Seminar- “Investigations of nanoscale heterogeneity with atomic-resolution STEM” with Dr. Michelle Smeaton (National Renewable Energy Lab)
Physics Seminar
January 15, 2025
3:00 PM - 4:00 PM
Location
2SES 238
Calendar
Download iCal FileMichelle Smeaton, Postdoctoral Researcher-Materials Science
National Renewable Energy Laboratory
Highly localized structure measurements using scanning transmission electron microscopy (STEM) enable the exploration of new and distorted crystal structures stabilized on nanometer to micrometer length scales. STEM also allows for the study of heterogeneity and defects in such systems over length scales too small to resolve with x-ray scattering techniques. One area where this ability is particularly impactful is the study of non-stoichiometric compounds, where nanoscale inclusions of different phases can have significant effects on properties measured by bulk characterization methods. I will discuss the case of oxygen-deficient lanthanum nickelate (LaNiO3-d), in which nanoscale coexistence of d = 0.25 and 0.5 phases can give rise to electronic and magnetic phase transitions otherwise unexpected in LaNiO3. By combining phase mapping with 4D-STEM and atomic displacement mapping with direct atomic column fitting, I will elucidate the nanostructure of these domains and extract their associated lattice distortions from the parent LaNiO3 crystal structure. I will further discuss the impact of electron channeling on such atomic fitting analyses, which have become more common with the accessibility of aberration-corrected STEM instruments, and suggest strategies to avoid potential unwanted or unexpected effects thereof. Finally, I will share my ongoing efforts to map the high temperature spin transition in LaCoO3, which is a promising candidate for energy-efficient neuromorphic switching devices, using in-situ heating in the STEM. I will discuss my progress and challenges and end with an outlook for in-situ electrical biasing experiments conducted on working devices.
Date posted
Dec 21, 2024
Date updated
Dec 21, 2024