Silica Research Articles

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.

Optical Second‐ and Third‐Order Nonlinearities in Plasma‐Enhanced Chemical Vapor Deposition‐Grown Silicon Oxides and Silicon Nitrides

Optical second‐ and third‐order nonlinearities ( and ) in nonstoichiometric silicon oxides and silicon nitrides grown by plasma‐enhanced chemical vapor deposition are investigated by second‐harmonic generation (SHG) and electric field‐induced second‐harmonic (EFISH) measurements. The free‐space SHG measurements with a fundamental wavelength of 1030 nm allow us to determine the bulk values of both material platforms for various material compositions. It is demonstrated that the bulk values can be strongly enhanced by increasing the silicon content, reaching maximum values of the main tensor component of for silicon‐rich nitrides and for silicon‐rich oxides. EFISH measurements demonstrate that the values can be pushed even further by adding a static electric field to the materials. Similar to the values, the values are strongly enhanced by increasing the silicon content, leading to a maximum value of m2 V−2 for the silicon‐rich nitrides and m2 V−2 for the silicon‐rich oxides.

Effect of Iron Contamination and Polysilicon Gettering on the Performance of Polysilicon‐Based Passivating Contact Solar Cells

ABSTRACTOver the past decade, silicon solar cells with carrier‐selective passivating contacts based on polysilicon capping an ultra‐thin silicon oxide (commonly known as TOPCon or POLO) have demonstrated promising efficiency potentials and are regarded as an evolutionary upgrade to the PERC (passivated emitter and rear contact) cells in manufacturing. The polysilicon‐based passivating contacts also exhibit excellent gettering effects that relax the wafer and cleanroom requirements to some extent. In this work, we experimentally explore the impact of bulk iron contamination and polysilicon gettering on the passivation quality of the polysilicon/oxide structure and the resulting solar cells performance. Results show that both n‐ and p‐type polysilicon/oxide passivating contacts are not affected by iron gettering, demonstrating robust and stable passivation quality. However, for a very high bulk iron contamination (1 × 1013 cm−3), the accumulated iron in the p‐type lightly boron‐doped emitter in crystalline silicon would degrade the emitter saturation current density. This can cause a reduction in both open‐circuit voltage and short‐circuit current. Meanwhile, this very high iron content (1 × 1013 cm−3) can further degrade the fill factor and temperature coefficient of the cells. On the other hand, for an initial iron content of 2 × 1012 cm−3, which should be well above the iron level in the current industrial Czochralski silicon wafers, the resulting cells demonstrate similar performance as the control group with no intentional iron contamination. This work brings attention to both the benefits of polysilicon gettering effects as well as the potential degradation due to the accumulation of metal impurities in the p‐type emitter region.

Synthesis and Characterization of Na-P1 (GIS) Zeolite Using Rice Husk

This work deals with the synthesis of Na-P1 (GIS) zeolite using rice husk as the starting material, instead of the more expensive chemicals currently used in the industry (i.e., Na aluminates and Na silicates). Rice husk is calcined at the temperature of 550 °C to obtain rice husk ash. Na-P1 is synthesized starting from rice husk ash, NaOH, and NaAlO2 by a protocol involving the mixing of a seed gel and a feedstock gel. Two synthesis runs are carried out at ambient pressure at the temperature of 110 °C by fixing the SiO2/Al2O3 ratio at 3.5 and 5.3, respectively. The synthesized products have been identified as well as the experiments developed by X-ray diffraction and scanning electron microscopy. Then, the most successful synthesized powders were also characterized by infrared spectroscopy, Raman spectroscopy, specific surface area (BET), and differential thermal analysis. The cell parameters are calculated using the Rietveld method. The combined Rietveld and reference intensity ratio methods allows us to exclude the presence of impurities and residual amorphous phase in the conducted experiments. Testing rice husk as a source of amorphous silica in the synthesis of Na-P1 represents both economic and environmental advantages. The high yields and the results of the experiment open the way for the transfer to an industrial production scale.

In-situ construction of dual-coated silicon/carbon composite anode for fast-charging Li-ion batteries

Silicon (Si) is regarded as a promising candidate anode for next-generation high-energy–density batteries due to its ultrahigh theoretical capacity of 4200 mAh g−1. However, silicon anodes face tremendous challenges during cycling, including huge volume expansion, highly unstable interfaces and inherently low conductivity. In this study, the dual-coated silicon/carbon composite anode (Si@SiOx@C) with high silicon content of 85 % is obtained by high-energy ball milling and combined with phenolic resin-assisted encapsulation. The amorphous SiOx layer (∼3 nm) facilitates the rapid Li+ transport and mitigates the volume expansion, while the hard carbon layer (∼3 nm) improves the electronic conductivity and helps to protect against silicon oxide layer erosion from electrolyte, synergistically contributing to the fast-charging performance. With the synergistic effect of dual coating, the Si@SiOx@C anode shows a high initial Coulombic efficiency of 91 % and maintains a high capacity of 1250 mAh g−1 even after 500 cycles at a high rate of 4 A/g. Moreover, the volume expansion of silicon anode during cycling is significantly reduced. This work provides a novel strategy for high silicon content anode in developing fast-charging batteries through dual-coating regulation.

