SiO2 Layer Research Articles

Removing boron from the diamond wire saw silicon powder by MgF2-sintering synergized with Na2CO3-enhanced refining to prepare low-boron silicon

Recycling environmentally hazardous diamond wire saw silicon powder (DWSSP) to prepare low-boron silicon is crucial for environmental pollution and waste resources recycling. For reutilization, the decomposition of impurity-containing SiO2 layers and the removal of boron are the two main issues that need to be addressed. Therefore, the addition of MgF2 to DWSSP for sintering to damage the containing-impurities SiO2 layers and remove harmful boron was first studied. The results showed the SiO2 layer was effectively decomposed by reaction with MgF2 and the removal rate of harmful boron impurity was 86.9 % at 1300 °C for 120 min with 20 % MgF2 addition. Subsequently, the effect of Na2CO3 on the removal of boron impurity in the refining process was analyzed, finding that 10 % Na2CO3 addition enhanced the boron removal rate to 95.6 % at 1600 °C for 60 min with CaO/SiO2 ratio of 1.2. Finally, the removal mechanism of harmful B impurities via MgF2-sintering synergized with Na2CO3-enhanced refining was analyzed. This work provides a simple and feasible alternative for recycling DWSSP to prepare low-boron silicon as feedstock for solar-grade silicon preparation.

Enhanced holding ability between resin and silanization modified diamonds through sintering Si[sbnd]N bond formation at low temperature

Resin-bonded diamond tools often suffer from poor durability and short lifespan due to the agglomeration of abrasive diamonds and the poor holding ability between diamonds and resin, resulting in diamond detachment during the working process. Modifying the diamond surface is necessary to improve the dispersion of diamonds and the holding ability between diamond and resin. However, common metallic modification methods can cause fine-grained diamonds (FGDs) to agglomerate, and metal plating cannot form a chemical bond with resin at low temperatures for preparing resin-bonded diamond tools. A practical non-metallic method for modifying diamond surfaces was proposed to address these issues, utilizing a silane coupling agent to enhance the binding forces between diamonds and binding agents. A uniform amorphous SiO2 film, with a thickness of 30–40 nm, was developed on FGDs with the hydrolysis and condensation reactions of tetraethylorthosilicate in a water and alcohol mixed solution. The SiO2 layer formed with the CO, CO, and C-O-Si chemical bonds can increase electrostatic repulsion between diamonds, overcoming diamond agglomeration. FGDs modified with SiO2 were combined with phenolic resin and pressed at 170 °C, forming SiN bonds between the resin and SiO2 film and improving the bonding force. Moreover, the SiN bonds can be produced at low temperatures, reducing the risk of diamond detachment during their operation. Hence, the lifespan of modified diamond wheel increase by 22 % than that of pristine diamond wheel. This study provides valuable guidance for developing high-performance, long-lasting, resin-bonded diamond tools.

A superhydrophobic wearable rubber band with a synergistic dual conductive layer for monitoring human motions

Wearable and flexible electronics attract increasing attention due to their outstanding stretchability and human friendliness, while the significant parameters to evaluate sensor performance such as sensitivity and working range are the main challenge for better sensor design. Herein, an ultrasensitive and flexible strain sensor with synergistic dual conductive layers was successfully fabricated by designing a silk wrinkles structure to largely broaden the stretchable range for the conductive layer. The organic conductive polypyrrole and silver nanowire are combined to construct the conductive layer with high conductivity and better stretchability. The as-obtained sensor possesses a wide working range (0–126 %) and high sensitivity (a GF of 15710.75 at a strain of 120 %-126 %). The additional SiO2 layer is applied to the sensor to achieve a contact angle of 143.4°, which is close to super-hydrophobicity. The resultant sensor also possesses fast response and recovery speed due to the elastomeric rubber band substrate with the response and recovery time of 105 and 101 ms respectively, and still keeps high stability over 5000 cyclic stretching and releasing tests. The sensor is promising to be used in wearable applications potentially.

