Boron Incorporation Research Articles

Reduced Pressure – Chemical Vapor Deposition of Monocrystalline and Polycrystalline Si(:B) and SiGe(:B) Layers on Blanket Wafers

In this paper, epitaxial growths or depositions were performed, in 300 mm RP-CVD chambers, on two types of templates: N-type Si substrates or poly-Si/oxide/ P-type Si substrates. SiH4+HCl+H2 and SiH2Cl2+HCl+GeH4+H2 chemistries were used to deposit Si and SiGe layers between 675-750°C and 10-20 Torr on such wafers. Monocrystalline and polycrystalline growth kinetics were similar for intrinsic SiGe. Meanwhile, growth kinetics and boron incorporation were different for mono-Si:B, mono-SiGe:B, poly-Si:B and poly-SiGe:B layers. While the impact of B atoms is well documented in monocrystalline layers, it is still poorly understood for polycrystalline layers. An attempt has therefore been made to quantify it by measuring the poly-structure, with a focus on the poly-grains size and the number of grain boundaries. A lattice contraction coefficient β = - 9.82 * 10-24 cm3 has otherwise been extracted from an in-depth study of the incorporation of B atoms into substitutional sites of the SiGe epitaxial lattice.

Bottom up approach of metal assisted electrochemical exfoliation of boron towards borophene

Electrochemical exfoliation of nonconductive boron to few-layered borophene is reported. This unique effect is achieved via the incorporation of bulk boron into metal mesh inducing electrical conductivity and opening a venue for borophene fabrication via this feasible strategy. The experiments were conducted in various electrolytes providing a powerful tool to fabricate borophene flakes with a thickness of ~ 3–6 nm with different phases. The mechanism of electrochemical exfoliation of boron is also revealed and discussed. Therefore, the proposed methodology can serve as a new tool for bulk scale fabrication of few-layered borophene and speed up the development of borophene-related research and its potential application.

Magnetic Characterization of Electrodeposited Pt1−xNix Alloy Films: Influence of Deposition Potential and the Presence of Boric Acid

Pt1-xNix (x = 0.25 to 0.92) thin films were examined for possible application as magnetic thermometers. The alloys were prepared by potentiostatic electrodeposition from aqueous chloride-based solutions in the presence and absence of 0.5 mol dm−3 B(OH)3. Alloy composition was controlled by the deposition potential with the Ni concentration increasing towards more reducing potentials. Films with x > 0.45 were ferromagnetic with the magnetization at 300 K increasing with nickel content. Magnetization vs temperature (M vs T) at 8 kA m−1 (100 Oe) showed an increase in the Curie temperature from less than 200 K to above 400 K for the alloys investigated. For films deposited at potentials >−0.6 V vs the saturated calomel electrode (SCE), boric acid had negligible effect on the magnetization at the maximum applied field in M vs H measurements. In contrast, for depositions at more reducing potentials <−0.6 V vs SCE the presence of boric acid resulted in diminished magnetization. This effect was attributed to elevated incorporation of oxygen (up to ∼4 atomic %), along with boron incorporation of about 400 μmol mol−1.

Surface-Enriched Boron-Doped TiO2 Nanoparticles as Photocatalysts for Propene Oxidation.

A series of nanostructured boron-TiO2 photocatalysts (B-X-TiO2-T) were prepared by sol–gel synthesis using titanium tetraisopropoxide and boric acid. The effects of the synthesis variables, boric acid amount (X) and crystallization temperature (T), on structural and electronic properties and on the photocatalytic performance for propene oxidation, are studied. This reaction accounts for the remediation of pollution caused by volatile organic compounds, and it is carried out at low concentrations, a case in which efficient removal techniques are difficult and costly to implement. The presence of boric acid during the TiO2 synthesis hinders the development of rutile without affecting the textural properties. X-ray photoelectron spectroscopy analysis reveals the interstitial incorporation of boron into the surface lattice of the TiO2 nanostructure, while segregation of B2O3 occurs in samples with high boron loading, also confirmed by X-ray diffraction. The best-performing photocatalysts are those with the lowest boron loading. Their high activity, outperforming the equivalent sample without boron, can be attributed to a high anatase and surface hydroxyl group content and efficient photo-charge separation (photoelectrochemical characterization, PEC), which can explain the suppression of visible photoluminescence (PL). Crystallization at 450 °C renders the most active sample, likely due to the development of a pure anatase structure with a large surface boron enrichment. A shift in the wavelength-dependent activity profile (PEC data) and the lowest electron–hole recombination rate (PL data) are also observed for this sample.

