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Highlights • Off-axis electron holography enables quantification of electrostatic fields. • Outline of theoretical basis and experimental aspects for electron holography. • Applications to many different types of materials problems briefly reviewed. • Challenges and opportunities for off-axis electron holography. Abstract Off-axis electron holography has evolved into a powerful electron-microscopy-based technique for characterizing electromagnetic fields with nanometer-scale resolution. In this paper, we present a review of the application of off-axis electron holography to the quantitative measurement of electrostatic potentials and charge density distributions. We begin with a short overview of the theoretical and experimental basis of the technique. Practical aspects of phase imaging, sample preparation and microscope operation are outlined briefly. Applications of off-axis electron holography to a wide range of materials are then described in more detail. Finally, challenges and future opportunities for electron holography investigations of electrostatic fields and charge density distributions are presented. [ABSTRACT FROM AUTHOR]

High-resolution transmission electron microscopy is used to study interactions between thiol-capped Au clusters and amorphous C support films. The morphologies of the clusters are found to depend both on their size and on the local structure of the underlying C. When the C is amorphous, larger Au clusters are crystalline, while smaller clusters are typically disordered. When the C is graphitic, the Au particles adopt either elongated shapes that maximize their contact with the edge of the C film or planar arrays when they contain few Au atoms. We demonstrate the influence of electron beam irradiation on the structure, shape and stability of the Au clusters, as well as on the formation of holes bounded by terraces of graphitic lamellae in the underlying C. [ABSTRACT FROM AUTHOR]

Benefitting from exceptional energy storage performance, dielectric-based capacitors are playing increasingly important roles in advanced electronics and high-power electrical systems. Nevertheless, a series of unresolved structural puzzles represent obstacles to further improving the energy storage performance. Compared with ferroelectrics and linear dielectrics, antiferroelectric materials have unique advantages in unlocking these puzzles due to the inherent coupling of structural transitions with the energy storage process. In this review, we summarize the most recent studies about in-situ structural phase transitions in PbZrO3-based and NaNbO3-based systems. In the context of the ultrahigh energy storage density of SrTiO3-based capacitors, we highlight the necessity of extending the concept of antiferroelectric-to-ferroelectric (AFE-to-FE) transition to broader antiferrodistortive-to-ferrodistortive (AFD-to-FD) transition for materials that are simultaneously ferroelastic. Combining discussion of the factors driving ferroelectricity, electric-field-driven metal-to-insulator transition in a (La1−xSrx)MnO3 electrode is emphasized to determine the role of ionic migration in improving the storage performance. We believe that this review, aiming at depicting a clearer structure–property relationship, will be of benefit for researchers who wish to carry out cutting-edge structure and energy storage exploration. [ABSTRACT FROM AUTHOR]

The rapid development of electron tomography, in particular the introduction of novel tomographic imaging modes, has led to the visualization and analysis of three-dimensional structural and chemical information from materials at the nanometre level. In addition, the phase information revealed in electron holograms allows electrostatic and magnetic potentials to be mapped quantitatively with high spatial resolution and, when combined with tomography, in three dimensions. Here we present an overview of the techniques of electron tomography and electron holography and demonstrate their capabilities with the aid of case studies that span materials science and the interface between the physical sciences and the life sciences. [ABSTRACT FROM AUTHOR]

Here we have developed an approach of three-dimensional (3D) measurement of magnetic moment vectors in three Cartesian directions using electron magnetic chiral dichroism (EMCD) at atomic scale. Utilizing a subangstrom convergent electron beam in the scanning transmission electron microscopy (STEM), beam-position-dependent chiral electron energy-loss spectra (EELS), carrying the EMCD signals referring to magnetization in three Cartesian directions, can be obtained during the scanning across the atomic planes. The atomic resolution EMCD signals from all of three directions can be separately obtained simply by moving the EELS detector. Moreover, the EMCD signals can be remarkably enhanced using a defocused electron beam, relieving the issues of low signal intensity and signal-to-noise-ratio especially at atomic resolution. Our proposed method is compatible with the setup of the widely used atomic resolution STEM-EELS technique and provides a straightforward way to achieve 3D magnetic measurement at atomic scale on newly developing magnetic-field-free TEM. [ABSTRACT FROM AUTHOR]

Abstract: Off-axis electron holography is used to characterize a linear array of transistors, which was prepared for examination in cross-sectional geometry in the transmission electron microscope (TEM) using focused ion beam (FIB) milling from the substrate side of the semiconductor device. The measured electrostatic potential is compared with results obtained from TEM specimens prepared using the more conventional ‘trench’ FIB geometry. The use of carbon coating to remove specimen charging effects, which result in electrostatic fringing fields outside ‘trench’ specimens, is demonstrated. Such fringing fields are not observed after milling from the substrate side of the device. Analysis of the measured holographic phase images suggests that the electrically inactive layer on the surface of each FIB-milled specimen typically has a thickness of 100nm. [Copyright &y& Elsevier]

