Si Compound Research Articles

Interfacial Si–O coordination for inhibiting the graphite phase enables superior SiC/Nb heterostructure joining by AuNi

The reaction between SiC and Ni-based brazing alloy is extremely intense, where the brittle Ni–Si compound and accompanied dissociate graphite phase as the interfacial reaction product in the joint damage the mechanical properties. In this study, the design of "graphite-controlled" heterogeneous integration component structure on SiC surface is developed to weaken the intense reaction of Ni and SiC. The high-quality surface Si–O coordination was successfully achieved by plasma-enhanced chemical vapor deposition (PECVD) method at relatively low temperature on SiC, which increases the Si bond strength due to that the higher binding energy of Si–O (451 kJ/mol) than that of Si–C (347 kJ/mol). SiO2 films enhance the mechanical properties of the joint through macro-weak side interface interlocking and micro-stress mismatch regulation. The shear strength of SiC/Nb heterostructure joints by AuNi alloy was increased by 44 %, which paves an inspiring way for boosting heterogeneous integration of SiC ceramic components.

Topological corner states in a silicon nitride photonic crystal membrane with a large bandgap.

The theory of band topology has inspired the discovery of various topologically protected states in the regime of photonics. It has led to the development of topological photonic devices with robust property and versatile functionalities, like unidirectional waveguides, compact power splitters, high-Q resonators, and robust lasers. These devices mainly rely on the on-chip photonic crystal (PhC) in Si or III-V compound materials with a fairly large bandgap. However, the topological designs have rarely been applied to the ultra-low-loss silicon nitride (SiN) platform which is widely used in silicon photonics for important devices and integrated photonic circuits. It is mainly hindered by the relatively low refractive index. In this work, we revealed that a rhombic PhC can open a large bandgap in the SiN slab, and thus support robust topological corner states stemming from the quantization of the dipole moments. Meanwhile, we propose the inclination angle of rhombic lattice, as a new degree of freedom, to manipulate the characteristics of topological states. Our work shows a possibility to further expand the topological protection and design flexibility to SiN photonic devices.

Biocontrol of bacterial seedling rot of rice plants using combination of Cytobacillus firmus JBRS159 and silicon.

Burkholderia glumae causes bacterial panicle blight (BPB) and bacterial seedling rot (BSR) which are difficult to control in rice plants. Seed disinfection using microbes and eco-friendly materials is an efficient alternative practice for managing BPB and BSR. In this study, we applied Cytobacillus firmus JBRS159 (JBRS159) in combination with silicon dioxide (SiO2) nanoparticle or potassium silicate (K2SiO3) solution to control BSR. JBRS159, SiO2 nanoparticle, and K2SiO3 independently suppressed the BSR disease and promoted growths of rice and Arabidopsis. Population of B. glumae in the treated rice seeds was suppressed by the application of JBRS159 via competitions for nutrients and niches. The mixture of JBRS159 and each Si compound (SiO2 nanoparticle or K2SiO3) was complementary for disease-suppressing and growth-promoting activities of individual treatment. The results of this study indicate that mixture of JBRS159 with each Si compound can be harnessed for disease control and growth promotion as efficient alternatives to chemical pesticides and synthetic fertilizers. The efficacy of JBRS159 and Si compounds in the control of BSR and BPB in the field remains to be evaluated.

A comparison of plasma generation, plasma transport, and film formation for a DC vacuum arc source with Ti–X compound cathodes (X = W, C, Al, and Si)

This investigation reports the influence of Ti–C and Ti–W cathode composition on an industrial-scale dc vacuum arc plasma source. Further, we analyze the influence of plasma generation and plasma properties on the resulting cathode surface after the operation and on basic film properties. The results are compared with previous work focused on Ti–Al and Ti–Si compound cathodes. For all Ti–X compound cathodes (X = W, C, Al, and Si), a direct correlation between plasma ion energy/charge and the cohesive energy of the cathode was demonstrated, with a small number of exceptions to a limited set of specific cathode compositions. Hence, the “velocity rule” and effects from different electron temperatures were suggested to be important for gaining a more detailed understanding of plasma properties. A discrepancy was found between the cathode and plasma ion composition, though the difference was reduced in a corresponding comparison between the cathode and the deposited film composition. A significant contribution of a flux of neutrals and/or macroparticles to the final film composition was, therefore, suggested. The effect of the melting point of the cathode phase composition on the intensity of macroparticle generation and the smoothness of the cathode surface operation was also investigated. The presented results contribute to the fundamental understanding of vacuum arc plasma generation and transport and are of importance for further development and applicability of Ti-based coatings from arc deposition.

