Graphene/diamond (sp2-sp3) heterojunctions have gained considerable attention as promising platforms for photomemristive devices; however, the detailed interfacial structure crucial for understanding the origin of resistance switching remains unclear. In this study, we analyzed the interfacial structure and electronic states of graphene/diamond junctions using transmission electron microscopy (TEM), wide-area four-dimensional scanning transmission electron microscopy (4D-STEM), and electron energy-loss spectroscopy (EELS). The samples were fabricated on boron-doped diamond by microwave plasma-assisted chemical vapor deposition (CVD) and copper (Cu) annealing. In the CVD-grown samples, (111)-faceted diamond twins form during graphene growth, and their domain size increases with increasing substrate temperature, leading to a larger interfacial area. STEM-EELS analysis also reveals the presence of sp3-rich diamond regions within the graphene layer on the diamond surface. By contrast, no diamond twins are observed in the Cu-annealed samples. Graphene forms multilayer domains whose size and coherency with the diamond substrate strongly depend on the fabrication method. CVD-grown graphene aligns parallel to the diamond (111) planes owing to high interfacial coherency, with an increased interlayer spacing near the interface. By contrast, Cu-annealed graphene grows predominantly perpendicular to the interface and exhibits a larger interlayer spacing that decreases toward the interface. These structural features are considered key factors governing the observed material properties.

The milled-Li1.2Cr0.4Mn0.4O2 (milled-LCMO) cathode, a promising material for next-generation Li ion batteries, is prepared by dry ball-milling of layered rocksalt-type Li1.2Cr0.4Mn0.4O2 (layered-LCMO) obtained by solid-state synthesis. Despite undergoing ball-milling treatment, resulting in separation into Cr-rich and Mn-rich phases along with Li2O, milled-LCMO still exhibited a reversible capacity of 277 mA h g-1 at a rate of 16 mA g-1. However, it was also revealed that its cyclability was poor due to the contribution of oxygen redox in the charging process. On the other hand, layered-LCMO exhibited better cyclability because charge and discharge reactions proceeded only through the Cr redox. The thermally treated Li1.2Cr0.4Mn0.4O2 was prepared as a cathode material that combines the favorable properties of these two materials. In fact, each thermally treated sample showed a larger reversible capacity than the layered-LCMO obtained by the solid-phase method, and the cyclability recovered as the heat treatment temperature increased.

The distribution of dopants in host crystals significantly influences the chemical and electronic properties of materials. Therefore, determining this distribution is crucial for optimizing material performance. The previously developed statistical ALCHEMI (St-ALCHEMI), an extension of the atom-location by channeling-enhanced microanalysis (ALCHEMI) technique, utilizes variations in electron channeling based on the beam direction relative to the crystal orientation. It statistically analyzes spectra collected across multiple beam directions. However, the total experimental time can be extensive, particularly for low dopant concentrations, where typical experiments can span several hours. In this study, we propose a scheme based on efficient sampling point selection that reduces the experimental time required while maintaining accuracy. Guidelines for selecting beam directions were derived from theoretical and experimental analyses of data redundancy. The strategies include choosing directions that exhibit greater variances in the host ionization channeling patterns and lower correlation coefficients between them. Additionally, an edge detection scheme using the dual tree complex wavelet transform, applied to electron channeling patterns, is proposed to significantly reduce measurement time. Our findings suggest that effective sampling can reduce experimental duration by at least two orders of magnitude without compromising accuracy. Implementing the proposed guidelines shortens total measurement times, minimizes electron irradiation damage and improves S/N ratio through extended data acquisition per tilt.

