Probing Light Atoms at Subnanometer Resolution: Realization of Scanning Transmission Electron Microscope Holography

Yasin, Fehmi; Harvey, Tyler R.; Chess, Jordan; Pierce, Jordan; Ophus, Colin; Ercius, Peter; McMorran, Benjamin

doi:10.1021/acs.nanolett.8b03166

Cited by 31 publications

(28 citation statements)

References 43 publications

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“…By combining 4D-STEM with phase plates, additional phase contrast imaging methods become possible [2]. The first topic of this talk will be to describe a related phase plate method called STEM holography (STEM-H) [3,4], and its extension using ptychographic reconstruction. STEM-H is performed by using a diffraction grating in the probe forming aperture to produce multiple STEM beams, and then using a pixelated detector to measure the holographic fringe patterns, shown in Figure 1a.…”

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confidence: 99%

Advanced Phase Reconstruction Methods Enabled by Four-Dimensional Scanning Transmission Electron Microscopy

Ophus¹,

Harvey

Yasin

et al. 2019

Microsc Microanal

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By converging an electron probe to small dimensions and measuring the diffracted signal, we can measure atomic-scale information about a sample's structure, orientation, deformation, composition, and more. A measurement of full 2D diffraction images over a 2D grid of probe positions produces a 4D dataset, referred to as four-dimensional scanning transmission electron microscopy (4D-STEM). With modern electron detectors, we can now measure thousands of diffraction patterns, which enables many new imaging methods. A large class of useful 4D-STEM imaging modes produce phase contrast images of specimens, for example differential phase contrast (DPC) and ptychography [1]. By combining 4D-STEM with phase plates, additional phase contrast imaging methods become possible [2]. The first topic of this talk will be to describe a related phase plate method called STEM holography (STEM-H) [3,4], and its extension using ptychographic reconstruction. STEM-H is performed by using a diffraction grating in the probe forming aperture to produce multiple STEM beams, and then using a pixelated detector to measure the holographic fringe patterns, shown in Figure 1a. The primary advantage of STEM-H is that it produces phase contrast images on an absolute scale, which for example can be used to measure weak, extended electrostatic or electromagnetic fields as in Figures 1b. There, we see that for a conductive lacey carbon sample both the HAADF intensity and STEM-H phase shift show a similar decay into the vacuum. By contrast, for a semiconducting nanoparticle sample, we measure a phase shift due to an electrostatic field extending from the vacuum edge beyond the sample, which does not generate contrast in the HAADF channel. We have also extended STEM-H imaging to atomic resolution, shown in Figure 1c. STEM-H can quantitatively image the absolute phase shift of a sample, with the simple addition of a diffraction grating and large area, high speed direct electron detector.

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confidence: 99%

Advanced Phase Reconstruction Methods Enabled by Four-Dimensional Scanning Transmission Electron Microscopy

Ophus¹,

Harvey

Yasin

et al. 2019

Microsc Microanal

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“…The best resolution reported for Lorentz microscopy is approximately 1 nm and was achieved by Lorentz STEM (LSTEM) with differential phase contrast (DPC) analysis in an aberration-corrected instrument [4]. STEM Holography (STEMH), a recently developed technique [5][6][7][8], can achieve comparable resolution.In STEMH, we place a nanofabricated diffraction grating in an aperture above the sample to produce multiple diffraction probe beams (Figure 1b). We scan the probes such that the zeroth order passes through vacuum and one side of the diffraction pattern interacts with the sample.…”

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“…We scan the probes such that the zeroth order passes through vacuum and one side of the diffraction pattern interacts with the sample. At the camera, the diffracted probes are overlapped to form an interference pattern from which the phase shift induced by the sample can be measured [5][6][7][8]. Like off-axis electron holography, STEMH measures the amplitude and phase of the sample's transmission function while DPC measures the local phase gradient.…”

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“…Like off-axis electron holography, STEMH measures the amplitude and phase of the sample's transmission function while DPC measures the local phase gradient. However, biprisms, which are typically used to divide the beam in off-axis holography, require a more complicated installation and a much larger coherence width than the diffraction gratings used in STEMH [5][6][7][8]. As in LSTEM, the resolution of STEMH is limited only by aberrations, coherence, and the convergence angle of the probe [8].…”

