SiO2 Layer Research Articles

Understanding the role of sodium lignosulphonate on obstructing the aggregation of fine serpentine particles on to the hydrophobized pyrite surface

The slime coatings of serpentine via its hydrophobic Si-O layers significantly weaken the floatability of the hydrophobized sulfide minerals. In this paper, sodium lignosulphonate (SLS) was adopted to avoid the aggregation of fine serpentine particles on to the hydrophobized pyrite surface. The micro-flotation findings indicated that for the artificial mixture of pyrite and serpentine (2:1 mass ratio), 1.0 × 10-4 mol/L sodium isobutyl xanthate (SIBX) only floated out ∼22% pyrite at pH ∼9.0, while, after extra addition of 70 mg/L SLS, the floatability of pyrite was restored and its recovery reached ∼90%. In situ AFM (Atomic Force Microscope), contact angle, zeta potential, fourier transform infrared spectrometer (FTIR) and optical microscope deduced that the strong affinity of SIBX to pyrite rendered it replace the most part of the pre-aggregated SLS from pyrite surface, thus to restore the hydrophobicity of pyrite and further decrease the zeta potential. In addition, SLS attached on the positively-charged Mg sites of serpentine through its carboxyl and phenolic hydroxyl groups reduce the hydrophobicity and zeta potential of serpentine. While, the hard base O atom/anion exhibited much stronger affinity to hard acid Mg cation than that of the soft base S atom/anion, SIBX hardly replaced the adsorbed SLS from serpentine surface. Therefore, the increased electrostatic repulsion and weakened hydrophobic attraction between the SLS-adsorbed serpentine and SIBX-hydrophobized pyrite avoided their aggregation. The combination of SLS and SIBX realized the selective flotation separation of pyrite from serpentine.

Low-temperature etching of silicon oxide and silicon nitride with hydrogen fluoride

Etching of high aspect ratio features into alternating SiO2 and SiN layers is an enabling technology for the manufacturing of 3D NAND flash memories. In this paper, we study a low-temperature or cryo plasma etch process, which utilizes HF gas together with other gas additives. Compared with a low-temperature process that uses separate fluorine and hydrogen gases, the etching rate of the SiO2/SiN stack doubles. Both materials etch faster with this so-called second generation cryo etch process. Pure HF plasma enhances the SiN etching rate, while SiO2 requires an additional fluorine source such as PF3 to etch meaningfully. The insertion of H2O plasma steps into the second generation cryo etch process boosts the SiN etching rate by a factor of 2.4, while SiO2 etches only 1.3 times faster. We observe a rate enhancing effect of H2O coadsorption in thermal etching experiments of SiN with HF. Ammonium fluorosilicate (AFS) plays a salient role in etching of SiN with HF with and without plasma. AFS appears weakened in the presence of H2O. Density functional theory calculations confirm the reduction of the bonding energy when NH4F in AFS is replaced by H2O.

Ultra-thin C/Si Shell Pieces as Amphiphilic Janus Materials for Efficient Oxidation Desulfurization.

Constructing favorable morphology is considered to be an effective strategy to enhance the amphiphilic performance of materials. The directional alignment of ultra-thin lamellar materials significantly facilitates utilization of active sites at the bi-phase interface. Herein, an ultra-thin amphiphilic C/Si shell pieces Janus material (d = 10.4nm) prepared by graphene oxide and SiO2 is reported. The outer SiO2 layer is associated with hydrophilicity, while the inner C layer exhibits hydrophobicity. A Pickering emulsion interface catalyst for fuel oil oxidative desulfurization is constructed by impregnating an amino-modified C/Si Janus material with keggin-type HPW. The results demonstrate that amphiphilic catalyst with an ultra-thin C/Si shell pieces exhibits superior performance in terms of emulsification rate (100%) and desulfurization rate (99.62%) in the O/W emulsion formed by n-octane/acetonitrile. The catalyst demonstrates the advantages of easy recovery and regeneration, maintains a higher activity after oxidative desulfurization (ODS) process, and has higher industrial application value.

