b><br/>(1) Höfling, M.; Zhou, X.; Riemer, L. M.; Bruder, E.; Liu, B.; Zhou, L.; Groszewicz, P. B.; Zhuo, F.; Xu, B.-X.; Durst, K.; Tan, X.; Damjanovic, D.; Koruza, J.; Rödel, J. Control of Polarization in Bulk Ferroelectrics by Mechanical Dislocation Imprint. <i>Science</i> <b>2021</b>, <i>372</i> (6545), 961–964. https://doi.org/10.1126/science.abe3810.<br/> <br/>(2) Jiang, T.; Ni, F.; Recalde-Benitez, O.; Breckner, P.; Molina-Luna, L.; Zhuo, F.; Rödel, J. Observation of Dislocation-Controlled Domain Nucleation and Domain-Wall Pinning in Single-Crystal BaTiO₃. <i>Applied Physics Letters</i> <b>2023</b>, <i>123</i> (20), 202901. https://doi.org/10.1063/5.0173819.<br/> <br/>(3) Pivak, Y.; Sun, H.; van Omme, T.; Bladt, E.; Pérez-Garza, H. H.; Conroy, M.; Molina-Luna, L. Development of a Stable Cryogenic <i>In Situ</i> Biasing System for Atomic Resolution (S)TEM. <i>Microscopy and Microanalysis</i> <b>2023</b>, <i>29</i> (Supplement_1), 1695. https://doi.org/10.1093/micmic/ozad067.873.