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A theoretical–experimental approach is proposed to convert the photoluminescence spectra of colloidal perovskite quantum dot ensembles into accurate estimates for their intrinsic particle size distribution functions. Two main problems were addressed and properly correlated: the size dependence of the first excitonic transition in a single cube-shaped quantum dot and the inhomogeneous broadening of the fluorescence line shape due to the size nonuniformity of the chemically prepared quantum dot suspension in addition to the single-dot homogeneous broadening. By applying the reported methodology to CsPbBr3 quantum dot samples belonging to the strong and intermediate confinement regimes, the calculated size distributions exhibited close agreement with those obtained from transmission electron microscopy, with precise estimates for the average particle size and standard deviation. Specifically for strongly confined ultrasmall CsPbBr3 quantum dots, the presented spectroscopic model for size distribution computation is based on a new analytical expression for the size-dependent bandgap, which was developed within the framework of the finite-depth square-well effective mass approximation accounting for band nonparabolicity effects. Such a quantum mechanical approach correctly predicts the expected transition to the intermediate confinement regime in sufficiently large quantum dots, which are traditionally described by the well-known bandgap equation in the infinite potential barrier limit with a spatially correlated electron–hole wavefunction and nonparabolic carrier effective masses. The proposed calculation scheme originates from general theoretical considerations so that it can be readily adapted to semiconductor quantum dots of many other systems, from all inorganic metal halides to hybrid perovskite materials, regardless of the adopted chemical synthesis route. [ABSTRACT FROM AUTHOR]

At present, intensive research is underway in the field of vacuum-sublimation growth of 3C-SiC. Transfer of a thin (001)3C-SiC layer onto a 6H-SiC wafer is a promising way to fabricate a 3C-SiC/6H-SiC substrate for growing device-quality homoepitaxial films of low defect density. The article presents the results of the structural characterization of an interface formed during the transfer of a 3C-SiC layer onto a 6H-SiC(0001) wafer, performed with transmission electron microscopy (TEM). A 3C-SiC film with a thickness of about 10 μ m, grown by chemical vapor deposition (CVD) on a Si(001) substrate, was utilized in the study. Silicon acted as a bonding material in the transfer process. The morphology and microstructure of the interface between a 6H-SiC substrate and a 3C-SiC (001)-oriented layer are under consideration. TEM investigation reveals an effect of "self"-orientation of the layer with respect to the wafer during the transfer process: an interaction between the molten silicon layer and silicon carbide throughout crystallization results in the generation of defined orientation relationships with respect to substrate axes. An analysis of selected area electron diffraction patterns taken from interfaces showed the relationships to be 3C-SiC{001} ‖ 6H-SiC(0001) and 3C-SiC ⟨ 1 1 ¯ 0 ⟩ ∼ ‖ 6H-SiC ⟨ 11 2 ¯ 0 ⟩. [ABSTRACT FROM AUTHOR]

In this paper, we explored the resistivity behavior of Sb7Se3 thin films on flexible mica. The films maintained their resistance characteristics through various thicknesses and bending cycles. With increasing bends, resistivity and phase transition temperature of both amorphous and crystalline states rose, while the resistance drift coefficient gradually increased. Raman and near infrared experiments confirmed the internal structural changes and bandgap enhancement after bending. Transmission electron microscopy showed enhanced crystallization and uniform element distribution after annealing. Atomic force microscopy observed cracks, explaining the property changes. Additionally, we developed a flexible Sb7Se3 thin-film resistive device with swift reversibility (∼10 ns) regardless of bending, opening new avenues for flexible information storage. [ABSTRACT FROM AUTHOR]

The in situ growth dynamics of colloidal silver–gold core–shell (Ag@Au CS) nanoparticles (NPs) are studied using time-dependent second harmonic generation (SHG) and extinction spectroscopy. Four sequential additions of chloroauric acid, sodium citrate, and hydroquinone are added to a silver nanoparticle solution to form a gold shell around a 45 nm silver core under different reaction conditions, resulting in final sizes ranging from 80 to 125 nm in diameter. In the first addition, a bumpy, urchin-like surface morphology is produced, while the second, third, and fourth additions provide additional nanoparticle growth with the surface morphology becoming more smooth and uniform, as shown using transmission electron microscopy measurements. The in situ extinction spectra increase in intensity for each addition, where blue-shifting and spectral narrowing are observed as the Ag@Au CS NPs grow in size. The extinction spectra are compared to Mie theory simulations, showing general agreement at later stages of the reactions for smooth CS surfaces. The in situ SHG signal is dominated by surface-enhanced plasmonic hotspots at the early stages of the shell growth, followed by gradual decreases in signal as the surface becomes more smooth. Two-photon fluorescence is also monitored during the CS growth, showing complementary information for comparisons to the extinction and SHG results. The holistic study of the synthesis and characterization of Ag@Au CS nanoparticles using in situ SHG spectroscopy, extinction spectroscopy, and Mie theory simulations allows for a comprehensive analysis of the complex growth dynamics occurring at the nanoscale for developing optimized plasmonic nanomaterial properties. [ABSTRACT FROM AUTHOR]

Ag-induced crystallization and layer exchange (AgILE) in a stack of amorphous Si/Ag/quartz substrate has been investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy (TEM), scanning TEM-high angle annular dark field (STEM-HAADF) imaging, and electron tomography, covering length scales from a few tens of micrometers to a few tens of nanometers. The size of Ag grains in the underlying as-deposited Ag film varied from ∼10 to 500 nm. The following processes could be discerned using in situ heating of plan-view samples at 500 °C in STEM: (i) AgILE propagation preferentially along regions of small Ag grains, (ii) formation of pushed-up Ag in the vicinity of AgILE reaction cells, (iii) migration and agglomeration of pushed-up Ag on small and large Ag grains, which tend to inhibit AgILE and promote dendricity, and (iv) dispersion of pushed-up Ag, which tend to reduce dendricity. The resulting dendricity was largely confined to the peripheral regions of the impinging reaction cells and decreased with annealing time. In contrast, dendricity due to AgILE and crystallization at 550 °C is stable and extends right from the center to the periphery of the reaction cells. The microscopic mechanism of AgILE and, in particular, the effect of annealing temperature is investigated. The results are discussed in the light of existing literature and compared with Al-induced layer exchange. Annealing at temperature equal to or slightly less than 500 °C is found to be necessary in the case of AgILE to avoid dendricity and to obtain a continuous Si layer with large Si grains. [ABSTRACT FROM AUTHOR]

This work reports heavy ion-irradiation effects in polycrystalline Fe3O4. For this matter, Fe/Fe3O4 heterostructures were irradiated in situ in a transmission electron microscopy with 1 MeV Kr ions at 50 K. Evidence of cubic to monoclinic transformation (a.k.a Verwey transition) was recorded in some magnetite grains upon cooling the sample (around 90 K); however, most of the oxide grains retain their cubic spinel structure. Irradiation effects were analyzed in the cubic phase up to a maximum dose of 38 dpa without the sign of amorphization. The extinction of first-order reflections was recorded at doses below 1 dpa, indicating the formation of a new (metastable) phase with half of the lattice parameters compared to the unirradiated Fe3O4 crystal. The formation of the new crystalline phase, which also presents a high resistance to amorphization, is related to the disordering of the cation lattice and the high mobility of the cation interstitials. The metastable phase readily recovers around 225 K during the natural warming of the sample from 50 K to room temperature. [ABSTRACT FROM AUTHOR]

