Magnetic topological insulators and their heterostructures provide significant opportunities to couple band topology with a nontrivial spin configuration for enhanced spintronic device performance, as well as designing magnetoelectric systems and functionalities. We find that Mn interdiffusion from MnTe when interfaced with (Bi,Sb)2Te3 stabilizes as self-organized Mn(Bi,Sb)2Te4 septuple lamellae among alternating (Bi,Sb)2Te3 quintuple layers, as observed using scanning transmission electron microscopy and depth-sensitive polarized neutron reflectometry. We further demonstrate a valuable combination of magnetic and topological orders in these naturally formed Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3 heterostructures, which are exchange-coupled with MnTe. Magnetotransport experiments and quantum magnetism simulations reveal that, above its own Néel temperature TN ∼ 20 K, Mn(Bi,Sb)2Te4 mediates the exchange field leading to an anomalous Hall effect at the (Bi,Sb)2Te3/MnTe interface, with an enhanced interfacial TN exceeding 200 K, approaching that of the bulk MnTe. This magnetic interface, in turn, allows a robust and deterministic spin-orbit torque switching without an external magnetic field at a low critical current density of 3 × 105 A cm-2. The antiferromagnetically coupled architecture of Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3/MnTe, featuring magnetic and topological proximity effects across a chalcogenide backbone, is rich in fundamental interface physics and holds the potential for practical applications in spintronics.

The direct observation of a solid-state chemical reaction can reveal otherwise hidden mechanisms that control the reaction kinetics. However, probing the chemical bond breaking and formation at the molecular level remains challenging because of the insufficient spatial-temporal resolution and composition analysis of available characterization methods. Using atomic-resolution differential phase-contrast imaging in scanning transmission electron microscopy, we have visualized the decomposition chemistry of K2PtCl4 to identify its transient intermediate phases and their interfaces that characterize the chemical reduction process. The crystalline structure of K2PtCl4 is found to undergo a disproportionation reaction to form K2PtCl6, followed by gradual reduction to crystalline Pt metal and KCl. By directly imaging different Pt─Cl bond configurations and comparing them to models predicted via density functional theory calculations, a causal connection between the initial and final states of a chemical reaction is established, showcasing new opportunities to resolve reaction pathways through atomistic experimental visualization.

The long-term operation of balance-of-plant (BoP) components in solid oxide fuel cells (SOFCs) relies on the presence of a stable and durable oxide layer. In this study, we investigate the oxidation and chromium (Cr) evaporation behaviors of two developmental alumina-forming austenitic (AFA) alloys compared to chromia-forming alloy 625 at 900 degrees C in air with 10% water vapor. Transpiration tests, weight gain tests, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, and scanning transmission electron microscopy with energy dispersive X-ray analysis are employed to evaluate the oxidation and Cr evaporation behaviors. Our findings reveal that alloy 625 exhibits significantly higher rates of Cr evaporation compared to OC11 (Y and Hf additions) and OC11LZ (Y and Zr additions), with evaporation amounts -56 and -28 times greater, respectively. The observed differences between OC11 and OC11LZ can be attributed to variations in the formed oxide scales during long-term operation. Furthermore, we examine the influence of Hf and Zr reactive elements on the long-term oxidation and chromium evaporation behaviors, providing insights into the role of these elements in enhancing the performance and stability of the alloys. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Properties and functions of nanomaterials, especially catalysts, are determined by their structure and its interplay with chemical, electrical, mechanical stimuli, and other media. Significant improvement in understanding nanomaterials structures and dynamics at the atomic scale has been made due to the advancement of new instrumentation and methods in electron microscopy. In this article we review the critical progresses made in visualizing the reaction at the solid-liquid interface using liquid cell in TEM, in probing the solid-state chemistry using dose-efficient and high speed electron detectors, and in characterizing the nanoparticle response to gas environment using gas cell and environmental electron microscopy, and discuss how imaging the dynamics with high resolution helps with the design and fabrication of new nanomaterials.