This study presents a classification model for nanoscale polymer characterization, utilizing low-loss spectral data obtained through scanning transmission electron microscopy combined with electron energy-loss spectroscopy. To enhance interpretability, spectral features are extracted via mixed Gaussian model fitting, where each Gaussian peak corresponds to a specific chemical bond state, facilitating the identification of key descriptors. These features enable effective clustering of seven standard polymers, achieving clear statistical separation based on four principal features. Furthermore, the extracted features are employed to visualize the progression of electron irradiation damage within an adequate data space. Feature changes under varying irradiation conditions are significantly correlated with alterations in the summed spectra. This methodology holds promise for advancing qualitative analyses of polymer alloys without electron staining, allowing detailed investigations into local denaturation and the presence of reaction layers. With the expansion of standard datasets, this approach offers a robust framework for characterizing and understanding polymer behavior at the nanoscale.

Conventional characterization techniques such as transmission electron microscopy (TEM) cannot visualize the subtle structural changes in Rh nanoparticles during the reduction of NO to N2 on their surface. Hence, in this study, we used an environmental reaction science high-voltage electron microscope equipped with a quadrupole mass spectrometer (QMS) system to conduct operando atomic-scale analysis of the NO reduction process on Rh nanoparticles supported on ZrO2. This innovative setup enabled us to observe dynamic surface structural changes while simultaneously monitoring the production of N2 and consumption of NO under relevant reaction conditions. High-resolution TEM observations and kinetic calculations based on QMS data confirmed the presence of a pseudocyclic transitional state between Rh metallic and RhO2 within an unstable oxide monolayer on the surface of the Rh nanoparticles, which is a hitherto undocumented phenomenon. A comparison of experimental data with the corresponding simulated images revealed plausible catalytic mechanisms for the reduction of NO to N2 at three different temperature ranges (200-500, 500-600, and 600-700 degrees C). At low temperatures, the reaction primarily occurs on a thin RhO2 film formed on the nanoparticle surface, which defies the longstanding consensus that the reduction of NO occurs on Rh metal sites. Our methodology enabled the direct observation of transient surface states and revealed their ability to dictate the overall reaction dynamics. The findings of this study provide insights into surface catalytic reactions on nanoparticles under practical conditions as well as can guide future studies on catalytic mechanisms.

This study proposes an advanced analytical method for evaluating the morphology and chemical states of polymer alloys using low-loss spectral imaging in scanning transmission electron microscopy. This approach involves extracting spectral features through Gaussian fitting, as established in our previous study, followed by statistical cluster analysis of 12 extracted spectral features. This technique enables the assessment of component distribution and the detection of reaction layers within polymer alloys. Furthermore, by comparing these feature plots with those of the standard samples, significant spectral shifts were observed, indicating chemical modifications such as conjugated double bond formation and crosslinking. In particular, thermoplastic polyurethane elastomer and Styrene-ethylene butylene-styrene block copolymer exhibited increases in the relative peak fractions of conjugated double bonds (NG2) and unsaturated C=C bonds (NG3), along with a red shift in the former peak position (mu G2), consistent with known thermal degradation mechanisms. In contrast, low-density polyethylene showed a blue shift of mu G2 with minimal change in NG2, suggesting limited conjugated bond formation. A supervised classification model using these features achieved over 99 % accuracy using support vector machine and random forest algorithms. Permutation importance analysis identified mu G2, NG5 (G5: bulk plasmon), and NG2 as the most influential features for classification, underscoring the role of pi-pi* transitions and bulk plasmon features in polymer identification. This method addresses the common limitations of conventional spectral decomposition techniques concerning ambiguity in determining the number of components. This approach offers insights into the chemical state changes induced by alloying, serving as a powerful tool for nanoscale analysis.

