Nitride Layer Research Articles

Mechanical Properties of Indentation in Plasma Nitrided and Nitrocarburized Austenitic Stainless Steel AISI 321

Austenitic stainless steels are widely used due to their resistance to corrosion and to the possibility of using them at temperatures above 600 °C. Plasma nitriding and nitrocarburizing consist of a thermochemical process that introduces nitrogen and nitrogen/carbon, in atomic form, allowing the formation of second phases of these elements with the substrate. These thermochemical treatments of plasma nitriding and nitrocarburizing were performed on austenitic stainless steel AISI 312 at temperatures of 400 °C and 500 °C, obtaining thicknesses of around 12 μm and 24 μm, respectively. Mechanical properties of indentation were obtained using a Hit 300 nanoindenter (Anton Paar), in a load-unload cycle and with a depth of up to 10% of the layer, with Berkovich indenter. The elastic moduli obtained for the nitrided layers were 281 ± 21 GPa (400 °C) and 163 ± 32 GPa (500 °C) and for the nitrocarburized were 214 ± 12 GPa (400 °C) and 169 ± 25 GPa (500 °C). The indentation nanohardness obtained for the nitrided layers were 14.1 ± 1.0 GPa (400 °C) and 3.5 ± 1.2 GPa (500 °C) and for the nitrocarburized layers were 10.8 ± 0.8 GPa (400 °C) and 4.3 ± 1.2 GPa (500 °C). Therefore, these results indicate slightly higher values for the two mechanical properties indentation (elastic modulus and nanohardness) at 400 °C than at 500 °C caused by nitriding compared to nitrocarburizing treatment; however, when considering the percentages of standard deviations, the treatments at 500 °C present much higher values for these properties, as compared to the treatments at 400 °C, a behavior associated with the presence of chromium and iron nitrides.

Boosted visible-light photocatalysis via p-n heterojunction synergy in 3D tin Sulfide-Graphitic carbon nitride nanohybrids

Creating superior nanohybrids with a narrow band gap to harness a larger portion of the solar spectrum is a contemporary necessity. In this study, we utilized a streamlined solvothermal approach to develop a three-dimensional, flower-like tin sulfide (3DF-SnS2) which was integrated atop graphitic nitride layers (g-C3N4). Using a suite of standardized characterization techniques, we delved deep into understanding the design intricacies, structural aspects, photophysical properties, chemical interplay, and surface dynamics of the produced nanohybrids. A noteworthy enhancement in the photocatalytic activity was observed in the p-n heterojunction (3DF-SnS2/g-C3N4) when tested under visible light using the benchmark organic pollutant, Rhodamine B (RhB). When pitted against other nanohybrids from this study, the optimized 3DF-SnS2/g-C3N4 structure displayed a remarkable aptitude for RhB degradation. This was largely due to its adept ability to segregate photo-generated charges efficiently and the harmonious synergy between the 3D and 2D structures, streamlining the charge transfer processes. This commendable photocatalytic efficacy can be attributed to several factors. First, band gap narrowing, the hybrid structure successfully reduces its band gap, allowing for a broader spectrum of solar energy absorption. Second, harmonized charge separation, the interplay between the 3D flower and the 2D sheet structures ensures an effective and efficient separation of photo-generated charges, optimizing their availability for catalytic reactions. 3D/2D Interface Dynamics: The interaction between the 3D floral configuration and the 2D sheet enhances charge mobility, further boosting efficiency. Third, enhanced surface area, the 3D flower-like design of SnS2, in conjunction with the planar nature of g-C3N4, offers abundant active sites for photocatalytic reactions.

Generalized Mie Theory for Full‐Wave Numerical Calculations of Scattering Near‐Field Optical Microscopy with Arbitrary Geometries

Scattering‐type scanning near‐field optical microscopy (s‐SNOM) is becoming a premier method for the nanoscale optical investigation of materials well beyond the diffraction limit. A number of popular numerical methods exist to predict the near‐field contrast for axisymmetric configurations of scatterers on a surface in the quasi‐electrostatic approximation. Here, a fully electrodynamic approach is given for the calculation of near‐field contrast of several scatterers in arbitrary configuration, based on the generalized Mie scattering method. Examples for the potential of this new approach are given by showing the coupling of hyperbolic phonon polaritons in hexagonal boron nitride (hBN) layers and showing enhanced scattering in core–shell systems. In general, this method enables the numerical calculation of the near‐field contrast in a variety of strongly resonant scatterers and is able to accurately recreate spatial near‐field maps.

