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Honeycomb‐layered oxides with monovalent or divalent, monolayered cationic lattices generally exhibit myriad crystalline features encompassing rich electrochemistry, geometries, and disorders, which particularly places them as attractive material candidates for next‐generation energy storage applications. Herein, global honeycomb‐layered oxide compositions, Ag2M2TeO6 (M=Ni,Mg,etc$M = \rm Ni, Mg, etc$.) exhibiting Ag$\rm Ag$ atom bilayers with sub‐valent states within Ag‐rich crystalline domains of Ag6M2TeO6 and Ag$\rm Ag$‐deficient domains of Ag2−xNi2TeO6${\rm Ag}_{2 - x}\rm Ni_2TeO_6$ (0

Abstract Honeycomb‐layered oxides with monovalent or divalent, monolayered cationic lattices generally exhibit myriad crystalline features encompassing rich electrochemistry, geometries, and disorders, which particularly places them as attractive material candidates for next‐generation energy storage applications. Herein, global honeycomb‐layered oxide compositions, Ag2M2TeO6 (M=Ni,Mg,etc$M = m Ni, Mg, etc$.) exhibiting Ag$ m Ag$ atom bilayers with sub‐valent states within Ag‐rich crystalline domains of Ag6M2TeO6 and Ag$ m Ag$‐deficient domains of Ag2−xNi2TeO6${ m Ag}_{2 - x} m Ni_2TeO_6$ (0

Double perovskites with cation ordering allow the coexistence of ferroelectricity and magnetization in the same phase, and thus become a good candidate for room-temperature multiferroic materials. In this paper, we successfully synthesized A- and B-site ordered double perovskites NaLnBWO 6 (Ln = La, Nd, and B Mg, Mn) ceramics, and investigated their microstructure by combining X-ray diffraction, aberration-corrected scanning transmission electron microscopy, and optical second harmonic generation measurements. At room temperature, both NaLaMgWO 6 and NaNdMgWO 6 ceramics possess the space group of P 2 1 / m , while NaLaMnWO 6 has a polar crystal structure (P 2 1) without inversion symmetry. All three samples exhibit the A-site layered ordering and B-site rock-salt ordering as directly imaged by the HAADF-STEM images. The observed structural domains arising from the cation ordering well explain the nonswitchable ferroelectric polarization due to a large energy barrier. These findings suggest that it is necessary to eliminate structural domains during the sample synthesis for obtaining large ferroelectric polarization in double perovskites. [ABSTRACT FROM AUTHOR]

Revealing the evolutional pathway of the nucleation and crystallization of nanostructures at the atomic scale is crucial for understanding the complex growth mechanisms at the early stage of new substances and spices. Real-time discrimination of the atomic mechanism of a nanodroplet transition is still a formidable challenge. Here, taking advantage of the high temporal and spatial resolution of transmission electron microscopy, the detailed growth pathway of Pb nanodroplets at the early stage of nucleation was directly observed by employing electron beams to induce the nucleation, growth, and fusion process of Pb nanodroplets based on PbTiO3 nanowires. Before the nucleation of Pb nanoparticles, the atoms began to precipitate when they were irradiated by electrons, forming a local crystal structure, and then rapidly and completely crystallized. Small nanodroplets maintain high activity and high density and gradually grow and merge into stable crystals. The whole process was recorded and imaged by HRTEM in real time. The growth of Pb nanodroplets advanced through the classical path and instantaneous droplet coalescence. These results provide an atomic-scale insight on the dynamic process of solid/solid interface, which has implications in thin-film growth and advanced nanomanufacturing. [ABSTRACT FROM AUTHOR]

The size-selected Au (923 ± 23 atoms) cluster soft-landed on amorphous carbon and MgO(100) surface were imaged by transmission electron microscope (TEM) and aberration-corrected scanning transmission electron microscopy (AC-STEM). Au923 clusters presents multiplicity geometries on amorphous carbon and epitaxial relationship with MgO(100) surface. It is found that there is a projected size of Au923 clusters shrinking when landed on the MgO surface. This is due to the limited observation direction caused by the epitaxial relationship between the facet of Au923 clusters and Mg(100) lattice. This study highlights the different observation direction of electron microscopy images of clusters can result in the change of projected area. Such visual size changes can not be neglected in the cluster studies at atomic resolution. [ABSTRACT FROM AUTHOR]