Al-Mg-Si alloys are extensively used in automotive panels because of their high formability and age-hardening capabilities during paint baking. Natural aging that occurs after the solution treatment inhibits formation of (3 '' precipitates during subsequent artificial aging, reducing the hardness. The precipitation behavior of Al-0.65Mg-0.81Si mass% alloy during isothermal aging at 100 degrees C over various durations is investigated in this study using scanning transmission electron microscopy (STEM) and STEM energy-dispersive X-ray spectroscopy (EDS). The analysis reveals the formation of Guinier-Preston (GP) zones and (3 '' precipitates, which influence the mechanical properties of the alloy. After 1 h of aging, no GP zones are observed; however, clusters with diameters of 1.0-1.5 nm formed, increasing and decreasing in density at 10 and 400 h, respectively. Further, (3 ''-related structures with a Mg/Si ratio of -1 started forming at 10 h and grew in number by 400 h, with most particles being spherical and some elongated along the [100]Al direction. These microstructural changes correlate with yield strength variations, highlighting the role of pre-aging in promoting (3 '' formation during subsequent artificial aging. In addition, a novel STEM-EDS intensity correlogram method is introduced to effectively distinguish aging products from the matrix and deepen the understanding of microstructural evolution in Al-Mg-Si alloys.

Silicon (Si) acts as an amphoteric impurity in gallium arsenide (GaAs), occupying various sites and exhibiting different coordination structures within the material. In this study, we employed electron microscopy, x-ray absorption spectroscopy, and theoretical simulations to analyze the Si-occupied sites and local coordination structures at concentrations ranging from 2 to 4 × 1019 atoms/cm3 in heavily doped GaAs. High angular resolution electron channeling x-ray spectroscopy was employed to analyze the Si-occupied sites. This method quantitatively estimates site occupancies through statistical analysis of atom site-dependent spectra. It was observed that Si substitutes for both Ga and As sites with nearly equal occupancies. Si K-edge x-ray absorption fine structure (XAFS) measurements and density functional theory calculations were used to explore the local coordination structures of Si. The peak positions of experimental XAFS spectra aligned closely with those of the calculated XAFS spectra for neutral SiGa–SiAs dumbbells, particularly when Si atoms were in close proximity. Considering the effect of vacancies, the experimental XAFS peak position corresponded well with that of the calculated Si dumbbell–VAs pair. In addition, the observed pre-peak was attributed to neutral Si, likely originating from Si clusters. These findings enhance our understanding of Si-related defect structures and their influence on the properties of heavily Si-doped GaAs.

Zn-doped W-type Sr hexaferrite (SrZnxFe18_xO27; x Fe 18 _ x O 27 ; SrZnx-WHF) x-WHF) is an anticipated rare-earth-free hard magnetic material with strong magnetocrystalline anisotropy and saturation magnetization. To examine the origin of its high magnetic performance, the site distribution of Zn over seven crystallographically inequivalent Fe sites and the site-dependent valence states of Fe were investigated using site-selective elemental/chemical analysis techniques. The dominant occupation of Zn2+ 2 + at the 4e tet(S) and 4f tet(S) tetrahedral sites was determined quantitatively using high-angular-resolution electron-channeling X-ray spectroscopy and statistical data analysis. The combined application of high-angular-resolution electron channeling electron spectroscopy and atomic-column resolution scanning transmission electron microscopy-electron energy-loss spectroscopy helped unambiguously clarify that most of the Fe2+ 2 + ions existed at the 6g oct(S-S) octahedral site. Density functional theory calculations have shown that Zn doping leads to a redistribution of the charges toward Fe ions at this site. This redistribution preserves the local charge balance and amplifies the total number of parallel spins. Hence, the enhanced magnetocrystalline anisotropy and saturation magnetization in SrZnx-WHF x-WHF can be inferred to originate from the charge redistribution at the 6g oct(S-S) site, which is influenced by the presence of nonmagnetic Zn.

This paper describes the development of a gas chromatography-quadrupole mass spectrometry system attached to a differential-pumping-type environmental cell of the reaction science high-voltage electron microscopy instrument at Nagoya University to distinguish unambiguously between different gas species with the same mass-to-charge ratio. Several model experiments were used to verify the efficacy of the newly proposed system, confirming its ability to analyse the atomic-level structural changes during heterogeneous catalysts and the associated gas-reaction kinetics simultaneously, providing new insights into operando measurements in the field of environmental transmission electron microscopy. Graphical Abstract.