Nano Conducting Particles Based Antireflection Coating for Silicon Solar Cells

An attempt has been made to investigate the effect of antireflection coating containing aluminum nanoparticles over the layer of silicon nitride on silicon surface. In this regard numerical calculations have been performed to obtain reflectance for varying radius (i.e., 50 nm, 62.5 nm and 70 nm) as well as periods (i.e., 100 nm, 110 nm 125 nm, 250 nm and 300 nm) of Al-NCPs using transfer matrix method (TMM). The refractive index of nanoparticles under consideration is wavelength dependent. Inclusion of metal nanoparticles in the antireflection coating has reduced reflectance significantly. Calculated reflectance has been used as an external file in PC1D simulator to study the performance of silicon solar cells.

Новые соединения нитрида бора с атомами в sp+sp2-гибридизованном состоянии, сформированные на основе слоя BN-L4-8

The density functional theory (DFT) method was used to determine the crystal structures and electronic properties of new layered polymorphic varieties of boron nitride with a graphyne-like structure. The structures of new graphyne-like monolayers consist of boron and nitrogen atoms in the sp- and sp2-hybridized state and were model-built from a layer of graphene-like boron nitride BN-L4-8 by partial replacement of atoms in the three-coordinated (sp2-hybridized) state by atoms in the two-coordinated state (sp-hybridized). As a result of theoretical analysis, the possibility of the existence of seven sp + sp2 new structures of boron nitride was established: one α-type, three β-types and three γ-types, differing in the proportion of atoms in the sp-hybridized state and their spatial arrangement. However, two of the three structural varieties with a minimum content of atoms in the sp-hybridized state (γ-type) turned out to be unstable and, in the process of geometric optimization, were transformed into structures of graphene-like layers of boron nitride. The structure of the BN-L4-8-γ2 layer passed into the structure of the original graphene-like layer BN-L4-8, while the structure of the BN-L4-8-γ3 layer passed into the structure of the graphene-like layer BN-L4-6-8, where there are no atoms in the sp-hybridized state. The sublimation energies of the new polymorphic varieties range from 16.23 eV/(BN) to 16.70 eV/(BN). The band gap varies from 3.777 eV to 3.878 eV.

Ionic liquid gating of YBa2Cu3O7−x with a BN capping layer for enhanced stability and efficiency

In this study, we explored the impact of ionic liquid gating on YBa2Cu3O7−x superconductivity. We observed that direct contact of YBa2Cu3O7−x and the ionic liquid N-diethyl-N-methyl-N-(2methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI) results in irreversible electrochemical reactions, despite the application of a relatively low gate voltage at 220 K. Capping a thin layer of boron nitride (BN) on YBa2Cu3O7−x enabled a reversible modulation of carrier density at 300 K. Benefiting from the higher ion mobility of ionic liquid at 300 K, this modification led to more than a one-time increase in carrier density, a 3-time improvement in voltage modulation efficiency, and a reversible tuning of the superconducting temperature. These findings suggest that using a BN capping layer holds promise for enhancing the stability and efficiency of devices using ionic liquid gating.

Effect of Nitrocarburizing and Post-oxidation Processes on the Microstructure and Surface Properties of AISI 4140 Steel