Numerical investigation on the polarization-dependent light extraction of 275-nm AlGaN based nanowire with bowtie antenna array or passivation layer

Abstract The low light extraction efficiency (LEE) is one of the major factors hindering the application of AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs). Here we investigate the LEE of AlGaN based nanowire (NW) DUV LEDs emitting at 275 nm for bare NW, NW integrated with aluminum (Al) bowtie antenna array, and NW with passivation layer under transverse-electric (TE) and transverse-magnetic (TM) polarization. It is observed that by integrating plasmonic Al bowtie antenna array with AlGaN based NW, the LEE up to 83% and 74% can be achieved under TE and TM polarization. In addition, the effect of the three different passivation layer SiO2, SiNx and AlN on the LEE of AlGaN based NW is also analysed, the results suggests that SiO2, which has smaller refractive index than NW core, could extract more photons from the NW and lead to large enhancement of LEE. For SiNx and AlN passivation layer, which has refractive index similar to the NW core, have strong coupling with the NW core, when the thickness of passivation layer satisfy resonance coupling conditions, the LEE could be achieved more than 80% for both TE and TM polarization. These integrated NW/antenna array and NW with passivation layer system can provide guidelines for designing other nano-photonic devices.

A Triple-Tunable Dual-Band Metamaterial Absorber Based on Dirac Semimetal and InSb

The dynamically triple-tunable dual-band metamaterial absorber that can be electrically, thermally, and magnetically controlled is proposed in this paper. The absorber is composed of bulk Dirac Semimetal (BDS), SiO2, and InSb layers. The physical absorption mechanism can be analyzed theoretically by the equivalent circuit model (ECM) and electric field intensity distributions at absorption peaks. In the absence of applied magnetic field, based on the bright–bright coupling effect, the average absorption rate of dual-band absorber can reach 99.4% when the Fermi energy of the BDS is 0.13 eV and the temperature of the InSb is 475 K. When the applied magnetic field is along the X axis, the absorption frequencies and rates of dual-band absorber can be electrically tuned by adjusting the BDS Fermi energy and thermally and magnetically controlled by adjusting the InSb temperature and magnetic field. Furthermore, the impacts of parameters in dual-band absorbers and the application prospects of the dual-band absorber model as a refractive index sensor are further discussed. This work provides a theoretical basis for the designs of triple-tunable absorbers and sensors.

Study on the Mechanism of Bubble Defects in the PECVD Amorphous Silicon Films on Dielectric Substrate

The amorphous silicon (a-Si) grown by plasma enhanced chemical vapor deposition (PECVD) has been widely applied in advanced semiconductor devices. However, it still suffers from the bubble defects when the deposition temperature goes above 450 °C. In this work, we have investigated the influence of underlying materials on the formation of bubbles of a-Si. The a-Si was deposited on different dielectric substrates, including silicon nitrides (SiN) and silicon dioxide (SiO2), using PECVD technique at a substrate temperature of 500 °C. A large number of bubbles of the a-Si has been observed on the thermal ALD deposited SiN underlayer, and some of them even burst. In contrast, no bubble defects were observed at the a-Si grown on PECVD SiN and PECVD SiO2 films. Such deviation may be attributed to the quality of the underlying material, which induces the H/H2 diffusion during the growth of a-Si and results in bubbles. A solution based on the model has been used to suppress the formation of such bubbles. An inserting layer of SiO2 was introduced in between SiN and a-Si to improve the density of the lower layer material and the adhesion between the two materials. As a result, there is no bubble defects at the surface of a-Si observed using optical microscope. Our work reveals the mechanism of the formation of bubble defects and paves a new method to eliminate the bubbles defects and to form high-quality a-Si, which shows potential in the manufacture of semiconductor devices.