The magnetic microstructure of a natural, finely exsolved intergrowth of submicron magnetite blocks in an ulvöspinel matrix is characterized by using off-axis electron holography in the transmission electron microscope. Single-domain and vortex states in individual blocks, as well as magnetostatic interaction fields between them, are imaged at a spatial resolution approaching the nanometer scale. The images reveal an extremely complicated magnetic structure dominated by the shapes of the blocks and magnetostatic interactions. Magnetic superstates, in which clusters of magnetite blocks act collectively to form vortex and multidomain states that have zero net magnetization, are observed directly. [ABSTRACT FROM AUTHOR]

The past decade has seen a growing trend toward utilizing (quasi) van der Waals growth for the heterogeneous integration of various materials for advanced electronics. In this work, pulsed‐laser deposition is used to grow HfO2 thin films on graphene/SiO2/Si. As graphene is easily damaged under standard oxide‐film deposition conditions, the process needs to be adjusted to minimize the oxidation and the collision‐induced damage. A systematic study is conducted in order to identify the crucial deposition parameters for diminishing the defect concentration in the graphene interlayer. For evaluating the quality of graphene, it is mainly relied on data obtained from Raman spectroscopy, using approaches beyond the Tuinstra‐Koenig relation. The results show that the defects are mainly a consequence of the high kinetic energy of the plasma‐plume particles. Using a relatively high Ar process pressure, a sufficiently low defect concentration is ensured, without compromising the quality of the HfO2 thin film. This enabled us to successfully prepare memristive devices with a filamentary type of switching, utilizing the graphene layer as a bottom electrode. The findings of this study can be easily transferred to other systems for the development of oxide electronic devices. [ABSTRACT FROM AUTHOR]

Examines the origin of the magnetization decay in spin-dependent tunnel junctions using Lorentz electron microscopy and micromagnetic simulations. Features of the spin-dependent magnetic tunnel junctions; Details on the Neel wall in thin magnetic films; Investigation on the demagnetization processes through the micromagnetic simulations.

High energy density electrochemical systems such as metal batteries suffer from uncontrollable dendrite growth on cycling, which can severely compromise battery safety and longevity. This originates from the thermodynamic preference of metal nucleation on electrode surfaces, where obtaining the crucial information on metal deposits in terms of crystal orientation, plated volume, and growth rate is very challenging. In situ liquid phase transmission electron microscopy (LPTEM) is a promising technique to visualize and understand electrodeposition processes, however a detailed quantification of which presents significant difficulties. Here by performing Zn electroplating and analyzing the data via basic image processing, this work not only sheds new light on the dendrite growth mechanism but also demonstrates a workflow showcasing how dendritic deposition can be visualized with volumetric and growth rate information. These results along with additionally corroborated 4D STEM analysis take steps to access information on the crystallographic orientation of the grown Zn nucleates and toward live quantification of in situ electrodeposition processes. [ABSTRACT FROM AUTHOR]

Presents research which correlated the physical and magnetic microstructure of magnetite nanocrystals in magnetotactic bacteria. Use of off-axis electron holography in the transmission electron microscope; Single magnetic domains; Magnetization directions; Shape anisotropy; Coercive field for one chain.

Stray electric fields in free space generated by two biased gold needles have been quantified in comprehensive finite-element (FE) simulations, accompanied by first moment (FM) scanning TEM (STEM) and electron holography (EH) experiments. The projected electrostatic potential and electric field have been derived numerically under geometrical variations of the needle setup. In contrast to the FE simulation, application of an analytical model based on line charges yields a qualitative understanding. By experimentally probing the electric field employing FM STEM and EH under alike conditions, a discrepancy of about 60% became apparent initially. However, the EH setup suggests the reconstructed phase to be significantly affected by the perturbed reference wave effect, opposite to STEM where the field-free reference was recorded subsequently with unbiased needles in which possibly remaining electrostatic influences are regarded as being minor. In that respect, the observed discrepancy between FM imaging and EH is resolved after including the long-range potential landscape from FE simulations into the phase of the reference wave in EH. • Electric field of biased needles mapped by first-moment STEM and electron holography • Quantitative understanding of both signals obtained by finite element (FE) simulations • Referencing to field-free cases is fundamentally different for both methods • Perturbed reference wave in electron holography reproducible by extensive FE simulations • Electrode stray fields in electrically biased specimens contribute significantly to signal [ABSTRACT FROM AUTHOR]

Over the past few years, electron ptychography has drawn considerable attention for its ability to recover high contrast and ultra-high resolution images without the need for high quality electron optics. In this Letter, we focus on electron ptychography's other potential benefits: quantitatively mapping phase variations resulting from magnetic and electric fields over extended fields of view. To this end, we propose an implementation of near-field ptychography that employs an amplitude mask located in the electron microscope's condenser aperture plane. We demonstrate the capabilities of our method by imaging a magnetic Permalloy sample and compare our results with those of off-axis electron holography. [ABSTRACT FROM AUTHOR]