Journal Article Machine Vision Software Enables Normalization of Electron Dose Calibration Between Microscopes and Delivers Accurate Quantifiable Tracking of Electron Dose for In-Situ, Operando, and Dose Sensitive Experiments Get access Madeline Dressel Dukes, Madeline Dressel Dukes Protochips, Inc.Morrisville, NC, United States Corresponding author: madeline@protochips.com Search for other works by this author on: Oxford Academic Google Scholar Yaofeng Guo, Yaofeng Guo Protochips, Inc.Morrisville, NC, United States Search for other works by this author on: Oxford Academic Google Scholar Stamp Walden, Stamp Walden Protochips, Inc.Morrisville, NC, United States Search for other works by this author on: Oxford Academic Google Scholar Nynke Krans, Nynke Krans Protochips, Inc.Morrisville, NC, United States Search for other works by this author on: Oxford Academic Google Scholar Kate Marusak, Kate Marusak Protochips, Inc.Morrisville, NC, United States Search for other works by this author on: Oxford Academic Google Scholar Tim Eldred, Tim Eldred Protochips, Inc.Morrisville, NC, United States Search for other works by this author on: Oxford Academic Google Scholar John Damiano John Damiano Protochips, Inc.Morrisville, NC, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 1849–1850, https://doi.org/10.1093/micmic/ozad067.955 Published: 22 July 2023

The need for clean, renewable energy has driven the expansion of research focused on new materials for electrocatalysts, fuel cells, and batteries. These materials need to be plentiful, inexpensive, and have high energy capacity operating lifetimes to power a growing consumer market that is seeking alternatives to fossil-based fuel sources.[1] However, energy materials often operate at the nanoscale, which involves structural or morphological changes that can only be observed using transmission electron microscopy (TEM). To get more insight in the nanoscale changes, operando TEM can be used to observe a catalyst or battery material under its native operating conditions. Operando TEM techniques enable dynamic, real-time imaging of a material’s nanoscale processes as they occur within their functional environment.[2] This enables researchers to simultaneously follow structural and morphological changes and correlate those to the material’s electrochemical behavior. Operando studies using liquid electrolytes can utilize liquid-EM. In this case, a sample is encapsulated in a liquid environment between electron transparent membranes, which enables researchers to study reactions as they occur in an electrolyte environment.[1] This technique has enabled researchers to better understand the mechanistic pathways that can result in electrocatalyst deactivation [3,4] battery capacity fading [5-7]and identify targets within these materials to improve their performance.[8,9,10] However, as operando TEM combines multiple challenging topics, e.g. battery studies, electrolyte degradation, radiolysis and dose management, it has so far been a laborious undertaking for any one researcher alone. Successful operando liquid-EM experiments are challenging due to many factors, beginning with experiment design and workflow, and culminating complex analysis of multiple streams of large, often cumbersome, datasets. Here, we have set out to address and develop hardware and software tools which mitigate some of the most common challenges associated with operando liquid-EM electrochemical studies. Using a machine vision software platform called AXON, a holistic, workflow-driven approach to address key challenges and pain points associated with in-situ and operando TEM studies has been developed. New hardware and MEMs-based features integrated into the liquid-EM solution, Poseidon Select (Figure 1A), include the ability to perform electrochemical studies beyond room temperature, and improved stabilization of electrochemical signals for correlation with bulk studies. Moreover, adding a Luggin-Haber metal probe for electrical measurements allows for the use of any reference electrode compared to the limitation of a pseudo-reference electrode, e.g. platinum (Figure 1B).[11] On top of this, AXON uses learning algorithms for improved stabilization and tracking of dynamic samples, accurate dose quantification and management, consolidation of experimental parameters and metadata, and an intuitive, free-to-use, visual data analysis tool, AXON Studio. In this talk, examples of liquid-EM microscopy work for energy materials will be shown, as shown in Figure 1C-D. In this figure, copper nanograins were used to convert CO2 to multicarbon products while observing the morphological changes to the nanograins over time and simultaneously observing the electrochemical changes in the sample. Moreover, explanations and examples will be shown on how machine-vision software solutions can improve the workflow of electrochemical in-situ experiments. These workflow methods elevate the operation of in-situ experiments so that any one researcher can now operate microscope and in-situ cell simultaneously. [1] Yang, Y. et al. (2021) ACS Catalysis 11, 1136–1178. [2] Chenna, S. et al. (2012) ACS Catalysis, 2, 2395–2402. [3] Shi, F. et al. (2020) Chem, 6, 2257–2271. [4] Impagnatiello, A. et al. (2020) ACS Applied Energy Materials, 3, 2360–2371. [5] Bhatia, A. et al. (2021) Small Methods, 2100891. [6] He, K. et al. (2018) Nano Energy, 49, 338–345 [7] Sasaki, Y. et al. (2021) Journal of Power Sources, 481, 228831. [8] Pu, S.D. et al. (2020) ACS Energy Letters, 5, 2283–2290. [9] Balaghi, S.E. et al. (2021) ACS Applied Materials & Interfaces, 13, 19927–19937. [10] Yang, Y. et al. (2023) Nature, 614, 262-270 [11] Choudhary, S. et al (2022) Journal of the Electrochemical Society, 169, 111505 Figure 1