Dual-oxides confined carbonyl iron enabling superior electromagnetic wave absorption and anticorrosion performance

With the increasing requirements of electromagnetic wave (EMW) absorption, developing EMW absorbers with high-efficiency anti-corrosion performance which can be effectively applied in extreme corrosive environments is imperative and constitutes a hot issue in the current research. Herein, based on the composition modulation of ZrO2 and SiO2 layer, the dual-oxides confined carbonyl iron (CI@ZrO2/SiO2) composite displays a minimum reflection loss (RLmin) of −48.58 ​dB@1.9 ​mm and an effective absorption bandwidth (EAB) of 7.62 ​GHz@1.6 ​mm. Besides, the CI@ZrO2/SiO2 displays superior corrosion resistance with corrosion current density (icorr) of 8.62 ​× ​10−7 A/cm2 and polarization resistance (Rp) of 3.64×105 ​Ω. This work proposes a strategy to optimize the broadband EMW absorption properties as well as the mass production toward the corrosion resistance applications.

Ability of a MoSi2 coating to resist erosion-corrosion from the impact of atomic oxygen

Atomic oxygen (AO), in the residual atmosphere of low-Earth-orbit space, may violently collide with spacecraft at a relative speed of up to 8 km/s and an impact energy of nearly 5 eV/atom. These collisions can lead to a series of physical and chemical reactions that may result in increased sputtering-erosion and corrosion of the exposed surface with performance degradation. This work examined the behavior of MoSi2, a commonly used coating, when exposed to AO using a ground-based space environment simulator. The erosion-corrosion kinetics and evolution of the microstructure and element distributions were analyzed. After MoSi2 was subjected to a total gas fluence of 9.72×1022 atoms/cm2 in 675 h, the erosion yield reached an exceptionally low value of 10-28 cm3/atom, indicative of its superior AO resistance, and XRD, SEM, XPS and EPMA were applied to analyze the phase transition of the coating surface: first it was released of adsorbed gas molecules and contaminants on the coating surface; then outside Mo and Si atoms were also sputtered, and the remaining Mo and Si atoms were gradually oxidized; finally, a continuous protective oxide film was generated which effectively resisting AO collisions. After AO impact, an ultrathin defensive granular oxide layer of MoO3 and SiO2 generated from the original smooth MoSi2 coating. Density functional theory calculations were conducted to clarify the thermodynamic and electronic structure mechanisms underlying the AO oxidation of the MoSi2 coating.

SERS-lateral flow immunoassay based on AuNR@Ag@SiO2-AuNP assembly for ultra-sensitive detection of deoxynivalenol in grain

In view of the serious harm and widespread pollution caused by deoxynivalenol (DON), it is crucial to quantify its presence in the food safety assessment process. Here, we designed a core-shell-satellite nano assembly structure as a probe, composed of an anisotropic AuNR@Ag core, an ultra-thin SiO2 layer and a high surface coverage AuNPs satellites, which showed outstanding SERS activity and high stability. Anti-DON antibodies were modified on the surface of the prepared core-shell-satellite nano-assembly structure as SERS immunoprobe for DON specific detection using SERS-based lateral flow immunoassay (LFIA) with the advantages of simplicity, rapidity, and high sensitivity. Under optimal conditions, the detection limit for detecting DON using the SERS-LFIA method was 0.053 fg/mL, and the linear detection ranged from 0.1 fg/mL to 1 μg/mL. The SERS-LFIA strips based on AuNR@Ag@SiO2-AuNP nanostructures demonstrated the great potential for quick quantitative DON detection, providing a reference for trace detection of highly toxin mycotoxins.

