The integration of high-quality, ultrathin van der Waals (vdW) dielectrics with 2D semiconductors remains a critical bottleneck in the development of reliable, ultra-scaled field-effect transistors (FETs). Here, we report a comprehensive study of MoS2-based FETs employing layered rhombohedral MnAl2S4 as the gate insulator, a previously unexplored vdW dielectric that can be isolated down to the monolayer limit. Devices fabricated in both top-gated (TG) and bottom-gated (BT) configurations exhibit excellent electrical performance, featuring low gate leakage, minimal hysteresis ( < 2 mV) under high electric fields up to 11 MV cm-1 across a wide range of gate voltage sweep rates (0.001–10 Vs-1). We observed a consistent counterclockwise hysteresis and an anomalous bias temperature instability (BTI), possibly caused by the diffusion of Mn interstitials and S vacancies formed inside the MnAl2S4 film during growth. Notably, we show that threshold voltage degradation at high temperatures was observed to be negligible, and hysteresis dynamics and very small BTI are reproducible over a long time, demonstrating the high reliability of our devices. In addition, the vdW interface between MnAl2S4 and MoS2 in our device is of good quality and is expected to provide a small density of insulator defects, a promising gate dielectric for reliable 2D devices. Integrating van der Waals (vdW) dielectrics with 2D semiconductors is a critical step in the fabrication of improved field effect transistors. Here, vdW MnAl2S4 is used as a gate insulator in MoS2-based transistors, achieving low gate leakage and hysteresis, and thermal stability.

This study investigates the effect of the gas atmosphere on the size limit for defect-free thermal binder removal in 3D-printed alumina bodies fabricated using digital light processing (DLP). Binder removal from cylindrical specimens with diameters ranging from 5 mm to 15 mm was carried out in either nitrogen or air atmospheres under different heating schedules. In nitrogen, defect-free debinding was achieved for specimens up to 15 mm in diameter. In contrast, defect-free binder removal in air was limited to specimens as small as 5 mm. Thermogravimetric analysis and microstructural characterization were employed to elucidate the role of the atmosphere in binder removal and defect formation. Microstructural differences between debinding in air and nitrogen were identified. Based on these results, mechanisms of binder removal in ceramic DLP printed bodies with acrylatebased crosslinked binder systems are proposed, and critical steps for achieving defect-free processing are discussed.

Palladium (Pd) is an active catalyst for various reactions, such as hydrogen evolution (HER) and hydrogen oxidation (HOR) reactions. However, its activity can be further optimized by introducing strain and ligand effects from Pd deposition onto suitable substrates like gold (Au). In this study, we use scanning electrochemical microscopy (SECM) to investigate the catalytic properties of such Pd/Au systems. For the HER, a sub-monolayer of Pd (PdML) was electrochemically deposited onto half of a polycrystalline (pc) Au substrate with underpotential deposition (UPD). The localized activity measurements revealed improved HER kinetics for Pd atoms at the Pd/Au border in 0.1 M HClO4. As a consequence, a set of Pd/Au samples with increasing density of Pd/Au borders was synthesized by atomic layer deposition (ALD). These ALD Pd deposits have an increased thickness compared to a sub-monolayer, which makes hydride formation thermodynamically viable. Because of this, the samples were investigated for the HOR/H absorption activity using the redox competition (RC) mode. We highlight the influence of cations in 0.1 M AMOH (AM = Li+, Na+, K+, Rb+, Cs+) electrolytes on the HOR/H absorption activity, displaying higher activities for larger cations: jLiOH < jNaOH < jKOH < jRbOH < jCsOH. From the spatial and temporal resolution of the activity, active spots are identified, which expand with time and diminishing hydrogen concentration in the electrolyte. Additional laser-induced current transient (LICT) experiments confirm the dependency between cation and electrocatalytic activity observed with RC-SECM.

