Step Structure Research Articles

Structural, chemical, and magnetic investigation of a graphene/cobalt/platinum multilayer system on silicon carbide

We investigate the magnetic interlayer coupling and domain structure of ultra-thin ferromagnetic (FM) cobalt (Co) layers embedded between a graphene (G) layer and a platinum (Pt) layer on a silicon carbide (SiC) substrate (G/Co/Pt on SiC). Experimentally, a combination of x-ray photoemission electron microscopy with x-ray magnetic circular dichroism has been carried out at the Co L-edge. Furthermore, structural and chemical properties of the system have been investigated using low energy electron diffraction (LEED) and x-ray photoelectron spectroscopy (XPS). In situ LEED patterns revealed the crystalline structure of each layer within the system. Moreover, XPS confirmed the presence of quasi-freestanding graphene, the absence of cobalt silicide, and the appearance of two silicon carbide surface components due to Pt intercalation. Thus, the Pt-layer effectively functions as a diffusion barrier. The magnetic structure of the system was unaffected by the substrate’s step structure. Furthermore, numerous vortices and anti-vortices were found in all samples, distributed all over the surfaces, indicating Dzyaloshinskii–Moriya interaction. Only regions with a locally increased Co-layer thickness showed no vortices. Moreover, unlike in similar systems, the magnetization was predominantly in-plane, so no perpendicular magnetic anisotropy was found.

Zig-zag surface step migration and structure modulation in metallic nanowires

Nanoscale metals frequently exhibit novel mechanical properties or physiochemical performances, due to the growing influence of surfaces. Here, we uncover a unique surface-mediated deformation behavior of Au nanowires by conducting in situ transmission electron microscope tensile testing. A zig-zag migration of surface steps via the transverse slips on alternate (111) and (001) planes is revealed in [112]-oriented Au nanowire, which contributes to unexpected uniform deformation with an elongation of 108.9%. Further, we discover that the unusual (001) slip can induce an anomalous stacking structure on the nanowire surface under uniaxial tension. These findings enrich our understanding of surface-mediated plasticity in metallic nanomaterials.

Sculpting Tiered Micro‐Nanogradient Structure by Anisotropic Stepped Anodization for Mediating Water Distribution and Transportation

AbstractTiered micro‐nanogradient structures with custom‐tailored profiles and dimensions can be fabricated by the anisotropic electrochemical anodization of aluminum, where the micro and nanostructures are simultaneously formed. The microgradient structures can be sculpted by the chronological and spatial order of polymer masking followed by step anodization; the nanostructures can be controlled by electrochemical conditions in step anodization. Water spatial distribution and directional transportation abilities of the exemplified micro‐nanogradient structures (i.e., tiered micro symmetric circular structure, microasymmetric circular structure, and microrectangular step structure which are all integrated with nanotip‐capped nanopore structure) are studied under the fogging condition. It is found that despite the directional self‐jumping of the microdroplets caused by the cooperation of asymmetric structure and wind blowing, microdroplets can also be quickly gathered on the topper tier of the gradient structures to form large droplets and then roll away along the descending direction of the structures (also wind blowing direction), which sweep the microdroplets they passed by. These tiered micro‐nanogradient structures not only have potentials to become high efficiency fog collector but also could be a platform for the preparation of tiered micro‐nanogradient structures of various materials with advanced functions.

Designing an optical gas chamber with stepped structure for non-dispersive infrared methane gas sensor

Compared to traditional semiconductor and electrochemistry gas sensors, the non-dispersive infrared (NDIR) gas detection technology presents notable advantages in terms of stability and selectivity. However, the high-performance NDIR gas sensor generally requires a long optical path, resulting in a large gas chamber. In this short communication, a simple and relatively small stepped optical gas chamber (45 mm × 20 mm × 30 mm) with long optical path (94.92 mm) is designed combining simulation method. Furthermore, the stepped optical gas chamber based on the simulation structure is fabricated by a computer number control technique, and used to fabricate a NDIR gas sensor. The results show that the NDIR gas sensor based on the stepped optical gas chamber can be successfully used for CH4 gas detection with a wide detection range and good repeatability. This work provides an optional reference for developing compact NDIR gas sensor.

