High Structural Quality Research Articles

2D-SnS-Embedded Schottky Device with Neurotransmitter-Like Functionality Produced Using Proximity Vapor Transfer Method for Photonic Neurocomputing.

Neuromorphic computing, which involves the creation of artificial synapses capable of mimicking biological brain activity, has intrigued researchers in the field of artificial intelligence (AI). To advance neuromorphic computing, a highly efficient 2D material-based artificial synapse capable of performing logical and arithmetic operations must be developed. However, fabricating large, uniform films or high-quality structures of 2D materials remains challenging because of their multistep and complex fabrication processes. In the present study, to produce large (Ø ≈ 3 in.), uniform, transparent neuromorphic devices, a novel single-step approach called proximity vapor transfer (PVT) that utilizes van der Waals (vdW) materials is employed. This single-step technique, which involves the fabrication of vdW materials on various substrates (glass, ITO, AZO, Mo, and Cu), allows control of the thickness and bandgap tunability. The Schottky device developed via the PVT method using vdW SnS with neurotransmitter (acetylcholine)-like functionality emulates biological synapses and exhibits photoelectronic synaptic behavior with wide-field-of-view synaptic plasticity. In addition, logic gate operations (NOT, OR, AND), reward-cascade neurotransmission, and imaging can be performed using 3 × 3 arrays of the device. This study represents a significant step toward the development of transparent and large-area synaptic devices, which are crucial for advancing AI applications.

High-Performance Vis–NIR Photodetectors Based on Two-Dimensional Bi2Te3 Thin Film and Applications

Two-dimensional materials have excellent optoelectronic properties and have great significance in the field of photodetectors. We have prepared a thin film photodetector based on bismuth telluride (Bi2Te3) topological insulator using dual-temperature-zone vapor deposition technology. Due to the high-quality lattice structure of Bi2Te3 and the uniform and dense surface morphology of the Bi2Te3 thin film, the device exhibits excellent photoelectric response and Vis–NIR spectral range. Under 405 nm illumination, the responsivity is 5.6 mA/W, the specific detectivity is 1.22 × 107 Jones, and the response time is 262/328 ms. We designed a photodetector single-point scanning imaging system and successfully achieved high-resolution imaging at a wavelength of 532 nm. This work provides guidance for the application of two-dimensional materials, especially Bi2Te3, in the fields of photodetectors and imaging.

TiB1.8 single layers and epitaxial TiB2-based superlattices by magnetron sputtering using a TiB (Ti:B = 1:1) target

Sputter-deposited titanium diborides are promising candidates for protective coatings in harsh and extreme conditions. However, growing these layers from TiB2 diboride targets by DC magnetron sputtering usually leads to over-stoichiometric layers with low crystal qualities. Moreover, superlattices with TiB2 as one of the constituents have been becoming popular, owing to their superior mechanical properties compared to single layer constituents in addition to their use in other applications such as neutron optics. Here, we propose the use of a TiB (Ti:B = 1:1) sputtering target in an on-axis deposition geometry and demonstrate the growth of epitaxial sub-stoichiometric TiB1.8 thin films. Furthermore, we present the growth of CrB1.7/TiB1.8 superlattices, from TiB (Ti:B = 1:1) and stoichiometric CrB2 targets, with abrupt interfaces as promising materials system for neutron interference mirrors. The high crystal quality structure with well-defined interfaces is the common feature of superlattices which, regardless of application, should be addressed during the growth process.Utilizing TiB target, all films crystallize in the hexagonal AlB2 structure. The sub-stoichiometry of the TiB1.8 films was accompanied by the presence of planar defects embedded in the films. CrB1.7/TiB1.8 superlattices exhibited a homogeneous boron distribution within the layers with no sign of B-rich tissue phases through the layers. This study demonstrates the feasibility for TiB as sputter target material, that offers a solution for deposition of TiB2-based superlattices without the need to adjust the deposition parameters. Such adjustments would otherwise be unavoidable for tuning the TiB2 composition and could affect the growth of the other constituent materials.