Beam shaping—the ability to engineer the phase and the amplitude of massive and massless particles—has long interested scientists working on communication, imaging, and the foundations of quantum mechanics. In light optics, the shaping of electromagnetic waves (photons) can be achieved using techniques that include, but are not limited to, direct manipulation of the beam source (as in x-ray free electron lasers and synchrotrons), deformable mirrors, spatial light modulators, mode converters, and holograms. The recent introduction of holographic masks for electrons provides new possibilities for electron beam shaping. Their fabrication has been made possible by advances in micrometric and nanometric device production using lithography and focused on ion beam patterning. This article provides a tutorial on the generation, production, and analysis of synthetic holograms for transmission electron microscopy. It begins with an introduction to synthetic holograms, outlining why they are useful for beam shaping to study material properties. It then focuses on the fabrication of the required devices from theoretical and experimental perspectives, with examples taken from both simulations and experimental results. Applications of synthetic electron holograms as aberration correctors, electron vortex generators, and spatial mode sorters are then presented. [ABSTRACT FROM AUTHOR]

Characterisation of the electron beams trajectory in an electron microscope is possible in a few select commercial software packages, but these tools and their source code are not available in a free and accessible manner. This paper introduces the free and open-source software TEMGYM Advanced, which implements ray tracing methods that calculate the path of electrons through a magnetic or electrostatic lens and allow evaluation of the first-order properties and third-order geometric aberrations. Validation of the aberration coefficient calculations is performed by implementing two independent methods – the aberration integral and differential algebra (DA) methods and by comparing the results of each. This paper also demonstrates parallelised electron ray tracing through a series of magnetic components, which enables near real-time generation of a physically accurate beam-spot including aberrations and brings closer the realisation of a digital twin of an electron microscope. TEMGYM Advanced represents a valuable resource for the electron microscopy community, providing an accessible and open source means of characterising electron lenses. This software utilises the Python programming language to complement the growing ecosystem of free and open-source software within the electron microscopy community, and to facilitate the application of machine learning to an electron microscope digital twin for instrument automation. The software is available under GNU Public License number Three (GPL 3). [ABSTRACT FROM AUTHOR]

An interactive simulation of a transmission electron microscope (TEM) called TEMGYM Basic is developed here, which enables users to understand how to operate and control an electron beam without the need to access an instrument. TEMGYM Basic allows users to familiarize themselves with alignment procedures offline, reducing the time and money required to become a proficient TEM operator. In addition to teaching the basics of electron beam alignments, the software enables users to create bespoke microscope configurations and develop an understanding of how to operate the configurations without sitting at a microscope. TEMGYM Basic also creates static ray diagram figures for a given lens configuration. The available components include apertures, lenses, quadrupoles, deflectors and biprisms. The software design uses first‐order ray transfer matrices to calculate ray paths through each electron microscope component, and the program is developed entirely in Python to facilitate compatibility with machine‐learning packages for future exploration of automated control. [ABSTRACT FROM AUTHOR]

Modern nanotechnology techniques offer new opportunities for fabricating structures and devices at the micrometer and sub-micrometer level. Here, we use focused ion beam techniques to realize micrometer-sized Janus bimetallic cylinders acting as drift tube devices, which are able to impart a controlled phase shift to an electron wave. The phase shift results from the presence of contact potentials in the cylinders, in a similar manner to the electrostatic Aharonov–Bohm effect in bimetallic wires. We use electron Fraunhofer interference to demonstrate that such bimetallic structures introduce phase shifts that can be tuned to desired values by varying the dimensions of the pillars, in particular their heights. Such devices are promising for electron beam shaping and for the realization of electrostatic Zernike phase plates (i.e., devices that are able to impart a constant phase shift between an unscattered and a scattered electron wave) in electron microscopy, in particular, cryo-electron microscopy. [ABSTRACT FROM AUTHOR]

The characteristic microstructure of Sm (Co , Fe , Cu , Zr) z (z = 6.7 – 9.1) alloys with SmCo 5 cell walls in Sm 2 Co 17 cells, all intersected by Zr-rich platelets, makes them some of the best performing high-temperature permanent magnets. Plentiful research has been performed to tailor their microstructure at the nanoscale; but due to its complexity, many questions remain unanswered about the effect of the individual phases on the magnetic performance at different temperatures. Here, we explore this effect for three different Sm (Co , Fe , Cu , Zr) z alloys by deploying high-resolution magnetic imaging via in situ transmission electron microscopy and three-dimensional chemical analysis via atom probe tomography. We show that their microstructures differ in terms of SmCo 5 cell-wall and Z-phase size and density as well as the Cu concentration in the cell walls and demonstrate how these features influence the magnetic domain size and density, thus forming different micromagnetic spin structures. Moreover, we illustrate that the dominant coercivity mechanism at room temperature is domain-wall pinning and show that magnets with a denser cell-wall network, a steeper Cu gradient across the cell-wall boundary, and thinner Z-phase platelets have a higher coercivity. We also show that the coercivity mechanism at high temperatures is domain-wall nucleation at the cell walls. Increasing the Cu concentration inside the cell walls decreases the temperature of transition between pinning and nucleation, significantly decreasing the coercivity with increasing temperature. We, therefore, provide a detailed explanation of how the microstructure on the atomic to nanoscale directly affects the magnetic performance and provide detailed guidelines for an improved design of Sm (Co , Fe , Cu , Zr) z magnets. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses the advanced optical magnetic imaging technique used to study the three-dimensional magnetic fields that originate from chains of magnetic nanocrystals inside the living cells of magnetotactic bacteria.