Effects of grain orientation and grain size on etching behaviors of high-strength and high-conductivity Cu alloy

Etching is a precise chemical material reduction processing method that can get small and precise components with specific size and pattern. In etching of the high-precision lead frames, microstructure of the Cu alloy plate has become an important factor that affects the etching rate, size accuracy and surface roughness of the etched products. In this study, the CuCrSn alloy samples with different grain size were etched by aqua regia and then comprehensively characterized to reveal the effects of grain orientation and grain size on the etching behavior. The results show that the etching morphologies and rates of the Cu alloy grains are significantly different and dominated by the grain orientation, and etching of the grains with their surface nearly parallel to the {100} crystal planes are the lowest, meanwhile the roughness of these etched surfaces is the lowest. After the etching, the grain surfaces show very fine stepped structures composed of two or more {100} crystal planes along which the Cu atoms dissolve. The priority corrosion is prone to occur at the grain boundaries (GBs), and the etching around the GBs is more significant when the grains are finer. With the increase in grain size, the etching at the GBs become less apparent, and the difference in etching rates between different grains increases, results in height difference and an increase in roughness of the etched surfaces.

Pushed to extremes: distinct effects of high temperature versus pressure on the structure of STEP

Protein function hinges on small shifts of three-dimensional structure. Elevating temperature or pressure may provide experimentally accessible insights into such shifts, but the effects of these distinct perturbations on protein structures have not been compared in atomic detail. To quantitatively explore these two axes, we report the first pair of structures at physiological temperature versus. high pressure for the same protein, STEP (PTPN5). We show that these perturbations have distinct and surprising effects on protein volume, patterns of ordered solvent, and local backbone and side-chain conformations. This includes interactions between key catalytic loops only at physiological temperature, and a distinct conformational ensemble for another active-site loop only at high pressure. Strikingly, in torsional space, physiological temperature shifts STEP toward previously reported active-like states, while high pressure shifts it toward a previously uncharted region. Altogether, our work indicates that temperature and pressure are complementary, powerful, fundamental macromolecular perturbations.

Density functional theory study on the effect of NO annealing for SiC(0001) surface with atomic-scale steps

The effect of NO annealing on the electronic structures of the 4H-SiC(0001)/SiO2 interface with atomic-scale steps is investigated. The characteristic behavior of conduction band edge (CBE) states is strongly affected by the atomic configurations in the SiO2 and the step structure, resulting in the discontinuity of the CBE states at the step edges, which prevents electrons from penetrating from the source to drain and decreases the mobile free-electron density. We found that the behavior of the CBE states becomes independent from the atomic configuration of the SiO2 and the density of the discontinuities is reduced after NO annealing.

Effects of the growth parameters on the surface quality of InN films

On the basis of the improved Stillinger–Weber potential model, the growth process of an indium nitride (InN) film on a gallium nitride (GaN) substrate has been simulated by molecular dynamics. The effects of growth conditions, including the incident energy, polarity of the surface of the GaN substrate, substrate temperature, and deposited N:In atomic ratio, on the surface quality of the InN film have been investigated. We find that atoms with high incident energy have high mobility, which significantly improves the structures of the protrusions and pits on the surface of the film, thereby enhancing the surface quality. However, too high incident energy enhances the sputtering effect of the deposited particles on the surface atoms of the substrate and the destruction of the film, thereby reducing the density. On the basis of the optimal incident energy, the difference in the growth mode of InN films on the Ga-termination polarity surface and N-termination polarity surface is analyzed. At low temperatures, a three-dimensional island growth mode is present on the N-termination polarity surface and a two-dimensional layer growth mode is present on the Ga-termination polarity surface. It is easier to produce InN films with excellent surface quality on the Ga-termination polarity at low temperatures. Furthermore, according to the results obtained under different substrate temperatures and atomic deposition ratios, in an In-enriched environment, excessive In atoms are prone to form agglomerated island structures on the film surface, and the low-temperature substrate is more prone to produce an InN film with high surface quality. In an N-enriched environment, excessive N atoms combine with In atoms on the film surface to form a stepped island structure, and they are more prone to grow into an InN film with high surface quality on a high-temperature substrate.