Collective Modes in the Luminescent Response of Si Nanodisk Chains with Embedded GeSi Quantum Dots

In this paper, we study the effects of GeSi quantum dot emission coupling with the collective modes in the linear chains of Si disk resonators positioned on an SiO2 layer. The emission spectra as a function of the chain period and disk radius were investigated using micro-photoluminescence (micro-PL) spectroscopy. At optimal parameters of the disk chains, two narrow PL peaks, with quality factors of around 190 and 340, were observed in the range of the quantum dot emission. A numerical analysis of the mode composition allowed us to associate the observed peaks with two collective modes with different electric field polarization relative to the chain line. The theoretical study demonstrates the change of the far-field radiation pattern with increasing length of the disk chain. The intensive out-of-plane emission was explained by the appearance of the dipole mode contribution. The obtained results can be used for the development of Si-based near-infrared light sources.

Oxidation mechanisms of a Cr[sbnd]Si alloyed coating-free press-hardened steel under simulated press hardening conditions

Press-hardened steel (PHS) undergoes severe high-temperature oxidation after press hardening, which significantly degrades surface quality and increases manufacturing cost. This work reports the mechanism by which a coating-free PHS (CF-PHS) with the simultaneous presence of Cr, Si, and Mn alloying elements achieves excellent high-temperature oxidation resistance. It is found that Si and Mn in the CF-PHS promote the formation of a continuous Cr2O3 layer with good protective effect, thereby improving high-temperature oxidation resistance, during the press hardening. Moreover, the continuous amorphous SiO2 layer formed at the oxide scale/matrix interface and the Mn-rich oxides that improve the compactness of the scale further enhance the oxidation resistance of the CF-PHS.

Enhanced electromagnetic wave absorption via optical fiber-like PMMA@Ti3C2Tx@SiO2 composites with improved impedance matching

Ti3C2Tx nanosheets have attracted significant attention for their potential in electromagnetic wave absorption (EWA). However, their inherent self-stacking and exorbitant electrical conductivity inevitably lead to serious impedance mismatch, restricting their EWA application. Therefore, the optimization of impedance matching becomes crucial. In this work, we developed polymethyl methacrylate (PMMA)@Ti3C2Tx@SiO2 composites with a sandwich-like core-shell structure by coating SiO2 on PMMA@Ti3C2Tx. The results demonstrate that the superiority of the SiO2 layer in combination with PMMA@Ti3C2Tx, outperforming other relative graded distribution structures and meeting the requirements of EWA equipment. The resulting PMMA@Ti3C2Tx@SiO2 composites achieved a minimum reflection loss of −58.08 dB with a thickness of 1.9 mm, and an effective absorption bandwidth of 2.88 GHz. Mechanism analysis revealed that the structural design of SiO2 layer not only optimized impedance matching, but also synergistically enhanced multiple loss mechanisms such as interfacial polarization and dipolar polarization. Therefore, this work provides valuable insights for the future preparation of high-performance electromagnetic wave absorbing Ti3C2Tx-based composites.

Catalytic combustion of lean methane over different Co3O4 nanoparticle catalysts

Three types of Co3O4 catalyst, namely Co3O4 nanoparticles (denoted as Co3O4-NPs, ∼12 nm in diameter), Co3O4 nanoparticles encapsulated in mesoporou s SiO2 (denoted as Co3O4@SiO2), and Co3O4 nanoparticles inside microporous SiO2 hollow sub-microspheres (denoted as Co3O4-in-SiO2), were explored to catalyze the combustion of lean methane. It was found that the methane conversion over the three catalysts has the order of Co3O4-NPs ≈ Co3O4@SiO2 > Co3O4-in-SiO2 due to the different catalyst structure. The comparison experiments at high temperatures indicate the Co3O4@SiO2 has a significantly improved anti-sintering performance. Combined with the TEM and BET measurements, the results prove that the presence of the mesoporous SiO2 layer can maintain the catalytical activity and significantly improve the anti-sintering performance of Co3O4@SiO2. In contrast, the microporous SiO2 layer reduces the catalytical activity of Co3O4-in-SiO2 possibly due to its less effective diffusion path of combustion product. Thus, the paper demonstrates the pore size of SiO2 layer and catalyst structure are both crucial for the catalytical activity and stability.