High-resolution transmission electron microscopy is often used to characterize grain boundaries, but it is usually limited to special high symmetry boundaries with a high density of coincident sites. For these 'special' boundaries, both crystals can be brought into a low-index zone-axis with the boundary plane parallel to the incident electron beam. In this case the atomistic structure of the boundary can be solved, which is not possible for other, more general grain boundaries. In the present study, general grain boundaries in SrTiO3 were analyzed using aberration-corrected transmission electron microscopy and scanning transmission electron microscopy. These boundaries included at least one type of disconnection (i.e., defects that can have a step and/or a dislocation component). Since the dislocation component of disconnections along general grain boundaries cannot be fully resolved using the methods currently available, a plane matching approach was used to compare disconnections at different boundaries. Using this approach, the dislocation component of the disconnections was partially characterized and was found to have an edge component mainly parallel to {100} and {110}, close to normal to the macroscopic grain boundary plane. The step component of the disconnections was found to be aligned mainly parallel to the same crystallographic planes ({100} and {110}). [ABSTRACT FROM AUTHOR]

Highlights • The paper describes a simple computational method that can be used to simulate the fine structure of an electron beam diffracted by a crystal in two-beam conditions. • The approach provides several advantages over other methods. It is simple and computationally effective, it is valid for a general crystal morphology, does not make use of the columnn approximation and can be used to simulate diffraction in the image and focal planes of a TEM. • Our method is easily applicable for the simulation of electron precession diffraction spots (a method that is becoming important for solving crystallographic structures using electrons). • We define the concept of the g-shape factor that allows to use the method presented in this paper for simulating the image contrast of crystalline defects. • The validity of the method is proved by comparing simulation with experimental images of different crystalline materials. Abstract A simple computational method that can be used to simulate TEM image contrast of an electron beam diffracted by a crystal under two-beam dynamical scattering conditions is presented. The approach based on slicing the shape factor is valid for a general crystal morphology, with and without crystalline defects, avoids the column approximation, and provides the complex exit wave at the focal and the image planes also under weak-beam conditions. The approach is particularly efficient for large crystals and the 3D model required for the calculations can be measured experimentally using electron tomography. The method is applied to show that the shape of a diffracted spot can be affected by shifts, broadening and secondary maxima of appreciable intensity, even for a perfect crystal. The methodology is extended for the case of electron precession diffraction, and to show how can be used to improve nanometrology from diffraction patterns. The method is used also to perform simulations of simple models of crystalline defects. The accuracy of the method is demonstrated through examples of experimental and simulated dark-field images of MgO and ZrO 2 nanocrystals and thin layers of CeO 2. [ABSTRACT FROM AUTHOR]

Highlights • Applicability of ICA for identification of EMCD discussed. • All k-space EMCD contributions identifiable for different sample orientations. • EMCD extraction demonstrated on experimental EFTEM images. Abstract Electron magnetic chiral dichroism (EMCD) is a promising technique to investigate local magnetic structures in the electron microscope. However, recognition of the EMCD signal, or also finding optimal parameter settings for given materials and sample orientations typically requires extensive simulations to aid the experiment. Here, we discuss how modern data processing techniques, in particular independent component analysis, can be used to identify magnetic signals in an unsupervised manner from energy filtered transmission electron microscopy (EFTEM) images. On the background of the recent advent of 4D scanning transmission electron microscopy, we discuss how this data processing may enable simultaneous tracking of all three spatial components of the magnetic momenta for arbitrary materials and several sample orientations without the previous need of complementary simulations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Upon impregnation of graphitic carbon nitride with Pd(NH 3) 4 (NO 3) 2 Pd single-atoms with twofold coordination to the support emerge. • These Pd single-atoms are inactive in ethylene hydrogenation and H 2 -D 2 exchange. • During ethylene hydrogenation at 100 °C inactive Pd single-atoms agglomerate to highly active clusters. • Both ethylene and hydrogen are required to induce this agglomeration process. Single-atoms on carbon–nitrogen supports are considered catalysts for a multitude of reactions. However, doubts remain whether really these species or subnanometer clusters formed under reaction conditions are the active species. In this work, we investigate the dynamics of palladium single-atoms on graphitic carbon nitride during ethylene hydrogenation and H 2 -D 2 exchange. By employing aberration-corrected scanning transmission electron microscopy, x-ray photoelectron spectroscopy and x-ray absorption spectroscopy, we will show that palladium, originally present as single-atoms, agglomerates to clusters at 100 °C in a gas atmosphere that contains both ethylene and hydrogen. This agglomeration goes in hand with the emergence of catalytic activity in both ethylene hydrogenation and H 2 -D 2 exchange, suggesting that clusters, rather than single-atoms, are the active species. The results presented herein highlight the potential of analytics over the course of reaction to identify the active species and provide new insights into the influence of gas atmosphere on metal speciation. [ABSTRACT FROM AUTHOR]