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Lorentz Implementation of STEM Holography

et al. 2019

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Lorentz TEM (LTEM) is one of few methods capable of imaging magnetic features at the nanoscale. However, the attainable resolution is relatively poor when compared to that of standard high-resolution TEM. The resolution of Lorentz TEM and off-axis electron holography is typically at best 5-10 nm [1,2]. This limits the possible understanding of magnetic materials. One important example is the skyrmion, which is a donut-shaped magnetic structure. There is interest in using them as low power memory storage and understanding their dynamics is vital. However, they can be as small as 1nm [3]. The best resolution reported for Lorentz microscopy is approximately 1 nm and was achieved by Lorentz STEM (LSTEM) with differential phase contrast (DPC) analysis in an aberration-corrected instrument [4]. STEM Holography (STEMH), a recently developed technique [5][6][7][8], can achieve comparable resolution.In STEMH, we place a nanofabricated diffraction grating in an aperture above the sample to produce multiple diffraction probe beams (Figure 1b). We scan the probes such that the zeroth order passes through vacuum and one side of the diffraction pattern interacts with the sample. At the camera, the diffracted probes are overlapped to form an interference pattern from which the phase shift induced by the sample can be measured [5][6][7][8]. Like off-axis electron holography, STEMH measures the amplitude and phase of the sample's transmission function while DPC measures the local phase gradient. However, biprisms, which are typically used to divide the beam in off-axis holography, require a more complicated installation and a much larger coherence width than the diffraction gratings used in STEMH [5][6][7][8]. As in LSTEM, the resolution of STEMH is limited only by aberrations, coherence, and the convergence angle of the probe [8]. Therefore, Lorentz STEMH (LSTEMH) should achieve resolution comparable to LSTEM with DPC analysis. Additionally, spherical aberration can be included in the design of the diffraction grating [9, 10], potentially enabling 1 nm resolution in an instrument lacking probe correction.We simulated Lorentz STEMH of three Bloch skyrmions with a radius of 4 nm in an 80nm thick uniform ferromagnetic thin film (Figure 1). We simulated the magnetization of this specimen ( Figure 1a) and calculated the phase shift imparted on an electron beam passing through it (Figure 1b) using the Mansuripur algorithm [11]. From this phase we calculated the magnetic induction of the specimen (Figure 1c). We then simulated LSTEMH of the thin film with a 1 nm probe. To produce a more realistic simulation, we added shot noise to the interference pattern obtained at each scan location. The phase of the thin film measured by STEMH is shown in Figure 1e. From this phase, we then calculated the magnetic induction (Figure 1f). Despite some noise, the structure of the three Bloch skyrmions is readily apparent and agrees well with the magnetic induction calculated directly from the simulated specimen (Figure 1c). 96

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Advanced material characterization techniques for sodium‐ion battery

Liu

Tong

Zhang

et al. 2022

Asia-Pacific J Chem Eng

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Sodium-ion batteries, which are viewed as the alternative candidate for lithium-ion batteries, are now receiving extensive attention in recent years. This is because of the earth's abundance, the widespread sodium resource, and the low cost of battery production. Despite tremendous effort has been made to improve the battery performance of sodium-ion batteries, several serious problems hinder the large-scale practical applications. These problems such as low energy density and efficiency, poor cycle life, and low charge/discharge rate are largely determined by fundamental mechanism issues of electrode materials that are not sufficiently understood yet. Therefore multiple techniques should be used to get an in-depth understanding of material properties.In this review, a comprehensive overview of the material characterization technique is provided and hope it could improve the battery research for all the scientific researchers.

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Probing Light Atoms at Subnanometer Resolution: Realization of Scanning Transmission Electron Microscope Holography

Cited by 31 publications

References 43 publications

Advanced Phase Reconstruction Methods Enabled by Four-Dimensional Scanning Transmission Electron Microscopy

Advanced Phase Reconstruction Methods Enabled by Four-Dimensional Scanning Transmission Electron Microscopy

Lorentz Implementation of STEM Holography

Advanced material characterization techniques for sodium‐ion battery

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