Search Results (1,236)

Resistive switching (RS) phenomena are nowadays one of the most studied topics in the area of microelectronics. It can be observed in Metal–Insulator–Metal (MIM) structures that are the basis of resistive switching random-access memories (RRAMs). In the case of commercial use of RRAMs, it is beneficial that the applied materials would have to be compatible with Complementary Metal-Oxide-Semiconductor (CMOS) technology. Fabricating methods of these materials can determine their stoichiometry and structural composition, which can have a detrimental impact on the electrical performance of manufactured devices. In this study, we present the influence of the Ar/N₂ ratio during reactive magnetron sputtering of titanium nitride (TiN) electrodes on the resistive switching behavior of MIM devices. We used silicon oxide (SiOx) as a dielectric layer, which was characterized by the same properties in all fabricated MIM structures. The composition of TiN thin layers was controlled by tuning the Ar/N₂ ratio during the deposition process. The fabricated conductive materials were characterized in terms of chemical and structural properties employing X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis. Structural characterization revealed that increasing the Ar content during the reactive sputtering process affects the crystallite size of the deposited TiN layer. The resulting crystallite sizes ranged from 8 Å to 757.4 Å. The I-V measurements of fabricated devices revealed that tuning the Ar/N₂ ratio during the deposition of TiN electrodes affects the RS behavior. Our work shows the importance of controlling the stoichiometry and structural parameters of electrodes on resistive switching phenomena. Full article

In response to the demand for advanced materials in extreme environments, researchers have developed a variety of bulk and thin-film materials. One of the best-known processes for altering the mechanical and tribological properties of materials is surface engineering techniques. These involve various approaches to synthesize thin-film coatings, along with post-deposition treatments. The need for self-lubricating materials in extreme situations such as high-temperature applications, cryogenic temperatures, and vacuum systems has attracted the attention of researchers. They have fabricated several types of thin films using CVD and PVD techniques to meet this demand. Among the various techniques used for fabricating self-lubricating coatings, sputtering stands out as a special one. It contributes to developing smooth, homogeneous, and crack-free dense microstructures, which further enhance the coatings’ properties. This review explains the need for self-lubricating materials and the different techniques used to synthesize them. It discusses and summarizes the concept of synthesizing various types of self-lubricating films. It shows the different types of self-lubricating material systems, like transition metal-based nitrides and carbides, diamond-like carbon-based materials, and so on. This work also reflects the governing factors like the deposition temperature, doping elements, thickness of the film, deposition pressure, gas flow rate, etc., that influence the deposition results and, consequently, the properties of the film, as well as their advanced applications in different areas. This work reflects the self-lubricating properties of different kinds of films exposed to various environments in terms of their coefficient of friction and wear rate, emphasizing how the friction coefficient affects the wear rate. Full article

Plasma nitriding is a thermo-chemical treatment widely used to improve the tribological properties of austenitic stainless steel, due to the formation of an expanded austenite layer, which presents increased hardness. Although low-temperature plasma nitriding of austenitic stainless steels has been extensively studied in recent years, the reported results consistently show similarly high nitrogen concentrations, owing to the diffusive nature of the process. Excess nitrogen in the expanded austenite can impair the integrity of the treated surface and thus compromise the overall viability of the treatment. In such a context, the present work evaluated the use of intermittent nitrogen flow during plasma nitriding of ISO 5832-1 steel to control nitrogen concentration in the layer formed. Throughout the treatments, alternated cycles were applied between nitrogen flow periods and periods of interruption, which were repeated throughout the process. Different pulse conditions were used, in which the nitrogen flow corresponded to 10%, 15% and 50% of the cycle time. The results indicated that, in the intermittent flow condition with 50% time of nitrogen offer, the layer thickness, nitrogen concentration, and hardness values were very close to those observed in treatments carried out with continuous flow. On the other hand, in the conditions where the nitrogen flow was kept at 10% and 15% of the cycle, more significant differences were observed compared to the results obtained in continuous flow treatments. Nevertheless, those samples presented a substantial improvement in the surface hardness compared with the untreated steel. Therefore, the intermittent nitrogen flow can be used during plasma nitriding to control expanded austenite properties, enabling the design of surface properties. Full article