A Boersch phase plate can shift the phase of electrons proportionally to the applied electrical potential, thereby allowing for in situ control of the electron phase shift. A device comprising multiple Boersch phase shifter elements will be able to modulate the wavefront of a coherent electron beam and control electron interference. Recently, fabrication of single and 2 × 2 element Boersch phase shifter devices by focused ion beam milling has been reported. Realization of a large-scale Boersch phase shifter array would demand further developments in the device design and the fabrication strategy, e.g., using lithographic processes. In the present work, we develop a fabrication method utilizing the state-of-the-art electron beam lithography and reactive ion etching processes, a combination that is widely used for high-throughput and large-scale micro- and nanofabrication of electronic and photonic devices. Using the developed method, we fabricated a three-element phase shifter device with a metal–insulator–metal structure with 100-nm-thick ring electrodes and tested its electron transmission characteristics in a transmission electron microscope with a beam energy of 200 keV. We observed voltage-controlled evolution of electron interference, demonstrating the voltage-controlled electron phase shift using the fabricated device with a phase shift of π rad per 1 V. We analyze the experimental results in comparison with a three-dimensional electrostatic simulation. Furthermore, we discuss the possible improvements in terms of beam deflection and crosstalk between phase shifter elements in a five-layer device structure. [ABSTRACT FROM AUTHOR]

Investigating the local micromagnetic structure of ferromagnetic nanowires (NWs) at the nanoscale is essential to study the structure–property relationships and can facilitate the design of nanostructures for technology applications. Herein, we synthesized high-quality iron and cobalt NWs and investigated the magnetic properties of these NWs using off-axis electron holography. The Fe NWs are about 100 nm in width and a few micrometers in length with a preferential growth direction of [100], while the Co NWs have a higher aspect-ratio with preferential crystal growth along the [110] direction. It is noted that compact passivation surface layers of oxides protect these NWs from further oxidation, even after nearly two years of exposure to ambient conditions; furthermore, these NWs display homogeneous ferromagnetism along their axial direction revealing the domination of shape anisotropy on magnetic behavior. Importantly, the average value of magnetic induction strengths of Fe NWs (2.07 {±} 0.10 T) and Co NWs (1.83 {±} 0.15 T) is measured to be very close to the respective theoretical value, and it shows that the surface oxide layers do not affect the magnetic moments in NWs. Our results provide a useful synthesis approach for the fabrication of single-crystalline, defect-free metal NWs and give insight into the micromagnetic properties in ferromagnetic NWs based on the transmission electron microscopy measurements. [ABSTRACT FROM AUTHOR]

Conventional methods for fabricating multilayered ceramic membranes with ion conducting dense thin layers are often cumbersome, costly, and limited by poor adhesion between layers. Inspired by the architectural structure of the rooted grasses in soil, here, we report an interface‐reaction‐induced reassembly approach for the direct fabrication of Ce0.9Gd0.1O2−δ (CGO) thin layers rooted in the parent multilayered ceramic membranes by only one firing step. The CGO dense layers are very thin, and adhered strongly to the parent support layer, ensuring low ionic transport resistance and structural integrity of the multilayered membranes. When using as an oxygen permeable membrane for upgrading fossil‐fuel‐derived hydrogen, it shows very long durability in harsh conditions containing H2O, CH4, H2, CO2 and H2S. Furthermore, our approach is highly scalable and applicable to a wide variety of ion conducting thin layers, including Y0.08Zr0.92O2−δ, Ce0.9Sm0.1O2−δ and Ce0.9Pr0.1O2−δ. [ABSTRACT FROM AUTHOR]

Conventional methods for fabricating multilayered ceramic membranes with ion conducting dense thin layers are often cumbersome, costly, and limited by poor adhesion between layers. Inspired by the architectural structure of the rooted grasses in soil, here, we report an interface‐reaction‐induced reassembly approach for the direct fabrication of Ce0.9Gd0.1O2−δ (CGO) thin layers rooted in the parent multilayered ceramic membranes by only one firing step. The CGO dense layers are very thin, and adhered strongly to the parent support layer, ensuring low ionic transport resistance and structural integrity of the multilayered membranes. When using as an oxygen permeable membrane for upgrading fossil‐fuel‐derived hydrogen, it shows very long durability in harsh conditions containing H2O, CH4, H2, CO2 and H2S. Furthermore, our approach is highly scalable and applicable to a wide variety of ion conducting thin layers, including Y0.08Zr0.92O2−δ, Ce0.9Sm0.1O2−δ and Ce0.9Pr0.1O2−δ. [ABSTRACT FROM AUTHOR]

An approach is presented that allows independent determination of the mean inner potential contribution to a phase image of a highly doped layer in a semiconductor measured using off-axis electron holography, in order to quantify the contribution to the recorded phase from the dopant potential alone. The method takes into account the possible presence of both substitutional and interstitial dopant atoms and is used here to analyse an experimental phase image of 12 delta-doped B layers in Si that are separated from each other by <6 nm. [ABSTRACT FROM PUBLISHER]