This study conducted a deep investigation of TiO2 nanotube (TNT) layers of two different thicknesses anodically grown on electrodeposited Ti films. The Ti films were grown from molten salts on Ni foils. The structure of the starting metals was compared by XRD (X -Ray Diffraction) and EBSD (Electron Backscatter Diffraction analyses), which showed a strong orientation towards the titanium (101) for the electrodeposited substrate, compared to the rather polycrystalline structure of the rolled Ti. The photoelectrochemical and electrochemical properties of 1 mu m and 5 mu m thick TNT layers anodically grown on these substrates were examined and compared with TNT layers of the same thickness. No significant morphological and compositional differences were found using SEM (Scanning Electron Microscopy) and XPS (X-ray Photoelectron Spectroscopy) between the TNT layers grown on the two substrates. However, higher photocurrent densities and ICPE values were observed for TNT layers grown on electrodeposited Ti. An in-depth investigation using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) analyses showed increased conductivity of the TNT layers produced on electrodeposited Ti compared to their counterparts. The carrier density (ND) for the TNT layers on electrodeposited Ti, calculated from Mott-Schottky measurements, showed a higher doping level than the TNT layers grown on Ti foils. This increase in ND results in more optimal photoelectrochemical performance of the TNT layers grown on electrodeposited Ti. All in all, the results presented herein pave the way for the use of electrodeposited Ti, with all its inherent benefits, and allow the further study of its promising properties in a wide range of applications.

Abstract Hematite is a common iron oxide found in nature, and the α‐Fe2O3(0001) plane is prevalent on the nanomaterial utilized in photo‐ and electrocatalytic applications. The atomic‐scale structure of the surface remains controversial despite decades of study, partly because it depends on sample history as well as the preparation conditions. Here, a comprehensive study is performed using an arsenal of surface techniques (non‐contact atomic force microscopy, scanning tunneling microscopy, low‐energy electron diffraction, and X‐ray photoemission spectroscopy) complemented by analyses of the near surface region by high‐resolution transmission electron microscopy and electron energy loss spectroscopy. The results show that the so‐called “bi‐phase” termination forms even under highly oxidizing conditions; a (1 × 1) surface is only observed in the presence of impurities. Furthermore, it is shown that the biphase is actually a continuous layer distorted due to a mismatch with the subsurface layers, and thus not the proposed mixture of FeO(111) and α‐Fe2O3(0001) phases. Overall, the results show how combining surface and cross‐sectional imaging provides a full view that can be essential for understanding the role of the near‐surface region on oxide surface properties.

Hematite α-Fe_2O_3(0001) is the most-investigated iron oxide model system in photo and electrocatalytic research. The rich chemistry of Fe and O allows for many bulk and surface transformations, but their control is challenging. This has led to controversies regarding the structure of the topmost layers. This comprehensive study combines surface methods (nc-AFM, STM, LEED, and XPS) complemented by structural and chemical analysis of the near-surface bulk (HRTEM and EELS). The results show that a compact 2D layer constitutes the topmost surface of α-Fe_2O_3(0001); it is locally corrugated due to the mismatch with the bulk. Assessing the influence of naturally-occurring impurities shows that these can force the formation of surface phases that are not stable on pure samples. Impurities can also cause the formation of ill-defined inclusions in the subsurface and modify the oxidation phase diagram of hematite. The results provide a significant step forward in determining the hematite surface structure that is crucial for accurately modeling catalytic reactions. Combining surface and cross-sectional imaging provided the full view that is essential for understanding the evolution of the near-surface region of oxide surfaces under oxidative conditions.

The impact of Gd addition on the structural and magnetic properties of L10-FePt alloy thin films, which were sputter-deposited on MgO(001) substrates at 800°C, was investigated. A rapid deterioration of L10 chemical ordering along with a strong amorphization effect is observed with addition of Gd. At more than 20 at. % Gd, additional crystalline phases occur. Due to the diminishing L10 chemical order, the perpendicular magnetic anisotropy (PMA) gets strongly reduced from about 3 down to 1 MJ/m3 with addition of 14 at. % Gd. For higher Gd concentrations, the easy axis of magnetization turns fully in-plane due to dominating magnetic shape anisotropy. Furthermore, the saturation magnetization gets reduced with Gd addition due to the antiferromagnetic coupling between the Fe and Gd magnetic moments. Also, the Curie temperature can be lowered. Interestingly, with addition of Gd, a change in film morphology takes place, changing from an isolated island structure to a more continuous film morphology, which is of particular interest for samples with low Gd concentration as these films exhibit still strong PMA but rather low coercive fields.

