Channelling contrast analysis of lattice images: Conditions for probe-insensitive STEM

Rossouw, C. J.; Dwyer, Christian; Katz-Boon, Hadas; Etheridge, Joanne

doi:10.1016/j.ultramic.2013.10.005

Cited by 11 publications

(7 citation statements)

References 26 publications

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“…1 show the mean, column and minimum intensities for a wide range of thicknesses. The mean signal should be strictly independent of aberrations due to the process of averaging over the unit cell [20,34]. The column and minimum signals -which, to reduce shot noise effects, constitute the average signal within a radius of 1.0 Å around the atomic column and minimum position, respectively, as determined from the simultaneously acquired HAADF image -should also be relatively insensitive to residual aberrations [35].…”

Section: Atomic Resolution Mapping On An Absolute Scalementioning

confidence: 99%

Quantitative atomic resolution elemental mapping via absolute-scale energy dispersive X-ray spectroscopy

et al. 2016

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Quantitative agreement on an absolute scale is demonstrated between experiment and simulation for two-dimensional, atomic-resolution elemental mapping via energy dispersive X-ray spectroscopy. This requires all experimental parameters to be carefully characterized. The agreement is good, but some discrepancies remain. The most likely contributing factors are identified and discussed. Previous predictions that increasing the probe forming aperture helps to suppress the channelling enhancement in the average signal are confirmed experimentally. It is emphasized that simple column-by-column analysis requires a choice of sample thickness that compromises between being thick enough to yield a good signal-to-noise ratio while being thin enough that the overwhelming majority of the EDX signal derives from the column on which the probe is placed, despite strong electron scattering effects.

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Section: Atomic Resolution Mapping On An Absolute Scalementioning

confidence: 99%

Quantitative atomic resolution elemental mapping via absolute-scale energy dispersive X-ray spectroscopy

et al. 2016

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Section: Methodsmentioning

confidence: 99%

“…All STEM simulations were performed using a GPU-based code (Dwyer, 2010) which was run on a Graphics Processing Unit (GPU) cluster. Lens aberrations and the finite source size were ignored since they have no effect on position-averaged signals acquired in the STEM (Rossouw et al, 2014). The model adopted for core-loss scattering does not incorporate the observed spin-orbit splitting of the L 2,3 and M 4,5 edges (considered below).…”

Section: Simulation Detailsmentioning

confidence: 99%

Quantitative Position-AveragedK-,L-, andM-Shell Core-Loss Scattering in STEM

Zhu

Dwyer

2014

Microsc Microanal

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We present a quantitative comparison between experimental position-averaged core-loss scattering from K-, L-, and M-shells of various elements and simulations based on a single-particle description of the core-loss process. To facilitate a direct comparison free of adjustable or compensating parameters, we compare absolute scattering cross-sections for zone-axis-aligned crystals whose thicknesses have been measured independently. The results show that the single-particle model accurately predicts the absolute scattering intensity from K-shells, and L-shells in some cases, but achieves only semi-quantitative agreement for M-shells.

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“…An atomically fine probe offers the experimental flexibility to survey regions of interest in a range of magnifications up to atomic resolution, potentially allowing for the correlation of atomistic structure with the larger scale electric field distribution. Also, larger probe-forming aperture angles tend to reduce channelling effects in on-axis conditions [28]. In addition, for spatially varying long-range fields, within the phase object approximation the simple deflection model of Eq.…”

Section: Imaging With An Atomically Fine Probe At Low Magnificationmentioning

confidence: 99%

Low magnification differential phase contrast imaging of electric fields in crystals with fine electron probes

et al. 2016

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To correlate atomistic structure with longer range electric field distribution within materials, it is necessary to use atomically fine electron probes and specimens in on-axis orientation. However, electric field mapping via low magnification differential phase contrast imaging under these conditions raises challenges: electron scattering tends to reduce the beam deflection due to the electric field strength from what simple models predict, and other effects, most notably crystal mistilt, can lead to asymmetric intensity redistribution in the diffraction pattern which is difficult to distinguish from that produced by long range electric fields. Using electron scattering simulations, we explore the effects of such factors on the reliable interpretation and measurement of electric field distributions. In addition to these limitations of principle, some limitations of practice when seeking to perform such measurements using segmented detector systems are also discussed.

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Channelling contrast analysis of lattice images: Conditions for probe-insensitive STEM

Cited by 11 publications

References 26 publications

Quantitative atomic resolution elemental mapping via absolute-scale energy dispersive X-ray spectroscopy

Quantitative atomic resolution elemental mapping via absolute-scale energy dispersive X-ray spectroscopy

Quantitative Position-AveragedK-,L-, andM-Shell Core-Loss Scattering in STEM

Low magnification differential phase contrast imaging of electric fields in crystals with fine electron probes

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