From Sample Preparation to Data Analysis: Refining STEM-Based Defect Detection in doped SrTiO₃

Atomic-scale defect detection in complex oxides such as SrTiO₃ (STO) is essential for optimizing functional properties. Introducing small amounts of dopants and/or vacancies into complex oxide materials can tailor magnetic and electronic properties over a wide range. Therefore, information about electronic and structural configurations of point defects play a major role regarding controlling and optimizing these materials.
This work presents a comprehensive approach that refines the entire workflow, from advanced sample preparation to sophisticated data analysis, for reliable point defect characterization using aberration-corrected scanning transmission electron microscopy (STEM).
Here, STO doped with low concentrations of Ta is the chosen material for method development and optimization. We analyze the atomic-scale distribution and defect structures introduced by doping, by employing integrated differential phase contrast (iDPC) and high angle annular dark field (HAADF) imaging. Multislice (MS) simulations guide the experimental parameters, while pre-cise sample preparation techniques, including wedge polishing, ensure optimal imaging conditions
To ensure accurate defect characterization, extremely thin samples (< 18 unit cells) were prepared via wedge polishing. Position-averaged convergent beam electron diffraction (PACBED) of crystal-line regions enables precise thickness determination and accurate comparison with MS simulations based on atomistic modeling. Our main focus lies on the presence of O and Sr vacancies in the vicinity of Ta dopants. By integrating HAADF imaging and iDPC techniques, we systematically in-vestigate the presence of Ta dopants and associated, Sr and O vacancies, in doped STO.