Galfenol owing excellent deformation due to lattice softening are regarded as a new generation of smart magnetostrictive materials. However, the lack of direct probes of phase transformation and intermediate phase related to lattice softening blocks the comprehensive understanding of their intrinsic magnetostrictive mechanism and further improvement of their performance. In this work, we firstly report an atomic observation of ω phase transformation in Galfenol under low temperature aging by spherical aberration-corrected transmission electron microscopy. The ω precipitates with two variants are directly probed to be decomposed from FeGa bcc matrix with the assistances of both spinodal decomposition and displacive transformation. Their orientation relationships with the long range ordered bcc structure of D03 can be well indexed into (0003)ω1[112¯0]ω1 || (44¯4¯)D03[01¯1]D03 || (4¯401¯)ω2[112¯0]ω2. Density functional theory calculations unveil the precipitate of ω phase in Galfenol is theoretically possible. Further magnetostrictive measurements reveal the ω phase precipitates deteriorate the magnetostriction of Galfenol as empirically expected. Our work is believed to contribute a further insight of precipitate and structural evolution in Galfenol and is significant to maintain the magnetostriction performance of Galfenol in service.

Revealing the evolutional pathway of the nucleation and crystallization of nanostructures at the atomic scale is crucial for understanding the complex growth mechanisms at the early stage of new substances and spices. Real-time discrimination of the atomic mechanism of a nanodroplet transition is still a formidable challenge. Here, taking advantage of the high temporal and spatial resolution of transmission electron microscopy, the detailed growth pathway of Pb nanodroplets at the early stage of nucleation was directly observed by employing electron beams to induce the nucleation, growth, and fusion process of Pb nanodroplets based on PbTiO3 nanowires. Before the nucleation of Pb nanoparticles, the atoms began to precipitate when they were irradiated by electrons, forming a local crystal structure, and then rapidly and completely crystallized. Small nanodroplets maintain high activity and high density and gradually grow and merge into stable crystals. The whole process was recorded and imaged by HRTEM in real time. The growth of Pb nanodroplets advanced through the classical path and instantaneous droplet coalescence. These results provide an atomic-scale insight on the dynamic process of solid/solid interface, which has implications in thin-film growth and advanced nanomanufacturing.

Abstract Understanding classical and nonclassical mechanisms of crystal nucleation and growth at the atomic scale is of great interest to scientists in many disciplines. However, fulfilling direct atomic‐scale observation still poses a significant challenge. Here, by taking a thin amorphous bismuth (Bi) metal nanosheet as a model system, direct atomic resolution of the crystal nucleation and growth initiated from an amorphous state of Bi metal under electron beam inside an aberration‐corrected transmission electron microscope is provided. It is shown that the crystal nucleation and growth in the phase transformation of Bi metal from amorphous to crystalline structure takes place via the particle‐mediated nonclassical mechanism instead of the classical atom‐mediated mechanism. The dimension of the smaller particles in two contacted nanoparticles and their mutual orientation relationship are critical to governing several coalescence pathways: total rearrangement pathway, grain boundary migration‐dominated pathway, and surface migration‐dominated pathway. Sequential strain analyses imply that migration of the grain boundary is driven by the strain difference in two Bi nanocrystals and the coalescence of nanocrystals is a defect reduction process. The findings may provide useful information to clarify the nanocrystal growth mechanisms of other materials on the atomic scale.