Low Crosstalk Plastic Optical Fiber-Based Dual-Parameter SPR Sensor With Stepped Side-Polished Structure and Differentiated Au-Film Thickness

Low Crosstalk Plastic Optical Fiber-Based Dual-Parameter SPR Sensor With Stepped Side-Polished Structure and Differentiated Au-Film Thickness

Exploring the Influencing Factors of English Classroom Teaching Quality in Colleges and Universities Based on Structural Equation Modeling

Abstract With the acceleration of globalization, the teaching quality of English, as an important tool for international communication, is getting more and more attention. In order to explore ways to improve the quality of English classroom teaching, this paper combines the characteristics of English classroom teaching in colleges and universities. It summarizes the structure of STEP influencing elements of English classroom teaching quality in colleges and universities based on teaching objectives and resource constraints. Then, taking X school as an example, the influence dimension structure of English classroom teaching quality in colleges and universities was mathematically analyzed and empirically examined using normality test, factor analysis, and least squares structural equation modeling (PLS-SEM). The results of the study show that the standardized path coefficients of teaching atmosphere and process on students’ competence and students’ competence on the quality of teaching in English classroom are 0.985 and 0.818, respectively, which passed the test of significance at the level of 1%. The post-standardized path coefficients of teaching atmosphere and process on students’ ability, students’ ability on teachers’ ability, and teachers’ ability on the quality of teaching in English classroom are 0.222, 0.674, and 0.073, respectively, and all of them passed the significance test on level 5%. Teaching English in classrooms in colleges and universities involves the interaction between teachers’ and students’ behaviors, as well as the integration of teaching and learning resources. The improvement of the quality of English classroom teaching in colleges and universities should pay more attention to the management and control of the process of how to realize the integration of teaching resources on the basis of students’ ability and teachers’ abilities.

An efficient particulate photocatalyst for overall water splitting based on scandium and magnesium co-doped strontium titanate

A high photocatalytic performance for overall water splitting was demonstrated over a photocatalyst based on a magnesium and scandium co-doped strontium titanate particle composed of a cubic shape having a nanosized step structure on the edge of the particle.

High Performance Sub-10nm Si-doped MoS2 based Step Structure DG-TFET

Two-dimensional (2D) nanomaterials, which include Molybdenum Disulfide (MoS2), are the focus research because of the wide possibilities of application in electronic and optoelectronic devices. Nanomaterials have potential use in high-performance transistors. The main objective of this study is to examine and evaluate a Silicon (Si)-doped MoS2 Step Structured Tunnel Field Effect Transistor (MoS2-SS-TFET). The energy gap in MoS2 is controlled by is controlled by thickness engineering, this unique property is used to design a device. At the source side and drain side of the channel, three layers and one layer of Si-doped MoS2 are used to build the step structure in order to increase the on-state current. The Subthreshold Swing (SS), threshold voltage (Vth), on-current (Ion), and off-current (Ioff) performance parameters for the device have been computed. In comparison of the study with other simulated devices, the Si-doped MoS2-SS-TFET has demonstrated enhanced device performance metrics. The device attributes such as work-function of dual metal, channel length ratio of proposed device, dielectric material and oxide thickness scaling are optimized for the improved device design.

Implementing the Merdeka Curriculum in English Language Teaching: A Study of Teacher Learning Steps

The Merdeka curriculum, a pivotal element in contemporary Indonesian education, encapsulates three key learning components: objectives, steps, and assessment. This study investigates into one of these components namely the learning steps in the context of English language instruction. Adopting a phenomenological approach, the research focuses on two English teachers at a junior high school in Central Java, aiming to illuminate the practical implementation of the learning steps. Data collection encompassed classroom observations, in-depth interviews with the teachers, and comprehensive documentation, including visual records from the classes. This multifaceted approach yielded rich qualitative insights into the pedagogical practices and experiences of these educators. The findings reveal a tripartite structure of the learning steps: the 'Opening' phase, where teachers connect new content with students' prior knowledge and motivate them towards the lesson; the 'Core Activities' phase, involving exploration, elaboration, and confirmation of the subject matter; and the 'Closing' phase, which includes summarizing key points, reflective activities, and preparing students for future lessons. Significantly, these structured phases highlight the holistic and effective methodology of the Merdeka curriculum in teaching English, offering valuable insights into its practical implementation and impact on educational outcomes.