Higher Water‐Splitting Performance of Boron‐Based Porous CoMnB Electrocatalyst over the Benchmarks at High Current in 1 m KOH and Real Sea Water

AbstractThe development of highly efficient and stable electrocatalysts at an affordable cost is an essential component for the large‐scale implementation of green hydrogen production. In this work, the fabrication of porous CoMnB electrocatalyst is demonstrated with the incorporation of boron into the Co‐Mn matrix by an electrochemical approach for bifunctional water electrocatalysis for the first time. The optimized CoMnB electrocatalyst demonstrates an excellent bifunctionality with a low 2‐E turnover voltage of 1.59 V at 20 mA cm−2 in 1 m KOH. The CoMnB shows a comparable water‐splitting current at low current range as compared with the standard benchmark electrodes of Pt/C||RuO2 in 1 m KOH. Then, the CoMnB outperforms the benchmarks at above 800 mA cm−2, indicating a better H2 and O2 generation performance at the industrial operational condition of high current range. The CoMnB also exhibits superior electrocatalytic activity in real sea water +1 m KOH. In addition, the porous CoMnB electrocatalyst exhibits an excellent stability with stable current for continuous 72 h operation at high current and excellent repeatability after 1000 cycles. The result ranks the CoMnB as one of the best transition metal‐based water‐splitting electrocatalysts at low cost with an easy fabrication approach.

Engineering d-band center of iron single atom site through boron incorporation to trigger the efficient bifunctional oxygen electrocatalysis

Modulating the microenvironment of single-metal active sites holds excellent promises for developing highly efficiently oxygen electrocatalysts. Herein, by combining theoretical predictions and experiments, we reported a general strategy to engineer the electronic properties of iron-nitrogen-carbon (FeN4/C) catalysts via the incorporation of the boron (B) atom for achieving improved catalytic activity in oxygen electrocatalysis. Our theoretical results revealed that B modulation effectively tunes the d-band center of the iron (Fe) active site to optimize its adsorption strength with oxygenated species, greatly enhancing oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) activity. Our experimental measurements then confirmed the above theoretical predictions: the as-synthesized B-doped FeN4/C (Fe-N4-B) material can perform as an eligible bifunctional catalyst for ORR and OER in alkaline media, and its catalytic activity even outperforms the commercial noble metal benchmarks. The present findings provide a promising strategy to further design the advanced catalysts for a wide range of electrochemical applications.

Photoreflectance studies of the band gap alignments in boron diluted BGaInAs/GaAs quantum wells

Band gap alignments of BGaInAs/GaAs quantum wells with mole fractions of indium around 40% and mole fractions of boron ranging from 0% up to 4.75% are studied experimentally by photoreflectance (PR) and photoluminescence (PL). Obtained results are explained within a k · p model within an envelope function approximation. The study shows an increase of the valence band offset with an addition of boron into the thin film at a rate of around 4.2% per 1% of boron incorporated. Non-zero bowing parameters of valence band offsets for ternary alloys with boron (BGaAs and BInAs) are estimated. Moreover, it was observed that unlike in other highly mismatched alloy systems the incorporation of boron does not significantly deteriorate the optical quality of the studied samples, i.e., the broadening of optical transitions observed in PR and PL is very comparable to that observed for the reference QW, and the PL properties of boron containing QWs are similar to the reference boron free QW. Some deterioration of optical quality due to the increased alloy inhomogeneity is observed only for the sample with the highest concentration of B (4.2%).