Zircaloy-4 (Zr-1.5%Sn-0.2%Fe-0.1%Cr wt%) was electrochemically charged with deuterium to create deuterides and subsequently analysed with atom probe tomography and scanning transmission electron microscopy to understand zirconium hydride formation and embrittlement. At the interface between the hexagonal close packed (HCP) α-Zr matrix and a face centred cubic (FCC) δ deuteride (ZrD 1.5–1.65 ), a HCP ζ phase deuteride (ZrD 0.25–0.5 ) has been observed. Furthermore, Sn is rejected from the deuterides and segregates to the deuteride/α-Zr reaction front. [ABSTRACT FROM AUTHOR]

Abstract: Understanding classical and nonclassical mechanisms of crystal nucleation and growth at the atomic scale is of great interest to scientists in many disciplines. However, fulfilling direct atomic‐scale observation still poses a significant challenge. Here, by taking a thin amorphous bismuth (Bi) metal nanosheet as a model system, direct atomic resolution of the crystal nucleation and growth initiated from an amorphous state of Bi metal under electron beam inside an aberration‐corrected transmission electron microscope is provided. It is shown that the crystal nucleation and growth in the phase transformation of Bi metal from amorphous to crystalline structure takes place via the particle‐mediated nonclassical mechanism instead of the classical atom‐mediated mechanism. The dimension of the smaller particles in two contacted nanoparticles and their mutual orientation relationship are critical to governing several coalescence pathways: total rearrangement pathway, grain boundary migration‐dominated pathway, and surface migration‐dominated pathway. Sequential strain analyses imply that migration of the grain boundary is driven by the strain difference in two Bi nanocrystals and the coalescence of nanocrystals is a defect reduction process. The findings may provide useful information to clarify the nanocrystal growth mechanisms of other materials on the atomic scale. [ABSTRACT FROM AUTHOR]

Edge structures are low-dimensional defects unavoidable in layered materials of the transition metal dichalcogenides (TMD) family. Among the various types of such structures, the armchair (AC) and zigzag (ZZ) edge types are the most common. It has been predicted that the presence of intrinsic strain localized along these edges structures can have direct implications for the customization of their electronic properties. However, pinning down the relation between local structure and electronic properties at these edges is challenging. Here, we quantify the local strain field that arises at the edges of MoS2 flakes by combining aberration-corrected transmission electron microscopy (TEM) with the geometrical-phase analysis (GPA) method. We also provide further insight on the possible effects of such edge strain on the resulting electronic behavior by means of electron energy loss spectroscopy (EELS) measurements. Our results reveal that the two-dominant edge structures, ZZ and AC, induce the formation of different amounts of localized strain fields. We also show that by varying the free edge curvature from concave to convex, compressive strain turns into tensile strain. These results pave the way toward the customization of edge structures in MoS2, which can be used to engineer the properties of layered materials and thus contribute to the optimization of the next generation of atomic-scale electronic devices built upon them. [ABSTRACT FROM AUTHOR]

Ferroelectric crystals feature asymmetric or polar structures that are switchable under an external electric field, holding promise for information storage. Nanoscale ferroelectrics might exhibit various exotic domain configurations and polar topologies, such as full flux-closure, vortex, skyrmion, and meron. These topological domains were theoretically switchable and may give rise to an unusually high density of memory bits. They would also undergo unusual phase transitions and form hidden, collective polar topological states under external stimulations. Similar domains and spin topologies are well known in ferromagnetic materials, and their topological properties and dynamics are under intensive investigation. However, in ferroelectric materials, the coupling of polarizations to spontaneous strains would be so pronounced that the formations of polar topologies were believed to be impossible. How to stabilize the polar topologies in ferroelectrics, especially in nanoscale ferroelectrics, was known as a big challenge. In this overview, we summarize the recent progress in polar topologies in ferroelectric oxides. We start from a review the discovery of polar topologies, including flux-closure quadrant, vortex, bubble, skyrmion, meron lattice, polar waves, and center-type domains. We also focus on the effects of mechanical and electrical boundary conditions and sample size on the formation of topological structures. In the meanwhile, we emphasize the use of aberration-corrected transmission electron microscope which enables to visualize the ion displacement at a sub-Ångström resolution in real space. And at the end, we envision several aspects to be considered in the future, such as imaging three dimensional (3D) atomic morphology of the topological polar structures, exploring novel polar topologies in other possible systems, and addressing the coupling of polar topologies with flexoelectricity by a combination of quantitative transmission electron microscopy and relevant theoretical approaches. [ABSTRACT FROM AUTHOR]

