A Scan Through the History of STEM

Pennycook, Stephen J.

doi:10.1007/978-1-4419-7200-2_1

Cited by 29 publications

(25 citation statements)

References 478 publications

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“…The detection of single atoms of Si and Pt using EDXS has also been demonstrated recently~Lovejoy et al, 2012!. Further details on the historical development and recent achievements of STEM imaging/spectroscopy and of aberration correction can be found in recent book chapters~Krivanek et al, 2008b;Crewe, 2009;Pennycook, 2011!. In this article, we show several examples of imaging and spectroscopy of single atoms, and we illustrate how the experimental results lead to an improved understanding of defects in 2D materials.…”

Section: Introductionmentioning

confidence: 80%

Single Atom Microscopy

et al. 2012

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We show that aberration-corrected scanning transmission electron microscopy operating at low accelerating voltages is able to analyze, simultaneously and with single atom resolution and sensitivity, the local atomic configuration, chemical identities, and optical response at point defect sites in monolayer graphene. Sequential fast-scan annular dark-field (ADF) imaging provides direct visualization of point defect diffusion within the graphene lattice, with all atoms clearly resolved and identified via quantitative image analysis. Summing multiple ADF frames of stationary defects produce images with minimized statistical noise and reduced distortions of atomic positions. Electron energy-loss spectrum imaging of single atoms allows the delocalization of inelastic scattering to be quantified, and full quantum mechanical calculations are able to describe the delocalization effect with good accuracy. These capabilities open new opportunities to probe the defect structure, defect dynamics, and local optical properties in 2D materials with single atom sensitivity.

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Section: Introductionmentioning

confidence: 80%

Single Atom Microscopy

et al. 2012

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“…In scanning transmission electron microscopy (STEM), a converged electron probe is rastered across the sample, and some of the scattered electrons (usually those scattered incoherently by thermal diffuse scattering) are measured to assign a value to each pixel [11]. Modern electron detector technology allows the full scattering pattern at each STEM probe position to be recorded, an experiment referred to as four-dimensional scanning transmission electron microscopy (4D-STEM) [12].…”

Section: Introductionmentioning

confidence: 99%

Patterned probes for high precision 4D-STEM bragg measurements

et al. 2020

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Nanoscale strain mapping by four-dimensional scanning transmission electron microscopy (4D-STEM) relies on determining the precise locations of Bragg-scattered electrons in a sequence of diffraction patterns, a task which is complicated by dynamical scattering, inelastic scattering, and shot noise. These features hinder accurate automated computational detection and position measurement of the diffracted disks, limiting the precision of measurements of local deformation. Here, we investigate the use of patterned probes to improve the precision of strain mapping. We imprint a "bullseye" pattern onto the probe, by using a binary mask in the probe-forming aperture, to improve the robustness of the peak finding algorithm to intensity modulations inside the diffracted disks. We show that this imprinting leads to substantially improved strain-mapping precision at the expense of a slight decrease in spatial resolution. In experiments on an unstrained silicon reference sample, we observe an improvement in strain measurement precision from 2.7% of the reciprocal lattice vectors with standard probes to 0.3% using bullseye probes for a thin sample, and an improvement from 4.7% to 0.8% for a thick sample. We also use multislice simulations to explore how sample thickness and electron dose limit the attainable accuracy and precision for 4D-STEM strain measurements.

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“…4, 6, 9a). The main advantage in this case is that the HAADF signal is generated by the incoherent Rutherford-like electrons scattered out to high angles, in which the registered images have different levels of contrast related to the atomic number (chemical composition) and the density and thickness (mass thickness) of the battery component (Pennycook, 2011). In STEM, partial temporal coherence may arise only because of the relatively low spread in energies of the illuminating beam if field-emission sources are used (Nellist, 2011).…”

Section: Analytical Multimode Scanning and Transmission Electron Imagmentioning

confidence: 99%

Analytical Multimode Scanning and Transmission Electron Imaging and Tomography of Multiscale Structural Architectures of Sulfur Copolymer-Based Composite Cathodes for Next-Generation High-Energy Density Li–S Batteries

et al. 2016

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Poly[sulfur-random-(1,3-diisopropenylbenzene)] copolymers synthesized via inverse vulcanization represent an emerging class of electrochemically active polymers recently used in cathodes for Li-S batteries, capable of realizing enhanced capacity retention (1,005 mAh/g at 100 cycles) and lifetimes of over 500 cycles. The composite cathodes are organized in complex hierarchical three-dimensional (3D) architectures, which contain several components and are challenging to understand and characterize using any single technique. Here, multimode analytical scanning and transmission electron microscopies and energy-dispersive X-ray/electron energy-loss spectroscopies coupled with multivariate statistical analysis and tomography were applied to explore origins of the cathode-enhanced capacity retention. The surface topography, morphology, bonding, and compositions of the cathodes created by combining sulfur copolymers with varying 1,3-diisopropenylbenzene content and conductive carbons have been investigated at multiple scales in relation to the electrochemical performance and physico-mechanical stability. We demonstrate that replacing the elemental sulfur with organosulfur copolymers improves the compositional homogeneity and compatibility between carbons and sulfur-containing domains down to sub-5 nm length scales resulting in (a) intimate wetting of nanocarbons by the copolymers at interfaces; (b) the creation of 3D percolation networks of conductive pathways involving graphiticlike outer shells of aggregated carbons; (c) concomitant improvements in the stability with preserved meso-and nanoscale porosities required for efficient charge transport.

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A Scan Through the History of STEM

Cited by 29 publications

References 478 publications

Single Atom Microscopy

Single Atom Microscopy

Patterned probes for high precision 4D-STEM bragg measurements

Analytical Multimode Scanning and Transmission Electron Imaging and Tomography of Multiscale Structural Architectures of Sulfur Copolymer-Based Composite Cathodes for Next-Generation High-Energy Density Li–S Batteries

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