Imaging Dynamics and 3D Complexity in Functional Oxides via Operando Electron Microscopy and Multislice Electron Ptychography
Oct 24, 2025
2:30PM to 3:30PM
Date/Time
Date(s) - 24/10/2025
2:30 pm - 3:30 pm
Categories
Prof. James M. LeBeau
Department of Materials Science & Engineering, Massachusetts Institute of Technology
Complex oxides can exhibit a wide range of functional properties that ultimately rely on the interplay between structure, chemistry, and stimuli. Relaxor ferroelectrics, such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), and antiferroelectrics (AFE), such as PbZrO3, exhibit remarkable piezoelectric and dielectric properties owing to their intricate chemical and/or structural order. While traditional imaging methods, such as scanning transmission electron microscopy (STEM), offer local insights into nanoscale features, challenges arise in resolving their field dependence and three-dimensional (3D) relationships between atomic, chemical, and polar structure. To overcome many of these challenges, operando imaging and multislice electron ptychography have emerged as powerful tools to more fully connect behavior to local structure and chemistry.
In this talk, I will first outline a general device?fabrication strategy for nanoscale capacitors that enables operando electron microscopy even on non-conductive substrates with nanometer?thick bottom electrodes. Using PbZrO3 as an example, we employ operando scanning transmission electron microscopy to directly resolve the antiferroelectric?to?ferroelectric transition pathway in PbZrO3 thin films under device?relevant conditions. This information is combined with nano-beam diffraction and in-situ biasing to map the multi-step AFEFE transition, identify a dead layer with suppressed switching, and track a moving transition front where internal and external fields compete to tilt the free-energy landscape of metastable intermediates.
Further, I will discuss how multislice electron ptychography provides a comprehensive understanding of polar domain structures in relaxor ferroelectrics. Compared to conventional annular dark-field (ADF) images, for example, the reconstructed object phase from ptychography provides significantly enhanced measurement precision and accuracy and enables polar displacements to be measured with depth sensitivity. These results reveal the 3D domain structures, including high-angle domain walls and polar nanodomains, in agreement with the ‘slush’ model of relaxor-ferroelectricity. We will further explore the impact of epitaxial strain on this 3D domain structure, uncovering complex polar texture correlated with Mg/Nb occupancy.
Together, these capabilities establish a device?relevant framework that links local energetics and 3D polar topology to field?driven functionality, providing quantitative constraints for phase?field and first?principles modeling and practical design rules for antiferroelectric and relaxor?based transducers, memories, and energy?storage technologies.
Biographical
James earned his B.S. in Materials Science & Engineering from Rensselaer Polytechnic Institute in 2006 and his Ph.D. from the University of California Santa Barbara in 2010. After his graduate work, he joined the Department of Materials Science and Engineering faculty at North Carolina State University in January 2011. In 2019, he moved his group to MIT’s Department of Materials Science & Engineering. His research focuses on applying and developing (scanning) transmission electron microscopy techniques to quantify materials’ atomic structure and chemistry to inform our understanding of relaxor/ferroelectric, mechanical, optical, and quantum properties. For his research, he has been honored with numerous awards, including the Presidential Early Career Award for Scientists and Engineers (PECASE), the NSF CAREER award, an AFOSR Young Investigator grant, the Microanalysis Society K.F.J Heinrich award, and the Microscopy Society of America Burton Medal.
In-Person: ABB 102
Online: Echo360