Bragg interferometry (BI) is an imaging technique based on four-dimensional scanning transmission electron microscopy (4D-STEM) wherein the intensities of select overlapping Bragg disks are fit or more qualitatively analyzed in the context of simple trigonometric equations to determine local stacking order. In 4D-STEM based approaches, the collection of full diffraction patterns at each real-space position of the scanning probe allows the use of precise virtual apertures much smaller and more variable in shape than those used in conventional dark field imaging such that even buried interfaces marginally twisted from other layers can be targeted. With a coarse-grained form of dark field ptychography, BI uses simple physically derived fitting functions to extract the average structure within the illumination region and is, therefore, viable over large fields of view. BI has shown a particular advantage for selectively investigating the interlayer stacking and associated moiré reconstruction of bilayer interfaces within complex multi-layered structures. This has enabled investigation of reconstruction and substrate effects in bilayers through encapsulating hexagonal boron nitride and of select bilayer interfaces within trilayer stacks. However, the technique can be improved to provide a greater spatial resolution and probe a wider range of twisted structures, for which current limitations on acquisition parameters can lead to large illumination regions and the computationally involved post-processing can fail. Here, we analyze these limitations and the computational processing in greater depth, presenting a few methods for improvement over previous works, discussing potential areas for further expansion, and illustrating the current capabilities of this approach for extracting moiré-scale strain. [ABSTRACT FROM AUTHOR]

Temperature dependent bonding behavior plays a significant role in deciding properties of high temperature ceramics like boron carbide. However, few studies to date have addressed the physical properties of this class of materials with respect to their temperature dependent bonding nature. In addition, materials with the flexibility to accommodate variations in interatomic bonding and lattice vibrations over a wide range of temperatures are less known. In this work, temperature dependent structural analyses of carbon-rich boron carbide microflakes using in situ powder x-ray diffraction techniques (up to 1000 °C) supported by transmission electron microscopy measurements reveal that while most bonds in the rhombohedral structure increase in length with temperature; there is no change in certain bond lengths. However, there is an unusual decrease in length (∼1.03%) of the inter-cluster –C–(central boron)BC–C– without any polyhedral redistribution. This is accompanied by an increase in lattice vibrations without significant alteration to the crystal structure over the wide temperature range studied. Temperature dependent micro-Raman experiments further confirmed the above observations. The above bonding behavior could be directly correlated to the trends in reported results of high temperature conductivity via the model of hole hopping through specific atomic positions of the rhombohedral framework, thus opening the scope to investigate structure–property relationships in high temperature functional materials. [ABSTRACT FROM AUTHOR]

A fabrication technique for high-quality AlN templates using only metalorganic vapor phase epitaxy, which involves a tiny-pit AlN layer optimized by changing the growth temperature and V/III ratio, is proposed. Combining the tiny-pit AlN layer with the main AlN layer can be beneficial for achieving epitaxial lateral overgrowth and reducing threading dislocation density (TDD). According to transmission electron microscopy observations, the TDD in the AlN layer on the tiny-pit layer was 7.3 × 109 cm–2, and the TDD was further reduced to 2.6 × 108 cm–2 by adopting multiple tiny-pit layers. Tiny voids were observed at the interface between the tiny-pit AlN and main AlN layers, and the radius of curvature of the AlN layer also increased compared with that for a conventional AlN template by reducing stress in the AlN layer. In addition, the N-polar AlN layer was grown using Al-polar tiny-pit AlN layers through polarity inversion on a sapphire substrate with an offcut angle of 2.0°. Consequently, it was found that the Al-polar tiny-pit AlN is highly effective in improving the crystalline quality of the N-polar AlN layer. The surface flatness of the N-polar AlN layer with the tiny-pit layer and polarity inversion retained the conventional N-polar AlN template. [ABSTRACT FROM AUTHOR]

N-polar InN/In0.61Al0.39N heterostructures are grown directly on sapphire by using metalorganic chemical vapor deposition. The thickness of Mg-doped In0.61Al0.39N is 340 nm, and the root-mean-square surface roughness of 20 nm thick InN is ∼3.2 nm. An optional AlN spike grown at 710 °C for 35 s is used either as an interlayer to separate the InAlN buffer from the InN channel or as a part of InAlN nucleation after sapphire nitridation. High-resolution transmission electron microscopy reveals approximately two monolayers of AlN if used as the interlayer. In this case, the concentration of screw and edge threading dislocations in partially strained InN decreased down to 6.5 × 109 and 38 × 109 cm−2, respectively. More importantly, the interlayer inclusion suppressed remote donor and alloy disorder scatterings, providing, at room temperature, the InN free electron mobility and concentration of 620 cm2/V s and 3 × 1013 cm−2, respectively. On the other hand, omitting the AlN spike by InAlN nucleation led to structural deteriorations while buffer resistivity increased to 1.7 kΩ/□. A current density of ∼12–16 A/mm, breakdown field of ∼75 kV/cm, and electron drift velocity of ∼2 × 107 cm/s were determined in InN by applying 10 ns voltage pulses on fabricated test resistors. [ABSTRACT FROM AUTHOR]

The temperature-induced phase and morphology changes of a thin layer sandwiched between two substrates which it partially wets are investigated using transmission electron microscopy, scanning electron microscopy, and x-ray scattering techniques. For this, SiC wafers were bonded with Si layers of various thicknesses and annealed at temperatures below and above the Si melting point. Below the melting point of Si, solid-state dewetting occurs. It starts with the heterogeneous nucleation of pits at the Si/SiC interfaces and progresses to their partial transformation into voids crossing the whole film. The further growth of voids is accompanied with an increase in the Si film thickness. Final equilibrium is shown to be impacted by Si crystallographic state evolution. Above the Si melting temperature, liquid Si drives SiC interfaces step bunching. When high steps and large terraces are formed over the two SiC surfaces, Si is shown to be trapped within quasi-closed pockets. Eventually, the interface locally closes around these Si inclusions with the creation of SiC/SiC direct contacts. The influence of both annealing temperatures and Si film thickness on all these processes is discussed. [ABSTRACT FROM AUTHOR]

In this study, nanostructures were introduced into bulk Si, and the P content in Si was increased. Arc melting, ball milling, and spark plasma sintering were used to prepare excess P-doped Si samples (Si1−xPx, x = 0.01, 0.03, 0.06, 0.09, and 0.12). In Si0.94P0.06, thermal conductivity decreased to 18 W m−1 K−1 at room temperature, which is about 10% of that of bulk Si. Transmission electron microscopy observation of Si0.94P0.06 revealed a linearly localized alignment, in addition to the nanostructures observed in the previous studies of P-doped Si samples. Linear alignments were composed of Si-P nanoprecipitates and defects linearly localized around dislocations. These sub-microstructures can reduce thermal conductivity; as a result, ZT at 973 K increased to 0.43, which is approximately three times higher than that of single-crystal Si. [ABSTRACT FROM AUTHOR]