The electrical properties of contacts to p-type nitride semiconductor devices, based on gallium nitride, were simulated by ab initio and drift-diffusion calculations. The electrical properties of the contact are shown to be dominated by the electron-transfer process from the metal to GaN, which is related to the Fermi-level difference, as determined by both ab initio and model calculations. The results indicate a high potential barrier for holes, leading to the non-Ohmic character of the contact. The electrical nature of the Ni–Au contact formed by annealing in an oxygen atmosphere was elucidated. The influence of doping on the potential profile of p-type GaN was calculated using the drift-diffusion model. The energy-barrier height and width for hole transport were determined. Based on these results, a new type of contact is proposed. The contact is created by employing multiple-layer implantation of deep acceptors. The implementation of such a design promises to attain superior characteristics (resistance) compared with other contacts used in bipolar nitride semiconductor devices. The development of such contacts will remove one of the main obstacles in the development of highly efficient nitride optoelectronic devices, both LEDs and LDs: energy loss and excessive heat production close to the multiple-quantum-well system. Full article

In this study, tin oxide (SnO₂) resistive random-access memory (RRAM) thin films were fabricated using the thermal evaporation and radiofrequency and dc frequency sputtering techniques for metal–insulator–metal (MIM) structures. The fabrication process began with the deposition of a silicon dioxide (SiO₂) layer onto a silicon (Si) substrate, followed by the deposition of a titanium nitride (TiN) layer to serve as the bottom electrode. Subsequently, the tin oxide (SnO₂) layer was deposited as the resistive switching insulator. Two types of top electrodes were developed to investigate the influence of different oxygen concentrations on the bipolar switching, electrical characteristics, and performance of memory devices. An aluminum (Al) top electrode was deposited using thermal evaporation, while a platinum (Pt) top electrode was deposited via dc sputtering. As a result, two distinct metal–insulator–metal (MIM) memory RRAM device structures were formed, i.e., Al/SnO₂/TiN/SiO₂/Si and Pt/SnO₂/TiN/SiO₂/Si. In addition, the symmetry bipolar switching characteristics, electrical conduction mechanism, and oxygen concentration factor of the tin oxide-based memory devices using rapid thermal annealing and different top electrodes were determined and investigated by ohmic, space-charge-limit-current, Schottky, and Poole–Frenkel conduction equations in this study. Full article

The design of photocatalysts capable of generating localized surface plasmon resonance (LSPR) effects represents a promising strategy for enhancing photocatalytic activity. However, the mechanistic role of plasmonic nanoparticles-induced interfacial electric fields in driving photocatalytic processes remains poorly understood. To produce a Schottky junction, varying amounts of Au nanoparticles widely utilized to broaden the light absorption were loaded onto ultrathin carbon nitride sheets (Au/UCN). The Au/UCN-20 Schottky junction exhibits exceptional photocatalytic activity, achieving a hydrogen evolution rate (14.2 mmol·g⁻¹ over a 4 h period) while maintaining robust stability through five consecutive photocatalytic cycles. The LSPR activity of Au nanoparticles are responsible for the broadened light absorption spectrum of Au/UCN nanocomposites. The interfacial electric field generated at the Au /UCN heterojunction is proposed to enhance charge-transfer efficiency through Schottky barrier penetration of photocarriers, mediated by electric field-driven carrier migration, according to surface potential and finite-difference time-domain (FDTD). These findings uncover a previously obscured photocatalytic mechanism driven by LSPR-induced interfacial electric fields, pioneering a quantum-dot-directed strategy to precisely engineer charge dynamics in advanced photocatalysts via targeted manipulation of nanoscale electric field effects. Full article

The objective of this study was to investigate the physicochemical properties of hybrid coatings with titanium nitride and boron nitride nanoparticles deposited on the TiAlV medical alloy via the sol–gel process. The developed layers were intended to impart bactericidal properties and provide protection against surgical abrasions during the implantation procedure. This study focused on evaluating the microstructure (SEM + EDS), structure (XRD, FTIR), and surface properties, including wettability, surface free energy, and roughness of the synthesized layers. Our results confirmed that it was feasible to produce hybrid layers with various microstructures and diverse layer morphologies. The FTIR and XRD structural analyses confirmed the presence of an organosilicon matrix incorporating the two aforementioned types of ceramic particles. Full article

As power electronic modules are increasingly required to provide improved heat dissipation, aluminum nitride (AlN) stands out against other ceramic materials. At the same time, more cost-efficient production of customized products demands shorter development cycles and innovative manufacturing processes. Conventional process chains in power electronics are usually long and inflexible; thus, innovative ways to reduce process steps and faster prototyping are needed. Therefore, this study investigates the usage of additive manufacturing technology—laser-based powder bed fusion of metal powder (PBF-LB/M)—namely copper (Cu), on AlN substrates for power electronic applications. It is found that specific electrical conductivity values can be achieved up to 31 MS/m, and adhesion measured by shear testing reaches 15 MPa. In reliability testing, the newly produced samples exhibit a 25% decrease in adhesion after 250 cycles, which is comparatively moderate. This study shows the feasibility of PBF-LB/M of Cu powder on AlN, emphasizing its strengths and highlighting remaining weaknesses. Full article

