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The vapor diffusion sol–gel (VDSG) method was employed for the room-temperature synthesis of ∼10 nm, aliovalently doped 0.4, 0.8, and 1.6 mol% La:BaTiO3 and 0.4, 0.6, and 1.2 mol% Dy:BaTiO3 nanocrystals. Maximum ensemble relative permittivities of 176 and 208 were observed in the 0.8 mol% La:BaTiO3 and the 1.2 mol% Dy:BaTiO3 nanocrystals, respectively, relative to 89 for undoped BaTiO3 (at 1 MHz, 25 °C) due to local disorder induced by aliovalent substitution. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy is a powerful imaging tool that has found broad application in materials science, nanoscience and biology. With the introduction of aberration-corrected electron lenses, both the spatial resolution and the image quality in transmission electron microscopy have been significantly improved and resolution below 0.5?ångströms has been demonstrated. To reveal the three-dimensional (3D) structure of thin samples, electron tomography is the method of choice, with cubic-nanometre resolution currently achievable. Discrete tomography has recently been used to generate a 3D atomic reconstruction of a silver nanoparticle two to three nanometres in diameter, but this statistical method assumes prior knowledge of the particle's lattice structure and requires that the atoms fit rigidly on that lattice. Here we report the experimental demonstration of a general electron tomography method that achieves atomic-scale resolution without initial assumptions about the sample structure. By combining a novel projection alignment and tomographic reconstruction method with scanning transmission electron microscopy, we have determined the 3D structure of an approximately ten-nanometre gold nanoparticle at 2.4-ångström resolution. Although we cannot definitively locate all of the atoms inside the nanoparticle, individual atoms are observed in some regions of the particle and several grains are identified in three dimensions. The 3D surface morphology and internal lattice structure revealed are consistent with a distorted icosahedral multiply twinned particle. We anticipate that this general method can be applied not only to determine the 3D structure of nanomaterials at atomic-scale resolution, but also to improve the spatial resolution and image quality in other tomography fields. [ABSTRACT FROM AUTHOR]

Using scanning transmission electron microscopy we image∼4nm platinum nanoparticles deposited on an insulating membrane, wherethe membrane is one of two electron-transparent windows separatingan aqueous environment from the microscope’s high vacuum. Uponreceiving a relatively moderate dose of ∼104 e/nm2, initially immobile nanoparticlesbegin to move along trajectories that are directed radially outwardfrom the center of the field of view. With larger dose rates the particlemotion becomes increasingly dramatic. These observations demonstratethat, even under mild imaging conditions, the in situelectron microscopy of aqueous environments can produce electrophoreticcharging effects that dominate the dynamics of nanoparticles underobservation. [ABSTRACT FROM AUTHOR]

Crystalline solids exhibiting glass-like thermal conductivity have attracted substantial attention both for fundamental interest and applications such as thermoelectrics. In most crystals, the competition of phonon scattering by anharmonic interactions and crystalline imperfections leads to a non-monotonic trend of thermal conductivity with temperature. Defect-free crystals that exhibit the glassy trend of low thermal conductivity with a monotonic increase with temperature are desirable because they are intrinsically thermally insulating while retaining useful properties of perfect crystals. However, this behavior is rare, and its microscopic origin remains unclear. Here, we report the observation of ultralow and glass-like thermal conductivity in a hexagonal perovskite chalcogenide single crystal, BaTiS3, despite its highly symmetric and simple primitive cell. Elastic and inelastic scattering measurements reveal the quantum mechanical origin of this unusual trend. A two-level atomic tunneling system exists in a shallow double-well potential of the Ti atom and is of sufficiently high frequency to scatter heat-carrying phonons up to room temperature. While atomic tunneling has been invoked to explain the low-temperature thermal conductivity of solids for decades, our study establishes the presence of sub-THz frequency tunneling systems even in high-quality, electrically insulating single crystals, leading to anomalous transport properties well above cryogenic temperatures. Defect-free crystals showing the glassy trend of low thermal conductivity with a monotonic increase with temperature are desirable but rare. Here, the authors observe atomic tunneling associated with low and glass-like thermal conductivity in a hexagonal perovskite chalcogenide single-crystal BaTiS3. [ABSTRACT FROM AUTHOR]