Modification of CaS:Eu phosphor under mild conditions toward an extreme stability at harsh environment over 1.5 months

The chemical instability of CaS:Eu phosphors is a curial problem that hinders its practical application, especially under high temperature and humid environment. In this work, CaS:Eu capped by methacrylate-functionalized Si compound are successfully prepared under a mild condition, without seriously sacrificing the photoluminescence capability. The stability of the as-prepared samples is subsequently tested in stirred hot water (90 °C) for over a month, the outstanding hydrophobicity and chemical stability of the as-prepared samples sufficiently reserve the optical and chemical properties. Systematic characterizations are conducted to reveal the chemical features of the modified CaS:Eu phosphor.

Synthesis and Reactivity of an Anti-van't Hoff/Le Bel Compound with a Planar Tetracoordinate Silicon(II) Atom.

For a long time, planar tetracoordinate carbon (ptC) represented an exotic coordination mode in organic and organometallic chemistry, but it is now a useful synthetic building block. In contrast, realization of planar tetracoordinate silicon (ptSi), a heavier analogue of ptC, is still challenging. Herein we report the successful synthesis and unusual reactivity of the first ptSi species of divalent silicon present in 3, supported by the chelating bis(N-heterocyclic silylene)bipyridine ligand, 2,2'-{[(4-tBuPh)C(NtBu)]2SiNMe}2(C5N)2, 1]. The compound resulted from direct reaction of 1 with Idipp-SiI2 [Idipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]. Alternatively, it can also be synthesized by a two-electron reduction of the corresponding Si(IV) precursor 2 with 2 molar equiv of KC10H8. Density functional theory calculations show that the lone pair at the ptSi(II) resides almost completely in its 3pz orbital, very different from known four-coordinate silylenes. Oxidative addition of MeI to the ptSi(II) atom affords the corresponding pentacoordinate Si(IV) compound 4, with the methyl group located in an apical position. Remarkably, the reaction of 2 with [CuOtBu] leads to the regeneration of the bis(silylene) arms via Si-Si bond scission and induces the Si(II) → Si(IV) oxidation of the central Si(II) atom and concomitant two-electron reduction of the bipyridine moiety to form the neutral bis(silylene)silyl Cu(I) complex 5.

Site-specific atomic substitution in a giant magnetocaloric Fe2P -type system

Giant magnetocaloric (GMC) materials constitute a requirement for near room temperature magnetic refrigeration. (Fe,Mn)$_2$(P,Si) is a GMC compound with strong magnetoelastic coupling. The main hindrance towards application of this material is a comparably large temperature hysteresis, which can be reduced by metal site substitution with a nonmagnetic element. However, the (Fe,Mn)$_2$(P,Si) compound has two equally populated metal sites, the tetrahedrally coordinated $3f$ and the pyramidally coordinated $3g$ sites. The magnetic and magnetocaloric properties of such compounds are highly sensitive to the site specific occupancy of the magnetic atoms. Here we have attempted to study separately the effect of $3f$ and $3g$ site substitution with equal amounts of vanadium. Using formation energy calculations, the site preference of vanadium and its influence on the magnetic phase formation are described. A large difference in the isothermal entropy change (as high as 44\%) with substitution in the $3f$ and $3g$ sites is observed. The role of the lattice parameter change with temperature and the strength of the magnetoelastic coupling on the magnetic properties are highlighted.

Large Cryogenic Magnetostriction Induced by Hydrostatic Pressure in MnCo0.92Ni0.08Si Alloy.

Giant magnetostriction could be achieved in MnCoSi-based alloys due to the magneto-elastic coupling accompanied by the meta-magnetic transition. In the present work, the effects of hydrostatic pressure on magnetostrictive behavior in MnCo0.92Ni0.08Si alloy have been investigated. The saturation magnetostriction (at 30,000 Oe) could be enhanced from 577 ppm to 5034 ppm by the hydrostatic pressure of 3.2 kbar at 100 K. Moreover, under a magnetic field of 20,000 Oe, the reversible magnetostriction was improved from 20 ppm to 2112 ppm when a hydrostatic pressure of 6.4 kbar was applied at 70 K. In all, it has been found that the magnetostrictive effect of the MnCo0.92Ni0.08Si compound is strongly sensitive to external hydrostatic pressure. This work proves that the MnCoSi-based alloys as a potential cryogenic magnetostrictive material can be modified through applied hydrostatic pressure.