Ultra-sensitive pressure sensing capabilities of defective one-dimensional photonic crystal

Present research work deals with the extremely sensitive pressure-sensing capabilities of defective one-dimensional photonic crystal structure (GaP/SiO2)N/Al2O3/(GaP/SiO2)N. The proposed structure is realized by putting a defective layer of material Al2O3 in the middle of a structure consisting of alternating layers of GaP and SiO2. The transfer matrix method has been employed to examine the transmission characteristics of the proposed defective one-dimensional photonic crystal in addition to MATLAB software. An external application of the hydrostatic pressure on the proposed structure is responsible for the change in the position and intensity of defect mode inside the photonic band gap of the structure due to pressure-dependent refractive index properties of the materials being used in the design of the sructure. Additionally, the dependence of the transmission properties of the structure on other parameters like incident angle and defect layer thickness has also studied. The theoretical obtained numeric values of the quality factor and sensitivity are 17,870 and 72 nm/GPa respectively. These results are enough to support our claim that the present design can be used as an ultra-sensitive pressure sensor.

Enhancement of the efficiency of solar collector by SiO2, TiO2, and ZnO thin films layers

Most scientific researchers are motivated to develop alternative energy applications and raise their efficiency as a result of rising global warming and pollution from traditional energy sources. In this study, Nanocoating thin films of ` have been prepared on different substrates (stainless steel 316 L, commercially pure Ti, Si-Wafer(100) and glass). Magnetron sputtering deposition technique at 2.8 × 10–7 Torr vacuum has been used to synthesize the nanocoated thin films. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), Atomic Force Microscopy (AFM), and UV–visible radiation tests have been used to characterize the thin films deposited. The investigation results showed that the thin films deposited do not have microcracks or defects with a uniform and homogenous structure at 400 nm magnification. It has a nanoparticle grain size of 60–90 nm with a crystal structure for TiO2, SiO2, and ZnO films. ZnO films have coarser grain and more aggregation than the other films. The highest efficiency of the collector was recorded for a collector integrated with ZnO thin-film. The efficiency of the ZnO-coated collector was about 66 % at midday compared to the conventional system (no thin film), which was 39 %.

Oxidation behavior and kinetics of (Zr, Ti)(C, N)–SiC ceramics with enhanced oxidation resistance at 850 °C–950 °C

The oxidation behavior and kinetics of (Zr, Ti)(C, N)–SiC ceramics subjected to a temperature of 850 °C-950 °C (typical operating temperatures range of Generation-IV nuclear reactors) for 1–4 h are investigated via X-ray diffraction, scanning electron microscopy, and weight gain testing. The results show that the microstructures of the ceramics after oxidation comprises primarily of m-(Zr, Ti)O2, c-(Zr, Ti)O2, and SiO2. After adding Si, the oxidation layer appears as a two-layer structure with both external and internal layers. The oxidation order of (Zr, Ti)(C, N)–SiC ceramics at 850 °C-950 °C is ZrSi > (Zr, Ti)(C, N) > SiC. Unoxidized SiC forms a “core-shell” structure with a dense external layer of SiO2. The dual effect of small SiO2 particles occupying cracks and the “core-shell” structure of SiC–SiO2 withstanding stresses can inhibit the propagation of cracks and reduce the porosity of the oxide layer. The oxidation of Z5T and Z5T5S exhibits linear oxidation kinetics, whereas the oxidation of Z5T10S and Z5T20S results in quasi-parabolic oxidation. By adding Si, the oxidation activation energy of Z5T20S (with the addition of 20 mol% Si) increases by 174 % compared to that of Z5T ceramic, thus improving the oxidation resistance of (Zr, Ti)(C, N)-based ceramics at 850 °C-950 °C.