• A route to obtain suspended single-wall nanotubes on nanoporous membranes. • Size-selective soft-landing of metal nanoparticles on suspended nanotubes. • High-yield, high-purity preparation of hybrid nanoparticle-nanotube systems. We describe a technique to prepare ensembles of neat, unbundled single-walled carbon nanotubes decorated with pure size-filtered metal nanoparticles. Polymer-encased nanotubes are drop-cast on nanoporous transmission electron microscope membrane grids, mounted within a nanoparticle-deposition apparatus, baked in situ to remove the polymer coating, and exposed to a beam of pure size-selected metal nanoparticles. Subsequent electron microscopy imaging reveals the presence of nanoparticles supported by pure suspended single-walled nanotubes. This method is promising for efficient production of prototype chemical and physical devices which require the presence of clean well-defined nanoparticle-nanotube hybrids for characterization, imaging, and applications. [ABSTRACT FROM AUTHOR]

Atomic layer deposition of Al2O3 is employed as ultrathin coating on LiNi0.5Mn1.5O4, a high voltage cathode in Li‐ion batteries. X‐ray absorption spectroscopy and scanning transmission electron microscopy electron energy loss spectroscopy show that the coating suppresses Mn2+ formation on the surface and decelerates impedance buildup. The detailed analysis by Chongwu Zhou and co‐workers is shown in article number 1602873. [ABSTRACT FROM AUTHOR]

High-temperature stability and segregation tendency of a Hf–Ti alloy is investigated using specimens sputtered in monolithic and multilayer configurations. Upon annealing at 800 °C for 96 h, the alloy shows segregation of Hf and Ti at the nanoscale even though the bulk Hf–Ti phase diagram predicts a homogeneous solid solution. The length scale of segregation is found to depend upon the initial as-deposited structure, with the monolithic film showing Ti segregation at grain boundaries, and the multilayered specimens showing a nanostructure of Hf-rich grains and Ti-rich intergranular amorphous regions. The multilayer specimens exhibit similar post-annealing grain diameters even when the initial layer thickness is varied. Thermodynamic Monte Carlo simulations show a solid solution when the bulk constraint is imposed, in line with the phase diagram expectation, and a polycrystalline nanostructure with solute segregated intergranular regions with full equilibration, in general agreement with the experimental observations. [ABSTRACT FROM AUTHOR]

Dielectric breakdown (DB) controls the failure, and increasingly the function, of microelectronic devices. Standard imaging techniques, which generate contrast based on physical structure, struggle to visualize this electronic process. Here in situ scanning transmission electron microscopy (STEM) electron beam‐induced current (EBIC) imaging of DB in Pt/HfO2/Ti valence change memory devices is reported. STEM EBIC imaging directly visualizes the electronic signatures of DB, namely local changes in the conductivity and in the electric field, with high spatial resolution and good contrast. DB is observed to proceed through two distinct structures arranged in series: a volatile, "soft" filament created by electron injection; and a non‐volatile, "hard" filament created by oxygen‐vacancy aggregation. This picture makes a physical distinction between "soft" and "hard" DB, while at the same time accommodating "progressive" DB, where the relative lengths of the hard and soft filaments can change on a continuum. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the effect of high flow rates (> 10−5 mol/min) of metalorganic precursors on compositional evolution in indium phosphide antimonide (InP1−x Sb x ) nanowires grown via chemical vapor deposition in the presence of indium droplets as catalysts on InP(111)B substrates maintained at ∼360°C. The as-grown nanowire morphology, composition, and crystallinity are determined using scanning and transmission electron microscopies, selected-area electron diffraction, and x-ray energy dispersive spectroscopy. For all of the precursor flow rates, we obtain zinc blende structured InP1-x Sb x wires that are tapered with wider tops, narrower bases, and In-rich In–Sb alloy tips—characteristic of the vapor–liquid–solid process. The Sb content within the InP1−x Sb x wires is found to increase non-linearly with increasing Sb precursor flow rate. At the interfaces between the In–Sb alloy tips and the InP1-x Sb x nanowires, we observe single-crystalline wurtzite-structured InSb segments whose volumes depend on the Sb precursor flow rate. We attribute this phenomenon to the rapid crystallization of InSb during cooling of the Sb-rich In–Sb alloy droplets. [Copyright &y& Elsevier]