Surface property control for 193 nm immersion resist by addition of Si compound

In ArF immersion lithography, the presence of immersion liquid between the resist surface and the lens causes problems, such as the leaching of the photoacid generator into the liquid and the presence of residual liquid on the resist surface, which can result in watermarks and other defects. One method to address such issues is adding an F-based compound with low dry-etch resistance to the resist. In the present study, we developed a novel resist for ArF immersion exposure that replaces the F compound with an Si (dimethylpolysiloxane)-based additive to enhance dry-etch resistance. We experimentally evaluated contact angles with respect to water and developer solution, depth concentration of the additives (segregation), agent dissolution (leaching), dry-etch resistance, and spectral transmittance of the comparative resists. Simulation studies were performed to evaluate pattern profiles. The developed resist with the Si-based additive showed improved properties compared with that with the F-based additive.

Analysis of Surface Microstructures Formed on Ir Substrate under Different Bias Conditions by Microwave Plasma Chemical Vapor Deposition

To understand the process window of bias‐enhanced nucleation of diamond, it is important to study surface modifications of Ir substrates that occur under different conditions. Herein, various microstructures formed on Ir substrates are reported. The first microstructure contains rectangular particles with a size of several hundred nanometers obtained at a relatively high pressure of 12.5 kPa and a high temperature of 880 °C; these particles consist of epitaxially grown Ir3Si species. The second microstructure includes particles oriented along the [110] direction; these particles, however, consist of etched Ir pillars with a height of 400 nm when the substrate temperature increases to 1110 °C. Both microstructures form because of Ir sputtering due to the bombardment of energetic charged ions and the transport of Ir surface atoms. This study demonstrates two types of surface modifications under different bias‐enhanced nucleation conditions and provides a method for preparing an epitaxial Ir–Si compound that can be applied in various silicon‐based electronic devices.

Comparative evaluation on calcium silicate and rice husk ash amendment for silicon-based fertilization of Malaysian rice (Oryza sativa L.) varieties

Rice (Oryza sativa L.) is the most important staple food in the South-east Asian region as a dominant portion of global rice supply is produced and consumed here. Rice plant is a high silicon (Si) accumulator. Constitutive deposition of Si in the form of “phytoliths” offers the plant resistance against various pests, pathogens and stresses, and enhances growth and development. In this study, two sources of Si namely calcium silicate (CaSiO3) and rice husk ash (RHA) were comparatively evaluated for their bio-fertilizing efficiencies on rice plants cultivated under a glasshouse condition. In addition, we added manganese (Mn), as a form of supplemental nutrient and tested it in combination with the two Si sources. A two-factorial pot experiment with Malaysian rice varieties (MR219 and MR253) and Si-based treatment combinations [NPK only (control), NPK + RHA, NPK + CaSiO3, NPK + RHA + manganese (Mn) and NPK + CaSiO3+Mn] indicated that soil amendment using both, a renewable and nonrenewable Si compound (with and without Mn) significantly improved the rice yield-related components and yield as compared to the control (Si-free treatment) at P < 0.05. At 100 day after planting (harvest stage), the grain yield per experimental pot (MR219 and MR253 rice varieties) treated with RHA (with and without Mn) showed no significant difference to the plants treated with CaSiO3 (with and without Mn). Our findings suggest that RHA, an excellent renewable source fetched from rice production system offers an environmentally sound solution for effective Si-based fertilization of rice plants (Malaysian varieties).

Reaction Mechanism and Selectivity Control of Si Compound ALE Based on Plasma Modification and F-Radical Exposure.

In this work, atomic layer etching (ALE) of Si compounds using H2 or N2 plasma modification followed by fluorine radical exposure is discussed. It is shown that the H2 plasma modification process promotes the selective etching of SiN, SiC, and SiCO versus SiO2. The N2 plasma modification, on the other hand, enables the selective etching of SiC and SiCO versus SiN and SiO2. The origin of the etching selectivity between different Si compounds is investigated using a combination of in situ SE and FTIR supported by several ex situ analysis techniques. It is shown that the formation of a hydrogen-rich layer after plasma modification is essential to enable the ALE process. The hydrogen-rich layer can be formed due to ion and radicals of the modification plasma (H2 plasma modification) or be a result of the reconfiguration of hydrogen that is already present in the film (N2 plasma modification). The obtained insights are expected to further enhance the etching selectivity of Si compound ALE processes. Furthermore, it is anticipated that the process can be extended to many other compound materials such as Ti and Hf, as well as enable selective etching between their oxides, carbides, and nitrides.