Electron enriched ternary NiMoB electrocatalyst for improved overall water splitting: Better performance as compared to the Pt/C || RuO2 at high current density

The high energy density and zero carbon emission makes the hydrogen energy most suitable for the next-generation alternative to reduce the greenhouse gas emissions and prevent the climate changes. In this work, the ternary nickel-molybdenum-boron (NiMoB) electrocatalyst is systematically studied and the best optimized NiMoB electrode demonstrates better electrochemical water splitting performance over the benchmark electrodes of Pt/C || RuO2 at high current density. Along with the systematic fabrication parameter optimization, the ternary NiMoB electrocatalyst with the multi-sphere morphology demonstrates significantly high active surface area, low impedance, and low reaction energy barriers with the improved crystallinity of electrodes and absorption and desorption of intermediates. The incorporation of boron in the transition metal matrix of Ni-Mo significantly boosts up the water splitting capability by lowering the kinetic barriers with the electron enriched metallic sites and improved stability of electrodes. Specifically, the turnover overpotential of 1.61 V is achieved at 50 mA/cm2 in 1 M KOH with the improved hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics in a 2-electrode system. More importantly, the NiMoB electrocatalyst demonstrates better performances at high current range above 1250 mA/cm2 in 1 M KOH and 1100 mA/cm2 in seawater (SW) + 1 M KOH. The NiMoB || NiMoB also demonstrates an equivalent water splitting performance in the real SW + 1 M KOH solution. In addition, a very stable chronoamperometry (CA) operation over 12 h at 500 mA/cm2 and 1,000-time repetition of linear sweep voltammetry (LSV) over 8 h in 6 M KOH at 60 °C confirm that the optimized electrode can demonstrate stable and repetitive operations in an industrial electrochemical water splitting condition.

Suppression and compensation effect of oxygen on the behavior of heavily boron-doped diamond films

This work investigates the suppression and compensation effect of oxygen on the behaviors and characteristics of heavily boron-doped microwave plasma chemical vapor deposition (MPCVD) diamond films. The suppression effect of oxygen on boron incorporation is observed by an improvement in crystal quality when oxygen is added during the diamond doping process. A relatively low hole concentration is expected and verified by Hall effect measurements due to the compensation effect of oxygen as a deep donor in diamond. A low acceptor concentration, high compensation donor concentration and relatively larger acceptor ionization energy are then induced by the incorporation of oxygen; however, a heavily boron-doped diamond film with high crystal quality can also be expected. The formation of an oxygen–boron complex structure instead of oxygen substitution, as indicated by the results of x-ray photoelectron spectroscopy, is suggested to be more responsible for the observed enhanced compensation effect due to its predicted low formation energy. Meanwhile, density functional theory calculations show that the boron–oxygen complex structure is easily formed in diamond with a formation energy of –0.83 eV. This work provides a comprehensive understanding of oxygen compensation in heavily boron-doped diamond.

Boron-modified perhydropolysilazane towards facile synthesis of amorphous SiBN ceramic with excellent thermal stability

SiBN ceramics are widely considered to be the most promising material for microwave-transparent applications in harsh environments owing to its excellent thermal stability and low dielectric constant. This work focuses on the synthesis and ceramization of single-source precursors for the preparation of SiBN ceramics as well as the investigation of the corresponding microstructural evolution at high temperatures including molecular dynamic simulations. Carbon- and chlorine-free perhydropolysilazanes were reacted with borane dimethyl sulfide complex at different molar ratios to synthesize single-source precursors, which were subsequently pyrolyzed and annealed under N2 atmosphere (without ammonolysis) to prepare SiBN ceramics at 1100, 1200, and 1300 °C with high ceramic yield in contrast to previously widely-used ammonolysis synthesis process. The obtained amorphous SiBN ceramics were shown to have remarkably improved thermal stability and oxidation resistance compared to amorphous silicon nitride. Particularly, the experimental results have been combined with molecular dynamics simulation to further study the amorphous structure of SiBN and the atomic-scale diffusion behavior of Si, B, and N at 1300 °C. Incorporation of boron into the Si—N network is found to suppress the crystallization of the formed amorphous silicon nitride and hence improves its thermal stability in N2 atmosphere.

Covalent Triazine Frameworks with Defective Accumulation Sites: Exceptionally Modulated Electronic Structure for Solar-Driven Oxidative Activation of Peroxymonosulfate.