Domain boundaries in perovskite oxides often exhibit abundant physical properties and phenomena. Here, epitaxial LaTiO3 thin films on (100) SrTiO3 substrates are prepared by pulsed-laser deposition. X-ray diffraction and transmission electron microscopy investigations reveal that the epitaxial LaTiO3 thin films have good crystallinity but a high density of domain boundaries. Atomic-scale scanning transmission electron microscopy observations reveal that two types of domain boundaries are formed in the LaTiO3 thin films. The type I domain boundaries are formed on the {100} crystal planes, while the type II domain boundaries on the {110} crystal planes. Electron energy-loss spectroscopy analyses suggest that the valence states of Ti ions at the type I domain boundaries are +3, while those at the type II domain boundaries are +4. First-principles calculations reveal that the bandgap decreases at both domain boundaries compared to the bulk. The carrier concentration at the type I domain boundaries is significantly higher than that of the bulk, while the carrier concentration at the type II domain boundaries is lower. These findings suggest that domain boundaries play an important role in tailoring the electrical properties of the LaTiO3 thin films, thereby promoting the potential applications and property modulation of related materials and devices. [ABSTRACT FROM AUTHOR]

The effect of carbon coating on a surface structure of a high-dose implanted/annealed silicon carbide (SiC) during annealing was examined using scanning probe microscopy (SPM), deep-ultraviolet (DUV) Raman spectroscopy, and transmission electron microscopy (TEM). In SPM, the surfaces of 500- and 30 °C-implanted/annealed SiC samples without coating exhibited a periodic-step structure and granular structure, respectively. The difference between these surfaces is attributed to the absence or presence of residual implantation damage. In contrast, surface flatness was maintained in the 500 °C-implanted/annealed SiC sample with carbon coating. However, the surface of the coated 30 °C-implanted/annealed SiC sample exhibited a geometric structure with a lattice pattern parallel to the ⟨ 11 2 ¯ 0 ⟩ axes. The DUV Raman spectra and TEM images indicated that the implanted layer of this sample metamorphosed into a mixture of 3C-SiC twin domains and amorphous-SiC regions. During the cooling process after annealing, the 3C-SiC region was more raised than the amorphous-SiC region owing to the difference in the thermal expansion coefficients, thus resulting in the generation of a geometric surface structure. In the metamorphosed implanted layer, the carbon coating does not completely prevent surface roughening. [ABSTRACT FROM AUTHOR]

Emerging quantum materials as well as novel traditional electronic and photonic materials may enable a new generation of information science devices if they can be synthesized on suitable substrates. Additionally, material and device designs may benefit from tunable properties through engineered epitaxial strain for the manipulation of the electronic character. In this work, three series of III–V ternary alloys, GaInSb, AlInSb, and InAsSb, are grown via molecular beam epitaxy on GaAs (001) substrates to explore the flexibility of abrupt metamorphic epitaxial layers with tunable lattice parameters between 6.135 and 6.479 Å. Their deposition on both homomorphic GaAs and pseudomorphic AlAs buffers is also explored. The structures of these alloys are characterized via reflection high-energy electron diffraction, high-resolution x-ray diffraction, atomic force microscopy, and transmission electron microscopy to assess their suitability as stable buffer layers with wide variability of accessible lattice parameters. [ABSTRACT FROM AUTHOR]

This work outlines conditions suitable for the heteroepitaxial growth of Cr2O3(0001) films (1.5–20 nm thick) on a Ru(0001)-terminated substrate. Optimized growth is achieved by sputter deposition of Cr within a 4 mTorr Ar/O2 20% ambient at Ru temperatures ranging from 450 to 600 °C. The Cr2O3 film adopts a 30° rotated honeycomb configuration with respect to the underlying Ru(0001) substrate and exhibits a hexagonal lattice parameter consistent with that for bulk Cr2O3(0001). Heating to 700 °C within the same environment during film preparation leads to Ru oxidation. Exposure to temperatures at or above 400 °C in a vacuum, Ar, or Ar/H2 3% leads to chromia film degradation characterized by increased Ru 3d XPS intensity coupled with concomitant Cr 2p and O 1s peak attenuations when compared to data collected from unannealed films. An ill-defined but hexagonally well-ordered RuxCryOz surface structure is noted after heating the film in this manner. Heating within a wet Ar/H2 3% environment preserves the Cr2O3(0001)/Ru(0001) heterolayer structure to temperatures of at least 950 °C. Heating an Ru–Cr2O3–Ru heterostacked film to 950 °C within this environment is shown by cross-sectional scanning/transmission electron microscopy (S/TEM) to provide clear evidence of retained epitaxial bicrystalline oxide interlayer structure, interlayer immiscibility, and epitaxial registry between the top and bottom Ru layers. Subtle effects marked by O enrichment and O 1s and Cr 2p shifts to increased binding energies are noted by XPS in the near-Ru regions of Cr2O3(0001)/Ru(0001) and Ru(0001)/Cr2O3(0001)/Ru(0001) films after annealing to different temperatures in different sets of environmental conditions. [ABSTRACT FROM AUTHOR]

The defect structure of α -phase gallium oxide thin films was investigated using transmission electron microscopy (TEM). Epitaxial Ga2O3 films were grown via halide vapor-phase epitaxy on c -plane sapphire substrates. TEM analysis revealed a high density of extended planar defects within the films, primarily located along prismatic planes of { 11 2 ¯ 0 } type. Displacement vectors were determined using the invisibility criterion for stacking faults. The study encompassed both planar and cross-sectional views of the films. It is hypothesized that these defects form due to the motion of edge partial dislocations with the 1 3 ⟨ 1 1 ¯ 00 ⟩ Burgers vector. Various mechanisms of their formation have been explored. [ABSTRACT FROM AUTHOR]

In this work, we show how diffraction-based chemically sensitive dark-field transmission electron microscopy (DFTEM) reveals the presence of Bi hetero-antisites (BiGa) at the interface of Ga(As,Bi)/(Al,Ga)As quantum well (QW) structures grown by molecular beam epitaxy on GaAs(001). The presence of BiGa is demonstrated by the striking appearance of "dark-lines" at the interfaces under two-beam DFTEM imaging conditions using the (002) diffraction spot. Additional analytical scanning (S)TEM procedures reveal Ga depletion and Bi accumulation at the exact position of the dark-lines, consistent with BiGa at this location. The precise location of the dark-lines agrees with the position of growth interruptions made to adjust substrate temperature and the As/Ga flux ratio and, most importantly, the realization of a Bi pre-treatment before QW growth. We believe the Bi pre-treatment may have favored formation of BiGa hetero-antisites. We validate the use of g002 DFTEM for further investigations of the intricate bismuth incorporation into the lattice and its dependence on the growth conditions. Finally, g002 DFTEM imaging is positioned as a very powerful technique for the detection of point defects in general in materials with the zinc-blende crystal structure, beyond dilute bismide alloys. [ABSTRACT FROM AUTHOR]