Efficient manipulation of antiferromagnetic (AF) domains and domain walls has opened up new avenues of research towards ultrafast, high-density spintronic devices. AF domain structures are known to be sensitive to magnetoelastic effects, but the microscopic interplay of crystalline defects, strain and magnetic ordering remains largely unknown. Here, we reveal, using photoemission electron microscopy combined with scanning X-ray diffraction imaging and micromagnetic simulations, that the AF domain structure in CuMnAs thin films is dominated by nanoscale structural twin defects. We demonstrate that microtwin defects, which develop across the entire thickness of the film and terminate on the surface as characteristic lines, determine the location and orientation of 180 ∘ and 90 ∘ domain walls. The results emphasize the crucial role of nanoscale crystalline defects in determining the AF domains and domain walls, and provide a route to optimizing device performance.

The interest in understanding scaling limits of magnetic textures such as domain walls spans the entire field of magnetism from its physical fundamentals to applications in information technologies. Here, we explore antiferromagnetic CuMnAs in which imaging by x-ray photoemission reveals the presence of magnetic textures down to nanoscale, reaching the detection limit of this established microscopy in antiferromagnets. We achieve atomic resolution by using differential phase-contrast imaging within aberration-corrected scanning transmission electron microscopy. We identify abrupt domain walls in the antiferromagnetic film corresponding to the Néel order reversal between two neighboring atomic planes. Our work stimulates research of magnetic textures at the ultimate atomic scale and sheds light on electrical and ultrafast optical antiferromagnetic devices with magnetic field–insensitive neuromorphic functionalities.

Iron (III) oxide, in the form of hematite (α-Fe2O3), is a n-type semiconductor which is photoactive in the visible spectral region. Therefore, use in photoelectrocatalysis and photoassisted water electrolysis may be suggested. For such implementations, stability of contacts with liquid phases is mandatory. Hematite is stable in alkaline media but less stable in acidic media. For the first time the coverage of porous photoactive Sn doped hematite by thin capping layers of TiO2, deposited by Atomic Layer Deposition (ALD) and its impact on photocurrent and chemical stability of hematite is shown. The nominal thicknesses of the TiO2 ALD coatings were 0.5, 2 and 7.5 nm. The presence of the TiO2 coatings was evidenced by X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy (HR-TEM) and scanning TEM coupled with energy dispersive X-ray (EDX) spectroscopy. HR-TEM analyses revealed that the TiO2 capping layers were amorphous and conformal. Exposure of uncovered hematite layers to 1 M sulfuric acid led to a nominal dissolution rate of 0.23 nm/h which was halved when a TiO2 ALD coating (7.5 nm thin) was applied. Due to mismatch of the valence band positions of the two semiconductors, photocurrents were strongly diminished as the capping layer thickness was increased. Post-calcination of as deposited ALD films on hematite resulted in an increase of photocurrent, which only exceeded photocurrents of pristine hematite when the ALD thickness was not more than 0.5 nm.

Compared to other magnesium alloys, the WE43 alloy is better able to resist corrosion thanks to its unique chemical composition, it decomposes harmlessly in the human body and its mechanical properties make it a suitable candidate for a new generation of biodegradable bone implants. The present study deals with the relative density, microstructure, and corrosion resistance of the WE43 material produced using selective laser melting. For these purposes, thin-walled and volumetric samples were produced using various combinations of laser settings, specifically laser power in the range of 125-225 W and laser scan speed in the range of 500-700 mm/s. The width of thin-walled samples served as a basis for setting the hatch distance of the weld tracks in volumetric samples. Porosity analysis revealed that the highest relative density achieved among volumetric samples was up to 99.5% and the Mg vapours generated during the printing process were reduced. The corrosion rates for different surface quality in Hanks' Balanced Salt Solution were observed. The grinded batches (grit 4000, 500, and 120) of samples achieved the corrosion rate 2.11 mm.year(-1) for SiC4000, 4.48 mm.year(-1) for SiC500, and 5.12 mmyear(-1) for SiC120. Corrosion rate of as-build samples was established on 7.04 mm.year(-1), which was worse by an order of magnitude in comparison of extrude material.