The atomic structure, stability, and dynamics of defects in hexagonal boron nitride (h-BN) are investigated using an aberration-corrected transmission electron microscope operated at 80 kV between room temperature and 1000 °C. At temperatures above 700 °C, parallelogram- and hexagon-shaped defects with zigzag edges become prominent, in contrast to the triangular defects typically observed at lower temperatures. The appearance of 120° corners at defect vertices indicates the coexistence of both N- and B-terminated zigzag edges in the same defect. In situ dynamics studies show that the hexagonal holes grow by electron-induced sputtering of B-N chains, and that at high temperatures these chains can migrate from one defect corner to another. We complement the experiments with first-principles calculation which consider the thermal equilibrium formation energy of different defect configurations. It is shown that, below a critical defect size, hexagonal defects have the lowest formation energy and therefore are the more-stable configuration, and triangular defects are energetically metastable but can be "frozen in" under experimental conditions. We also discuss the possible contributions of several dynamic processes to the temperature-dependent defect formation. [ABSTRACT FROM AUTHOR]

Aberration-corrected transmission electron microscope images taken under optimum-defocus conditions or processed offline can correctly reflect the projected crystal structure with atomic resolution. However, dynamical scattering, which will seriously influence image contrast, is still unavoidable. Here, the multislice image simulation approach was used to quantify the impact of dynamical scattering on the contrast of aberration-corrected images for a 3 C -SiC specimen with changes in atomic occupancy and thickness. Optimum-defocus images with different spherical aberration ( C S ) coefficients, and structure images restored by deconvolution processing, were studied. The results show that atomic-column positions and the atomic occupancy for SiC ‘dumbbells’ can be determined by analysis of image contrast profiles only below a certain thickness limit. This limit is larger for optimum-defocus and restored structure images with negative C S coefficient than those with positive C S coefficient. The image contrast of C (or Si) atomic columns with specific atomic occupancy changes differently with increasing crystal thickness. Furthermore, contrast peaks for C atomic columns overlapping with neighboring peaks of Si atomic columns with varied Si atomic occupancy, which is enhanced with increasing crystal thickness, can be neglected in restored structure images, but the effect is substantial in optimum-defocus images. [ABSTRACT FROM AUTHOR]

It has been a long-lived research topic in the field of heterogeneous catalysts to find a way of stabilizing supported gold catalyst against sintering. Herein, we report highly stable AuIr bimetallic nanoparticles on TiO2 synthesized by sequential deposition-precipitation. To reveal the physical origin of the high stability of AuIr/TiO2, we used aberration-corrected scanning transmission electron microscopy (STEM), STEM-tomography, and density functional theory (DFT) calculations. Three-dimensional structures of AuIr/TiO2 obtained by STEM-tomography indicate that AuIr nanoparticles on TiO2 have intrinsically lower free energy and less driving force for sintering than Au nanoparticles. DFT calculations on segregation behavior of AuIr slabs on TiO2 showed that the presence of Ir near the TiO2 surface increases the adhesion energy of the bimetallic slabs to the TiO2 and the attractive interactions between Ir and TiO2 lead to higher stability of AuIr nanoparticles as compared to Au nanoparticles. [ABSTRACT FROM AUTHOR]

The incommensurate modulated structure (IMS) of Bi 2 Sr 1.6 La 0.4 CuO 6+ δ (BSLCO) has been studied by aberration-corrected transmission electron microscopy in combination with a high-dimensional (HD) space description. Two images are deconvoluted in the negative C s imaging (NCSI) and positive C s imaging (PCSI) modes. Similar results for the IMS have been obtained from two corresponding projected potential maps (PPMs), and the size of the dots representing atoms in the NCSI PPM is found to be smaller than that in the PCSI PPM. Considering that the object size is one of the factors that influence the precision of the structural determination, modulation functions for all unoverlapped atoms in BSLCO were determined on the basis of the NCSI PPM in combination with the HD space description. [ABSTRACT FROM AUTHOR]