Visualizing the network of a solvent-swollen polymer gel remains problematic. To address this challenge, open transmission electron microscopy (TEM) was applied to thin gel films permeated by a nonvolatile ionic liquid. The targeted physical gels were prepared by cooling concentrated solutions of poly(ethylene glycol) in 1-ethyl-3-methyl imidazolium ethyl sulfate [EMIM][EtSO4]. During the cooling, gelation occurred by a frustrated crystallization of the dissolved polymer, leading to a percolated, solvent-permeated semicrystalline network in which nanoscale polymer crystals acted as crosslinks. Crystalline features ranging from ~5 to ~200 nm were observed, with the visible network strands dominantly consisting of long curvilinear crystallites of ~15–20 nm diameter. Nascent spherulites irregularly decorated the network, creating a complex structural hierarchy that complicated analyses. Lacking diffraction contrast, TEM did not visualize the many disordered, fully solvated PEG chains present in the voids between crystals. Recognizing that a network's three dimensionality is ambiguous when assessed through two-dimensional microscopy projections, a small gel region was studied by TEM tomography, revealing a nearly isotropic three-dimensional arrangement of the curvilinear crystallites, which displayed remarkably uniform cylindrical cross sections.

Layered or chain materials have received significant research attention owing to their interesting physical properties, which can dramatically change when the material is thinned from bulk (three-dimensional) to thin two-dimensional sheet or one-dimensional (1D) chain form. Materials with the stoichiometry AX2 with A = Si or Ge and X = S or Se form an especially intriguing semiconducting class. For example, bulk silicon dichalcogenides (SiX2) consist of 1D chains held together by van der Waals forces. Although this structural configuration has the potential to reveal interesting physical phenomena within the 1D limit, obtaining SiX2 single chains has been challenging. We here examine experimentally and theoretically SiX2 materials in the low chain number limit. Carbon nanotubes serve as growth templates and stabilize and protect the structures, and atomic-resolution scanning transmission electron microscopy directly identifies the atomic structure. Two distinct chain structures are observed for SiX2. SixGe1-xS2(1-y)Se2y quaternary alloy chains are also synthesized and characterized, demonstrating tunable semiconducting properties at the atomic-chain level. Density functional theory calculations reveal that the band gap of these alloy chains can be widely tuned through composition engineering. This work offers the possibilities for synthesizing and controlling semiconductor compositions at the single-chain limit to tailor material properties.

We employ analytical transmission electron microscopy (TEM) to correlate the structural and chemical environment variations within a stacked epitaxial thin film of the high entropy oxide (HEO) Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O (J14), with two layers grown at different substrate temperatures (500 and 200 °C) using pulsed laser deposition (PLD). Electron diffraction and atomically resolved STEM imaging reveal the difference in out-of-plane lattice parameters in the stacked thin film, which is further quantified on a larger scale using four-dimensional STEM (4D-STEM). In the layer deposited at a lower temperature, electron energy loss spectroscopy (EELS) mapping indicates drastic changes in the oxidation states and bonding environment for Co ions, and energy-dispersive X-ray spectroscopy (EDX) mapping detects more significant cation deficiency. Ab initio density functional theory (DFT) calculations validate that vacancies on the cation sublattice of J14 result in significant electronic and structural changes. The experimental and computational analyses indicate that low temperatures during film growth result in cation deficiency, an altered chemical environment, and reduced lattice parameters while maintaining a single phase. Our results demonstrate that the complex correlation of configurational entropy, kinetics, and thermodynamics can be utilized for accessing a range of metastable configurations in HEO materials without altering cation proportions, enabling further engineering of functional properties of HEO materials.

TiO2 and SrTiO3 are stable and efficient materials for photoelectrochemical (PEC) water splitting. PEC activity is influenced by carrier recombination in crystals of these materials. In this study, we analyzed the effect of dislocations on carrier recombination in TiO2 and SrTiO3 using microwave photoconductive decay measurements on polished and unpolished faces. The apparent slow decay in the unpolished face implies that dislocations trap minority carriers. Based on the different dependences of the injected photon density and temperature, the recombination processes in the polished and unpolished faces differ. A high concentration of oxygen vacancies or hydroxyl in the unpolished face of SrTiO3 was observed by x-ray photoelectron spectroscopy, and dislocations in the unpolished faces of both materials were observed using transmission electron microscopy. Additionally, we found that the photocurrent duration in the unpolished faces was shorter than that in the polished faces for both TiO2 and SrTiO3, confirming that dislocations inhibited photoelectrochemical activity. [ABSTRACT FROM AUTHOR]

The effects of isothermal annealing on the self-assembled nanostructures of spinel manganese oxide ZnMnGaO4 were investigated using transmission electron microscopy and x-ray diffraction. The checkerboard nanostructures and zigzag nanostructures (named "Sierra" nanostructures) coexisted owing to the chemical phase separation of Mn3+ and Ga3+ ions by isothermal annealing at 575 °C. It was observed that the checkerboard nanostructures were dominant in short-time annealing and that the volume fraction of the Sierra nanostructures became more prominent as the annealing period increase. The interdiffusion of Mn3+ and Ga3+ is indicated to play an important role in gaining the total energy of the system by the reduction in the local strain caused by the formation of nanostructures. These results provide further insights into the fabrication of distinct types of nanostructures in complex transition-metal compounds. [ABSTRACT FROM AUTHOR]

The effects of isothermal annealing on the self-assembled nanostructures of spinel manganese oxide ZnMnGaO4 were investigated using transmission electron microscopy and x-ray diffraction. The checkerboard nanostructures and zigzag nanostructures (named "Sierra" nanostructures) coexisted owing to the chemical phase separation of Mn3+ and Ga3+ ions by isothermal annealing at 575 °C. It was observed that the checkerboard nanostructures were dominant in short-time annealing and that the volume fraction of the Sierra nanostructures became more prominent as the annealing period increase. The interdiffusion of Mn3+ and Ga3+ is indicated to play an important role in gaining the total energy of the system by the reduction in the local strain caused by the formation of nanostructures. These results provide further insights into the fabrication of distinct types of nanostructures in complex transition-metal compounds. [ABSTRACT FROM AUTHOR]

The role of threading dislocations in the intrinsic degradation of lateral GaN devices during high reverse bias stress tests (RBSTs) is largely unknown. We now present the results on lateral p-GaN/AlGaN/2DEG heterojunctions with a width of 200 μm in GaN-on-Si. A time-dependent permanent degradation of the heterojunction under high reverse bias and elevated temperatures can be observed, ultimately leading to a hard breakdown and device destruction. By using an integrated series p-GaN resistor, the device is protected from destruction and, consequently, the influence of dislocations on the degradation mechanism could be studied. Localization by emission microscopy could show that the transient current increase during a RBST is the result of the creation of a limited amount of highly localized leakage paths along the whole device width. We could establish a 1:1 correlation of leakage sites with a structural material degradation within the AlGaN barrier for nine individual positions on two different devices by planar transmission electron microscopy analysis. To unambiguously show whether dislocations in GaN-on-Si even should be considered a potential trigger for the RBST degradation in lateral heterojunctions, a combined planar and cross-sectional lamella approach was used for the first time for larger devices. This enabled the visualization of the three-dimensional propagation path of the dislocations close to the degradation sites. It was found that there is no statistically significant link between the material degradation and pre-existing dislocations. Our findings offer new insights into the GaN-on-Si material system, upon which upcoming power technologies are built upon. [ABSTRACT FROM AUTHOR]

