Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session S58: Viewing the Future, with ElectronsIndustrial Invited Live
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Sponsoring Units: FIAP Chair: Todd Brintlinger, United States Naval Research Laboratory |
Thursday, March 18, 2021 11:30AM - 12:06PM Live |
S58.00001: Exploring Nanocrystal Nucleation Mechanisms with Liquid Cell Transmission Electron Microscopy Invited Speaker: Taylor Woehl Heterogeneous nucleation at solid-liquid interfaces underlies a number of technologically important processes, from catalyst synthesis to fabrication of thin films, but remains poorly understood due to the dearth of techniques for quantifying nucleation energetics. In this talk, I will discuss development of a liquid cell transmission electron microscopy (LC-TEM) method for quantifying important parameters of heterogeneous nucleation, including supersaturation ratio and interfacial energy, and our efforts to utilize this approach to visualize nanoscale variations in nucleation kinetics at a solid-liquid interface. We quantify the supersaturation ratio of solute with numerical simulations of the electron beam induced chemistry during LC-TEM experiments, which enables fitting nucleation data using classical nucleation theory. Multiparticle tracking analysis applied to LC-TEM movies of nanoparticle nucleation reveals local variations in nucleation kinetics and preferential nucleation sites with nanometer scale spatial resolution. With this approach, we have demonstrated that heterogeneous nucleation of silver nanocrystals at a planar, uniform silicon nitride-water interface occurs preferentially in discrete nanoscale domains of the interface. Characterization of the solid-liquid interface with atomic force microscopy and covalent nanoparticle labeling revealed domains of surface functional groups on the interface acted as preferential nucleation sites. These results challenge previously held beliefs about nucleation on uniform interfaces, showing that nanoscale variations in surface chemistry can propagate nanoscale variations in nucleation kinetics. |
Thursday, March 18, 2021 12:06PM - 12:42PM Live |
S58.00002: Combined-Extreme In-Situ Experiments by Redesign of a Transmission Electron Microscope Pole-Piece Gap Invited Speaker: Zachary Milne In-situ transmission electron microscopy (TEM) has allowed for site-specific probing of reactions and transformations with atomic-scale spatial resolution and ultrafast temporal resolution that can be coupled with quantitative property measurements. In moving toward operando experiments, more detector access and environmental control over the specimen is required to understand nanoscale mechanisms in complex environments. Currently, commercial TEM’s provide a limited number of access ports to the pole piece gap where the specimen resides, therefore commonly in-situ stimuli and property measurements are integrated into a side entry specimen holder. Side entry holders have stability and steric limitations that prevent many feedthroughs to be combined on one holder. Therefore, our redesign of the TEM pole piece gap provides enhanced manipulation of the specimen, integrated stimuli introduction, quantitative property measurements (temperature, strain, and current), and increased spatial accessibility for signal detection (backscattered electrons, x-rays, and light). This redesign includes a cartridge holder and an objective lens chamber for optimized specimen control and signal detection for studying materials under combined environmental extremes within a TEM. |
Thursday, March 18, 2021 12:42PM - 1:18PM Live |
S58.00003: Theoretical Limits of Atomic Resolution Electron Tomography: New Bounds for Resolution, Object Size, and Dose Invited Speaker: Robert Hovden The theoretical limits of electron tomography have long been defined by the Crowther criterion, which relates 3D resolution to the number of projections acquired. However, these relations are invalid for aberration-corrected scanning transmission electron microscopy (STEM) where high convergence angles limit 3D reconstruction. We present a theoretical foundation for aberration-corrected electron tomography by establishing analytic descriptions for resolution, sampling, object size, and dose—with direct analogy to the Crowther criterion. The 3D structure of a contrast transfer function (CTF) for through focal tomography where every specimen tilt measures a toroid with petal-shaped cross-section. A remarkable feature of the 3D CTF is the overlapped regions that permit complete information collection—unachievable with conventional tomography. This breaks expected Crowther relationships and the maximum reconstructable object size is unlimited up to spatial frequency kc. At resolutions beyond 2/kc, Crowther-like tradeoffs define the maximum object size (D) allowed for given 3D resolution (d). |
Thursday, March 18, 2021 1:18PM - 1:54PM Live |
S58.00004: Vibrational spectroscopy in the electron microscope Invited Speaker: Ondrej Krivanek Vibrational spectroscopy in the electron microscope (EM) has progressed remarkably since it was introduced 6 years ago (Nature 514 (2014) 209). |
Thursday, March 18, 2021 1:54PM - 2:30PM Live |
S58.00005: In Situ Liquid Cell Transmission Electron Microscopy Imaging of Nanocrystal Transformations Invited Speaker: Haimei Zheng Nanocrystals often change structure and morphology during growth and self-assembly. This |
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