Abnormal mechanical hysteresis behavior of Tyranno-ZMI SiC/SiC containing Ti3Si(Al)C2

This work studied the effect of tough phase Ti3Si(Al)C2 on the mechanical hysteresis behavior of SiC/SiC. Different from continuous fibers reinforced brittle ceramic matrix composites, the mechanical hysteresis behavior of SiC/SiC containing Ti3Si(Al)C2 shows some abnormal phenomena: as peak applied stress increases during cyclic loading-unloading-reloading tests, the thermal residual stress values exhibit highly dispersion and the thermal misfit relief strain shows abnormally slow growth. These abnormal phenomena are caused by the reduction of transvers cracks (perpendicular to loading fibers) and the generation of hoop cracks (parallel to loading fibers). The plastic deformations of Ti3Si(Al)C2 prevents the transverse cracking of modified matrix, while promoting the hoop cracking of SiC matrix prepared by chemical vapor infiltration (CVI-SiC). Hoop cracking occurs within the transition zone containing amorphous SiO2 layer and carbon layer in CVI-SiC matrix. The combination of weak transition zone and strong modified matrix finally leads to the occurrence of hoop cracking.

Reactively-sputtered super-hydrophilic ultra-thin titania films deposited at 120 °C

Abstract We investigate super-hydrophilic TiO2 (titania) films for concentrated solar-thermal power applications. Reactive magnetron sputtering has been used to deposit 8 to 12 nm thick titania thin films onto borosilicate microscope glass slides, low-Fe extra-clear architectural glass, or Si(100) wafers with a 500 nm thick thermal SiO2 layer. The effects of deposition temperature and O2 fraction of the O2/Ar working gas were investigated. We demonstrate the importance of the O2 fraction for obtaining optically transparent, super-hydrophilic (contact angle below 1°) thin films. In particular, we show that as the O2 fraction increases, contact angle decreases, obtaining super-hydrophilic titania thin films at deposition temperatures as low as 120 °C. Our work enables to develop low thermal budget cost-efficient industrial synthesis processes, paving the way for commercial applications.

Improving the minority carrier lifetime of PERC solar cells via bi-layer rear interface passivation strategy

Passivated emitter and rear contact (PERC) based solar cells are dominating the current photovoltaic (PV) market due to their high power conversion efficiency (PCE) and low cost. However, issues like the lower minority carrier lifetime (MCLT) and high density of surface dangling bonds are limiting their further improvement in PCE. To overcome this issue, a bi-layer rear interface passivation strategy is developed with the ultra-thin Al2O3 and SiO2 layers in PERC solar cells. Applying single (Al2O3) and double (SiO2/Al2O3) passivation layers revealed that each process parameter such as plasma conditions, deposition temperature, post-annealing temperature, and the film thickness in the ALD process affect the MCLT values as well as overall device performance. Especially, post-annealing treatment which improves crystallinity, and reduces interfacial defects was found to be most influential for the MCLT value. The single Al2O3 layer applied in PERC solar cells revealed an increase and decrease in MCLT values at a relatively lower (<10 nm) and higher thickness (>15 nm), respectively. Further, integration of SiO2 with the Al2O3 layer showed its more prominent effect than just single Al2O3 and SiO2 passivation layers. An optimal SiO2 thickness combination (4 nm) with an Al2O3 layer (12 nm), demonstrated reduced density of surface dangling bonds and diffusion of Al atoms from Al2O3 layers. As a result, it improved the carrier extraction yield by increasing the negative fixed charge. Finally, SiO2/Al2O3 (4/12 nm) double passivation layer post-annealed at 450 °C for 15 min delivers improved PCE from 19.4% to 19.9% in PERC solar cells.