AISI 4140 çeliği, orta karbonlu düşük alaşımlı çelikler sınıfında yer almakta olup, yüksek sertleşebilirliğe sahip olması ve nispeten ekonomik bir çelik olması nedeniyle endüstride yaygın olarak kullanılmaktadır. AISI 4140 çeliği aynı zamanda nitrürlebilen çelikler arasında yer almaktadır. Nitrürleme işlemiyle, yüzeyde elde edilen sert nitrür tabakası sayesinde sadece aşınmaya dirençli bir yüzey değil aynı zamanda yorulma dayanımında da artış sağlanmaktadır. Bu çalışmada, düşük basınçlı gaz nitrokarbürleme işlemi ve farklı sürelerde son oksidasyon işlemi uygulanmış AISI 4140 çeliğinin mikroyapısal ve yüzey özellikleri araştırılmıştır. Bu amaçla, AISI 4140 çelik numuneler, 850 °C'de 60 dk östenitlenmiş 60 °C’de yağda soğutulmuştur. Soğutma sonrası numuneler 630 °C’de 60 dk temperlenmiştir. Gaz nitrokarbürleme işlem basamakları; 350 °C’de 45 dk ön oksidasyon, 550 °C’de 90 dk nitrürleme ve 550°C’de 480 dk nitrokarbürleme uygulanmış ve ardından numuneler 45-180 dakika aralığında su buharı kullanılarak son oksidasyon işlemine tabi tutulmuştur. Mikroyapısal karakterizasyon çalışmaları optik mikroskop, tarama elektron mikroskobu (SEM), enerji dağılımlı X ışını spektrum analizi (EDX), X ışını kırınımı (XRD) analizi, mikrosertlik ve yüzey pürüzlülüğü ölçümleriyle gerçekleştirildi. X ışını analiz sonuçlarından, numunelerin yüzey katmanının demir nitrür, ɛ-Fe2-3N ve ɣ’-Fe4N fazlarını ve demir oksit (Fe3O4) içerdiği tespit edilmiştir. Son oksidasyon süresi arttıkça, demir oksit (Fe3O4) tabaka kalınlığını arttığı belirlendi. Nitrokarbürlenmiş ve son oksidasyon işlemi uygulanmış AISI 4140 çelik numuneler içerisinde, en iyi sertlik derinliği, yüzey sertliği ve yüzey pürüzlülüğü birleşimi 150 dakikada son oksidasyon uygulanmış elde edilmiştir.

Improved Stability of Graphene-Coated CMOS ISFETs for Biosensing.

A polymer-assisted graphene transfer method is used to transfer sheets of monolayer and multilayer graphene onto the passivation layer of ion-sensitive field effect transistor arrays. The arrays are fabricated using commercial 0.35 μm complementary metal-oxide-semiconductor (CMOS) technology and contain 3874 pixels sensitive to pH changes on the top silicon nitride surface. By inhibiting dispersive ion transport and hydration of this underlying nitride layer, the transferred graphene sheets help address non-idealities in the sensor response while retaining some pH sensitivity due to the presence of ion adsorption sites. Improvements in hydrophilicity and electrical conductivity of the sensing surface after graphene transfer, as well as in-plane molecular diffusion along the graphene-nitride interface, also greatly improve spatial consistency across an array, allowing for ∼20% more pixels to remain within operating range and enhancing sensor reliability. Multilayer graphene offers a better performance trade-off than monolayer graphene, reducing drift rate by ∼25% and drift amplitude by ∼59% with minimal reduction in pH sensitivity. Monolayer graphene offers slightly better temporal and spatial uniformity in performance of a sensing array, which is associated with the consistency in layer thickness and a lower defect density.

Phonon Thermal Transport at Interfaces of a Graphene/Vertically Aligned Carbon Nanotubes/Hexagonal Boron Nitride Sandwiched Heterostructure

Molecular dynamics simulation is used to calculate the interfacial thermal resistance of a graphene/carbon nanotubes/hexagonal boron nitride (Gr/CNTs/hBN) sandwiched heterostructure, in which vertically aligned carbon nanotube (VACNT) arrays are covalently bonded to graphene and hexagonal boron nitride layers. We find that the interfacial thermal resistance (ITR) of the Gr/VACNT/hBN sandwiched heterostructure is one to two orders of magnitude smaller than the ITR of a Gr/hBN van der Waals heterostructure with the same plane size. It is observed that covalent bonding effectively enhances the phonon coupling between Gr and hBN layers, resulting in an increase in the overlap factor of phonon density of states between Gr and hBN, thus reducing the ITR of Gr and hBN. In addition, the chirality, size (diameter and length), and packing density of sandwich-layer VACNTs have an important influence on the ITR of the heterostructure. Under the same CNT diameter and length, the ITR of the sandwiched heterostructure with armchair-shaped VACNTs is higher than that of the sandwiched heterostructure with zigzag-shaped VACNTs due to the different chemical bonding of chiral CNTs with Gr and hBN. When the armchair-shaped CNT diameter increases or the length decreases, the ITR of the sandwiched heterostructure tends to decrease. Moreover, the increase in the VACNT packing density also leads to a continuous decrease in the ITR of the sandwiched heterostructure, attributed to the extremely high intrinsic thermal conductivity of CNTs and the increase of out-of-plane heat transfer channels. This work may be helpful for understanding the mechanism for ITR in multilayer vertical heterostructures, and provides theoretical guidance for a new strategy to regulate the interlayer thermal resistance of heterostructures by optimizing the design of sandwich layer thermal interface materials.