AlGaN-Based Ultraviolet PIN Photodetector Grown on Silicon Substrates Using SiN Nitridation Process and Step-Graded Buffers

The integration of aluminum gallium nitride (AlGaN) with silicon substrates attracts significant attention due to the superior UV sensitivity of AlGaN and the cost-effectiveness as well as mechanical robustness of silicon. A PIN ultraviolet photodetector with a peak detection wavelength of 274 nm is presented in this paper. By employing a SiN nucleation layer and a step-graded buffer, a high-quality AlGaN-based photodetector structure with a dislocation density of 2.4 × 109/cm2 is achieved. A double-temperature annealing technique is utilized to optimize the Ohmic contact of the n-type AlGaN. The fabricated UV photodetector attains a dark current of 0.12 nA at −1 V and a peak responsivity of 0.12 A/W.

SCUBA-D: a freshly trained diffusion model generates high-quality protein structures.

SCUBA-D: a freshly trained diffusion model generates high-quality protein structures.

Electrospun fibers of zein and pea protein to create high-quality fibrous structures in meat analogs.

The importance of developing plant-based meat similar to animal meat lies in the fact that sensory similarity is a crucial factor in encouraging consumers to adopt this alternative. The present study reports the morphology, hydrophilicity, and thermal analysis of different fibers obtained by the electrospinning method. In the first step of this work, zein and zein/poly(ethylene oxide) (PEO) in 80% aqueous ethanol solution with varying concentrations of these polymers were investigated. It was observed that the diameters of the electrospun fibers are related to the concentration and viscosity of the solutions. Moreover, the addition of small percentages of PEO makes the fibers more hydrophilic and leads to an increase in the polymeric solution viscosity. Because of its low toxicity, PEO is used in various edible products. In the second step of this work, an ideal zein/PEO combination was found to allow the pea protein (PP) to be electrospun. Adding PP to the zein/PEO blend (20:1) leads to a more hydrophilic fiber and improves thermal stability. The results suggest that the zein/PEO and zein/PEO/PP blends can offer an innovative solution to enhance the texture and appearance of plant-based meats. These simulated electrospun fibers can mimic the fibers in animal meat and are a potential alternative to provide a sensory experience as close to animal meat as possible.

Enhanced Crystallinity of SrTiO3 Films on a Silicon Carbide Substrate: Structural and Microwave Characterization

Thin films of strontium titanate, which reveal high structure quality and tunable properties prospective for microwave applications at room temperature, were grown on a semi-insulating silicon carbide substrate using magnetron sputtering for the first time. The films’ growth mechanisms were studied using medium-energy ion scattering, and the films’ structures were investigated using X-ray diffraction. The electrical characteristics of planar capacitors based on strontium titanate films were measured at a frequency of 2 GHz using a high-precision resonance technique. It is shown that the tendency to improve the crystalline structure of strontium titanate film with an increase in the substrate temperature is most pronounced for films deposited at elevated working gas pressure under low supersaturation conditions. Planar capacitors formed on the basis of oriented SrTiO3 films on silicon carbide showed tunability n = 36%, with a loss tangent of 0.008–0.009 at a level of slow relaxation of capacitance, which is significantly lower than the data published currently regarding planar tunable ferroelectric elements. This is the first successful attempt to realize a planar SrTiO3 capacitor on a silicon carbide substrate, which exhibits a commutation quality factor more than 2500 at microwaves.

Experimental and Numerical Analysis of Bolted Repair for Composite Laminates with Delamination Damage

Composite materials are widely used in aircraft due to the urgent need for high-quality structures in aerospace engineering. In order to verify the effectiveness of complex bolt repairs on composite structures, compression tests have been performed on three types (intact, damaged, and repaired) of composite plate specimens, and finite element simulation results of these three types’ specimens were obtained. The experimental results show that for damaged composite laminates, the strength recovery after bolt repair can reach an impressive 107%, and the delamination propagation caused by over-buckling deformation is considered to be the main cause of failure, which also suggests that although bolt repair can improve the strength of the specimens, it has a limited ability to inhibit delamination propagation. The simulation results of the finite element model in this paper are in good agreement with the actual experimental results, and the maximum error does not exceed 7.9%. In conclusion, this paper verifies the suitability of the proposed repair scheme in engineering applications and the correctness of the modeling method for repaired composite laminates.