Precisely tailoring the electronic structure and surface chemistry of metal-free covalent triazine frameworks (CTFs) for efficient photoactivation of oxyanions is environmentally desirable but still challenging. Of interest to us in this work was to construct artificial defective accumulation sites into a CTF network (CTF-SDx) to synchronously modulate both thermodynamic (e.g., band structure) and kinetic (e.g., charge separation/transfer/utilization and surface adsorption) behaviors and probe how the transformation affected the subsequent activation mechanism of peroxymonosulfate (PMS). With the incorporation of terminal cyano (-CN) groups and boron (B) dopants, the delocalized CTF-SD underwent a narrowed electronic energy gap for increased optical absorption as well as a downshifted valence band position for enhanced oxidation capacity. Moreover, the localized charge accumulation regions induced by the electron-withdrawing -CN groups facilitated the exciton dissociation process, while the adjacent electron-deficient areas enabled strong affinity toward PMS molecules. All of these merits impelled the photoactivation reaction with PMS, and a 15-fold enhancement of bisphenol-A (BPA) removal was found in the CTF-SD2/PMS/vis system compared with the corresponding pristine CTF system. Mechanistic investigations demonstrated that this system decomposed organics primarily through a singlet oxygen-mediated nonradical process, which originated from PMS oxidative activation over photoinduced holes initiated by an electron transfer process, thereby opening a new avenue for designing an efficient PMS activation strategy for the selective oxidation of organic pollutants.

Boron Incorporation in Silicate Melt: Pressure-induced Coordination Changes and Implications for B Isotope Fractionation

Ab initio molecular dynamics simulations have been employed to investigate the nature of boron incorporation in a haplobasalt melt at pressures up to 8 GPa. At ambient pressure, boron is predominantly incorporated as trigonal planar BO3 units. With increasing pressure, the proportion of tetrahedral BO4 increases markedly in parallel with increases in the coordination of other cations in silicate liquids. In contrast to studies of high-pressure boron-rich silicate glasses and liquids where boron units are polymerized, simulations of low B-concentration liquid here indicate that boron does not adopt a significant role as a network-forming cation. Marked changes in the proportion of BO4 in silicate melt at even moderate pressures (from 5 to 20%, over the pressure range 0–3 GPa) imply that pressure may significantly affect the extent of melt/fluid and melt/crystal boron isotope fractionation. This pressure-effect should be considered when using boron isotope data to elucidate processes occurring within the mantle.

Exploring original properties of GaN-BN alloys using high-throughput ab initio computation

GaN alloyed with boron (B) is a potential candidate for wide band gap materials and for ultraviolet optoelectronic device applications. Using evolutionary algorithm and density functional theory, we investigate here the thermodynamic, mechanical, dynamical and optical properties of GaN-BN alloys. Three ordered BxGa1-xN structures: cubic (BGa3N4, and B3GaN4, space group P-43 m), and tetragonal (BGaN2, space group P-42 m) have been explored. The calculated relatively large mixing enthalpies point out that large miscibility gap exists in BGaN system (i.e., ΔH∼80 meV for x = 0.5). However, weak ΔH for x = 0.25 (ΔH∼24 meV) suggests that BGa3N4 compound is –thermodynamically- slightly unstable. Analysis of the computed elastic constants and phonon dispersion curves reveal that the three ordered structures are mechanically and dynamically stable. Our results show that BGa3N4 exhibits outstanding mechanical properties, such as a large bulk modulus (~328 GPa), important shear modulus (~248 GPa), and strong Vickers hardness of ~ 33 GPa. Moreover, the use of LDA-1/2 functional evidences that the incorporation of boron in GaN gives a huge optical band-gap bowing parameter of b∼11 eV for the entire range of composition, which is in agreement with experiment. In addition, we highlight the prevailing role of chemical and stress effects responsible of the giant disorder in this ternary system.