Curvature-induced effects allow us to tailor the static and dynamic response of a magnetic system with a high degree of freedom. We study corrugated magnonic waveguides deposited on a sinusoidally modulated substrate prepared by focused electron beam deposition. The surface curvature in films with thicknesses comparable to the amplitude of modulation locally modifies the contributions of dipolar and exchange energies and results in an effective anisotropy term which can be tuned on-demand based on the exact geometry. We show, by Brillouin light scattering microscopy, that without the presence of an external magnetic field, spin waves propagate over a distance 10$\times$larger in the corrugated waveguide than in the planar waveguide. Further, we analyze the influence of the modulation amplitude on spin-wave propagation and conclude that for moderate modulation amplitudes, the spin-wave decay length is not affected. For larger amplitudes, the decay length decreases linearly with increasing modulation.

This paper focuses on the research and development of a suitable method for creating a selective emitter for the visible and near-infrared region to be able to work optimally together with silicon photovoltaic cells in a thermophotovoltaic system. The aim was to develop a new method to create very fine structures beyond the conventional standard (nanostructures), which will increase the emissivity of the base material for it to match the needs of a selective emitter for the VIS and NIR region. Available methods were used to create the nanostructures, from which we eliminated all unsuitable methods; for the selected method, we established the optimal procedure and parameters for their creation. The development of the emitter nanostructures included the necessary substrate pretreatments, where great emphasis was placed on material purity and surface roughness. Tungsten was purposely chosen as the main material for the formation of the nanostructures; we verified the effect of the formed structure on the resulting emissivity. This work presents a new method for the formation of nanostructures, which are not commonly formed in such fineness; by this, it opens the way to new possibilities for achieving the desired selectivity of the thermophotovoltaic emitter.

Silver and gold nanoparticles were produced using the pinhole discharge generated by dc non-pulsing high voltage directly in a precursor solution. Silver nitrate solution was used as the precursor for silver nanoparticles, and chloroauric acid was used as the precursor for gold nanoparticles. Effects of discharge time, precursor concentration, and additives such as reduction agent (ethylene glycol) and capping agent (polyethylene glycol and sucrose) were studied. Nanoparticles were mainly analyzed by UV-VIS spectrometry. The size of prepared nanoparticles was determined by the dynamic light scattering with backscattering detection. To determine the stability of nanoparticles, the zeta potential was measured by the electrophoretic light scattering. It was found that the absorption maximum of nanoparticles increases with the time of the discharge treatment and concentration of the precursor. The size of silver nanoparticles ranged from 10 to 1000 nm and the final solution had higher polydispersity. The size of Au nanoparticles ranged from 10 to 100 nm, depending on the precursor concentration. The most stable particles were prepared from the pure precursor solution without any additives. The addition of ethylene glycol stimulated the reduction process of nanoparticles from the solution but it decreased their zeta potential. Final particles were less stable, which started to form larger structures that tended to sediment. Added capping agent decreased the input of power needed for the stable discharge operation. The formation of silver and gold nanoparticles was confirmed by scanning electron microscopy with the energy dispersion spectrometer. Both silver and gold particles had spherical shapes.

We present a detailed study of the growth of the tetragonal polymorph of antiferromagnetic CuMnAs by the molecular beam epitaxy technique. We explore the parameter space of growth conditions and their effect on the microstructural and transport properties of the material. We identify its typical structural defects and compare the properties of epitaxial CuMnAs layers grown on GaP, GaAs and Si substrates. Finally, we investigate the correlation between the crystalline quality of CuMnAs and its performance in terms of electrically induced resistance switching.