Surface Dual-Modification of Nano-Cu2o for Controlling CO2 Electrochemical Reduction to Ethylene and Syngas

Carbon dioxide (CO2) is an important substance in the natural carbon cycle, and the gradual increase of CO2 emissions has exceeded the amount that can be absorbed by the nature, which has brought a huge impact on climate conditions and ecological environment. In addition, CO2 is an important C1 resource, and it is of great significance to convert it by electrochemical methods to important chemical raw materials (such as ethylene and syngas) needed for human life. Cu2O is an ideal electrocatalyst due to its relatively low cost and unique product selectivity, as well as the abundant Cu reserves on the earth. However, there is still a lack of systematic studies on the improvement of the C2H4 selectivity of Cu2O-based catalyst and the regulation of product selectivity.In this work, different exposed facet nano-Cu2O were obtained by induction of reducing agent. Combined with in-situ characterization and theoretical calculation, it was found that the terrace × step structure (332) crystal surface can significantly reduce the free energy of C-C coupling process, and greatly improve the selectivity of electrochemical CO2 reduction to C2H4, which is the highest value (74.1%) obtained by Cu2O based catalyst with neutral electrolyte.Subsequently, the ZIF-8 shell is introduced in-situ on the surface of Cu2O nanoparticles. The coated ZIF-8 shell effectively regulates the hydrophilic and hydrophobic environment of the material, and provides a material exchange channel for reactants and product molecules simultaneously, which promote the desorption of CO molecules and improve the adsorption of CO2, realizing the switch of product from C2H4 to syngas.In carbon dioxide reduction, it is an important strategy to modify the surface of metal/metal oxide by interface engineering to regulate the microenvironment at the reaction interface. In this paper, from the aspects of material design, synthesis and regulation of reaction products, the great advantages of facet structure and MOFs for improving the stability and activity of catalyst are demonstrated. Combined with in situ characterization and theoretical calculation, a new idea is provided for the design of efficient carbon dioxide electroreduction catalyst in the future. Figure 1

3D-printed stepped structure based on graphene-FeSiAl composites for broadband and wide-angle electromagnetic wave absorption

The design and preparation of absorbers with ultra-wide bandwidth and wide-angle absorption characteristics are crucial technologies for addressing electromagnetic (EM) pollution. In this paper, a stepped structure absorber was fabricated of graphene (GR)-FeSiAl/polylactic acid (PLA) composite by 3D printing technology. The absorber contains four layers, the bottom layer being a slab with periodic square holes, and the upper layer is a periodic distribution of three cubes with equal thickness and gradient changes in side length. It is shown that the stepped structure achieves a minimum reflection loss (RLmin) of −36.01 dB, with an effective absorption bandwidth (EAB, corresponding to the bandwidth of RL < −10 dB) of 12.75 GHz. These results were obtained when the unit cell had a side length of 22.5 mm, the slab thickness was 1.5 mm, and the cube had a thickness and edge length difference of 2.5 mm and 4.0 mm, respectively. Furthermore, the value of EAB is greater than 10 GHz for both transverse electric (TE) polarization and transverse magnetic (TM) polarization when the incident angle changes from 0° to 50°. The broadband and efficient EM wave (EMW) absorption characteristics of this absorber can be attributed to integration of excellent impedance matching and the multi-scale loss mechanisms.

PROSPECTS OF OIL AND GAS POTENTIAL IN THE ARAL SEDIMENTARY BASIN IN LIGHT OF NEW GEOLOGICALGEOPHYSICAL DATA

The article presents the results of comprehensive interpretation of new seismic materials and existing drilling data, which allowed for refining the geological structure of the Aral sedimentary basin. The Aral sedimentary basin has been studied geologically and geophysically, and through deep drilling, but very unevenly and generally insufficiently. The least studied area is characterized by the Aral Sea basin and the adjacent coastal areas. The sedimentary basin (SB) within the MesozoicCenozoic structural stage has a stepped structure submerging from east to west: the Kazalinsk, Uyalinsk, Kokaral, South Aral steps, and the Tadjin trough. The seismostratigraphic framework for the Paleozoic section in the Aral basin is based on the geological model of the region. The only stratigraphic tie within the sedimentary complex is the Pz horizon, representing a blurred surface of Jurassic deposits. As a result of seismic surveys conducted earlier by subsoil users, new structures have been identified in the sedimentary complex of the Aral oil and gas promising province. A forecast assessment of the hydrocarbon potential resources of the identified prospective objects in the Jurassic, Neocomian, and Eocene deposits is provided, carried out by specialists who conducted a comprehensive interpretation of geological-geophysical data in recent years.