Abstract: Interstitial titanium ions in TiO2 substrates with gold nanoparticle (Au/TiO2) are found to be observable by aberration corrected transmission electron microscopy. The local distribution of the interstitial Ti ions was obtained from TEM images. The interstitial ions are found to exist at a perimeter/interface of Au/TiO2, whereas they are deficient in a peripheral region of the gold nanoparticles. The interstitial ions at the perimeter/interface of Au/TiO2 need attention in CO oxidation catalysis. [Copyright &y& Elsevier]

Single Pd atom doped Au 23 Pd 1 clusters stabilized by polyvinylpyrrolidone (Au 23 Pd 1 :PVP) were selectively synthesized by kinetically controlled coreduction of the Au and Pd precursor ions. The geometric structure of Au 23 Pd 1 :PVP was investigated by density functional theory calculation, aberration-corrected transmission electron microscopy, extended X-ray absorption fine structure analysis, Fourier transform infrared spectroscopy of adsorbed CO, and hydrogenation catalysis. These results showed that Au 23 Pd 1 :PVP takes polydisperse but the same atomic arrangements as undoped Au 24 :PVP while exposing all the atoms including the Pd atom on the surface. Au 23 Pd 1 :PVP exhibited a significantly higher catalytic activity than Au 24 :PVP for the aerobic oxidation of p -substituted benzyl alcohols. The kinetic studies showed that the rate-determining step was the hydride abstraction from the α-carbon of the alkoxides for both systems. The activation energy for hydride abstraction by Au 23 Pd 1 :PVP was lower than that by Au 24 :PVP, indicating that the doped Pd atom acts as the active center.

A single layer of LaAlO3 with a nominal thickness of one unit cell, which is sandwiched between a SrTiO3 substrate and a SrTiO3 capping layer, is quantitatively investigated by high-resolution transmission electron microscopy. By the use of an aberration-corrected electron microscope and by employing sophisticated numerical image simulation procedures, significant progress is made in two aspects. First, the structural as well as the chemical features of the interface are determined simultaneously on an atomic scale from the same specimen area. Second, the evaluation of the structural and chemical data is carried out in a fully quantitative way on the basis of the absolute image contrast, which has not been achieved so far in materials science investigations using high-resolution electron microscopy. Considering the strong influence of even subtle structural details on the electronic properties of interfaces in oxide materials, a fully quantitative interface analysis, which makes positional data available with picometer precision together with the related chemical information, can contribute to a better understanding of the functionality of such interfaces. [ABSTRACT FROM AUTHOR]

We explore the possibility of applying physical phase plates (PPs) in combination with aberration-corrected transmission electron microscopy. Phase-contrast transfer characteristics are calculated and compared for a thin-film based Zernike PP, a hole-free (HF) or Volta PP and an electrostatic Zach PP, considering their phase-shifting properties in combination with partial spatial coherence. The effect of slightly converging illumination conditions, often used in high-resolution applications, on imaging with PPs is discussed. Experiments with an unheated Zernike PP applied to various nanomaterial specimens and a qualitative analysis clearly demonstrates the general compatibility of PPs and aberration-corrected transmission electron microscopy. Calculations and experiments show the benefits of the approach, among which is a strong phase-contrast enhancement of a large range of spatial frequencies. This allows the simultaneous imaging of atomic-resolution structures and morphological features at the nanometer scale, with maximum phase contrast. The calculations can explain why the HFPP damps contrast transfer at higher spatial frequencies., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Peak-finding procedures and the geometric phase method of quantitative high resolution electron microscopy (qHRTEM) were applied to determine the local strain and the chemical composition of nanostructured semiconductor materials. The growth of the structures investigated was induced by minimization of strain energy. The analysis of strain distribution is necessary for the understanding of the self-organized formation of nanostructures. The possibilities and limitations of the methods are discussed in detail by analysing HRTEM images of (Si,Ge) islands and of a double layer of stacked quantum dots of (In,Ga)As and Ga(Sb,As). [ABSTRACT FROM AUTHOR]