Electron tomography is an essential imaging technique for the investigation of morphology and 3D structure of nanomaterials. This method, however, suffers from well-known missing wedge artifacts due to a restricted tilt range, which limits the objectiveness, repeatability and efficiency of quantitative structural analysis. Discrete tomography represents one of the promising reconstruction techniques for materials science, potentially capable of delivering higher fidelity reconstructions by exploiting the prior knowledge of the limited number of material compositions in a specimen. However, the application of discrete tomography to practical datasets remains a difficult task due to the underlying challenging mathematical problem. In practice, it is often hard to obtain consistent reconstructions from experimental datasets. In addition, numerous parameters need to be tuned manually, which can lead to bias and non-repeatability. In this paper, we present the application of a new iterative reconstruction technique, named TVR-DART, for discrete electron tomography. The technique is capable of consistently delivering reconstructions with significantly reduced missing wedge artifacts for a variety of challenging data and imaging conditions, and can automatically estimate its key parameters. We describe the principles of the technique and apply it to datasets from three different types of samples acquired under diverse imaging modes. By further reducing the available tilt range and number of projections, we show that the proposed technique can still produce consistent reconstructions with minimized missing wedge artifacts. This new development promises to provide the electron microscopy community with an easy-to-use and robust tool for high-fidelity 3D characterization of nanomaterials. [ABSTRACT FROM AUTHOR]

Liquid methanol has the potential to be the hydrogen energy carrier and storage medium for the future green economy. However, there are still many challenges before zero-emission, affordable molecular H2 can be extracted from methanol with high performance. Here, we present noble-metal-free Cu--WC/W plasmonic nanohybrids which exhibit unsurpassed solar H2 extraction efficiency from pure methanol of 2,176.7 µmol g-1 h-1 at room temperature and normal pressure. Macro-to-micro experiments and simulations unveil that local reaction microenvironments are generated by the coperturbation of WC/W's lattice strain and infrared-plasmonic electric field. It enables spontaneous but selective zero-emission reaction pathways. Such microenvironments are found to be highly cooperative with solar-broadband-plasmon-excited charge carriers flowing from Cu to WC surfaces for efficient stable CH3OH plasmonic reforming with C3-dominated liquid products and 100% selective gaseous H2. Such high efficiency, without any COx emission, can be sustained for over a thousand-hour operation without obvious degradation. [ABSTRACT FROM AUTHOR]

CO2‐oxidative dehydrogenation of propane (CO2‐ODHP) provides a promising route for propylene production. Sufficient propane conversion and propylene selectivity remain a great challenge due to the difficulty in activating inert propane and CO2 simultaneously. Herein, a Sn doped CeO2 supported Pt (Pt/Sn‐CeO2) catalyst in CO2‐ODHP reaction is reported. Sn doping appears to kill two birds with one stone for propane and CO2 activation. On the one side, it increases the electron density of Pt species via PtSn alloy formation, promoting propane adsorption and C−H bond cleavage. On the other side, it enhances oxygen vacancy concentrations of CeO2 support, facilitating CO2 dissociation. A higher propylene selectivity (63.9 % vs 22.3 %) was obtained on 0.1 wt % Pt/1.0 wt % Sn‐CeO2 than that on 0.1 wt % Pt/CeO2 with a comparable propane conversion (15.1 % vs 14.3 %) at 550 °C after 240 min on stream. This work provides a reference for designing efficient catalysts. [ABSTRACT FROM AUTHOR]

Reports that the nanocrystals of magnetite in a meteorite from Mars has provided the strongest, albeit controversial, evidence for the former presence of extraterrestrial life. Reason behind the morphological and size resemblance of the crystals from the meteorite to crystals formed by certain terrestrial bacteria; Usage of this meteorite in support of the biological origin of the extraterrestrial minerals.

The role of the crystal lattice, temperature and magnetic field for the spin structure formation in the 2D van der Waals magnet Fe5GeTe2 with magnetic ordering up to room temperature is a key open question. Using Lorentz transmission electron microscopy, we experimentally observe topological spin structures up to room temperature in the metastable pre-cooling and stable post-cooling phase of Fe5GeTe2. Over wide temperature and field ranges, skyrmionic magnetic bubbles form without preferred chirality, which is indicative of centrosymmetry. These skyrmions can be observed even in the absence of external fields. To understand the complex magnetic order in Fe5GeTe2, we compare macroscopic magnetometry characterization results with microscopic density functional theory and spin-model calculations. Our results show that even up to room temperature, topological spin structures can be stabilized in centrosymmetric van der Waals magnets. Magnetic skyrmionic bubbles have been reported for Fe5GeTe2 and other layered van der Waals materials and are good candidates for applications in spintronics. Here, the authors report a near room temperature skyrmionic structure for Fe5GeTe2 and study the magnetic ordering for pre and post-cooling states using a combination of magnetic measurements and DFT calculations. [ABSTRACT FROM AUTHOR]

Inline holography in the transmission electron microscope is a versatile technique which provides real-space phase information that can be used for the correction of imaging aberrations, as well as for measuring electric and magnetic fields and strain distributions. It is able to recover high-spatial-frequency contributions of the phase effectively but suffers from the weak transfer of low-spatial-frequency information, as well as from incoherent scattering. Here, we combine gradient flipping and phase prediction in an iterative flux-preserving focal series reconstruction algorithm with incoherent background subtraction that gives extensive access to the missing low spatial frequencies. A procedure for optimizing the reconstruction parameters is presented, and results from Fe-filled C nanospheres, and MgO cubes are compared with phase images obtained using off-axis holography. [ABSTRACT FROM AUTHOR]