Fracture morphology of desiccation cracks in clayey soil

Desiccation cracks compromise soil integrity and weaken its strength, causing a range of detrimental consequences across various domains. Elucidating the cracking mechanism can aid in managing crack propagation and mitigating the associated risks. This study monitored and compared the evolution of crack patterns on the soil surface and fracture morphologies on the soil cross-section during the drying process using a tested soil sample. Multiple fracture morphological features are discerned on the soil cross-section, encompassing initiation points and plumose structures. Soil fracture morphologies are categorized into three cases based on the initiation point's location, referred to as “Top-initiated structure”, “Bottom-initiated structure”, and “Truncated structure”. Experimental results demonstrate that plumose structures result from the division of the crack front under mixed-mode loading. Cracking under mixed-mode I + II loading leads to cross-section tilting, resulting in curved surface cracks. Conversely, cracking under mixed-mode I + III loading causes cross-section twisting, generating hackle lines and step structures. Furthermore, the crack front radiates from the initiation point, creating orthogonal hackle lines. The geometric relationship confirms that the soil fracture morphology is a good indicator of the cracking process, both in laboratory tests and field observations.

The effect of molten pool evolution on the formation of surface structures during laser polishing

As a novel surface treatment technology, in-situ laser polishing aims to improve surface finish of 3D printed parts, while laying the foundation for the integrated processing of 3D printing and laser polishing. However, the polishing process will introduce a few new surface structures (undercuts, step structures, ripples, etc.), which will affect the surface roughness. In this work, the surface roughness and surface structure after high power and low power polishing were compared respectively through experiments. In addition, a 2D transient numerical model was developed to explore the forming mechanism of different structures. The evolution of temperature field, velocity field and freedom surface of melting pool under different parameters were analyzed by the model. The results showed that the solidification induced surface structure with large roughness was generated after high power polishing. During its formation, the thermocapillary force was dominant and drove the tangential flow of fluid. While, low power polishing resulted in ripple structure with small roughness. The emergence of this structure was primarily due to the capillary force as the leading force in the melting pool flow process, which drove the normal flow of the melt, thus eliminating the large surface curvature. Furthermore, the width of the melting pool in the simulation was compared with the width of the single scanning track, and they were in good agreement. Finally, by adjusting the test strategy, it was found that the surface roughness could reach the lowest (0.88 ± 0.06 μm) only when the two structures coexisted.

The role of dynamics in heterogeneous catalysis: Surface diffusivity and N2 decomposition on Fe(111).

Dynamics has long been recognized to play an important role in heterogeneous catalytic processes. However, until recently, it has been impossible to study their dynamical behavior at industry-relevant temperatures. Using a combination of machine learning potentials and advanced simulation techniques, we investigate the cleavage of the N[Formula: see text] triple bond on the Fe(111) surface. We find that at low temperatures our results agree with the well-established picture. However, if we increase the temperature to reach operando conditions, the surface undergoes a global dynamical change and the step structure of the Fe(111) surface is destabilized. The catalytic sites, traditionally associated with this surface, appear and disappear continuously. Our simulations illuminate the danger of extrapolating low-temperature results to operando conditions and indicate that the catalytic activity can only be inferred from calculations that take dynamics fully into account. More than that, they show that it is the transition to this highly fluctuating interfacial environment that drives the catalytic process.

Multi-parameter sensor based on dumbbell stepped fiber core structure with the composite interferometric effect

Based on the composite interference structure, fiber optic multiparameter sensors can be constructed, however, this type of sensor has two bottlenecks, which are difficult to fabricate and the parameters interfere with each other. This paper proposes to simultaneously measure force, temperature, and salinity using a compact sensor with minimal signal crosstalk. The sensor structure consists of three cascaded Mach-Zehnder interferometers (MZI). The use of different diameter fiber cores fused together creates a dumbbell Stepped taper-like structure, which ensures that more higher order modes are excited while maintaining the mechanical integrity of the sensor. By creating detecting regions of various sizes, signal interference between parameters is reduced. Theoretical and experimental findings demonstrate that sensors with the dumbbell structure provide a good foundation for three-parameter sensing. and its force, temperature, and salinity sensitivity can reach −2593 dB/N, 53 pm/°C and −145.4nm/RIU. The two bottlenecks mentioned above are effectively resolved by the proposed dumbbell stepped sensor, which may also be applied to multi-parameter measurements for structural health monitoring.