Optical coordinate measurement is a universal technique that aligns with the rapid development of industrial technologies and new materials. Nevertheless, can this technique be consistently effective when applied to the precise measurement of all types of materials? As shown in this article, an analysis of optical measurement systems reveals that some materials cause difficulties during the scanning process. This article details the matting process, resulting, as demonstrated, in lower measurement uncertainty values compared to the pre-matting state, and identifies materials for which applying a matting spray significantly improves the measurement quality. The authors propose a classification of materials into easy-to-scan and hard-to-scan groups, along with specific procedures to improve measurements, especially for the latter. Tests were conducted in an accredited Laboratory of Coordinate Metrology using an articulated arm with a laser probe. Measured objects included spheres made of ceramic, tungsten carbide (including a matte finish), aluminum oxide, titanium nitride-coated steel, and photopolymer resin, with reference diameters established by a high-precision Leitz PMM 12106 coordinate measuring machine. Diameters were determined from point clouds obtained via optical measurements using the best-fit method, both before and after matting. Color measurements using a spectrocolorimeter supplemented this study to assess the effect of matting on surface color. The results revealed correlations between the material type and measurement accuracy. Full article

In recent years, significant attention has been directed toward the development of coating materials capable of tailoring surface properties for various functional applications. Transition metal nitrides, in particular, have garnered interest due to their superior physical and chemical properties, including high hardness, excellent wear resistance, and strong corrosion resistance. In this study, a fabrication process for CrN-based thin films was developed by combining reactive direct current magnetron sputtering (dcMS) with post-deposition annealing in air. CrN coatings were deposited by reactive dcMS using different argon-nitrogen (Ar:N₂) gas ratios (4:1, 3:1, 2:1, and 1:1), followed by annealing at 550 °C for 1.5 h in ambient air. XRD and EDS analysis revealed that this treatment results in the formation of a composite phase comprising CrN and Cr₂O₃. The resulting coating exhibited favorable mechanical and tribological properties, including a maximum hardness of 12 GPa, a low wear coefficient of 0.254 and a specific wear rate of 7.05 × 10⁻⁶ mm³/N·m, making it a strong candidate for advanced protective coating applications. Full article

Over efficient photocatalysts, CO₂ photoreduction typically converts CO₂ into low-carbon chemicals, which serve as raw materials for downstream synthesis processes. Here, an efficient composite photocatalyst heterojunction (Cu₂O-u/g-C₃N₄) has been fabricated to reduce CO₂. Graphitic carbon nitride (g-C₃N₄) was synthesized via thermal polymerization of urea at 550 °C, while pre-dispersed Cu₂O derived from urea pyrolysis (Cu₂O-u) was prepared by thermal reduction of urea and CuCl₂·2H₂O at 180 °C. The heterojunction Cu₂O-u/g-C₃N₄ was subsequently constructed through hydrothermal treatment at 180 °C. This heterojunction exhibited a bandgap of 2.10 eV, with dual optical absorption edges at 485 nm and above 800 nm, enabling efficient harvesting of solar light. Under 175 W mercury lamp irradiation, the heterojunction catalyzed liquid-phase CO₂ photoreduction to formic acid, acetic acid, and methanol. Its formic acid production activity surpassed that of pristine g-C₃N₄ by 3.14-fold and TiO₂ by 8.72-fold. Reaction media, hole scavengers, and reaction duration modulated product selectivity. In acetonitrile/isopropanol systems, formic acid and acetic acid production reached 579.4 and 582.8 μmol·h⁻¹·g_cat⁻¹. Conversely, in water/triethanolamine systems, methanol production reached 3061.6 μmol·h⁻¹·g_cat⁻¹, with 94.79% of the initial conversion retained after three cycles. Finally, this work ends with the conclusions of the CO₂ photocatalytic reduction to formic acid, acetic acid, and methanol, and recommends prospects for future research. Full article

This study investigates the effects of ultrasonic nanocrystalline surface modification (UNSM) on the formation of nitride layers in Ti-6Al-4V alloy during ion-plasma nitriding (IPN). Various UNSM parameters, including vibration amplitude, static load, and processing temperature, were systematically varied to evaluate their influence on microstructure, hardness, elastic modulus, and tribological behavior. The results reveal that pre-treatment with optimized UNSM conditions significantly enhances nitrogen diffusion, leading to the formation of dense and uniform TiN/Ti₂N layers. Samples pre-treated under high-load and elevated-temperature UNSM exhibited the greatest improvements in surface hardness (up to 25%), elastic modulus (up to 18%), and wear resistance, with a reduced and stabilized friction coefficient (~0.55). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses confirmed microstructural densification, grain refinement, and increased nitride phase intensity. These findings demonstrate not only the scientific relevance but also the practical potential of UNSM as an effective surface activation technique. The hybrid UNSM + IPN approach may serve as a promising method for extending the service life of load-bearing biomedical implants and engineering components subjected to intensive wear. Full article