[Display omitted] • Atomic observation of ω phase transformation in Galfenol was reported firstly. • The displacive-diffusive transformation in Galfenol was confirmed. • A new insight into the precipitate and structural evolution in Galfenol was provided. • Our work may be significant to maintain the magnetostriction performance of Galfenol in service. Galfenol owing excellent deformation due to lattice softening are regarded as a new generation of smart magnetostrictive materials. However, the lack of direct probes of phase transformation and intermediate phase related to lattice softening blocks the comprehensive understanding of their intrinsic magnetostrictive mechanism and further improvement of their performance. In this work, we firstly report an atomic observation of ω phase transformation in Galfenol under low temperature aging by spherical aberration-corrected transmission electron microscopy. The ω precipitates with two variants are directly probed to be decomposed from FeGa bcc matrix with the assistances of both spinodal decomposition and displacive transformation. Their orientation relationships with the long range ordered bcc structure of D0 3 can be well indexed into (0003) ω1 [ 11 2 ¯ 0 ] ω1 || (4 4 ¯ 4 ¯ ) D03 [ 0 1 ¯ 1 ] D03 || ( 4 ¯ 40 1 ¯) ω2 [ 11 2 ¯ 0 ] ω2. Density functional theory calculations unveil the precipitate of ω phase in Galfenol is theoretically possible. Further magnetostrictive measurements reveal the ω phase precipitates deteriorate the magnetostriction of Galfenol as empirically expected. Our work is believed to contribute a further insight of precipitate and structural evolution in Galfenol and is significant to maintain the magnetostriction performance of Galfenol in service. [ABSTRACT FROM AUTHOR]

Flexoelectricity is an effective tool in modulating the crystallographic structures and properties of oxides for multifunctional applications. However, engineering the nonuniform strain to obtain tunable flexoelectric behaviors at the atomic scale remains an ongoing challenge in conventional substrate-imposed ferroelectric films. Here, the regulatable flexoelectric behaviors are demonstrated at atomic scale in [110]-oriented BiFeO 3 thin films, which are triggered by the strain-field coupling of high-density interfacial dislocations. Using aberration-corrected scanning transmission electron microscopy, the asymmetric polarization rotation around the single dislocation is revealed, which is induced by the gradient strain fields of the single dislocation. These strain fields are highly correlated to generate huge strain gradients between neighboring dislocations, and thereby, serial flexoelectric responses are engineered as a function of dislocation spacings in thicker BiFeO 3 films. This work opens a pathway for the modulation of flexoelectric responses in ferroelectrics, which could be extended to other functional materials to create exotic phenomena.

Granular magnetic systems consisting of magnetic nanoparticles embedded in a nonmagnetic metallic matrix have emerged as an attractive building block for nanodevices. A key challenge for building interface-based nanodevice applications, such as magnetic memory devices, is to clearly know about the influences of interfacial roughness on the scattering of conduction electrons. Here, we demonstrate a granular magnetic system composed of Co and Cu nanoparticles and further link the atomic structure of the Co/Cu interface to the scattering mechanism of conduction electrons. The multiple scattering is caused by the dislocations at the rough interface, which lead to a reduction of conduction efficiency and an increase of energy consumption. These dislocations mostly originate from the lattice defects on the surface of nanoparticles, the lattice mismatch of two crystal structures, and the different surface energies. Based on the negative effects of a rough interface on electronic transport, we first develop a nanometal-fuse resistor, which could hopefully be used in the protection circuits of nanodevices. Our results may open up the possibility of implementing the low-dimensional granular magnetic materials in nanodevice applications.