Dual-mode photoluminescent microspheres with silica core, separator layer and envelope for anti-counterfeiting ink

The microsphere is concentrically constructed on the basis of SiO2 nanocore on which Gd2O3:Yb,Er upconversion luminescent layer, SiO2 separator, Gd2O3:Ln@SiO2 (Ln3+ = Tb3+, Eu3+) downconversion luminescent layer, and SiO2 envelope are successively deposited by means of wet chemistry method. Under 980 nm near-infrared laser excitation, the microspheres emit bright upconverted green light due to Gd2O3:Yb,Er luminescent layer. While, under 254 nm portable ultraviolet lamp irradiation, they produce red and green downconversion fluorescence because of Gd2O3:Ln (Ln3+ = Tb3+ or Eu3+) luminescent layer. The silica core fixes the luminescence center, reduces non radiative transitions caused by molecular vibration, enhances fluorescence intensity, and saves rare earth resources. Impressively, the silica separator layer isolates the upconversion luminescence of Er3+ and downconversion of Eu3+, preventing cross relaxation and quenching of Er3+ fluorescence. The silica envelope plays a crucial role in the photoluminescence of the prepared microspheres. The photoluminescence quantum yield of the microspheres initially increases from 90.4 % to 95.9 % and then decreases to 82.9 % as the thickness of SiO2 layer on the ∼3 nm-thick Gd2O3:Ln shell rises from 3 nm to 16 nm. The absorption of photons reaches its maximum when the SiO2 layer is 8 nm thick. This thickness corresponds to the lowest rate constant for non-radiative transitions. The proto inks prepared from the dual-mode microspheres exhibit good performance including good luminescence and high dispersibility for practical anti-counterfeiting applications.

Tuning of SiO2/Si interface by a hybrid plasma process combining oxidation and atom-migration

As a common oxide-semiconductor interface, SiO2/Si plays an important role in silicon-based electronics and optoelectronics. In order to effectively obtain an ultra-smooth and thin SiO2/Si interface, a hybrid tuning process based on inductively coupled plasma (ICP) was proposed, which combined oxidation (plasma-OX) and atom-migration manufacturing (plasma-AMM). In plasma-OX process, a thick oxide film was rapidly prepared on Si wafer surface in 2 min, which included a SiO2 layer on the top and a SiOx (x < 2) layer between the top layer and the bulk crystalline silicon (c-Si). In subsequent plasma-AMM process, ICP steadily delivered energy to the Si wafer surface and induced the migration of unsaturated Si from SiOx layer to c-Si, which enhanced the crystallization of silicon wafer. The roughness of SiO2/Si interface was reduced to Sa 0.171 nm at 620 W in 5 min. However, a 2–3 nm thickness SiOx layer still existed, and several defects causing by residual thermal stress can be observed. Further optimizing plasma-AMM process by setting multi-step slow cooling, the SiOx layer can be almost completely decomposed. The interface roughness Sa was reduced to <0.1 nm and the interface thickness was reduced to 1–2 atom layer. Both OX and AMM process were conducted in the same setup, which is convenient for switching. This study proposed and demonstrated the feasibility of a hybrid plasma tuning process, which provided an efficient tuning technology at atomic level for semiconductor interface.

Study on the electrical breakdown failure mode transition of TSV-RDL

This study investigates the electrical breakdown failure modes and mechanisms of TSV-RDL (Through-Silicon Via with Redistribution Layer) structures through experiments and finite element simulation analysis. By employing a Taguchi method-based finite element simulation, the impact of structural parameters on the electrical breakdown failure modes of TSV-RDLs has been explored. The study reveals two electrically induced breakdown failure modes for TSV-RDLs. One case involves failures occurring at the RDL_pad/SiO2 interface, while the other involves failures within the SiO2 layer along the TSV sidewall interface. The design of TSV-RDLs can influence the distribution of electric field strength and subsequently lead to different electrical breakdown failure modes. In the case of double-blind solid TSV-RDLs, double-through solid TSV-RDLs, and double-blind hollow TSV-RDLs, the pad pitch is identified as a crucial parameter that affects their failure modes. As the pad pitch increases, the location of electrical breakdown failure shifts from the RDL_pad/SiO2 interface to the SiO2 layer along the TSV sidewall interface. Conversely, for the double-through hollow TSV-RDL structure, the structural parameters of TSV, including TSV height, TSV pitch, and SiO2 layer thickness, are the principal factors influencing its failure modes. As these parameters decrease, the position of electrical breakdown failure transitions from the RDL_pad/SiO2 interface to the SiO2 layer along the TSV interface.