Enhancement of breakdown strength and electromigration reliability for cobalt lines lightly doped with boron

Conventional copper interconnect is facing a considerable rise in electrical resistivity for applications in nanoscale devices due mainly to its significant-high electron mean free path. Cobalt, a metal with a shorter electron mean free path, has been suggested as the most promising interconnecting material for the next-generation device. Thus, this work studies alloying cobalt film with a small amount of boron as an electromigration retarder without sacrificing its electrical conductivity through evaluating its electrical properties, electromigration resistance, bonding structure, and thermal stability. Examining composition of the boron lightly-doped cobalt films shows that it can be intentionally controlled by the deposition power, yielding the incorporating boron not significantly increasing its electrical resistivity. Additionally, boron incorporation strongly intensifies the breakdown strength and electromigration reliability of the cobalt film. However, boron addition leads to a higher surface energy, and thus causes a degradation of the thermal stability. Nevertheless, the studied boron lightly-doped cobalt film is still thermally stable up to 600 °C, making it a promising interconnecting material for application in nanoscale devices.

Effect of chromium and boron incorporation methods on structural and catalytic properties of hierarchical ZSM-5 in the methanol-to-propylene process

We introduced chromium and boron into the hierarchical structure of ZSM-5 by following an incipient wet impregnation and hydrothermal synthesis approach to enhance the performance of the catalysts in the methanol-to-propylene process. Crystal structure, preferred orientation, and crystal symmetry of synthesized zeolites were discussed using Rietveld refinement and revealed that all synthesized zeolites crystallized in a monoclinic structure, whereas the boron-incorporated sample exhibited an orthorhombic symmetry. Large-scale defect-free single-crystalline structures of hierarchical zeolite created by CTAB and F127 mesoporogens are confirmed by electron microscopy and magic angle spinning nuclear magnetic resonance (MAS NMR). The formation of surface metal oxides and extra-framework metal oxides caused changes in the electronic structure of the components as visible in Si 2p and O 1s spectra. The predominant presence of OH groups and the higher Cr (VI) /Cr (III) ratio account for the better performance of impregnated chromium-ZSM-5 especially in the production of light olefins. The introduction of boron by impregnation further preserved the preferred growth orientation, hierarchical structure with high crystallinity and caused surface acidity changes in favor of increasing propylene selectivity to 67% with a propylene/ethylene ratio of close to 8.

Influence of boron addition on the phase transformation, microstructure, mechanical and in-vitro cellular properties of bredigite-type coatings deposited by a spin coating technique

Doped calcium silicates, e.g. bredigite (Ca7MgSi4O16) have recently become a growing interest in biomedicine thanks to outstanding biocompatibility, bioactivity, and improved mechanical properties when compared to calcium phosphate counterparts. Here, we have produced thin bredigite-type coatings on Ti6Al4V substrate by the polyvinyl alcohol (PVA) assisted sol-gel spin-coating technique and studied the influence of boron incorporation (0.5 and 1.0 mol) on the microstructural, phase, nanomechanical, and in-vitro cellular properties of deposited coatings. Chemical and structural analysis of the coatings was thoroughly performed by Focussed Ion Beam Scanning Electron Microscope (SEM/FIB), Atomic Force Microscopy (AFM), differential thermal analysis (DTA-TG), X-ray diffraction (XRD), and Fourier-Transform Infrared spectroscopy (FTIR), while the nanomechanical properties were evaluated by nanoindentation and nanoscratch tests. Overall, all deposited films were smooth and porous composed of ∼25–50 nm nanoparticles. The boron incorporation increased the coating thickness as a result of PVA interaction with borate ions. The nanomechanical properties (Young's modulus, nanohardness, critical load for cracking) decreased by the boron addition as a result of decreasing the strength of grain boundaries between the nanoparticles. The in-vitro contact cytotoxicity testing revealed high proliferation of the osteoblast cells in all coatings giving the potential of application in orthopedics.

Interfacial boron modification on mesoporous octahedral rhodium shell and its enhanced electrocatalysis for water splitting and oxygen reduction

The research of active and efficient electrocatalysts is of great importance for the practical application of some energy conversion devices. Improving the catalytic activity and utilization efficiency of noble metal is of great importance for the practical application. Here, we report a one-pot synthesis of porous rhodium octahedra through a corner-induced-selective-deposition (CISD) process. After simple interfacial boron modification, the performances towards oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) in alkaline media were greatly enhanced. Especially, a small overpotential of 31 mV at 10 mA/cm2 was achieved for HER, and a high half-wave potential of 914 mV was obtained for ORR, much better than the commercial Pt/C catalysts (55 mV, 891 mV). Density functional theory (DFT) calculation reveals that the boron incorporation optimizes the adsorption properties of catalyst surface and in turn, lowers the overpotentials for the three reactions. This work may be extended to design other nanoscale functional materials with delicate nanostructures and optimized compositions.