Surface properties of electrode materials play a critical role in the function of batteries. Therefore, surface modifications, such as coatings, have been widely used to improve battery performance. Understanding how these coatings function to improve battery performance is crucial for both scientific research and applications. In this study the electrochemical performance of coated and uncoated LiNi0.5Mn1.5O4 (LNMO) electrodes is correlated with ensemble-averaged soft X-ray absorption spectroscopy (XAS) and spatially resolved scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) to illustrate the mechanism of how ultrathin layer Al2O3 coatings improve the cycle life of LiNi0.5Mn1.5O4. Mn2+ evolution on the surface is clearly observed in the uncoated sample, which results from the reaction between the electrolytic solution and the surfaces of LiNi0.5Mn1.5O4 particles, and also possibly atomic structure reconstructions and oxygen loss from the surface region in LiNi0.5Mn1.5O4. The coating effectively suppresses Mn2+ evolution and improves the battery performance by decelerating the impedance buildup from the surface passivation. This study demonstrates the importance of combining ensemble-averaged techniques (e.g., XAS) with localized techniques (e.g., STEM-EELS), as the latter may yield unrepresentative information due to the limited number of studied particles, and sheds light on the design of future coating processes and materials. [ABSTRACT FROM AUTHOR]

Recently, we reported enhanced H 2 evolution on TiO 2 -passivated GaAs. Based on density functional theory (DFT) calculations, this enhancement was attributed to Ti 3+ states, which bind reactant species and increase charge transfer across the semiconductor–liquid interface. Here, we provide a quantitative correlation between Ti 3+ density, as measured by X-ray photoemission spectroscopy (XPS) and photoluminescence (PL) spectroscopy, and photocatalytic performance, which substantiates the hypothesis put forth previously. In the photo- I – V characteristics reported here, passivating GaAs with TiO 2 produces a shift in the onset potential of +0.35 V at 1 mA/cm 2 and enhances the photocurrent by 32-fold over bare GaAs (at 0 V vs. RHE), resulting in a peak photoconversion efficiency of 1.5% under AM1.5 G illumination. We find that just 1 nm of TiO 2 produces the best conditions for photocatalysis. XPS spectra show that thinner TiO 2 films (1 nm) have a higher density of Ti 3+ states than thicker films (5 nm), which have lower photocatalytic performance. PL spectroscopy provides further evidence for these Ti 3+ surface states, which cause increased surface recombination. While it is apparent that the TiO 2 films cause strong electron–hole recombination, the benefit that they provide by providing catalytically active sites outweighs their detriment associated with charge recombination. No enhancement is observed for TiO 2 thicknesses above 10 nm, which are crystalline and, therefore, considerably more insulating than thinner amorphous TiO 2 films. [ABSTRACT FROM AUTHOR]

We report a unique method to construct hierarchical superstructures based on molecular programming of peptidomimetics. Chiral steric hindrance in the polymer backbone stabilizes peptoid helices that crystallize into nanosheets during solvent evaporation. The stacking of nanosheets results in flower-like superstructures. The helical peptoid, nucleated from chiral monomers, is characterized as locally stiffer and more extended than the unstructured peptoid. Molecular dynamics (MD) simulations further suggest a constraint on the dihedral angles and a preference toward the trans configuration, resulting in an extended chain structure. The nanosheet assemblies at various length scales indicate an extent of intermolecular ordering amplified by chiral steric hindrance. Such molecular programming and processing protocols will benefit the future design and controlled assembly of hierarchical peptidomimetics.

Electrodeposition of lithium (Li) metal is critical for high-energy batteries 1 . However, the simultaneous formation of a surface corrosion film termed the solid electrolyte interphase (SEI) 2 complicates the deposition process, which underpins our poor understanding of Li metal electrodeposition. Here we decouple these two intertwined processes by outpacing SEI formation at ultrafast deposition current densities 3 while also avoiding mass transport limitations. By using cryogenic electron microscopy 4-7 , we discover the intrinsic deposition morphology of metallic Li to be that of a rhombic dodecahedron, which is surprisingly independent of electrolyte chemistry or current collector substrate. In a coin cell architecture, these rhombic dodecahedra exhibit near point-contact connectivity with the current collector, which can accelerate inactive Li formation 8 . We propose a pulse-current protocol that overcomes this failure mode by leveraging Li rhombic dodecahedra as nucleation seeds, enabling the subsequent growth of dense Li that improves battery performance compared with a baseline. While Li deposition and SEI formation have always been tightly linked in past studies, our experimental approach enables new opportunities to fundamentally understand these processes decoupled from each other and bring about new insights to engineer better batteries., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)