Dissimilar fabrication of the TC4/Ni60 bimetallic structure by laser melting deposition using a V/Cu transition bilayer

The bonding of Ti and Ni alloys to manufacture high-quality bimetallic structures represents an optimal integration strategy for fully leveraging their superior performance. However, the metallurgical bonding between TC4 and Ni60 dissimilar metals is extremely challenging due to the formation of TiNi, TiC and TiFe brittle intermetallic compounds and the differences in thermophysical properties. To address this issue, this paper presents a solution based on the compatibility of elemental components. A V/Cu transition bilayer was designed to achieve defect-free bonding between TC4 and Ni60 by laser melting deposition. The microstructure of the TC4/Ni60 bimetallic structure was analyzed by SEM, XRD and EBSD to evaluate its feasibility. The results indicate that the generation of brittle intermetallic compound phases was reduced to a certain extent when a V/Cu transition bilayer was employed, thus preventing cracking and peeling of the TC4 substrate and Ni60 cladding layer. Additionally, the mechanical properties of the bimetallic structure were evaluated through micro-shear tests and tensile tests. The micro-shear test results indicate that the weakest layer of the bimetallic structure is the Cu transition layer with a shear strength of 183.0 ± 108.8 MPa and an indentation rate of 8.25 ± 3.3 %. The room temperature tensile results demonstrate that the developed bimetallic structure fractured at the Cu/Ni60 interface, exhibiting a tensile strength of 286.3 ± 54.1 MPa and an elongation of 6.3 ± 0.5 %. The expected research can provide valuable references for improving the mechanical properties of TiNi dissimilar bimetallic structures produced by laser melting deposition.

Sn-doped n-type GaN freestanding layer: Thermodynamic study and fabrication by halide vapor phase epitaxy

Results of a thermodynamic study of Sn doping and fabrication of a Sn-doped GaN freestanding layer with high structural quality by halide vapor phase epitaxy (HVPE) are described in this paper. Thermodynamic analysis revealed that SnCl2 and/or SnCl act as Sn precursors through the reaction between Sn metal and HCl gas. The equilibrium partial pressures of SnCl2 and SnCl increase with the input HCl partial pressure. To generate Sn precursors effectively, it is desirable that the reaction between Sn metal and HCl gas occurs in the inert gas ambient. On the basis of results of the thermodynamic study, the Sn-doped GaN freestanding layer with a Sn concentration of 5.7 × 1019 cm−3 is fabricated by removing the GaN seed substrate after HVPE growth. The Sn-doped GaN freestanding layer has high crystal quality, and the lattice constants along the c- and a-axes of the Sn-doped GaN freestanding layer are larger than those of the GaN seed substrate because of the high electron density and the size effect of Sn atoms.

Unmasking AlphaFold to integrate experiments and predictions in multimeric complexes.

Since the release of AlphaFold, researchers have actively refined its predictions and attempted to integrate it into existing pipelines for determining protein structures. These efforts have introduced a number of functionalities and optimisations at the latest Critical Assessment of protein Structure Prediction edition (CASP15), resulting in a marked improvement in the prediction of multimeric protein structures. However, AlphaFold's capability of predicting large protein complexes is still limited and integrating experimental data in the prediction pipeline is not straightforward. In this study, we introduce AF_unmasked to overcome these limitations. Our results demonstrate that AF_unmasked can integrate experimental information to build larger or hard to predict protein assemblies with high confidence. The resulting predictions can help interpret and augment experimental data. This approach generates high quality (DockQ score > 0.8) structures even when little to no evolutionary information is available and imperfect experimental structures are used as a starting point. AF_unmasked is developed and optimised to fill incomplete experimental structures (structural inpainting), which may provide insights into protein dynamics. In summary, AF_unmasked provides an easy-to-use method that efficiently integrates experiments to predict large protein complexes more confidently.