Electron holography is a powerful technique for characterizing electrostatic potentials, charge distributions, electric and magnetic fields, strain distributions and semiconductor dopant distributions with sub-nm spatial resolution. Mapping internal electrostatic and magnetic fields within nanoparticles and other low-dimensional materials by TEM requires both high spatial resolution and high phase sensitivity. Carrying out such an analysis fully quantitatively is even more challenging, since artefacts such as dynamical electron scattering may strongly affect the measurement. In-line electron holography, one of the variants of electron holography, features high phase sensitivity at high spatial frequencies, but suffers from inefficient phase recovery at low spatial frequencies. Off-axis electron holography, in contrast, can recover low spatial frequency phase information much more reliably, but is less effective in retrieving phase information at high spatial frequencies when compared to in-line holography. We investigate gold nanoparticles using hybrid electron holography at both atomic-resolution and intermediate magnification. Hybrid electron holography is a novel technique that synergistically combines off-axis and in-line electron holography, allowing the measurement of the complex wave function describing the scattered electrons with excellent signal-to-noise properties at both high and low spatial frequencies. The effect of dynamical electron scattering is minimized by beam tilt averaging. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO2) is a well-known thermochromic material with large IR modulating ability, promising for energy-saving smart windows. The main drawbacks of VO2 are its high phase transition temperature (τc = 68 °C), low luminous transmission (Tlum), and weak solar modulating ability (ΔTsol). In this paper, the terbium cation (Tb3+) doping was first reported to reduce τc and increase Tlum of VO2 thin films. Compared with pristine VO2, 2 at. % doping level gives both enhanced Tlum and ΔTsol from 45.8% to 54.0% and 7.7% to 8.3%, respectively. The Tlum increases with continuous Tb3+ doping and reaches 79.4% at 6 at. % doping level, representing ~73.4% relative increment compared with pure VO2. This has surpassed the best reported doped VO2 thin films. The enhanced thermochromic properties is meaningful for smart window applications of VO2 materials. [ABSTRACT FROM AUTHOR]

Quantitative materials characterization using electron holography frequently requires knowledge of the mean inner potential, but reported experimental mean inner potential measurements can vary widely. Using density functional theory, we have simulated the mean inner potential for materials with a range of different surface conditions and geometries. We use both “thin-film” and “nanowire” specimen geometries. We consider clean bulk-terminated surfaces with different facets and surface reconstructions using atom positions from both structural optimization and experimental data and we also consider surfaces both with and without adsorbates. We find that the mean inner potential is surface-dependent, with the strongest dependency on surface adsorbates. We discuss the outlook and perspective for future mean inner potential measurements. [ABSTRACT FROM AUTHOR]

Since the discovery of Rochelle salt a century ago, ferroelectric materials have been investigated extensively due to their robust responses to electric, mechanical, thermal, magnetic, and optical fields. These features give rise to a series of ferroelectric‐based modern device applications such as piezoelectric transducers, memories, infrared detectors, nonlinear optical devices, etc. On the way to broaden the material systems, for example, from three to two dimensions, new phenomena of topological polarity, improper ferroelectricity, magnetoelectric effects, and domain wall nanoelectronics bear the hope for next‐generation electronic devices. In the meantime, ferroelectric research has been aggressively extended to more diverse applications such as solar cells, water splitting, and CO2 reduction. In this review, the most recent research progress on newly emerging ferroelectric states and phenomena in insulators, ionic conductors, and metals are summarized, which have been used for energy storage, energy harvesting, and electrochemical energy conversion. Along with the intricate coupling between polarization, coordination, defect, and spin state, the exploration of transient ferroelectric behavior, ionic migration, polarization switching dynamics, and topological ferroelectricity, sets up the physical foundation ferroelectric energy research. Accordingly, the progress in understanding of ferroelectric physics is expected to provide insightful guidance on the design of advanced energy materials. [ABSTRACT FROM AUTHOR]

The shuttling behavior and sluggish conversion kinetics of intermediate lithium polysulfides (LiPS) represent the main obstacles to the practical application of lithium–sulfur batteries (LSBs). Herein, an innovative sulfur host is proposed, based on an iodine‐doped bismuth selenide (I‐Bi2Se3), able to solve these limitations by immobilizing the LiPS and catalytically activating the redox conversion at the cathode. The synthesis of I‐Bi2Se3 nanosheets is detailed here and their morphology, crystal structure, and composition are thoroughly. Density‐functional theory and experimental tools are used to demonstrate that I‐Bi2Se3 nanosheets are characterized by a proper composition and micro‐ and nano‐structure to facilitate Li+ diffusion and fast electron transportation, and to provide numerous surface sites with strong LiPS adsorbability and extraordinary catalytic activity. Overall, I‐Bi2Se3/S electrodes exhibit outstanding initial capacities up to 1500 mAh g−1 at 0.1 C and cycling stability over 1000 cycles, with an average capacity decay rate of only 0.012% per cycle at 1 C. Besides, at a sulfur loading of 5.2 mg cm−2, a high areal capacity of 5.70 mAh cm−2 at 0.1 C is obtained with an electrolyte/sulfur ratio of 12 µL mg−1. This work demonstrated that doping is an effective way to optimize the metal selenide catalysts in LSBs. [ABSTRACT FROM AUTHOR]