Uncovering kinetics of sublimation atomically is critical to understanding both natural phenomena and advanced manufacturing technologies. Here, direct in situ atomic‐scale observations to understand the effects of size, surface, and defects in the sublimation process of supported silver nanoparticles upon heating within an aberration‐corrected transmission electron microscopy are conducted. Atomic‐scale evidence to sublimation and atomic rearrangement in small Ag nanoparticles during heating is provided, and it is demonstrated that the sublimation‐induced stable surfaces in the particles with a size smaller than ≈30 nm are {111} and {100} planes. The role of surface energy and defects in the uniform and nonuniform sublimation pathways at the atomic scale is also revealed, and it is found that the nanoparticles with low surface energy tend to undergo a uniform sublimation pathway, while those with high surface energy or five‐fold twin grain boundary proceed via a nonuniform sublimation pathway. Further dynamic analysis unravels a critical size of ≈8 nm for the transformation from linear to nonlinear sublimation rates in the two pathways. These findings demonstrate that the size, shape, and defects are of paramount importance for the sublimation dynamics in the first‐order phase transformation, helping to advance the general understanding of many technological applications. [ABSTRACT FROM AUTHOR]

Edge structures are low-dimensional defects unavoidable in layered materials of the transition metal dichalcogenides (TMD) family. Among the various types of such structures, the armchair (AC) and zigzag (ZZ) edge types are the most common. It has been predicted that the presence of intrinsic strain localized along these edges structures can have direct implications for the customization of their electronic properties. However, pinning down the relation between local structure and electronic properties at these edges is challenging. Here, we quantify the local strain field that arises at the edges of MoS 2 flakes by combining aberration-corrected transmission electron microscopy (TEM) with the geometrical-phase analysis (GPA) method. We also provide further insight on the possible effects of such edge strain on the resulting electronic behavior by means of electron energy loss spectroscopy (EELS) measurements. Our results reveal that the two-dominant edge structures, ZZ and AC, induce the formation of different amounts of localized strain fields. We also show that by varying the free edge curvature from concave to convex, compressive strain turns into tensile strain. These results pave the way toward the customization of edge structures in MoS 2 , which can be used to engineer the properties of layered materials and thus contribute to the optimization of the next generation of atomic-scale electronic devices built upon them.

Unraveling dynamical processes of liquid droplets at liquid/solid interfaces and the interfacial ordering is critical to understanding solidification, liquid-phase epitaxial growth, wetting, liquid-phase joining, crystal growth, and lubrication processes, all of which are linked to different important applications in material science. In this work, we observe direct in situ atomic-scale behavior of Bi droplets segregated on SrBi 2 Ta 2 O 9 by using aberration-corrected transmission electron microscopy and demonstrate ordered interface and surface structures for the droplets on the oxide at the atomic scale and unravel a nucleation mechanism involving droplet coalescence at the liquid/solid interface. We identify a critical diameter of the formed nanocrystal in stabilizing the crystalline phase and reveal lattice-induced fast crystallization of the droplet at the initial stage of the coalescence of the nanocrystal with the droplet. Further sequential observations show the stepped coalescence and growth mechanism of the nanocrystals at the atomic scale. These results offer insights into the dynamic process at liquid/solid interfaces, which may have implications for many functionalities of materials and their applications.

It has been a long-lived research topic in the field of heterogeneous catalysts to find a way of stabilizing supported gold catalyst against sintering. Herein, we report highly stable AuIr bimetallic nanoparticles on TiO2 synthesized by sequential deposition-precipitation. To reveal the physical origin of the high stability of AuIr/TiO2, we used aberration-corrected scanning transmission electron microscopy (STEM), STEM-tomography, and density functional theory (DFT) calculations. Three-dimensional structures of AuIr/TiO2 obtained by STEM-tomography indicate that AuIr nanoparticles on TiO2 have intrinsically lower free energy and less driving force for sintering than Au nanoparticles. DFT calculations on segregation behavior of AuIr slabs on TiO2 showed that the presence of Ir near the TiO2 surface increases the adhesion energy of the bimetallic slabs to the TiO2 and the attractive interactions between Ir and TiO2 lead to higher stability of AuIr nanoparticles as compared to Au nanoparticles.