Fabrication of high-quality surface microtextures on GaN by femtosecond laser direct writing

Gallium nitride (GaN), as a third-generation semiconductor, is highly attractive due to its exceptional physical and chemical properties. Laser direct writing offers an efficient method for the precise processing of hard and brittle materials. In this work, various types of surface microtexture were processed on GaN epilayers using a femtosecond laser with a wavelength of 1030 nm. The effects of the laser energy, single-pulse interval, number of pulses, and number of scan passes on groove machining were investigated with a view to achieving high-quality micromachining. The depth, width, surface morphology, and roughness of the grooves were analyzed using scanning electron microscopy, laser scanning confocal microscopy, and atomic force microscopy. Damage and stress were characterized at the microscale using Raman spectroscopy. High-quality precision machining of different types of periodic surface microtexture at 40 mW laser power was achieved by controlling the process parameters and laser trajectory. Finally, an initial exploration was conducted to examine vector-light-based micro- and nanostructure processing. The findings demonstrate the potential of femtosecond lasers for efficient micromachining of hard and brittle materials without the creation of heat-affected zones or microcracks. The high-quality textured structures achieved through this processing technique have broad and promising applications in optoelectronic devices and tribology.

Wear behavior of all-ceramic micro end mills in micro milling of PMMA

Micro milling is a state-of-the-art micro manufacturing method employed, for instance, in the context of prototyping applications. Due to the high specific cutting forces and small tool diameters inherent to micro milling, tool wear represents a significant challenge for the fabrication of large, high-quality structures. In conventional cutting applications, ceramic tool substrates have been demonstrated to exhibit greater wear resistance than cemented carbides. In the case of micro milling of polymethylmethacrylate (PMMA), all-ceramic micro end mills made from zirconia (Y-TZP) have been observed to exhibit less tool wear than common cemented carbide micro end mills. In previous experiments, these tools exhibited a feed per tooth-dependent wear behavior, regardless of the spindle speed employed. The objective of this study was to investigate the wear behavior of the all-ceramic micro end mills at higher feeds per tooth (up to 7.5 µm) and spindle speeds (up to 110,000 rpm) in PMMA. The objective was to fully characterize the interactions between the all-ceramic micro end mills and the milling parameters for this thermoplastic workpiece material. The wear at the cutting edge was quantified by analyzing the topography with an atomic force microscope, and the results were correlated with the cutting forces and process outcomes. The results were found to be highly sensitive to the spindle speed used, with higher speeds leading to higher temperatures in the cutting zone and thus softening of the PMMA material. In general, micro milling parameters of 110,000 rpm and a feed per tooth of 5 µm resulted in significantly reduced tool wear with no adverse effect on surface quality when micro milling PMMA with all-ceramic micro end mills.

TCRcost: a deep learning model utilizing TCR 3D structure for enhanced of TCR-peptide binding.

Predicting TCR-peptide binding is a complex and significant computational problem in systems immunology. During the past decade, a series of computational methods have been developed for better predicting TCR-peptide binding from amino acid sequences. However, the performance of sequence-based methods appears to have hit a bottleneck. Considering the 3D structures of TCR-peptide complexes, which provide much more information, could potentially lead to better prediction outcomes. In this study, we developed TCRcost, a deep learning method, to predict TCR-peptide binding by incorporating 3D structures. TCRcost overcomes two significant challenges: acquiring a sufficient number of high-quality TCR-peptide structures and effectively extracting information from these structures for binding prediction. TCRcost corrects TCR 3D structures generated by protein structure tools, significantly extending the available datasets. The main and side chains of a TCR structure are separately corrected using a long short-term memory (LSTM) model. This approach prevents interference between the chains and accurately extracts interactions among both adjacent and global atoms. A 3D convolutional neural network (CNN) is designed to extract the atomic features relevant to TCR-peptide binding. The spatial features extracted by the 3DCNN are then processed through a fully connected layer to estimate the probability of TCR-peptide binding. Test results demonstrated that predicting TCR-peptide binding from 3D TCR structures is both efficient and highly accurate with an average accuracy of 0.974 on precise structures. Furthermore, the average accuracy on corrected structures was 0.762, significantly higher than the average accuracy of 0.375 on uncorrected original structures. Additionally, the average root mean square distance (RMSD) to precise structures was significantly reduced from 12.753Å for predicted structures to 8.785Å for corrected structures. Thus, utilizing structural information of TCR-peptide complexes is a promising approach to improve the accuracy of binding predictions.