Antiferroelectric and ferroelectric materials are prominent non-linear dielectric materials with significant applications across various fields. To fully understand their electrical properties, it is crucial to accurately discriminate the two phases, especially in compositions with the coexistence of antiferroelectric and ferroelectric phases. In this study, we propose an easy method for differentiating domain structures from phase coexistence based on split outskirt reflections. The proposed method addresses existing limitations in the spatial phase distribution and lays the groundwork for understanding their structure–property relationships. [ABSTRACT FROM AUTHOR]

We investigate a synaptic device with short-term memory characteristics using IGZO/SnOx as the switching layer. The thickness and components of each layer are analyzed by using x-ray photoelectron spectroscopy and transmission electron microscopy. The memristor exhibits analog resistive switching and a volatile feature with current decay over time. Moreover, through ten cycles of potentiation and depression, we demonstrate stable conductance modulation, leading to high-accuracy Modified National Institute of Standards and Technology pattern recognition. We effectively emulate the learning system of a biological synapse, including paired-pulse facilitation, spiking-amplitude-dependent plasticity, and spiking-rate-dependent plasticity (SRDP) by pulse trains. Ultimately, 4-bit reservoir computing divided into 16 states is incarnated using a pulse stream considering short-term memory plasticity and decay properties. [ABSTRACT FROM AUTHOR]

Neural networks are promising tools for high-throughput and accurate transmission electron microscopy (TEM) analysis of nanomaterials, but are known to generalize poorly on data that is "out-of-distribution" from their training data. Given the limited set of image features typically seen in high-resolution TEM imaging, it is unclear which images are considered out-of-distribution from others. Here, we investigate how the choice of metadata features in the training dataset influences neural network performance, focusing on the example task of nanoparticle segmentation. We train and validate neural networks across curated, experimentally collected high-resolution TEM image datasets of nanoparticles under various imaging and material parameters, including magnification, dosage, nanoparticle diameter, and nanoparticle material. Overall, we find that our neural networks are not robust across microscope parameters, but do generalize across certain sample parameters. Additionally, data preprocessing can have unintended consequences on neural network generalization. Our results highlight the need to understand how dataset features affect deployment of data-driven algorithms.

The investigation and tunning of positive exchange bias (PEB) and negative exchange bias (NEB) are reported at room temperature (RT) and low temperature (20 K), respectively, in a series of top-pinned Ni81Fe19(tFM = 5, 8, 11, 14, 17, and 20 nm)/Ir7Mn93(10 nm) polycrystalline heterostructure thin films grown in the presence of a 1 kOe in situ magnetic field by systematically controlling the microstructural parameters such as thickness, roughness, and crystallite/grain size. On decreasing the thickness (roughness) of NiFe from 20 nm (0.49 nm) to 5 nm (0.28 nm), an enhancement in PEB and NEB is observed from +12 to +22 Oe and −300 to −556 Oe at RT and 20 K, respectively. It is observed that both exchange bias and coercivity substantially depend on the atomic scale roughness of the interface width (NiFe/IrMn). The representative plane-view of transmission electron microscopy (TEM) measurements revealed the enhanced antiferromagnet (AF) grain size on decreasing the thickness of ferromagnetic, whereas cross-sectional TEM studies exhibited the sharp interfaces in the bilayer samples after magnetic annealing. A unique correlation between the training mechanism and the degree of asymmetry is established. Further, the training measurement data are fitted with various theoretical models that support the fact that not only interfacial but also bulk AF spins play a vital role in the exchange bias. Thus, the present study reveals the microstructural insights by varying the thickness of NiFe to address the unresolved issues of the EB by directly correlating it with interface roughness and the crystallite/grain size of AF in it, probed using the magnetoresistance technique. [ABSTRACT FROM AUTHOR]

In the current work, laser thermal treatment of the FeSiB amorphous foil with a single linear laser track was carried out. The resultant microstructure and phase evolution were examined with the aid of x-ray diffraction, differential scanning calorimetry, and site-specific transmission electron microscopy. The laser power was kept constant at 100 W, whereas, laser beam scanning speeds were varied in the range of 500–235 mm/s, generating corresponding laser fluences of 0.42–0.91 J/mm 2 on the sample surface. Laser fluences of up to 0.48 J/mm 2 structurally relaxed the FeSiB foil, retaining the amorphous structure. Laser fluences of higher than 0.48 J/mm 2 led to partial crystallization of FeSiB amorphous foils. The crystallite sizes were in the range of 11–31 nm (laser fluence of 0.49–0.91 J/mm 2). α -FeSi formed as a major phase of partial crystallization while its quantity steadily increased from 3.6 to 46 vol. % with laser fluence (laser fluence 0.49–0.91 J/mm 2). Fe 2 B formed in recognizable quantities (≥ 2%) for laser fluences ≥ 0.53 J/mm 2. Laser fluences leading to structural relaxation and evolution of predominantly α -FeSi phase exerted minimal effects on ratios of intrinsic coercivities to saturation compared to the as-cast FeSiB amorphous foil. On the contrary, formation of Fe 2 B in significant quantities (≥ 2 %) led to the steady increase in intrinsic coercivities and remanence to saturation ratios as a function of laser fluence indicating a loss in soft magnetic characteristics. Nonetheless, continuous increase in fractions of α -FeSi with laser fluence led to a steady improvement in saturation magnetostriction of the FeSiB foil. [ABSTRACT FROM AUTHOR]

InAs nanowires (NWs) were grown on SiOx pinholes formed on Si(111) substrates by molecular beam epitaxy. Influences of electron-beam (EB) irradiation on the SiOx layer on the pinhole formation and the subsequent InAs NW growth were studied. As the EB irradiation dose increased, the pinhole density in the SiOx layer decreased. From atomic force microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy results, it was found that the pinhole etching of the SiOx layer by Ga droplets was suppressed by carbon adsorption due to the EB irradiation. By forming high-density pinholes on the SiOx layer without the EB irradiation, high-density InAs NWs with 1–2 × 1010 cm−2 were grown successfully, and the uniformity in the NW diameter improved. The standard deviation of the NW diameter was 1.8 nm (8.8%) for high-density NWs. In addition, the NW diameter decreased with decreasing EB dose, and the NW diameter was controlled by adjusting the diameter of Ga droplets forming the pinholes. As the NW diameter decreased, photoluminescence spectra of the NWs shifted to higher energies than the bandgap energy of the wurtzite InAs bulk. From these results, we successfully fabricated high-density and high-uniformity InAs NWs with quantum size effects on EB-unirradiated SiOx/Si(111). [ABSTRACT FROM AUTHOR]

