Optimizing disk registration algorithms for nanobeam electron diffraction strain mapping

Pekin, Thomas C.; Gammer, Christoph; Ciston, Jim; Minor, Andrew M.; Ophus, Colin

doi:10.1016/j.ultramic.2016.12.021

Cited by 88 publications

(83 citation statements)

References 25 publications

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“…This precision is not sufficient for several potential applications of 4D-STEM strain mapping, such as temperature mapping by thermal expansion measurement or mapping certain structural transformations via the lattice parameters, where strains may be on the order of 10 −4 . We note that direct comparison between precision limits reported in the literature is difficult because the precision limit depends on the sample properties, microscope image distortions, and the electron dose [20,26,27].…”

Section: Introductionmentioning

confidence: 95%

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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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Section: Introductionmentioning

confidence: 95%

“…The crosscorrelation is given when p = 0, and phase correlation is defined by p = 1. Values of p between 0 and 1 define a hybrid image correlation [20].…”

Section: Measuring Disk Positionsmentioning

confidence: 99%

Patterned probes for high precision 4D-STEM bragg measurements

et al. 2020

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“…High-pass filtering was performed prior to this step to remove the internal structure of diffraction disks. A pure cross-correlation method with filtering was optimal due to the thickness of the sample [24]. A peak-fitting algorithm was used on the original diffraction pattern to refine the initial peak position determined from the crosscorrelation routine.…”

Section: Nanoprobe Diffraction Analysis Algorithmmentioning

confidence: 99%

Multiscale analysis of nanoindentation-induced defect structures in gum metal

et al. 2018

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Using ex-situ transmission electron microscopy and the recently developed nanoprobe diffraction (NPD) technique, we characterize a nanoindented solution treated gum metal.Lattice rotations are resolved at a 1.2 nanometer length-scale and shown to be continuous within the nanoindentation pit; further, it is shown that these can be accommodated by a reasonable number of geometrically necessary dislocations at a density of ~10^15/m 2 . We additionally provide direct evidence that dislocations within the nanoindent, rather than secondary phase nanoparticles, can serve as potent barriers to dislocation motion. We also demonstrate that plasticity in these alloys under nanoindentation can be accommodated solely by dislocation nucleation and propagation, with no competing deformation mechanisms present. Conventional transmission electron microscopy and "gb" analysis reveal the presence of dislocations on <-111>{110} slip systems and highly localized plastic deformation in the form of shear bands on <111>{-1-12} slip systems, similar to previously observed "giant faults". Keyword

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“…4D-STEM can deliver much more structural information [1,2] than conventional STEM where only integrated electron intensities are acquired. The 4D dataset of CBED patterns can be utilized for structural analysis such as ptychographic reconstruction [3][4][5][6][7][8][9], strain mapping [10][11][12], electric and magnetic fields imaging using differential phase contrast [13,14], and composition and thickness measurements [15] with position-averaged CBED (PACBED) [16].…”

Section: Introductionmentioning

confidence: 99%

4D-Data Acquisition in Scanning Confocal Electron Microscopy for Depth-Sectioned Imaging

Hamaoka

Hashimoto

Mitsuishi

et al. 2018

e-J. Surf. Sci. Nanotech.

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We propose an experimental depth-sectioned imaging method based on annular dark-field scanning confocal electron microscopy (ADF-SCEM). Four-dimensional (4D) datasets, consisting of 2D probe images taken at every probe position during 2D raster scanning, were acquired with an aberration-corrected scanning transmission electron microscope. A series of depth-sectioned images were constructed by processing a single 4D dataset. A pinhole and a stage-scan system used in earlier studies were not required in the present data acquisition. Optimal observation conditions for the 4D data acquisition in the ADF-SCEM mode are outlined from multislice simulations.

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Optimizing disk registration algorithms for nanobeam electron diffraction strain mapping

Cited by 88 publications

References 25 publications

Patterned probes for high precision 4D-STEM bragg measurements

Patterned probes for high precision 4D-STEM bragg measurements

Multiscale analysis of nanoindentation-induced defect structures in gum metal

4D-Data Acquisition in Scanning Confocal Electron Microscopy for Depth-Sectioned Imaging

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