The dielectric adjustment in SiCf/mullite composites limited carbon content by in situ growth SiO2 layer

The dielectric adjustment in SiCf/mullite composites limited carbon content by in situ growth SiO2 layer

ModulatioAn of Hybrid Plasmon Phonon Polaritons Mode in Circular Cylindrical Three-Layer Graphene Waveguide

In this present research article, we have investigated analytically the characteristics of the fundamental mode of hybrid surface plasmon phonon polariton (HSPPhPs) mode in a circular cylindrical three-layer graphene (CTLG) waveguide structure. The dispersion equation of HSPPhPs is derived by using Maxwell’s equations and continuity conditions of tangential components of electric and magnetic fields in cylindrical geometry. The dispersion curve has been illustrated and thoroughly examined in relation to the effects of temperature and chemical potential (μc) of graphene, as well as variations in the thickness of silicon dioxide (SiO2) and hexagonal boron nitride (hBN) layers, and found that in the presence of hBN, the effective mode index exhibits hyperbolic behavior with wave number. Up to the first Reststrahlen band (∼830.57cm⁻¹), it varies slightly with graphene temperature; increasing graphene's (μc) lowers the index, while a thicker hBN layer reduces it, whereas the index increases with SiO₂ layer thickness. Also, we looked at how the CTLG waveguide structure is affected by the electric field distribution, phase speed, and propagation length.

High‐Temperature Oxidation Response of 444 Ferritic Stainless Steel in a Synthetic Automotive Exhaust Gas

The high‐temperature oxidation behavior of 444 ferritic stainless steel has been studied in cyclic oxidation experiments using synthetic automotive exhaust gas atmospheres at 950 and 1050 °C. The weight gain per unit area of the 444 ferritic stainless steel following oxidation at 950 °C for 100 h iss 85.7% lower than recorded at 1050 °C. The oxide scale at both temperatures consisted of Fe–Cr and Mn–Cr spinels in the outer layer and Cr2O3 in the inner layer. Nodule formation and spallation of the oxide scale are identified as the main causes of breakaway oxidation. The depth of the internal oxides gradually increases with the oxidation time. The nucleation and growth of internal SiO2 result in the formation of metal protrusions, which are eventually consumed in the formation of a SiO2 layer. The SiO2 layer is formed at the interface between the oxide scale and the substrate at 1050 °C. The nucleation and growth of internal SiO2, in combination with lateral growth of SiO2 at the Cr2O3 layer/substrate interface contributed to the formation of the SiO2 layer.

Large-scale high purity and brightness structural color generation in layered thin film structures via coupled cavity resonance

Abstract Structural colors, resulting from the interaction of light with nanostructured materials rather than pigments, present a promising avenue for diverse applications ranging from ink-free printing to optical anti-counterfeiting. Achieving structural colors with high purity and brightness over large areas and at low costs is beneficial for many practical applications, but still remains a challenge for current designs. Here, we introduce a novel approach to realizing large-scale structural colors in layered thin film structures that are characterized by both high brightness and purity. Unlike conventional designs relying on single Fabry–Pérot cavity resonance, our method leverages coupled resonance between adjacent cavities to achieve sharp and intense transmission peaks with significantly suppressed sideband intensity. We demonstrate this approach by designing and experimentally validating transmission-type red, green, and blue colors using an Ag/SiO2/Ag/SiO2/Ag configuration on fused silica substrate. The measured spectra exhibit narrow resonant linewidths (full width at half maximum ∼60 nm), high peak efficiencies (>40 %), and well-suppressed sideband intensities (∼0 %). In addition, the generated color can be easily tuned by adjusting the thickness of SiO2 layer, and the associated color gamut coverage shows a wider range than many existing standards. Moreover, the proposed design method is versatile and compatible with various choices of dielectric and metallic layers. For instance, we demonstrate the production of angle-robust structural colors by utilizing high-index Ta2O5 as the dielectric layer. Finally, we showcase a series of printed color images based on the proposed structures. The coupled-cavity-resonance architecture presented here successfully mitigates the trade-off between color brightness and purity in conventional layered thin film structures and provides a novel and cost-effective route towards the realization of large-scale and high-performance structural colors.