Strain-related piezoelectric polarization is detrimental to the radiative recombination efficiency for InGaN-based long wavelength micro-LEDs. In this paper, partial strain relaxation of InGaN multiple quantum wells (MQWs) on the wafer scale has been demonstrated by adopting a partially relaxed InGaN superlattice (SL) as the pseudo-substrate. Such a pseudo-substrate was obtained through an electro-chemical etching method, in which a sub-surface InGaN/InGaN superlattice was etched via threading dislocations acting as etching channels. The degree of strain relaxation in MQWs was studied by x-ray reciprocal space mapping, which shows an increase of the in-plane lattice constant with the increase of etching voltage used in fabricating the pseudo-substrate. The reduced strain in the InGaN SL pseudo-substrate was demonstrated to be transferable to InGaN MQWs grown on top of it, and the engineering of the degree of strain relaxation via porosification was achieved. The highest relaxation degree of 44.7% was achieved in the sample with the porous InGaN SL template etched under the highest etching voltage. Morphological and structural properties of partially relaxed InGaN MQWs samples were investigated with the combination of atomic force and transmission electron microscopy. The increased porosity of the InGaN SL template and the newly formed small V-pits during QW growth are suggested as possible origins for the increased strain relaxation of InGaN MQWs. [ABSTRACT FROM AUTHOR]

The dependence of electron work function, Φ , on the thickness of Ti layers was investigated by making use of the Kelvin method under ambient conditions. Layers were produced by vacuum phase deposition and were analyzed by x-ray photoelectron spectroscopy and transmission electron microscopy. A quantum size effect was revealed finding work function to increase as the layer thickness, z, decreased below 4 nm. The extent of increase, Δ Φ , was understood in terms of a simple particle-in-a-box model arriving at the function Δ Φ = ℏ 2 π 2 / 2 m e z 2 . This equation being free of any adjustable parameter, consisting only of the Planck constant and electron mass, seems to be a reasonable first approximation. [ABSTRACT FROM AUTHOR]

The precipitation of struvite, a magnesium ammonium phosphate hexahydrate (MgNH4PO4 · 6H2O) mineral, from wastewater is a promising method for recovering phosphorous. While this process is commonly used in engineered environments, our understanding of the underlying mechanisms responsible for the formation of struvite crystals remains limited. Specifically, indirect evidence suggests the involvement of an amorphous precursor and the occurrence of multi-step processes in struvite formation, which would indicate non-classical paths of nucleation and crystallization. In this study, we use synchrotron-based in situ x-ray scattering complemented by cryogenic transmission electron microscopy to obtain new insights from the earliest stages of struvite formation. The holistic scattering data captured the structure of an entire assembly in a time-resolved manner. The structural features comprise the aqueous medium, the growing struvite crystals, and any potential heterogeneities or complex entities. By analysing the scattering data, we found that the onset of crystallization causes a perturbation in the structure of the surrounding aqueous medium. This perturbation is characterized by the occurrence and evolution of Ornstein-Zernike fluctuations on a scale of about 1 nm, suggesting a non-classical nature of the system. We interpret this phenomenon as a liquid-liquid phase separation, which gives rise to the formation of the amorphous precursor phase preceding actual crystal growth of struvite. Our microscopy results confirm that the formation of Mg-struvite includes a short-lived amorphous phase, lasting >10 s. [ABSTRACT FROM AUTHOR]

While it is widely recognized that purely organic molecular systems with multiple bonds undergo chemical condensation at sufficiently high pressures (from tenths to tens of GPa), the fate of organometallics at extreme conditions remains largely underexplored. We have investigated the high pressure (up to 41 GPa) chemical transformations in a simple molecular system known as nickelocene, (C5H5)2Ni, which serves as a representative example of a class of organometallics called sandwich compounds. Nickelocene decomposed above 13 GPa, at room temperature, while lower pressure thresholds have been observed at higher temperatures (295–573 K). The products were identified as nanocomposite materials, primarily composed of disordered, nickel-rich nanoparticles segregated within an extended, amorphous matrix of hydrogenated carbon (a-C:H). The investigation was conducted by means of diamond anvil cells in combination with optical spectroscopies and microscopy, synchrotron x-ray absorption spectroscopy and diffraction, as well as transmission electron microscopy. Our findings have the potential to stimulate further research into the high-pressure chemical reactivity of organometallics and open up new synthesis routes for the production of metal-based nanoparticles, which find a wide range of applications. [ABSTRACT FROM AUTHOR]

This work investigates the structural properties of HgCdTe thin films grown on InSb (211)B substrates using molecular beam epitaxy (MBE). The Cd composition of thin films is accurately determined using non-destructive approaches based on x-ray diffraction (XRD) and reflectance infrared spectroscopy. The as-grown HgCdTe thin films exhibit characteristic surface defects with a size of 7–10 μm and density of ∼105 cm−2, resulting in an additional spread in XRD full width at half maximum. Cross-sectional transmission electron microscopy results indicate that these defects are caused by surface In droplet formation during the oxide removal process of InSb substrate, which subsequently results in the formation of In4Te3 inclusions and extended defects in MBE-grown HgCdTe. Our findings provide additional confirmation that suppressing thermally induced damage of the InSb substrate is necessary for fabricating high-performance infrared detectors using HgCdTe grown on InSb substrates. [ABSTRACT FROM AUTHOR]

BACKGROUND: The infection of the liver by Plasmodium parasites is an obligatory step leading to malaria disease. Following hepatocyte invasion, parasites differentiate into replicative liver stage schizonts and, in the case of Plasmodium species causing relapsing malaria, into hypnozoites that can lie dormant for extended periods of time before activating. The liver stages of Plasmodium remain elusive because of technical challenges, including low infection rate. This has been hindering experimentations with well-established technologies, such as electron microscopy. A deeper understanding of hypnozoite biology could prove essential in the development of radical cure therapeutics against malaria. RESULTS: The liver stages of the rodent parasite Plasmodium berghei, causing non-relapsing malaria, and the simian parasite Plasmodium cynomolgi, causing relapsing malaria, were characterized in human Huh7 cells or primary non-human primate hepatocytes using Correlative Light-Electron Microscopy (CLEM). Specifically, CLEM approaches that rely on GFP-expressing parasites (GFP-CLEM) or on an immunofluorescence assay (IFA-CLEM) were used for imaging liver stages. The results from P. berghei showed that host and parasite organelles can be identified and imaged at high resolution using both CLEM approaches. While IFA-CLEM was associated with more pronounced extraction of cellular content, samples features were generally well preserved. Using IFA-CLEM, a collection of micrographs was acquired for P. cynomolgi liver stage schizonts and hypnozoites, demonstrating the potential of this approach for characterizing the liver stages of Plasmodium species causing relapsing malaria. CONCLUSIONS: A CLEM approach that does not rely on parasites expressing genetically encoded tags was developed, therefore suitable for imaging the liver stages of Plasmodium species that lack established protocols to perform genetic engineering. This study also provides a dataset that characterizes the ultrastructural features of liver stage schizonts and hypnozoites from the simian parasite species P. cynomolgi.