High transparent conductive Ga-doped ZnO-based multilayer thin films with embedded ultrathin TiN layer deposited in oxygen-containing atmosphere.

To avoid metal layer oxidation during the deposition of transparent conductive oxide (TCO)/metal/TCO multilayer films in an oxygen-containing atmosphere, the ultra-thin (<10 nm) titanium nitride (TiN) layer has been proposed to replace metal embedding in gallium-doped zinc oxide (GZO) film for the development of indium-free transparent electrodes. The effects of TiN thickness on the structure, morphology, electrical, and optical properties of GZO/TiN/GZO multilayer thin films deposited in argon-oxygen mixtures on glass substrates by magnetron sputtering are investigated. The experimental results reveal that multilayers with the 8 nm-thick TiN layer have the optimal performance (figure of merit of 2.75 × 10-1 Ω-1): resistivity of 4.68 × 10-5 Ω cm, and optical transmittance of above 91% in the visible region, which is superior to the sandwich film with the metal embedded layer.

To elucidate the effect of alloying elements for enhanced nitriding of aluminum: A multiscale computational study

The limitations of aluminum (Al) are discussed in certain industrial applications, owing to its low hardness and wear resistance. To overcome these limitations, surface modification techniques, such as the formation of aluminum nitride (AlN) layers on the Al surface, have been explored. However, conventional surface-nitriding processes have low productivity, and it is essential to develop a cost-effective method to ensure higher nitriding rates. This paper presents the results of a multiscale computational study on the atomic-scale mechanisms involved in gas nitriding processes and the effects of alloying elements on reaction kinetics using density functional theory calculations. This study also provides insights into the thermodynamic stability and kinetics of the process, contributing to the design and optimization of the nitriding process for the formation of AlN on Al surfaces using Thermo-Calc. and microkinetic analyses. This study demonstrates the potential of multiscale computational methods for advancing the understanding of surface modification techniques and their applications for nitriding on the surface of Al and suggests the best alloying element to enhance the nitriding rate.

Sandwich-Structured Anode Enables High Stability and Enhanced Zinc Utilization for Aqueous Zn-Ion Batteries

Constructing a current collector is a promising approach to modifying the zinc anode. However, most collectors exhibit top zinc deposition patterns, leading to unsatisfactory zinc utilization and instability. To address this issue, we have developed a new sandwich deposition approach in which a boron nitride layer (BN layer) is applied onto Cu foils as the current collector, which allows us to achieve the sandwich-structured anode (BN-Zn-Cu). Through experimental characterization and theoretical calculations, the deposition mechanisms of Zn2+ have been explored and verified. The insulating BN layer, the upper layer of the anode, acts as the protective barrier of deposited zinc and accelerates the transmission of zinc ions. The zincophilic Cu substrate, the bottom layer of the anode, promotes Zn deposition without dendrites. Under the synergistic effect of the BN layer and substrate, the sandwich-structured anode enables superior reversibility with 99.49 % coulombic efficiency over 700 cycles and realizes 66.7% zinc utilization at 4 mAh cm−2. Moreover, the assembled BN-Zn-Cu||CNT/MnO2 cells display high stability with an average fading of 0.06% per cycle for 600 cycles. Our work verifies the feasibility of sandwich-structured anodes in enhancing the performance of aqueous zinc-ion batteries, providing an innovative idea for the structural design of metal anodes.

