SiO2 Layer Research Articles

Grafting SiO2 layer on CaCO3 whisker to enhance the mechanical properties with oil well cement

Grafting SiO2 layer on CaCO3 whisker to enhance the mechanical properties with oil well cement

Photocatalytic Degradation of PCB 153 Using Fe3O4@SiO2@TiO2‐Co Core‐Shell Nanocomposite

AbstractThis study investigates the photocatalytic degradation of PCB 153 using Fe3O4@SiO2@TiO2‐Co core‐shell nanocomposites under LED irradiation. The unique core‐shell structure, incorporating a magnetic Fe3O4 core, a protective SiO2 layer, and a photoactive TiO2 shell doped with Co, enhances light absorption, charge separation, and stability. The effects of various parameters, including catalyst dosage, initial pollutant concentration, solution pH, H2O2 concentration, reaction time, and cosolvent type, were investigated to optimize the degradation process. The results demonstrated the high efficiency of the Fe3O4@SiO2@TiO2‐Co nanocomposite in degrading PCB 153, with a maximum degradation efficiency of 95.2% under optimal conditions. The magnetic properties of the Fe3O4 core enable easy separation and recovery of the catalyst, making it a sustainable and cost‐effective solution. This study provides valuable insights into the design and application of advanced photocatalysts for environmental remediation.

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.

Ion‐Beam‐Induced Biaxial Tensile Strain Engineering in Nanoscale Zinc Oxide Films on Silicon Dioxide

AbstractStrain engineering is a powerful tool for adjusting the electrical and optical properties of materials, particularly in 2D materials on flexible polymer substrates. However, current strain‐engineering techniques are primarily utilized for thin 2D materials on flexible substrates, with limited research on thicker materials on traditional substrates. In this study, the enhancement in electrical properties resulting from strain effects in 30‐nm‐thick ZnO films deposited on SiO2 wafers through N2 ion beam irradiation is proposed. The N2 ion beam, at an optimal energy level, induces strain in the underlying SiO2 layer, leading to a 2.5‐fold increase in the saturation mobility and charge‐carrier density of the overlying ZnO film. Density functional theory calculations reveal that the introduction of N2 molecules into the SiO2 crystal induces biaxial lattice expansion, which, in turn, strains the overlying ZnO film. These findings demonstrate the effective application of strain engineering in films of relatively large thickness, even on traditional substrates. It is anticipated that this strain engineering approach using ion‐beam irradiation will significantly broaden the range of applications for strain engineering technology.

Near-zero TCF 11.6-GHz lamb wave resonator based on 128°Y-cut LiNbO3

In this paper, a high-frequency lamb wave resonator (LWR) with near zero temperature coefficient of frequency (TCF) is designed, fabricated, and measured. The reported resonator is of a bi-layer structure consisting of lithium niobate (LiNbO3 or LN) and silicon dioxide (SiO2), and lithographically patterned aluminum (Al) inter-digitated electrode fingers on top of the bi-layer structure. By adjusting the thickness ratio of LN and SiO2 layers, both the electromechanical coupling (k2) and the TCF, including both TCF at resonant frequency (TCFr) and TCF at anti-resonant frequency (TCFa), of the thickness shear (TS) type LWR are optimized. Experimental results, which are in excellent agreement with theoretical analysis, show that the fabricated 11.6-GHz LWR achieves a k2 of 12.2%, with TCFr and TCFa being −4.2 and −5.4 ppm/K over a temperature range from 30 °C to 85 °C, respectively, demonstrating huge potential in applications for future wireless communication systems above 10 GHz.

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.

High-quality temperature-complementary bulk acoustic wave resonators fabricated with strippable single-crystalline AlN films grown on sapphire

To satisfy the strict demands of 5G radio frequency communication, we propose high-quality, flexible temperature-compensated single-crystalline AlN film bulk acoustic wave resonators (TC-SABARs) based on a 6-inch sapphire substrate. An AlGaN sacrificial layer and a 600-nm-thick single-crystalline AlN epitaxial layer are deposited on a sapphire substrate by metal organic chemical vapor deposition (MOCVD). Two types of TC-SABARs are fabricated and their performances are compared with published results. The results indicate that one of the TC-SABARs has a maximum Bode Q of 3406, an effective coefficient (Keff2) of 6.21%, and a temperature coefficient of frequency (TCF) of −9.5 ppm/°C. The other TC-SABAR exhibits a maximum Bode Q of 3022, a Keff2 of 5.99%, and a TCF of +0.7 ppm/°C. This performance can be attributed to the high-quality single-crystalline AlN film and the temperature-compensation structure with nonmetallic flip-chip bonding film transfer process and a thick SiO2 layer.

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.

Modulation 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 (∼830.57 cm⁻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.

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.

Ultrahigh-reflectivity chiral mirrors based on the metasurface of the quarter-waveplate

A study is conducted on a GaAs-based high-contrast subwavelength chiral metasurface (HCCM) designed for 1064 nm. The metasurface integrates a high-contrast subwavelength grating (HCG) for TM mode modulation, a SiO2 support layer, and a compact quarter-waveplate (QWP) to convert linearly polarized light to circularly polarized light. The HCG achieves ultra-high reflectivity at 1064 nm, attributed to the large refractive index contrast between the Si grating and SiO2 layer. The designed HCCM has a reflectivity of more than 99 % for the TM mode and less than 80 % for the TE waves in the wavelength range of 1050 nm–1085nm, and it can also excite the circularly polarized light with an absolute error of less than 0.03 at the transmitting end in the case of the 1064 nm TM wavelength. These results suggest that circular dichroic metasurfaces could offer a promising approach for photonic manipulation in circular polarization VCSELs, potentially reducing the manufacturing challenges and costs associated with traditional methods.

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

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.