Complicated nano- and atomic-scale processes with sub-angstrom spatial resolution and millisecond time resolution visualized by in situ transmission electron microscopy (TEM) are often highly dynamical and time consuming to analyze and interpret. Here, we report how variational autoencoders (VAEs) can provide an artificial intelligence's interpretation of high-resolution in situ TEM data by condensing and deconvoluting complicated atomic-scale dynamics into a latent space with reduced dimensionality. We designed a VAE model with high latent dimensions capable of deconvoluting information from complex high-resolution TEM data. We demonstrate how this model, with high latent dimensions trained on atomically resolved TEM images of lead sulfide (PbS) nanocrystals, is able to capture movements and perturbations of periodic lattices in both simulated and real in situ TEM data. The VAE model shows the capability of detecting and deconvoluting dynamical nanoscale physical processes, such as the rotation of crystal lattices and intra-particle ripening during the annealing of semiconductor nanocrystals.

Interleukin-6 (IL-6) belongs to the cytokine family and plays a vital role in regulating immune response, bone maintenance, body temperature adjustment, and cell growth. The overexpression of IL-6 can indicate various health complications, such as anastomotic leakage, cancer, and chronic diseases. Therefore, the availability of highly sensitive and specific biosensing platforms for IL-6 detection is critical. In this study, for the first time, epitope-mediated IL-6-specific magnetic molecularly imprinted core–shell structures with fluorescent properties were synthesized using a three-step protocol, namely, magnetic nanoparticle functionalization, polymerization, and template removal following thorough optimization studies. The magnetic molecularly imprinted polymers (MMIPs) were characterized using dynamic and electrophoretic light scattering (DLS and ELS), revealing a hydrodynamic size of 169.9 nm and zeta potential of +17.1 mV, while Fourier transform infrared (FTIR) spectroscopy and fluorescence spectroscopy techniques showed characteristic peaks of the polymer and fluorescent tag, respectively. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) investigations confirmed the successful encapsulation of the magnetic core within the ca. 5-nm-thick polymeric shell. The MMIP-based electrochemical sensing platform achieved a limit of detection of 0.38 pM within a linear detection range of 0.38–380 pM, indicating high affinity (dissociation constant KD = 1.6 pM) for IL-6 protein in 50% diluted serum samples. Moreover, comparative investigations with the non-imprinted control polymer demonstrated an imprinting factor of 4, confirming high selectivity. With multifunctional features, including fluorescence, magnetic properties, and target responsiveness, the synthesized MMIPs hold significant potential for application in various sensor techniques as well as imaging. [ABSTRACT FROM AUTHOR]

A new set of metal-organic frameworks was designed by functionalizing g-C3N4 with benzoic acid and using them as structure-directing ligands during the metal-organic framework (MOF) formation. One such MOF exhibited dual emissions, both metal- and ligand-centered, enabling ratiometric sensing of the carcinogenic industrial solvent dioxane. The fabricated MOFs possessed a unique fluffy spherical morphology that enabled atomic level resolution in transmission electron microscopy--a rarity in MOFs due to the 'Knock-on' effect. Sensor experiments showed a rapid response within 5 s of analyte introduction and achieved a low limit of detection (LOD) of 0.026 ppm, well below the FDA-approved level of 10 ppm. In addition, the sensor exhibited exceptional selectivity, discriminating 1,4-dioxane from a pool of 16 solvents. This increased sensing capability was attributed to the formation of complexes and precise alignment of energy levels between the host and analyte, facilitating photoinduced electron transfer (PET). This material is equally efficient for colorimetric detection of the same solvent under excitation of UV light as well as gas phase detection of this volatile organic compound through I-V characteristics. Density functional theory (DFT) analysis supported the crucial role of Eu and the ligand system in efficiently detecting 1,4-dioxane by fluorescence spectroscopy, as shown in the energy level diagram. Future research could focus on optimizing these metal-organic frameworks for enhanced industrial applications in the detection of dioxane and exploring their potential applications in real-world environmental monitoring and public health safety. [ABSTRACT FROM AUTHOR]

Collagen is the most abundant protein in human and mammalian structures and is a component of the mammalian extracellular matrix (ECM). Recombinant collagen is a suitable alternative to native collagen extracted from animal tissue for various biomaterials. However, due to the limitations of the expression system, most recombinant collagens are collagen fragments and lack triple helix structures. In this study, Chinese hamster ovary (CHO) cells were used to express the full-length human type I collagen α1 chain (rhCol1α1). Moreover, Endo180 affinity chromatography and pepsin were used to purify pepsin-soluble rhCol1α1 (PSC1). The amino acid composition of PSC1 was closer to that of native human type I collagen, and PSC1 contained 9.1 % hydroxyproline. Analysis of the CD spectra and molecular weight distribution results revealed that PSC1 forms a stable triple helix structure that is resistant to pepsin hydrolysis and has some tolerance to MMP1, MMP2 and MMP8 hydrolysis. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) revealed that PSC1 can self-assemble into fibers at a concentration of 1 mg/ml; moreover, PSC1 can promote the proliferation and migration of NIH 3T3 cells. In conclusion, our data suggest that PSC1 is a highly similar type of recombinant collagen that may have applications in biomaterials and other medical fields. • CHO cells were used to express full-length human type I collagen α1 chain (rhCol1α1). • Endo180 affinity chromatography and pepsin were used to purify rhCol1α1. • PSC1 can self-assemble into larger fibers at the suitable concentration and temperature. • PSC1 have stable structure and can promote the proliferation and migration of NIH 3T3 cells. [ABSTRACT FROM AUTHOR]

CO gas sensing properties of 1-D ZnO nanostructures deposited on films of Multi-Wall carbon nanotubes were investigated using a vapor transport approach. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray, Raman spectroscopy, diffused reflectance spectroscopy, and photoluminescence, techniques were used to carry out the structural, morphological, and optical characterizations. The development of carbon-doped hybrid MWCNTs/ZnO nanostructures was demonstrated by the current results. The synthesized nanostructures were dense tapering belts and pedal-like crystalline structures as evidenced by their structural and morphological characteristics. Multiple networks of pure ZnO and hybrid MWCNTs-ZnO nanostructures were used to synthesize the gas sensors. Doped ZnO nanostructures sensing technique for CO gas detection was investigated in the present study. The combined impact of ZnO and MWCNTs was shown to be beneficial in boosting the response towards CO gas, as the response to CO gas at a concentration of 20 parts per million (ppm) was found to be five-times greater than that of ZnO sensors with good stability. [Display omitted] [ABSTRACT FROM AUTHOR]

In recent years, numerous studies have focused on the use of mixed ionic-electronic conducting oxides for coupled oxygen separation and catalytic reactions in membrane reactors. A promising strategy for the efficient fabrication of oxygen separation membranes involves modification of the membrane surface via exsolved metal nanoparticles decoration. Here, we present a detailed characterization of the structural and transport properties of a novel membrane material La 0.4 Sr 0.6 Fe 0.95 Nb 0.05 O 3−δ (LSFNb5). The exsolution of Fe nanoparticles was observed after heating of LSFNb5 in a reducing atmosphere (5 % Н 2 /Ar) and was confirmed by X-ray diffraction analysis, Mössbauer spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The formation of Fe nanoparticles on the surface of LSFNb5 hollow fiber membrane in the reduction process leads to the enhancement of oxygen fluxes and reduces the apparent activation energy. Kinetic parameters for oxygen transport through LSFNb5 hollow fiber membrane estimated using two different models, are in good agreement with the experimental results. Furthermore, LSFNb5 hollow fiber membrane demonstrates stable performance both before and after surface treatment. [ABSTRACT FROM AUTHOR]