Optoelectronic properties of GaP:Ti photovoltaic devices

Supersaturated GaP is of interest for the photovoltaic field since optical transitions at energies below the bandgap (2.26 eV) could enhance the overall device efficiency up to theoretically 60%. We have previously demonstrated that Ti supersaturated GaP can be obtained by means of ion implantation and pulsed-laser melting with high structural quality and measured its below-bandgap photoconductivity. In this work we report the first results of a GaP:Ti based photovoltaic device. We have fabricated and measured photovoltaic devices with a GaP:Ti absorber layer showing enhanced external quantum efficiency at wavelengths above 550 nm. Also, we have measured the absorption coefficient (around 104 cm-1) and refractive index of this absorber layer. Finally, current-voltage curves in darkness were measured and analysed using a two-diodes model, showing improvable characteristics. Ideas to enhance the properties of the devices are suggested.

Important Practical Conditions for Getting the High-Quality Foam Concretes

Introduction. The most important reasons justifying the relevance of the research on the practical methods of reducing the consumption of materials in construction industry have been distinguished. The priorities of the Russian Federation referring to the foam concrete technology have been outlined. The level of reliability of the Internet resources describing properties of the dispersedly reinforced foam concretes has been briefly evaluated. The aim of the study is to establish the relationships between the individual properties of fiber, its quantity to the mass of cement ratio, and the most important operational properties of foam concrete manufactured using a single-stage technology.Materials and methods. The types and properties of raw materials used in the experimental research, the methods for controlling the properties of mixes and hardened foam concretes have been defined.Results. The relationship between the speed of phase transition of the viscoplastic properties of the foam concrete mixes into the elastic ones and the possibility of getting a high-quality structure of the hardened foam concrete have been briefly theoretically justified. The physical reasons influencing the direction and speed of forming the raw material dispersed particle clusters in the structure of the interpore partitions of foam concrete mixes have been revealed, which are the important factors to be considered in practice to get the high-strength foam concretes. Depending on the fiber concentration in the concrete mixture composition, the specifics of the fiber physical nature influence on the speed of phase transition from viscoplastic to elastic state have been established. It has been proved that the synergetic effect of dispersed reinforcement is achieved when fiber concentration is enough to provide the significant acceleration of the phase transition. New experimental data on the influence of the individual properties of fiber on the rheological and physico-mechanical properties of D500 foam concrete has been obtained.Discussion and Conclusion. The scientific explanation of the reasons for emergence of the electret effect on the surface of synthetic fiber has been given. It has been revealed that the discovered effect is induced by the specifics of the foam concrete mixture preparation using a single-stage technology. The most important practical conditions due to be met to get the high-strength foam concrete have been determined.

Mesoporous Vinylene-Linked Covalent Organic Frameworks with Heteroatom-Tuned Crystallinity and Photocatalytic Behaviors.

Owing to its prominent π-delocalization and stability, vinylene linkage holds great merits in the construction of covalent organic frameworks (COFs) with promising semiconducting properties. However, carbon-carbon double bond formation reaction always exhibits relatively low reversibility, unfavorable for the formation of high crystalline frameworks through self-error correction and assembling processes. In this work, we report a heteroatom-tuned strategy to build up a series of two-dimensional (2D) vinylene-linked COFs by Knoevenagel condensation of an electron-deficient methylthiazolyl-based monomer with different triformyl substituted (hetero-)aromatic derivatives. The resulting COFs show high-quality periodic mesoporous structures with high surface areas. Embedding heteroatoms into the backbones enables significantly improving their crystallinity, and finely tailoring their semiconducting structures. Upon visible light stimulation, one of the as-prepared COFs with donor-π-acceptor structure could deliver a nearly seven-fold increase in the catalytic activity of hydrogen generation as compared with the other two. Meanwhile, in combination with high crystallinity and the matched conduction band energy level, such kind of COFs can be able to selectively generate singlet oxygen and superoxide radicals in a high ratio of up to 30:1, allowing for catalyzing aerobic thioanisole oxidation in distinctly tunable activities through the substituent electronic effect of the substrates.

Immunoinformatic approach to design an efficient multi-epitope peptide vaccine against melanoma.