An Innovative Fuel Design for HTGRs: Evaluating a 10-Hour High-Temperature Oxidation of the SiC Fuel Matrix During Air Ingress Accident Conditions

Preventing severe corrosion incidents caused by air ingress accidents in high-temperature gas-cooled reactors (HTGRs) while improving heat removal efficiency from the core is of paramount importance. To enhance both safety and efficiency, a sleeveless silicon carbide (SiC)-matrix fuel compact has been proposed. This study evaluates the 10-hour oxidation of reaction-sintered SiC (RS-SiC)-matrix fuel compact under the conditions of an air ingress accident within the temperature range of 1000 to 1400 °C. The oxidation tests were conducted in a stagnant air environment without flow. As a result, it is demonstrated that RS-SiC exhibits exceptional resistance to air oxidation up to 1400 °C, as shown by the thermogravimetric analysis (TGA), with minimal mass loss due to the oxidation of free carbon. Scanning electron microscopy with energy-dispersive X-Ray spectroscopy (SEM–EDX) analysis reveals that the morphology and thickness of the SiO2 layer formed on the RS-SiC surface vary with temperature. At 1400 °C, uniform oxide layer thickness ranging from 1.59 to 4.10 μm and localized nodule-like oxide formations of approximately 10 μm are observed. In contrast, at 1000–1200 °C, thinner oxide layers are identified, indicating that oxide growth accelerates at higher temperatures. The oxidation rates measured provide insights into the mechanisms of oxide growth.

Mesoporous silica-confined ultrafine ruthenium nanoparticles supported by graphene: Robust catalysts for biphasic oxidation at the oil-water interface

Graphene-supported ultrafine ruthenium nanoparticles covered by mesoporous silica (mSiO2) were synthesized as interfacially active catalysts for biphasic oxidation at the oil-water interface. These mesoporous SiO2 layers serve to confine metal nanoparticles of specific sizes, preventing their sintering even under harsh conditions, which is attributed to the confinement effects within porous materials. Furthermore, Pickering emulsion systems formulated with these amphiphilic catalysts exhibit significantly higher catalytic efficiency compared to conventional organic-aqueous biphasic systems with Ru/rGO and commercial Ru/C catalysts. The catalytic performance is directly influenced by surface wettability, and the catalytic efficiency reveals a parabolic distribution with respect to the content of mSiO2, indicative of the optimal activity over Ru/rGO@mSiO2-100 with a conversion of up to > 92 % and a selectivity to benzaldehyde of up to > 99 % under base-free conditions after 2 h. Moreover, rGO–silica hybrids demonstrate the excellent reusability for over five cycles which benefits from the protective effect of mSiO2.

Simulation of silicon conical field effect GAA nanotransistors with stack SiO2/HfO2 dielectric of gate

The issues of modeling the electrophysical characteristics of a silicon conical field effect GAA nanotransistor are discussed. An analytical model of the drain current of a transistor with a fully enclosing conical gate with a stack sub-gate oxide SiO2/HfO2 has been developed, taking into account the effect of the charge of the interphase trap at the Si/SiO2 interface. To simulate the potential distribution in a conical working area under the condition of constant trap density, an analytical solution of the Poisson equation was obtained using the method of parabolic approximation in a cylindrical coordinate system with appropriate boundary conditions. The potential model was used to develop an expression for the GAA drain current of a nanotransistor with a stack gate oxide. The key electrophysical characteristics are numerically investigated depending on the density of traps and the thicknesses of SiO2 and HfO2 layers.