A nano-multilayered ZrN/TiAlN was deposited as the interlayer to enhance the coating hardness and wear resistance between the inner TiAlN and outer ZrN layers. The structural evolution and mechanical performance of the multilayer coatings were significantly achieved. High-resolution transmission electron microscopy (HRTEM) revealed a local epitaxial growth between the nano multilayers, in which (111) crystal planes for TiAlN was parallel to (111) crystal planes for ZrN. Nanoindentation experiments were conducted to evaluate the mechanical properties. TiAlN-ZrN/TiAlN-ZrN and ZrN-TiAlN-ZrN/TiAlN-ZrN featuring a multilayered architecture, exhibited the higher hardness values of 24.68 ± 3.27 GPa and 25.34 ± 3.42 GPa respectively. Additionally, The wear mechanism for coatings under a load of 10N was dominated by abrasive wear, whereas that under a load of 15N was mainly oxidation wear and abrasive wear. Furthermore, in comparison to TiAlN-ZrN, the wear tracks on TiAlN-ZrN/TiAlN-ZrN exhibited a lower width value about 423 μm, indicating a better wear resistance. This enhancement could attribute to the alternating stress fields hindering the dislocation movement, which arose from coherency strains due to a mismatch in the lattice differences between nano multilayers. Simultaneously, the interface of nano layers inhibited oxygen diffusion, enhanced the antioxidant effects and further improved the wear behavior. [ABSTRACT FROM AUTHOR]

A SiC-SiO 2 nano-composite coating was prepared via a novel liquid-phase plasma-assisted particle deposition and sintering (LPDS) method to enhance the oxidation resistance of the Ti-6Al-4V alloy. For comparison, a conventional plasma electrolytic oxidation (PEO) ceramic coating is fabricated on the Ti-6Al-4V alloy. The microstructure and formation mechanisms of both ceramic coatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results indicated that the thickness of the SiC nano-composite coating (∼40 μm) increased significantly by 285 % compared to the PEO coating (∼14 μm). The microstructural evolution and isothermal oxidation performance of the PEO and SiC-SiO 2 nano-composite coating were comparatively investigated at 800 °C. After 100 h, the thickness gain of the SiC-SiO 2 nano-composite coating (∼14 μm) was lower than that of the PEO coating (∼26 μm). The improved oxidation performance is primarily attributed to the outermost layer containing abundant SiC nanoparticles, which transform into SiO 2 during the oxidation process and effectively inhibiting the inward penetration of oxygen. [ABSTRACT FROM AUTHOR]

In this research, the accumulative roll bonding (ARB) technique was employed as a severe plastic deformation method to manufacture a unique bi-metal Pb/W composite reinforced by Co 3 O 4 ceramic oxide. For this purpose, composites with different amounts of reinforcement particles (0.25, 0.5, 1, 1.5, and 2 wt%) were successfully produced using the ARB process (up to 10 cycles). Also, the mechanical properties were evaluated using microhardness, tensile, and shear punch tests. For microstructural investigations, the X-ray diffraction method (XRD), transmission electron microscopy (TEM), and fractography analysis by scanning electron microscopy (SEM) were employed. The Pb-0.5%W/Co 3 O 4 following 10 ARB cycles exhibited optimal mechanical and microstructural properties. For this composite, the tensile strength showed a markable increase of 2.17 times, yield strength by 4.7 times, shear strength by 3.6 times, and hardness by 4.2 times compared to the pure Pb sample subjected to the same ARB cycles. However, the strain was reduced by 3.85 times. These enhanced properties are also followed by increased stiffness and improved anode dimensional stability, creep resistance, and operational lifespan. [Display omitted] [ABSTRACT FROM AUTHOR]

In this research, a two-step hydrothermal technique is used to fabricate a NO 2 gas sensor based on MoS 2 nanoflowers with SnO 2 nanoparticles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) , were used to determine the morphologies, nanostructures, and compositions of the materials. The nanocomposites consisting of MoS 2 /SnO 2 demonstrated a remarkable sensing response (38.6) towards 100 ppm of NO 2. Moreover, the nanocomposites showed a rapid response and recovery time (42/147 S) when exposed to 100 ppm at temperature (250 °C). The MoS 2 /SnO 2 nanocomposites demonstrated exceptional selectivity to NO 2 against CO, NH 3 , and H 2 S, as well as demonstrated good repeatability. The significant gas detection characteristics could potentially be controlled by the distinctive structures of thin layers assembled into flower-like formations of two-dimensional MoS 2. The multi-joint nanostructures promote the process of transferring the electrical charge of the carrier and the response to MoS 2 /SnO 2 and NO 2. The fabricated sensors are considered as potential candidates for the commercial in the nitrogen dioxide gas-sensing applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The present work reports a synthesis of octahedron (A55NO) and cube-shaped (A55NC) Mn 0.5 Zn 0.5 Fe 2 O 4 ferrite nanoparticle dispersion in distilled water. The crystal structure analyzed using powder X-ray diffraction (XRD) shows the crystallite sizes of 17.7 ± 0.4 nm and 11.9 ± 1.0 nm, respectively, for the A55NO and A55NC particles. The morphology as seen from transmission electron microscopy (TEM) confirms 17.8 ± 0.3 nm (σ = 0.27) and 8.7 ± 0.3 nm (σ = 0.33) edge lengths, respectively, for octahedron and cube-shaped particles. The thermogravimetric analyzer (TGA) and Fourier transform infrared (FTIR) spectroscopy are used to confirm the chemical binding of the surfactant with a sharp transition at 208.67 °C and 218.32 °C, respectively, for octahedron and cube-shaped particles, indicating the removal of the surfactant due to its decomposition from the particle surface. Both the particles are highly magnetic and have 75.32 Am2/kg and 72.93 Am2/kg saturation magnetization, as revealed by their M − H loops using a vibrating sample magnetometer (VSM). The stability of the sample is confirmed using the particle size analyzer (DLS) and the Zeta potential analyzer. The induction heating capacity of the fluid was investigated using the Embrell Easy Heat model LA6310 at 330 kHz. The heating response shows that even a minimum concentration of 1 mg/mL is sufficient to achieve the hyperthermic window temperature of 42 °C for both samples, which, unlike the same composition prepared by other routes, makes it impossible to go beyond 38 °C. Moreover, octahedron particle dispersion can reach this window temperature within 10 min, whereas cube particle dispersion requires only 15 min. The findings of this study hold significant practical value since it confirms that Mn 0.5 Zn 0.5 Fe 2 O 4 composition with tuneable shape has the potential to work as a temperature-controlled magnetic switch for magnetic fluid hyperthermia under the defined safety limit with the minimum concentration. [ABSTRACT FROM AUTHOR]