Dislocation cell structures significantly influence the fatigue failure process. Research on the cell structures in multiple-slip-oriented copper single crystals has focused primarily on the [111] orientation, whereas formation mechanisms and development processes of cell structures in [001] and [011] copper single crystals remain unclear. Therefore, this study examines the dislocation structures of near-[001] and near-[011] copper single crystals under cyclic deformation at high strain amplitudes. The cyclic stress-strain curve of the [011] crystals showed a distinct plateau at plastic shear strain amplitudes <= 7.5 x 10-3. In the plateau region, the dislocation structures consisted of cell structures along the (111) primary slip plane and matrix wall structures. Furthermore, (111) cell structures were formed in the single-slip deformation bands (DBs). After the plateau region, several types of new DBs could be observed due to the activation of multiple-slip systems. Multiple-slip DBs have a higher degree of plastic strain concentration than single-slip DBs, leading to the preferential formation of cell structures. For the near-[001] crystals, (111) cell structures were uniformly formed throughout the matrix, without the formation of DBs. The formation mechanism of the (111) cell boundary was independent of the stress axis and resulted from the interaction between the primary and coplanar slip systems.

The milled-Li1.2Cr0.4Mn0.4O2 (milled-LCMO) cathode, a promising material for next-generation Li ion batteries, is prepared by dry ball-milling of the layered rocksalt-type Li1.2Cr0.4Mn0.4O2 (layered-LCMO) obtained by solid-state synthesis. Despite undergoing ball-milling treatment, resulting in the separation into Cr-rich and Mn-rich phases along with Li2O, the milled-LCMO still exhibited a reversible capacity of 277 mAh g-1 at a rate of 16 mA g-1. However, it was also revealed that its cyclability was poor due to the contribution of oxygen redox or release in the charging process. On the other hand, layered-LCMO exhibited better cyclability because charge and discharge reactions proceeded only through the Cr redox. The thermally treated Li1.2Cr0.4Mn0.4O2 was prepared as a cathode material that combines the favorable properties of these two materials. In fact, each thermally treated sample showed a larger reversible capacity than the layered-LCMO obtained by the solid-phase method, and the cyclability recovered as the heat treatment temperature increased.

Pseudo-ternary CrP4-type (V,Cr,Mo)P-4 was successfully synthesized at the conditions of 4 GPa and 900 degrees C by using a large volume multi-anvil-type press. SEM-EDS and STEM analyses revealed that the synthesized pseudo-ternary (V,Cr,Mo)P-4 contains almost equimolar amounts of transition metals. The lattice parameters and unit cell volume of (V,Cr,Mo)P-4 yield the average value of its end-members. The low-temperature (133 K-333 K) in-situ synchrotron XRD measurements demonstrated that the c-axis showed the highest coefficient of thermal expansion, followed by the b-axis and the a-axis. These thermal behaviors are the same as the binary end-members and pseudo-binary (V,Cr)P-4. While from the high-pressure (P < 10 GPa) in-situ synchrotron XRD measurements, it was found that (V,Cr,Mo)P-4 showed no phase transition and compression behaviors in which the c-axis was more compressible than the other two axes (b and a) and the b-axis was slightly compressible more than the a-axis. The zero-pressure bulk modulus of 106 (1) GPa and 122.1 (7) GPa were obtained for (V,Cr)P-4 and (V,Cr,Mo)P-4, respectively. MoP6 octahedral is highly distorted in comparison with VP4 and CrP4, thus the incorporation of MoP4 greatly yields incompressible behaviors of CrP4-type phosphides with respect to temperature and pressure.

This report revisits the statistical atom location by channeling enhanced microanalysis method, correcting the dopant site occupancy error by applying an appropriate error propagation rule. A revised equation for calculating the uncertainty in the determined dopant fractions is proposed. The revised equation is expected to correct the uncertainty in the determined dopant fractions, which is particularly significant in cases of low dopant concentrations and variable dopant occupancies across inequivalent host atomic sites. The approach is validated using Eu-doped Ca2SnO4 as a typical model system.