Dynamical diffraction of high-energy electrons investigated by focal series momentum-resolved scanning transmission electron microscopy at atomic resolution

Robert, Hoel Laurent; Lobato, Iván; Lyu, F.; Chen, Qing; Aert, Sandra Van; Dyck, D. Van; Müller‐Caspary, Knut

doi:10.1016/j.ultramic.2021.113425

Cited by 8 publications

(3 citation statements)

References 51 publications

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“…19,38 For high convergence angles, it has been shown that proper adjustment of the probe focus position can mitigate the effects of probe broadening and maintain the qualitative accuracy expected for samples in the 5-20 nm thickness range. [38][39][40] In summary, we have applied 4D STEM electric field imaging to a (PTO) 16 /(STO) 16 superlattice with both a picometer-sized and a nanometer-sized electron probes, and observed different patterns in the electric field at atomic and nanometer scales. The electric field measured by a picometer-sized probe shows a vortex pattern and is mainly determined by the asymmetry introduced to lead atomic columns by the bonding configuration of lead 6s, lone-pair electrons, which generates a dipole in each unit cell.…”

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confidence: 94%

Multiscale electric-field imaging of polarization vortex structures in PbTiO3/SrTiO3 superlattices

et al. 2023

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In ferroelectric heterostructures, the interaction between intrinsic polarization and the electric field generates a rich set of localized electrical properties. The local electric field is determined by several connected factors, including the charge distribution of individual unit cells, the interfacial electromechanical boundary conditions, and chemical composition of the interfaces. However, especially in ferroelectric perovskites, a complete description of the local electric field across micro-, nano-, and atomic-length scales is missing. Here, by applying four-dimensional scanning transmission electron microscopy (4D STEM) with multiple probe sizes matching the size of structural features, we directly image the electric field of polarization vortices in (PbTiO3)16/(SrTiO3)16 superlattices and reveal different electric field configurations corresponding to the atomic scale electronic ordering and the nanoscale boundary conditions. The separability of two different fields probed by 4D STEM offers the possibility to reveal how each contributes to the electronic properties of the film.

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confidence: 94%

Multiscale electric-field imaging of polarization vortex structures in PbTiO3/SrTiO3 superlattices

et al. 2023

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“…We note that the efficiency of information transfer in 4D-STEM experiments is highly dependent on the sample and experimental conditions, in particular, the convergence angle and diffraction space sampling [9,[14][15][16][17]. Experimental parameters, therefore, need to match each application case, and structural information out of 4D-STEM datasets usually needs to be extracted with appropriate post-acquisition algorithms, from using simple virtual apertures, and Bragg peak analysis [9], to momentum space weighting like first-or second-moment measurements [18,19] to more complex inverse problem solving including multi-slice ptychography [12,20]. Figure 1 illustrates examples of such 4D-STEM application cases that we have recently studied, ranging from momentum-resolved STEM imaging for revealing heavy and light elements simultaneously, to studying vacancies in 2D oxides with multi-slice ptychography reconstruction, to nano-crystalline thin film orientation mapping.…”

Section: Introduction 14d-stem Experiments For Materials Characteriza...mentioning

confidence: 99%

Using a fast hybrid pixel detector for dose-efficient diffraction imaging beam-sensitive organic molecular thin films

Wu,

Stroppa,

Pelz

et al. 2023

J. Phys. Mater.

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We discuss the benefits and showcase the applications of using a fast, hybrid-pixel detector (HPD) for 4D-STEM experiments and emphasize that in diffraction imaging the structure of molecular nano-crystallites in organic solar cell thin films with a dose-efficient modality 4D-scanning confocal electron diffraction (4D-SCED). With 4D-SCED, spot diffraction patterns form from an interaction area of a few nm while the electron beam rasters over the sample, resulting in high dose effectiveness yet highly demanding on the detector in frame speed, sensitivity, and single-pixel count rate. We compare the datasets acquired with 4D-SCED using a fast HPD with those using state-of-the-art complementary metal-oxide-semiconductor (CMOS) cameras to map the in-plane orientation of π-stacking nano-crystallites of small molecule DRCN5T in a blend of DRCN5T: PC71BM after solvent vapor annealing. The high-speed CMOS camera, using a scintillator optimized for low doses, showed impressive results for electron sensitivity and low noise. However, the limited speed restricted practical experimental conditions and caused unintended damage to small and weak nano-crystallites. The fast HPD, with a speed three orders of magnitude higher, allows a much higher probe current yet a lower total dose on the sample, and more scan points cover a large field of view in less time. A lot more faint diffraction signals that correspond to just a few electron events are detected. The improved performance of direct electron detectors opens more possibilities to enhance the characterization of beam-sensitive materials using 4D-STEM techniques.

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“…2(a) for dataset A. Electron-opticsrelated elliptical distortions at the level of the detector were accounted for by an anisotropic coordinate frame for the scattering angles. 20,21 Note that the azimuthal integration forms the basis for angle-resolved STEM (AR-STEM), which initially revealed the importance of inelastic scattering employing annular detectors. 13,22 By convention, the data are normalized to the incident intensity I 0 and to the solid angle.…”

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confidence: 99%

Contribution of multiple plasmon scattering in low-angle electron diffraction investigated by energy-filtered atomically resolved 4D-STEM

Robert

Diederichs

Müller‐Caspary

2022

Applied Physics Letters

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We report the influence of multiple plasmon losses on the dynamical diffraction of high-energy electrons, in a scanning transmission electron microscopy (STEM) study. Using an experimental setup enabling energy-filtered momentum-resolved STEM, it is shown that the successive excitation of up to five plasmons within the imaged material results in a subsequent and significant redistribution of low-angle intensity in diffraction space. An empirical approach, based on the convolution with a Lorentzian kernel, is shown to reliably model this redistribution in dependence of the energy-loss. Our study demonstrates that both the significant impact of inelastic scattering in low-angle diffraction at elevated specimen thickness and a rather straightforward model can be applied to mimic multiple plasmon scattering, which otherwise is currently not within reach for multislice simulations due to computational complexity.

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Dynamical diffraction of high-energy electrons investigated by focal series momentum-resolved scanning transmission electron microscopy at atomic resolution

Cited by 8 publications

References 51 publications

Multiscale electric-field imaging of polarization vortex structures in PbTiO3/SrTiO3 superlattices

Multiscale electric-field imaging of polarization vortex structures in PbTiO3/SrTiO3 superlattices

Using a fast hybrid pixel detector for dose-efficient diffraction imaging beam-sensitive organic molecular thin films

Contribution of multiple plasmon scattering in low-angle electron diffraction investigated by energy-filtered atomically resolved 4D-STEM

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