Joining of textured PLS-SiC ceramic with CaO-Al2O3-MgO-TiO2-SiO2 glass filler

The pressureless-sintered silicon carbide ceramic with and without surface texturing was joined with CaO-Al2O3-MgO-TiO2-SiO2 glass filler. The experimental results showed that without texturing applied to SiC substrates, the shear strength of SiC joints was 40.8 ± 6.3 MPa, with failure occurring at the interlayer. Unfilled regions in the interlayer limited the shear strength of the joints. When texturing was applied to SiC substrates, SiO2 layer was formed on the surface of substrates due to high-temperature oxidation, which subsequently promoted the wettability of filler on substrates. The textured grooves on SiC substrates could be filled with glass material during joining process. The shear strength of textured SiC joints was 69.3 ± 9.9 MPa with a mixed-mode failure when the direction of shear load was perpendicular to the texturing direction. The better wettability, larger joining area, and interlocking structure between the glass filler and substrates enhanced the shear strength of textured joints.

HfC[sbnd]HfO2[sbnd]SiO2 nanocomposite ceramic coating formed on TiAlNb medium-entropy alloy by LPDS: Microstructure evolution and ablation behavior

HfCHfO2SiO2 nanocomposite ceramic coating was prepared on the TiAlNb medium-entropy alloy by a novel one-step liquid plasma-assisted particle deposition sintering (LPDS) method to improve the ablation resistance. Meanwhile, PEO coatings were prepared as a comparison at different voltages (400 V, 450 V, 500 V). When the PEO coating fabricated at 500 V was ablated for 360 s, the peeling area was the largest at 41.05 %, which was 2.3 times larger than the PEO coating (400 V, 18.03 %). However, the HfCHfO2SiO2 nanocomposite coating exhibits no surface peeling. The surface particles of the coating were sintered together, reducing the presence of pores and enhancing the structure density. Additionally, a large amount of HfO2 and stable HfSiO4 particles were embedded in the amorphous SiO2 layer, which improved the melting point and stability of the glass layer while reducing oxygen permeability. The formed HfSiO4 after ablation acted as “nails”, effectively suppressing the generation of cracks.

Universal design method for bright quantum light sources based on circular Bragg grating cavities.

We theoretically develop an efficient and universal design scheme of quantum light sources based on hybrid circular Bragg grating (CBG) cavity with and without electrical contact bridges. As the proposed design scheme strongly alleviates the computational cost of numerical simulation, we present high-performance CBG designs based on the GaAs/SiO2/Au material system for emission wavelengths ranging from 900 nm to 1600 nm, covering the whole telecom O-band and C-band. All designs achieve remarkable Purcell factors surpassing a value of 26 and extraction efficiencies (into a numerical aperture of 0.8) exceeding 92% without contact bridges and 86% with contact bridges. Additionally, we show that our design approach easily deals with realistic structural constraints, such as preset thicknesses of a semiconductor membrane or SiO2 layers or with a different material system. The high design flexibility greatly supports the experimental deterministic fabrication approaches, allowing one to perform in-situ design adaptation and to integrate single quantum emitters of an inhomogeneously broadened ensemble on the same chip into wavelength-adapted structures without spectral constraints, which highly increase the yield of quantum device fabrication.

Synthesis of Fe3O4@SiO2@C/Ni microspheres for enhanced electromagnetic wave absorption

With the rapid development of electromagnetic and radar technology, military stealth technology has become an essential measure of a country's military strength. In this paper, hydrothermal and improved Stober methods prepared the composite absorbing material Fe3O4@SiO2@C/Ni with a double core-shell structure. The minimum reflection loss of the sample is −38.9 dB, and the maximum effective bandwidth is 10.1 GHz. By changing the thickness of the carbon layer and the thickness of the SiO2 layer, the absorption performance of the prepared sample can be adjusted to achieve the best impedance matching. The synergistic effect of the composite's dielectric loss and magnetic loss improves its microwave absorption capacity, making it a promising choice for absorptive material applications.