All-BN distributed Bragg reflectors fabricated in a single MOCVD process

Distributed Bragg Reflectors (DBR) are well-established photonic structures that are used in many photonic applications. However, most of the DBRs are based on different materials or require post-process etching which can hinder integration with other components in the final photonic structure. Here, we demonstrate the fabrication of DBR structures consisting only of undoped boron nitride (BN) layers with high refractive index contrast by using metal–organic chemical vapor deposition (MOCVD). This has been achieved in a single process, without the need for any post-process etching. The difference in the refractive index of the component BN layers stems from different degrees of porosity of the individual BN layers, which is a direct result of a different growth temperature. The fabricated DBR structures consist of 15.5 pairs of BN layers and exhibit a reflectance of 87 ± 1% at the maximum. The wavelength of maximum reflectance can be tuned from 500 nm up to the infrared region (IR), by simply adjusting the growth periods of subsequent BN layers. We also demonstrate that the fabricated structures can be used to create an optical microcavity. The fabricated DBRs are very promising candidates for future applications, for example in combination with single-photon emitters in h-BN, which could allow the building of a cavity-based all-BN single-photon source.

Hexagonal Boron Nitride as an Intermediate Layer for Gallium Nitride Epitaxial Growth in Near-Ultraviolet Light-Emitting Diodes.

We introduce the development of gallium nitride (GaN) layers by employing graphene and hexagonal boron nitride (h-BN) as intermediary substrates. This study demonstrated the successful growth of GaN with a uniformly smooth surface morphology on h-BN. In order to evaluate the crystallinity of GaN grown on h-BN, a comparison was conducted with GaN grown on a sapphire substrate. Photoluminescence spectroscopy and X-ray diffraction confirmed that the crystallinity of GaN deposited on h-BN was inferior to that of GaN grown on conventional GaN. To validate the practical applicability of the GaN layer grown on h-BN, we subsequently grew an NUV-LED structure and fabricated a device that operated well in optoelectrical performance experiments. Our findings validate the potential usefulness of h-BN to be a substrate in the direct growth of a GaN layer.

Germanium surface cleaning and ALD of a protective boron nitride overlayer

Germanium exhibits superior hole and electron mobility compared with silicon, making it a promising candidate for replacement of silicon in certain future CMOS applications. In such applications, achieving atomically clean Ge surfaces and the subsequent deposition of ultrathin passivation barriers without interfacial reaction are critical. In this study, we present in situ x-ray photoelectron spectroscopy (XPS) investigations of hydrocarbon removal from the Ge surface utilizing atomic oxygen at room temperature, as well as removal of hydrocarbons and of germanium oxide (GeO2) through atomic hydrogen treatment at 350 °C. Subsequently, atomic layer deposition (ALD) was used to create a protective layer of hexagonal boron nitride (h-BN) with an average thickness of 3 monolayers (ML). Tris(dimethylamino)borane and ammonia precursors were utilized at 450 °C for the deposition process. Intermittent in situ XPS analysis during ALD confirmed h-BN growth, stoichiometry, and the absence of interfacial reaction with Ge. XPS analysis after subsequent exposure of the Ge film with a h-BN overlayer of ∼9 Å average thickness to 7.2 × 104 l of atomic O (O3P) at room temperature yielded no evidence of Ge oxidation, with only the surface layer of the h-BN film exhibiting oxidation. These results present a practical and scalable route toward the preparation of clean Ge surfaces and subsequent deposition of protective, nanothin h-BN barriers for subsequent processing.

High-performance SiO2-SiNx distributed Bragg reflectors fabricated by ion-assisted reactive magnetron sputtering

With the rapid improvement of photonics, the demand for high-performance distributed Bragg reflectors (DBRs) is increasing. In this study, high-performance DBRs stacked by silica and high refractive index silicon nitride layers were designed and fabricated, which were deposited by ion-assisted reactive magnetron sputtering. TEM, EDX, and XPS were utilized to investigate the crystal properties, elemental composition, and bonding properties of the films. Additionally, AFM, SEM, and Raman spectra were used to analyze the morphology, roughness, and stress of DBRs. The result shows that the films prepared by ion-assisted reactive magnetron sputtering are mainly amorphous. DBRs have extremely smooth surfaces with a root mean square roughness (Rq) of approximately 0.5 nm. No obvious defects are found in their surface and cross-section. And the residual stresses of DBRs are relatively low. The reflectance results show that the maximum reflectance of 6-pair DBR on the silicon substrate is higher than 99.9%. The stopband bandwidth covers approximately 800–1150 nm. In this work, DBRs deposited by ion-assisted reactive magnetron sputtering feature high deposition quality, thinness, and broadband high reflection, which have great application potential in high-performance optical devices.