Melanoma is known to be the most hazardous and life-threatening type of skin cancer. Although numerous treatments have been authorized in recent years, they often result in severe side effects and may not fully cure the disease. To combat this issue, immunotherapy has emerged as a promising approach for the prevention and treatment of melanoma. Specifically, the use of epitope melanoma vaccine, a subset of immunotherapy, has recently gained attention. The aim of this study was to create a multi-epitope melanoma vaccine using immunoinformatic methods. Two well-known antigens, NYESO-1 and MAGE-C2, were selected due to their strong immunogenicity and high expression in melanoma. To enhance the immunogenicity of the peptide vaccine, Brucella cell-surface protein 31 (BCSP31), the G5 domain of resuscitation-promoting factor B (RpfB) adjuvants, and the helper epitope of pan HLADR-binding epitope (PADRE) were incorporated to vaccine construct. These different segments were connected with suitable linkers and the resulting vaccine structure was evaluated for its physicochemical, structural, and immunological properties using computational tools. The designed vaccine was found to have satisfactory allergenicity, antigenicity, and physicochemical parameters. Additionally, a high-quality tertiary structure of the vaccine was achieved through modeling, refinement, and validation. Docking and molecular dynamics studies showed that the vaccine had a stable and appropriate interaction with the cognate TLR2 and TLR4 receptors during the simulation period. Finally, in silico immune simulation analysis revealed a significant increase in the levels of helper and cytotoxic T cells, as well as the cytokines interferon-gamma and interleukin-2, after repeated exposure to the melanoma vaccine. These results suggest that the designed vaccine has the potential to be an effective therapeutic option for melanoma. However, additional in vitro and in vivo validations are crucial to assess real-world efficacy and safety.

EC-Conf: A ultra-fast diffusion model for molecular conformation generation with equivariant consistency

Despite recent advancement in 3D molecule conformation generation driven by diffusion models, its high computational cost in iterative diffusion/denoising process limits its application. Here, an equivariant consistency model (EC-Conf) was proposed as a fast diffusion method for low-energy conformation generation. In EC-Conf, a modified SE (3)-equivariant transformer model was directly used to encode the Cartesian molecular conformations and a highly efficient consistency diffusion process was carried out to generate molecular conformations. It was demonstrated that, with only one sampling step, it can already achieve comparable quality to other diffusion-based models running with thousands denoising steps. Its performance can be further improved with a few more sampling iterations. The performance of EC-Conf is evaluated on both GEOM-QM9 and GEOM-Drugs sets. Our results demonstrate that the efficiency of EC-Conf for learning the distribution of low energy molecular conformation is at least two magnitudes higher than current SOTA diffusion models and could potentially become a useful tool for conformation generation and sampling.Scientific ContributionsIn this work, we proposed an equivariant consistency model that significantly improves the efficiency of conformation generation in diffusion-based models while maintaining high structural quality. This method serves as a general framework and can be further extended to more complex structure generation and prediction tasks, including those involving proteins, in future steps.

Additive manufacturing of Diels-Alder self-healing polymers: Separate heating system to enhance mechanical, healing properties and assembly-free smart structures

Over the past decades, self-healing polymers have become increasingly popular due to their unique ability to recover mechanical and functional properties after sustaining structural damage, which significantly extends their lifespan compared to traditional polymers. Material Extrusion (MEX) 3D printing has recently emerged as a possible manufacturing approach for processing self-healing polymers; however, commercial MEX 3D printers lack of the flexibility to fabricate complex and functional structures based on such materials. In this work, an innovative MEX setup for extruding self-healing polymer networks based on a thermo-reversible reaction is presented. The proposed approach is based on the leverage of a separate heating system (SHS), enabling the degelation of the self-healing polymer network into a printable ink. This SHS regulates both the syringe-barrel, and nozzle temperatures during the processing (degelation and extrusion) of self-healing inks, leading to enhanced mechanical performance (Young modulus, tensile strength), and extrusion accuracy of 3D printed structures. The effectiveness of the SHS-based approach is demonstrated by an improved geometrical accuracy (filament deviation reduced by 26 %), which is directly correlated to the mitigation of the extrusion force (variability reduced by 77 %). Moreover, the SHS approach also improved both the mechanical properties and the self-healing performance of the printed parts. Finally, two different self-healing polymers a dielectric and an electrically conductive were extruded in a single manufacturing cycle to fabricate a self-sensing structure. This structure is capable of detecting bending with a sensitivity of 3.10 Ω/degree, even after healing. This paper aims to advance the role of MEX beyond its current limitations by enabling processing of high-quality self-healing structures with embedded sensors.