Transmission electron microscopy (TEM) enables users to study materials at their fundamental, atomic scale. Complex experiments routinely generate thousands of images with numerous parameters that require time-consuming and complicated analysis. AXON synchronicity is a machine-vision synchronization (MVS) software solution designed to address the pain points inherent to TEM studies. Once installed on the microscope, it enables the continuous synchronization of images and metadata generated by the microscope, detector, and in situ systems during an experiment. This connectivity enables the application of machine-vision algorithms that apply a combination of spatial, beam, and digital corrections to center and track a region of interest within the field of view and provide immediate image stabilization. In addition to the substantial improvement in resolution afforded by such stabilization, metadata synchronization enables the application of computational and image analysis algorithms that calculate variables between images. This calculated metadata can be used to analyze trends or identify key areas of interest within a dataset, leading to new insights and the development of more sophisticated machine-vision capabilities in the future. One such module that builds on this calculated metadata is dose calibration and management. The dose module provides state-of-the-art calibration, tracking, and management of both the electron fluence (e-/Å2·s-1) and cumulative dose (e-/Å2) that is delivered to specific areas of the sample on a pixel-by-pixel basis. This enables a comprehensive overview of the interaction between the electron beam and the sample. Experiment analysis is streamlined through a dedicated analysis software in which datasets consisting of images and corresponding metadata are easily visualized, sorted, filtered, and exported. Combined, these tools facilitate efficient collaborations and experimental analysis, encourage data mining and enhance the microscopy experience.

Mg-doped, graded AlGaN films showed the formation of an impurity band and high, temperature-invariant p-conductivity even for doping levels well below the Mott transition. However, compensating point defects disrupted the impurity band, resulting in an Anderson transition from the impurity band to valence band conduction and a more than tenfold reduction in room-temperature conductivity. This is the first demonstration of Anderson-like localization in AlGaN films.

Magnetic transition metal chalcogenides form an emerging platform for exploring spin-orbit driven Berry phase phenomena owing to the nontrivial interplay between topology and magnetism. Here we show that the anomalous Hall effect in pristine Cr2Te3 thin films manifests a unique temperature-dependent sign reversal at nonzero magnetization, resulting from the momentum-space Berry curvature as established by first-principles simulations. The sign change is strain tunable, enabled by the sharp and well-defined substrate/film interface in the quasi-two-dimensional Cr2Te3 epitaxial films, revealed by scanning transmission electron microscopy and depth-sensitive polarized neutron reflectometry. This Berry phase effect further introduces hump-shaped Hall peaks in pristine Cr2Te3 near the coercive field during the magnetization switching process, owing to the presence of strain-modulated magnetic domains. The versatile interface tunability of Berry curvature in Cr2Te3 thin films offers new opportunities for topological electronics.

High-entropy oxides (HEOs) have a large tuning space in composition and crystal structures, offering the possibility for improved material properties in applications including catalysis, energy storage, and thermal barrier coatings. Understanding the nucleation and growth mechanisms of HEOs at the atomic scale is critical to the design of their structure and functions but remains challenging. Herein, we visualize the entire formation process of a high-entropy fluorite oxide from a polymeric precursor using atomic resolution in situ gas-phase scanning transmission electron microscopy. The results show a four-stage formation mechanism, including nucleation during the oxidation of a polymeric precursor below 400 °C, diffusive grain growth below 900 °C, liquid-phase-assisted compositional homogenization under a "state of supercooling" at 900 °C, and entropy-driven recrystallization and stabilization at higher temperatures. The atomistic insights are critical for the rational synthesis of HEOs with controlled grain sizes and morphologies and thus the related properties.