The interaction between the impurities (such as carbon, nitrogen, oxygen) and the plasma-facing materials (PFMs) can profoundly influence the performance and service of the PFMs. In this paper, we investigated the influence of oxygen (O-2) impurity in the helium radio frequency (RF) plasma on the surface morphology of polycrystalline tungsten (W) irradiated at the surface temperature of 1450 +/- 50 K and the ion energy of 100 eV. The pressure ratio of O-2 to He (R) in RF source varied from 4.0 x 10(-6) to 9.0 x 10(-2). The total irradiation flux and fluence were (similar to)1.2 x 10(22) ions.m(-2).s(-1) and (similar to)1.0 x 10(26) ions.m(-2), respectively. After He+ irradiation, the specimen surface morphology was observed by scanning electron microscopy. It was found that with increasing R from 4.0 x 10(-6) to 9.0 x 10(-2) the thickness of nano-fuzz layer at the W surface was thinner and thinner, accompanied by the formation of rod-like structures. The erosion yield increased from 5.2 x 10(-4) to 2.3 x 10(-2) W/ion when R varied from 4.0 x 10(-6) to 9.0 x 10(-2) . The X-ray diffraction analysis shows that tungsten oxides were formed at the near surface of specimens when R exceeded 1.8 x 10(-2) . The erosion yield measurements revealed that in addition to surface physical sputtering process, the chemical erosion process could occur due to the interaction between oxygen-containing species and W at the surface. The results indicated that the presence of O-2 impurity in He plasma can obviously affect the surface microstructure of W. The study suggested that O-2 impurity can effectively reduce the growth of nano-fuzz structures.

Microstructural changes of magnesium alloy AZ91 after fatigue loading in the EX-ECAP state were evaluated using EBSD. It was found that both the number fraction of low-angle boundaries and parameter KAM decreased after the testing at a stress amplitude of 160 MPa but started to increase with the increasing stress amplitude. This behaviour can be explained with a mutual influence of dislocation accumulation (which is stronger with a higher stress amplitude) and dynamic softening (which is weaker with a decreasing number of cycles/cycles to failure). The average grain size remained almost unchanged except at a stress amplitude of 180 MPa, which could have been caused by certain conditions allowing an ideal development of both mentioned phenomena.

Numerical analysis was applied to three-dimensional (3D) images for a quantitative description of evolution of surface topography of CdTe after oxidation. The results of fractal analysis show the correlation of fractal dimension and statistical characteristics of surface topography. Surface texture analysis provides dependence of topography characteristics on oxidation process. The comprehensive description of the surface micromorphology of the CdTe is an important challenge and it is essential for understanding their properties and their potential technological exploitation. The changes in surface topography were evaluated by atomic force microscopy (AFM). This characterization was carried out for the quantitative analysis of specific microstructural characteristics of samples.

Finishing technologies of machining such as grinding or wire electrical discharge machining (WEDM) represent the most frequently used applications when mechanical engineering components that are subject to high requirements for the accuracy of shapes and dimensions as well as quality of machined areas. The study was focused on the evaluation of the machined surface contamination due to grinding and WEDM elements of tool material. In addition, the machined surface morphology was studied using light microscopy, atomic force microscopy (AFM) technique and 3D profile meter. Both area and profile parameters of the surfaces were evaluated by means of two different contactless profilometers based on the principle of coherence correlation interferometry.

The present work points out the importance of chemical heterogeneity on the destabilization of austenitic structure and the formation of deformation induced martensite (DIM) in AISI 300 grade austenitic stainless steels (ASSs) of different level of austenite stability (316L, 304, 301LN). Color etching reveals that the structure of wrought Cr–Ni type steels is never fully chemically homogeneous. Confrontation of distribution and morphology of DIM formed in the volume of material after static and cyclic straining under well controlled different conditions with the characteristic local variations in chemical composition of diverse wrought semi-product forms (plates, sheets, bars) proved prominent and very important role of chemical banding in the destabilization of originally fully austenitic structure. This fact should be considered especially when interpreting the results of hydrogen embrittlement tensile testing of Cr–Ni ASSs with lowered Ni content. An impact of chemical heterogeneity on microstructural changes during production of UFG structure of 301LN and its cyclic straining is highlighted.