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks as high-performance electrode material for supercapacitors

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks is prepared as electrode material for supercapacitors. AAEMs1 in rice husks and CO2 promote the development of pores, which act as pore-forming agent and catalyst respectively. The rice husks carbon is used as the substrate and the SiO2 in rice husks is converted into Ni–Si compound by loading Ni. The C/NiSi-600-1 shows remarkable electrochemical performance with 237.07 F/g at 0.5 A/g. The performance declines with crystalline SiO2 formed above 900 °C. A high-performance asymmetric water-system supercapacitor device is fabricated by C/NiSi-600-1 and activated carbon. This device shows capacitance of 142 mF/cm2 at 4 mA/cm2, the energy density of 25.24 Wh/kg at 551.4 W/kg and great cycle stability with 90% after 10,000 cycles. This work provides new insights into the green application of rice husks and promotes the development of electrode materials for supercapacitors.

Comparative Phosphorus Removal Efficiency from Municipal Wastewater Using Acid Mine Drainage Sludge and Its H2O2 Activated form As Adsorbents

Acid mine drainage (AMD) sludge is by-product from AMD treatment that formed by iron deposition. This sludge has a potential to be used as an active adsorbent to remove phosphate from domestic wastewater. The adsorbent that was used in this research is AMD sludge from PT Bukit Asam Tbk., Tanjung Enim that majorly composed of Si, Fe and Al compound (determined by the XRD test). Phosphate adsorption was done by AMD sludge and MD sludge that was activated by hydrogen peroxide. Activation process by hydrogen peroxide affected the chemical and physic characteristic of sludge and it showed from the results that the concentration of Si, Fe and Al were shifted by 7.33%, 7.03%, and 1.49%, respectively. Meanwhile for the physical characteristic; specific surface area, pore volume, and pore size were shifted by 19.51 m2/g, 0.0635 cm3/g, and 142.694 nm, respectively. Phosphate removal by AMD sludge has a greater result than activated sludge. Adsorption capacity of AMD sludge was well described by Freundlich isotherm model, which is equal to 6.358 mg P/g. Meanwhile, adsorption capacity of activated sludge was well described by Langmuir isotherm model, which is equal to 0.48 mg P/g. Results in this study indicated that the activation process with hydrogen peroxide affects the ability of phosphate adsorption that was showed by the difference of removal percentage.

New insights into boron species in acidic digestion solutions of boron-doped silicon

A previously unknown B–Si compound is identified in the HF/HNO3 digestions of p-type Si and the conditions that lead to erroneous results in the analysis of boron in Si are investigated.

Mechanochemical conversion of chrysotile asbestos tailing into struvite for full elements utilization as citric-acid soluble fertilizer

Chrysotile asbestos tailing (CAT) are rich in magnesium and silicon which are of great value for crop growth. In this work, CAT was transformed to struvite and silicate salt for the first time by one-step milling with phosphates (NH4H2PO4, (NH4)2HPO4, KH2PO4 and CaHPO4) for full elements utilization as citric acid soluble fertilizer (CASF). The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG) and Scanning electron microscopy (SEM) were used to characterize the obtained samples. The nutrients release data revealed that CAT milling with (NH4)2HPO4 and CaHPO4 was optimal for the production of Mg, N, P, and Si compound CASF which released 0% Mg, 9.37% N, 2.02% P, and 9.86% Si in water and 94.54% Mg, 96.79% N, 96.97% P, and 14.02% Si in 2% citric acid. The prepared product held the nutrients by the mechanism of struvite crystallization in water and released the nutrients by acid-dissolution in citric acid solution. Techno-economic analysis proved the feasibility and economic value of the CASF produced by the proposed mechanochemical approach. This facile and environmentally friendly process would surely contribute to the improvement of resource utilization efficiency and create a sustainable and environmental friendly agricultural production system.