This study presents the development of a novel Cu–Co–O-codoped graphitic carbon nitride (g-C₃N₄) catalyst for efficient peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX) in aqueous environments. The synthesized Cu–Co–O-g-C₃N₄ catalyst demonstrated exceptional catalytic performance, achieving 90% SMX removal within 10 min—significantly outperforming pristine g-C₃N₄ (14%) and O-doped g-C₃N₄ (22%)—with a reaction rate constant of 0.63 min⁻¹. The superior activity was attributed to the synergistic effects of Cu-Co bimetallic doping and oxygen incorporation, which enhanced the active sites, stabilized metal ions, and minimized leaching. Mechanistic studies revealed a dual-pathway degradation process: (1) a radical pathway dominated by sulfate radicals (SO₄•⁻) and (2) a non-radical pathway driven by singlet oxygen (¹O₂), with the latter identified as the dominant species through quenching experiments. The catalyst exhibited broad pH adaptability and optimal performance at neutral to alkaline conditions. Characterization techniques (XRD, FTIR, XPS) confirmed successful doping and revealed that oxygen incorporation modified the electronic structure of g-C₃N₄, improving charge carrier separation. This work provides a sustainable strategy for antibiotic removal, addressing key challenges in advanced oxidation processes (AOPs), and highlights the potential of multi-heteroatom-doped carbon nitride catalysts for water purification. Full article

Hot work die steel is an alloy steel with good high-temperature performance, which is widely used in mechanical manufacturing, aerospace, and other fields. During the working process of hot working mold steel, it is subjected to high temperature, wear, and other effects, which can lead to a decrease in the surface hardness of the mold, accelerate surface damage, shorten the service life, and reduce the quality of the workpiece. In order to improve the wear resistance of the mold, this paper conducts two surface treatments, chrome plating and nitriding, on the surface of hot work mold steel, and compares the high-temperature wear behavior of the materials after the two surface treatments. The results indicate that the hot work die steel obtained higher surface hardness and wear resistance after nitriding surface modification. After nitriding treatment, the surface of hot work die steel contains ε phase (Fe_2–3N), which improves its surface hardness and wear resistance, thus exhibiting better surface hardness and wear resistance than the chrome-plated sample. In this study, the high-temperature wear behavior of hot work die steel after two kinds of surface strengthening treatments was deeply discussed, and the high-temperature wear mechanism of steel after surface strengthening was revealed. It provides a theoretical basis and experimental basis for the surface modification of hot working die steel, and also provides new ideas and methods for improving the service life and workpiece quality of hot working die steel in industrial production. In this study, the advantages and disadvantages of high-temperature wear resistance of hot working die steel after chromium plating and nitriding were systematically compared for the first time, which provided a scientific basis for the selection of surface strengthening technology of hot working die steel and had important academic value and practical application significance. Full article

Silicon nitride (Si₃N₄) ceramic is widely used in the production of structural components. The surface wettability is closely related to the service life of materials. Laser surface texturing is considered an effective method for controlling surface wettability by processing specific patterns. This research focused on the laser surface texturing of a Si₃N₄ ceramic, employing rectangular patterns instead of the typical dimple designs, as these had promising applications in heat transfer and hydrodynamic lubrication. The effects of scanning speed and number of scans on the change of the morphologies and dimensions of the grooves were investigated. The results indicated that the higher scanning speed and fewer number of scans resulted in less damage to the textured surface. As the scanning speed increased, the width and depth of the grooves decreased significantly first, and then fluctuated. Conversely, increasing the number of scans led to an increase in the width and depth of the grooves, eventually stabilizing. The analysis of the elemental composition of different areas on the textured surface presented a notable increase in oxygen content at the grooves, while Si and N levels decreased. It was mainly caused by the chemical reaction between Si₃N₄ ceramic and oxygen during laser surface texturing in an air environment. This study also assessed the wettability of the textured surface, finding that the contact angle of the water droplet was significantly affected by the groove dimensions. After laser surface texturing, the contact angle increased from 35.51 ± 0.33° to 57.52 ± 1.83°. Improved wettability was associated with smaller groove volume, indicating better hydrophilicity at lower scanning speed and enhanced hydrophobicity with a fewer number of scans. Full article