A study on the microstructure of argon-beam activated n-GaSb/n-Ga0.32In0.68P bond interfaces is presented, focusing on the behavior of the bond upon thermal annealing and the relationship with electrical bond properties. Structural investigations of annealed samples utilizing high-resolution transmission electron microscopy combined with energy dispersive x-ray spectroscopy are discussed and compared with electrical current-voltage measurements. An amorphous interlayer of ~1.4nm thickness between the n-GaSb and n-Ga0.32In0.68P originates from the argon sputtering process. This layer continuously recrystallizes upon thermal annealing, creating a mostly crystalline interface at an annealing temperature of 500 °C. Additionally at 400 °C, In enrichment is observed in the near-surface regions of GaSb and pores are generated at the interface. At 500 °C, larger pores are observed and the In enrichment continues, leading to the formation of crystalline In precipitates within the GaSb crystal. The observed changes in the interfacial microstructure upon annealing correlate with variations in the electrical bond resistances. All bonds show ohmic IV-characteristics with resistances in the range of few mΩcm2. However, the bond resistance decreases after annealing at temperatures up to 350 °C but increases after annealing at higher temperatures. This behaviour agrees with the observation of reduced amorphous layer thickness upon annealing and with the formation of new induced interfacial defects for annealing temperatures above 350 °C. [ABSTRACT FROM AUTHOR]

Hybrid (organic shell–inorganic core) nanoparticles have important applications in nanomedicine. Although the inorganic components of hybrid nanoparticles can be characterized readily using conventional transmission electron microscopy (TEM) techniques, the structural and chemical arrangement of the organic molecular components remains largely unknown. Here, we apply TEM to the physico-chemical characterization of Au nanoparticles that are coated with plasma-polymerized-allylamine, an organic compound with the formula C 3 H 5 NH 2 . We discuss the use of energy-filtered TEM in the low-energy-loss range as a contrast enhancement mechanism for imaging the organic shells of such particles. We also study electron-beam-induced crystallization and amorphization of the shells and the formation of graphitic-like layers that contain both C and N. The resistance of the samples to irradiation by high-energy electrons, which is relevant for optical tuning and for understanding the degree to which such hybrid nanostructures are stable in the presence of biomedical radiation, is also discussed. [ABSTRACT FROM AUTHOR]

• The feasibility analysis of EMCD measurements in three orthogonal directions are conducted for 2D magnets to provide a guide for future experiments under zone axial orientation. • The low voltage EMCD technique is beneficial to 2D magnets at a ultrathin thickness. • The number of atomic layers could lead to a strong modulation of EMCD signals under zone axial orientation. • The slight beam tilt can be utilized to enhance the EMCD signals under zone axial orientation. • The SNR and required electron dose are quantitatively evaluated for EMCD measurement on 2D magnets. Two-dimensional (2D) van der Waals magnets have drawn considerable attention in recent years triggered by the huge interest in novel magnetism and spintronic devices. Magnetic measurement of 2D van der Waals (vdW) magnets is crucial to understand the physical origin of magnetism in 2D limits. Therefore, advanced magnetic characterization techniques are highly required. However, only a limited number of such techniques are available due to the extremely small volume of 2D vdW magnets. Here, we introduce the electron magnetic chiral dichroism (EMCD) technique in transmission electron microscope (TEM) to measure 2D vdW crystals. In comparison with some other already-employed techniques in 2D magnets, EMCD is able to quantitatively measure magnetic parameters in three orthogonal directions at nanometer or even at atomic scale. We then perform EMCD simulations on several typical 2D vdW magnets with respect to the accelerating voltage, the number of atomic layers and beam tilt under zone axial orientation. The intensity and distribution of EMCD signals in three orthogonal directions are given in the diffraction plane, thereby providing an optimized design to achieve EMCD measurements. Finally, we discuss the signal-to-noise-ratio and required electron dose in order to obtain a measurable EMCD signal for 2D vdW magnets. Our results provide a feasibility analysis and guideline to measure 2D vdW magnets in future experiments. [ABSTRACT FROM AUTHOR]

Conformal coating of silicon (Si) anode particles is a common strategy for improving their mechanical integrity, to mitigate battery capacity fading due to particle volume expansion, which can result in particle crumbling due to lithiation induced strain and excessive solid–electrolyte interface formation. Here, we use operando transmission electron microscopy in an open cell to show that TiO2 coatings on Si/SiO2 particles undergo thickness dependent rupture on battery cycling where thicker coatings crumble more readily than thinner (∼5 nm) coatings, which corroborates the difference in their capacities. [ABSTRACT FROM AUTHOR]