Joining SiC ceramic and metal Mo with AuPdCoMnNi alloy and interfacial reactions

For high-temperature joining of SiC ceramics, a multi-element AuPdCoMnNi alloy was designed and used as filler metal to join SiC ceramics to metal Mo. The brazing experiment was conducted under the condition of 1150 °C for 5 min and 10 min, respectively. The results show that numerous micro-cracks are visible in the directly brazed Mo/SiC joints, which are continuously distributed in bands of (Co, Ni)-Si and (Pd, Ni)2Si compounds. SiC was further joined to Mo using a Kovar interlayer under the same brazing conditions, and the metallurgical quality of the joints was evidently improved compared with the joints without this interlayer. The joining layer was mainly composed of (Au, Mn)ss layer mixed with element C, (Fe, Co, Ni, Mo)-Si compound layer and (Fe, Co, Ni)-Si compound with discontinuous (Pd, Ni)2Si phases and some small fragments of (Fe, Co, Ni, Mo)-Si compounds. In addition, the shear strength of the joints with Kovar interlayer reaches 55.36 MPa, remarkably higher than the void. The joining mechanism was also discussed.

Magnetic Properties and Crystal Structure of (Fe,Ni)&lt;sub&gt;2&lt;/sub&gt;( P,Si) Quaternaries of Fe&lt;sub&gt;2&lt;/sub&gt;P-Type

(Fe,Ni)2(P,Si) compounds were synthesized and characterized. Ni substitution in Fe1.95-xNixP0.7Si0.3 is found to favor the formation of Fe2P-type hexagonal structure. The samples appear nearly single phase. Powder oriented in the magnetic field shows a pronounced uniaxial magnetic anisotropy with c axis as the easy axis. Magnetization measurements carried out along and perpendicular to the c crystal axis demonstrate a significant magnetic anisotropy, making these materials potential candidates for permanent magnet applications. We found that (Fe,Ni)2(P,Si) compound has no remanent magnetic field and coercivity, but it has a large magnetocrystalline anisotropy at room temperature. Therefore, doping Fe2P type compounds with a small amount of Ni and Si may be a promising way to create new materials with large magnetocrystalline anisotropy at room temperature, and thus rare-earth free permanent magnet.

Morphological and antibacterial effects of silver, magnesium, silicon and strontium modified calcium phosphate bone cements prepared by the sol–gel method

ABSTRACT In this study, the sol–gel method was used to add MgO and SrBr2 to biografts containing Ca(NO3)2·4H2O, SiO2, P2O5, H3BO3 and AgNO3. In addition, urea (15–35% by weight) was added to these biografts in different ratios. FTIR, XRD and SEM–EDX analyses were performed in order to observe the morphological effects. Antibacterial tests were carried out using S.aureus and E.coli bacteria. As a result of FTIR analysis, it was observed that H–OH, CO3−, , , Si–O and Si–O–Si compound structures were formed in the biografts. XRD analysis was found that HA (Hydroxyapatite), β-TCP, CaSiO3, CaMgSi2O6, Ca3MgSi2O8, CaMgSi2O6 and Mg17Sr2 compound structures were formed. Antibacterial analysis with E. coli showed that all biografts except the one that contained the highest amount of urea (35% by weight) yielded colony counting values close to the negative control. For S. aureus, the opposite result was observed.

Ab initio prediction of the elastic, electronic and optical properties of a new family of diamond-like semiconductors, Li2HgMS4 (M = Si, Ge and Sn)

We have performed comprehensive DFT-based ab initio calculations of the structural parameters, elastic constants and related properties, electronic structures and optical constants of new quaternary diamond-like compounds, Li2HgMS4 (M = Si, Ge and Sn), which are novel promising infrared nonlinear optical materials. Both the GGA-PBEsol and TB-mBJ functionals were used to describe the exchange-correlation interactions. The spin-orbit coupling was incorporated to account for relativistic effects. The optimized structural parameters, viz., lattice parameters and atomic position coordinates, are in very good agreement with the experimental counterparts. The full set of anisotropic single-crystal elastic constants were predicted through the stress-strain technique and the isotropic polycrystalline elastic moduli and related physical parameters were predicted via the Voigt–Reuss–Hill approximation. The elastic anisotropy was characterized through several different anisotropic indexes. Calculated electronic band structures and density of states diagrams show that the studied compounds are wide direct bandgap semiconductors. The calculated bandgaps, ranging from 2.65 eV (for the Sn compound) to 3.23 eV (for the Si compound), are in acceptable agreement with the available experimental counterparts. The energy-dependent anisotropic linear optical coefficients, viz., complex dielectric function, complex refractive index, reflectivity and energy-loss function, were determined and discussed.