Effect of Ion Flux Variation in DC Magnetron Sputtering on the Deposition of Cubic Boron Nitride Film

Cubic boron nitride (cBN) thin films were deposited using DC magnetron sputtering, and the effect of the ion flux on the deposition behavior and residual stress of the cBN thin films was investigated. To increase the ion flux, the magnetic force ratio of the central/peripheral permanent magnets inserted in the magnetron sputtering source was reduced. Due to the complementary relationship between ion flux and energy for cBN deposition, the critical bias voltage required for cBN nucleation decreased as the ion flux increased. The cBN content of the films was relatively higher under the deposition condition of the increased ion flux. This was interpreted to indicate the thinning of the intervening hexagonal boron nitride (hBN) layer formed prior to cBN nucleation. Comparing the compressive residual stress of the cBN films, the residual stress was relieved as the bias voltage decreased regardless of the ion flux. The increase in ion flux made it possible to deposit the cBN films at a low bias voltage, thereby depositing cBN films with lower residual stress. The results showed that reducing ion energy by increasing ion flux for cBN deposition is a promising method for depositing low-stress cBN thin film having thin intervening hBN layer.

Depth profiling analysis of the nitriding layer formed by gas nitriding of Ti13Nb13Zr alloy

The gas nitriding of Ti13Nb13Zr alloy was performed in a pure nitrogen atmosphere at 1200 °C with different holding times. The variations in the phase constituents, microstructure, and mechanical properties of the nitriding layer with depth were characterized by SEM, XRD, and nanoindentation. Depending on the phase distributions in depth, the nitriding layer could be sequentially divided into an external nitride layer mainly consisting of TiN, an internal nitride layer consisting of TiN, Ti2N and TiN0.3, and an N diffusion region consisting of TiN0.3. The mechanical properties were closely associated with the phase constituents, where the nanohardness of the internal nitride layer, internal nitride layer N diffusion region and substrate were about 17.126±0.399, 12.120±0.386, 5.627±1.080, and 3.632±0.116 GPa, respectively. In the nitriding process, the N diffusion region containing needle-like TiN0.3 precipitates formed in the initial nitriding stage, and then the precipitates were gradually converted to the external and internal nitride layers, whose thickness increased with the nitriding time. Furthermore, the influence of the alloying element redistribution on the N diffusion mechanism was discussed.

Magnetic MXene: A Machine-Learning Model With Small Data

MXenes, comprising of atomically thin layers of transition metal nitrides, carbides, and carbonitrides, exhibit properties which are not found in their corresponding bulk materials. Interestingly, because of the presence of transition metal, MXenes may also provide the candidate materials for observing low-dimensional magnetism. This can be of interest to various applications such as data storage, electromagnetic interference shielding, and spintronic devices. Here, we focus on the magnetic MXenes, which are only a few in number out of known MXenes. We propose machine learning models to predict the magnetic moments of the MXenes and to classify the MXenes based on their chemical stability. Using these models, we propose four new chemically stable MXene materials having a potentially high magnetic moment.

Electrochemical Quantification of Dopamine Sensing in Human Samples Using Bromine Doped Layered gC3N4 Nanosheets

The halogen, bromine (Br) doped layered graphitic carbon nitride (gCN) nanosheets are constructed for a novel electrochemical detection of dopamine (DA). The Br is successfully immobilized in the gCN host lattice, in which Br provides an N-vacancy for -C-N bonding to improve electron transfer and enhance its electrocatalytic properties. The prepared nanosheets are studied by various analytical analyses and the electrochemical behavior of the designed electrode is studied using cyclic voltammetry (CV). The Br-gCN decorated screen-printed carbon electrode (SPCE) has superior electrochemical activity and is stable during exposure to varied pH, however, exhibited better catalytic activity at pH 7. The Br-gCN/SPEC electrodes and their high electrocatalytic performance are used for the detection of dopamine with a lower limit of detection (LoD) of 5 nM concentration. The Br-gCN decorated electrodes exhibited satisfactory results for cyclic stability (up to 100th cycle), repeatability (up to 6 cycles), reproducibility of similarly constructed 6 electrodes, and their electrochemical performance. Furthermore, the fabricated sensor also exhibited a better recovery (>80%) for real-time urine sample analyses.