Water vapor oxidation of SiC layer of tristructural isotropic particles

AbstractTristructural isotropic (TRISO) fuel particles, developed for use in high‐temperature gas‐cooled nuclear reactors, can be subjected to oxidizing environments in off‐normal accident scenarios. In this study, surrogate TRISO fuel particles were oxidized at 1000–1350°C for 4 h in 20 kPa water vapor atmosphere balanced with ultrahigh‐purity helium gas. The oxide scale morphology and thickness were studied via scanning electron microscopy, focused ion beam, and transmission electron microscopy. The oxide thickness increased as the oxidation temperature was increased. Although the oxide scale at 1000°C was completely amorphous, pockets of crystalline oxide were observed on particles oxidized at 1200 and 1300°C. Kinetic analysis was performed to deduce the oxidation mechanism by determining the apparent activation energy using linear regression analysis. The oxidation mechanism was consistent for temperatures from 1000 to 1200°C with an activation energy of 412.4 ± 8.8 kJ/mol. The activation energy then dropped to approximately 201 ± 7.1 kJ/mol for temperatures 1200–1350°C. Therefore, there is a change in oxidation mechanism at ∼1200°C. This change is attributed to the existence of a network of significant bubbles in the oxide layer at higher temperatures, which serve as rapid diffusion pathways for the transport of oxidants from the surface to the SiC/SiO2 interface, instead of relying on the bulk diffusion through the SiO2 layer at lower temperatures where only small bubbles are present along the SiC/SiO2 interface.

Double Layer SiO2-Coated Water-Stable Halide Perovskite as a Promising Antimicrobial Photocatalyst under Visible Light.

Halide perovskite nanocrystals (HPNCs) have emerged as promising materials for various light harvesting applications due to their exceptional optical and electronic properties. However, their inherent instability in water and biological fluids has limited their use as photocatalysts in the aqueous phase. In this study, we present highly water-stable SiO2-coated HPNCs as efficient photocatalysts for antimicrobial applications. The double SiO2 layer coating method confers long-term structural and optical stability to HPNCs in water, while the in situ synthesis of lead- and bismuth-based perovskite NCs into the SiO2 shell enhances their versatility and tunability. We demonstrate that the substantial generation of singlet oxygen via energy transfer from HPNCs enables efficient photoinduced antibacterial efficacy under aqueous conditions. More than 90% of Escherichia coli was inactivated under mild visible light irradiation for 6 h. The excellent photocatalytic antibacterial performance suggests that SiO2-coated HPNCs hold great potential for various aqueous phase photocatalytic applications.

Intense violet electroluminescence of thin SiO2 layers with SnO2 nanocrystals

It has been shown that Sn implantation with subsequent annealing in air leads to an increase in the electroluminescence (EL) intensity of SiO2/Si structure by two orders of magnitude. Intense violet EL with a maximum at 3.21 eV was observed at room temperature by the naked eye at forward bias. The observed emission was attributed to radiative recombination in SnO2 nanocrystals synthesized in SiO2 layers. The external quantum efficiency (EQE) increased with decreasing Sn concentration The maximum external quantum efficiency was found to be 0.7 % for the silica film Sn-implanted at the lowest fluence of 2.5 × 1016cm−2. The non-radiative charge transport (shunt current) through the sample and mechanism of EL excitation are discussed. It has been concluded that the Poole–Frenkel mechanism, or tunneling between traps are the most likely mechanisms of charge transport to light-emitting centers.

Sodium-based plasmonic waveguides with high confinement factors and ultra-low gain thresholds.

The noble metal-based hybrid plasmon mode features low loss and strong field localization, making it widely applicable in the field of nanophotonic devices. However, due to the high loss of noble metals, the gain threshold is unacceptably high, usually larger than 0.1 µm-1. Here we present a hybrid plasmonic waveguide consisting of a SiO2 layer coated Na nanowire and a hexagonal semiconductor nanowire. Based on the high performance of the proposed waveguide, the Purcell factor exceeding 120 and a confinement factor above 90% are achieved, leading to an ultra-low gain threshold of 0.02117 µm-1. In addition, the proposed waveguide exhibits an extremely low cross talk, making it highly suitable for applications in compact photonic integrated devices. The proposed waveguide may contribute to the development of low-threshold nano-lasers and promote other applications in nanophotonics.