Effect of substrate crystalline orientation on boron-doped homoepitaxial diamond growth

Boron-doped diamond layers have been grown by MW PECVD on substrates with a misorientation over the range of 0 to 90° relative to the (100) crystalline plane while keeping all other growth conditions constant. Deposited layers were characterized by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. The deposition rate, surface roughness, and boron incorporation vary according to the substrate misorientation. These results show the essential need for rigorous control of the substrate crystalline orientation in the synthesis of doped diamond for electronic applications. Thick, smooth, and free of surface defects boron-doped epitaxial diamond layers were obtained over a broad range of crystalline orientations at high growth rates and high boron incorporation efficiency. Novelty statementThis work reports on the effect of the substrate crystalline orientation on the morphology, growth rate, and boron incorporation in epitaxial diamond layers deposited by plasma-enhanced chemical vapor deposition.

In vitro biomineralization potential in simulated wound fluid and antibacterial efficacy of biologically-active glass nanoparticles containing B2O3/ZnO

In the present study, SiO2-CaO-B2O3-ZnO (SCBZ), SiO2-CaO-B2O3 (SCB), SiO2-CaO-ZnO (SCZ) and SiO2-CaO (SC) silicate-based glasses were synthesized by the sol-gel method to elucidate the influence of B2O3 and ZnO substitution on glass characteristics aiming to further use in wound healing applications. The amorphous nature, spherical-shaped morphology and nano-sized primary particles of glasses were revealed by XRD and SEM analysis. Moreover, investigating the antibacterial activity of glasses against E.coli and S.aureus bacteria indicated the improved antibacterial properties of SCBZ glass against both bacterial strains compared with SCB and SCZ glasses. Assessment of ion release revealed that the incorporation of zinc induces a more stable glass network with a lower tendency to dissolution contrary to the incorporation of boron, which facilitated the dissolution of glass by the formation of more reactive SiOB and BO bonds. Glasses were immersed in Simulated Wound Fluid (SWF) to predict their mineralization susceptibility. Morphological studies and FTIR analysis showed the formation of cauliflower-like hydroxy-carbonated apatite on the surface of SCB and SC glasses after 14 days. In contrast, the presence of Zn in SCBZ and SCZ glasses inhibited the formation of crystalline apatite and induced the deposition of spherical-shaped amorphous apatite. Our study suggests that the co-incorporation of B and Zn in SCBZ glass make this material a potential multifunctional candidate for accelerating the healing of skin wounds.

Growth and comparison of high-quality MW PECVD grown B doped diamond layers on {118}, {115} and {113} single crystal diamond substrates

The use of {113} oriented single crystal diamond substrates has been reported for CVD growth of high-quality p-type layers with increased doping efficiency, compared to the {100} orientation, and excellent electrical properties. In this work we expand the range of crystal orientations to include the {118} and {115} planes and study the effect of B doping level in the gas phase with B/C ratios from 250 up to 2000 ppm. We demonstrate the growth of high-quality B doped SCD layers, with low RMS roughness (<2 nm) and high surface chemical purity (99% C with >1% B) for all orientations. Boron incorporation is shown to be dependent not only on the B/C in the gas phase, but also on the crystallographic orientation, with orientations with a higher density of {100}/{111} steps and risers exhibiting higher B incorporation into the solid from the gas phase (4 × 1019 cm−3 up to 1 × 1021 cm−3). Finally, using electro-chemical techniques, we confirm, for the first-time, high-quality electrodes on such orientations. Novelty statementIn this work we report, for the first time, MW PECVD of high-quality boron doped diamond layers on vicinal {118} and {115} single crystal substrates, which are confirmed, via electro- chemical characterisation, to be excellent electrodes.