Development in lattice strain mapping using four-dimensional scanning transmission electron microscopy (4D-STEM) method now offers improved precision and feasibility. However, automatic and accurate diffraction analysis is still challenging due to noise and the complexity of intensity in diffraction patterns. In this work, we demonstrate an approach, employing the blob detection on cross-correlated diffraction patterns followed by a lattice fitting algorithm, to automate the processing of four-dimensional data, including identifying and locating disks, and extracting local lattice parameters without prior knowledge about the material. The approach is both tested using simulated diffraction patterns and applied on experimental data acquired from a Pd@Pt core-shell nanoparticle. Our method shows robustness against various sample thicknesses and high noise, capability to handle complex patterns, and picometer-scale accuracy in strain measurement, making it a promising tool for high-throughput 4D-STEM data processing.

Oxidative dehydrogenation (ODH) of n -butane has the potential to efficiently produce butadiene without equilibrium limitation or coke formation. Despite extensive research efforts, single-pass butadiene yields are limited to <23% in conventional catalytic ODH with gaseous O 2 . This article reports molten LiBr as an effective promoter to modify a redox-active perovskite oxide, i.e., La 0.8 Sr 0.2 FeO 3 (LSF), for chemical looping–oxidative dehydrogenation of n -butane (CL-ODHB). Under the working state, the redox catalyst is composed of a molten LiBr layer covering the solid LSF substrate. Characterizations and ab initio molecular dynamics (AIMD) simulations indicate that peroxide species formed on LSF react with molten LiBr to form active atomic Br, which act as reaction intermediates for C─H bond activation. Meanwhile, molten LiBr layer inhibits unselective CO 2 formation, leading to 42.5% butadiene yield. The redox catalyst design strategy can be extended to CL-ODH of other light alkanes such as iso -butane conversion to iso -butylene, providing a generalized approach for olefin production.

Al2O3-forming austenitic (AFA) stainless steels are potential replacements for the existing balance of plant (BoP) components in solid oxide fuel cells (SOFCs). In this study, chromium (Cr) poisoning of anode supported cells (ASCs) coupled with various alloys was analyzed by the distribution of relaxation times (DRT). The performance deterioration of ASCs was mainly attributed to the increased polarization resistances of chemisorption of oxygen on the cathode and the oxygen diffusion and reaction in the cathode. The superior performance of ASC coupled with AFA alloys was due to the formed continuous alumina layer which can vastly decrease the evaporated gaseous Cr species, thus alleviating the Cr poisoning on the cathode region.

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We demonstrate a pathway employing crystal polarity controlled asymmetric impurity incorporation in the wide bandgap nitride material system to enable 3D doping control during the crystal growth process. The pathway involves polarity specific supersaturation modulated growth of lateral polar structures of alternating Ga- and N-polar GaN domains. A STEM technique of integrated differential phase contrast is used to image the atomic structure of the different polar domains and their single atomic plane boundaries. As a demonstration, 1 μm wide alternating Ga- and N-polar GaN domains exhibiting charge balanced and periodic domains for superjunction technology were grown. The challenges in characterizing the resulting 3D doping profile were addressed with atom probe tomography with atomic scale compositional resolution corroborating capacitance measurements and secondary-ion mass spectroscopy analysis.

The chromium evaporation and oxidation behaviors of alumina-forming austenitic stain-less steels are systematically investigated at 800 degrees C in air +10% H2O relative to 310S for 5000 h. Cr evaporation rates of 310S are about 35 times higher than AFA alloys after 5000 h. Relatively rapid oxidation is observed on 310S after only one 500 h cycle, followed by a modest degree of mass loss and spallation, while the AFA alloys show high oxidation resistance throughout the entire test. Continuous inner alumina layer formed on AFA al-loys stays compact and stable after 5000 h which greatly reduces the Cr evaporation.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Diffraction analysis in four-dimensional scanning transmission electron microscopy now enables the mapping of local structures including symmetry, strain, and polarization of materials. However, measuring the distribution of these configurations at the unit cell level remains a challenge because most analysis methods require the diffraction disks to be separated, limiting the electron probe sizes to be larger than a unit cell. Here, we show improved spatial resolution in mapping the polarization displacement and phases of BaTiO3 sampled at a rate equivalent to the size of the projected unit cells using 4D-STEM. This improvement in spatial resolution is accomplished by masking out the overlapping regions in partially overlapped convergent beam electron diffraction patterns. By reducing the probe size to the order of single projected unit cells in size, the measurement shows local fluctuation within the nanosized rhombohedral domains in tetragonal phased BaTiO3, indicating the origin of phase transition and evolution across different length scales.