Thermal conductivity of polar nitride perovskite LaWN3

ABX3-type nitride perovskites offer promising avenues for the future electronic industry, renowned for exceptional ferro- and piezo-electric properties with facile integration into prevalent nitride semiconductors. However, the paucity of in-depth investigations of thermal transport of nitride perovskites poses a substantial impediment to the practical implementation. Here, we experimentally investigate the thermal conductivity of orthorhombic polar LaWN3, synthesized by high-pressure high-temperature technique. The observed thermal conductivity exhibits drastic reduction with decreasing temperature, reminiscent of the behavior in amorphous silica. We postulate the anomalous glass-like thermal conductivity to a synergistic interplay of potential Ferron–phonon interactions, lattice disorders from octahedral distortions, and wave-like atomic tunneling. This study represents a pioneering exploration of thermal transport within nitride perovskites, paving the way for future advancements in nitride-based electronics.

Frazil ice changes winter biogeochemical processes in the Lena River

The ice-covered period of large Arctic rivers is shortening. To what extent will this affect biogeochemical processing of nutrients? Here we reveal, with silicon isotopes (δ30Si), a key winter pathway for nutrients under river ice. During colder winter phases in the Lena River catchment, conditions are met for frazil ice accumulation, which creates microzones. These are conducive to a lengthened reaction time for biogeochemical processes under ice. The heavier δ30Si values (3.5 ± 0.5 ‰) in river water reflect that 39 ± 11% of the Lena River discharge went through these microzones. Freezing-driven amorphous silica precipitation concomitant to increased ammonium concentration and changes in dissolved organic carbon aromaticity in Lena River water support microbially mediated processing of nutrients in the microzones. Upon warming, suppressing loci for winter intra-river nitrogen processing is likely to modify the balance between N2O production and consumption, a greenhouse gas with a large global warming potential.

Array of Graphene Solar Cells on 100 mm Silicon Wafers for Power Systems

High electrical conductivity and optical transparency make graphene a suitable candidate for photovoltaic-based power systems. In this study, we present the design and fabrication of an array of graphene-based Schottky junction solar cells. Using mainstream semiconductor manufacturing methods, we produced 96 solar cells from a single 100 mm diameter silicon wafer that was precoated with an oxide layer. The fabrication process involves removing the oxide layer over a select region, depositing metal contacts on both the oxide and bare silicon regions, and transferring large-area graphene onto the exposed silicon to create the photovoltaic interface. A single solar cell can provide up to 160 μA of short-circuit current and up to 0.42 V of open-circuit voltage. A series of solar cells are wired to recharge a 3 V battery intermittently, while the battery continuously powers a device. The solar cells and rechargeable battery together form a power system for any 3-volt low-power application.

Z-slotted Silicon Dioxide Based Tunable Polarization Converter Design Using Graphene-VO2 Composite for Detection of Cancer

Z-slotted Silicon Dioxide Based Tunable Polarization Converter Design Using Graphene-VO2 Composite for Detection of Cancer

HWCVD growth of hydrogenated nanocrystalline silicon oxide window layers for SHJ solar cells

In recent years, successful development of n-type hydrogenated nanocrystalline silicon oxide (n-nc-SiOx:H) window layers with high conductivity and low parasitic absorption, grown by plasma enhanced chemical vapor deposition (PECVD) technology, has significantly enhanced the power conversion efficiency of silicon heterojunction (SHJ) solar cells. Although SHJ solar cells have significant advantages in efficiency, the high cost of the PECVD equipment presents a significant barrier to their mass production. The utilization of the more cost-effective hot wire chemical vapor deposition (HWCVD) technology presents a promising solution. Nevertheless, HWCVD technology currently lacks an industrially viable methodology for growing high-performance window layers due to a phenomenon of associated severe loss of passivation. In this work, the phenomenon and the solution have been investigated. The results demonstrate that, in HWCVD processes, large amounts of hydrogen and small amounts of oxygen, which are essential for enhancing the crystallinity and conductivity and reducing the parasitic absorption, both induce significant damage to the previously grown intrinsic hydrogenated amorphous silicon layer, leading to poor passivation, and hence much lower cell efficiency. Introduction of a densified amorphous silicon barrier layer was found to be an effective solution to the aforementioned passivation loss, resulting in the successful growth of nc-SiOx:H window layers by HWCVD, with an efficiency enhancement of 0.37%abs. Finally, a commercial-size SHJ solar cell with an efficiency of 24.74 % was fabricated using a home-made HWCVD-based pilot SHJ cell line.

The Influence of Temperature on Charging Effects in Mask During Plasma Etching

ABSTRACTThis research examines the correlation between temperature effects and surface charging problems on a silicon dioxide mask using simulation techniques. The findings of this study validate the significance of considering electron–solid interactions, especially when influenced by varying temperatures. The impacts of temperature changes on the spatial distributions of net charge deposition, electric potential, and electric field are examined. It was noted that the temperature rise leads to an increase in the concentration of positively charged holes near the surface of the mask, thereby diminishing the spatial dispersion of positive potential. This results in a less conspicuous alteration of the mask profile as the temperature increases. This investigation is anticipated to possess substantial significance and offer valuable insights for optimizing mask design.

Inverse Vulcanization of Aziridines: Enhancing Polysulfides for Superior Mechanical Strength and Adhesive Performance

This study introduces a novel approach to inverse vulcanization by utilizing a commercially available triaziridine crosslinker as an alternative to conventional olefin‐based crosslinkers. The model reactions reveal a self‐catalyzed ring‐opening of "unactivated" aziridine with elemental sulfur, forming oligosulfide‐functionalized diamines. The triaziridine‐derived polysulfides exhibit impressive mechanical properties, achieving a maximum stress of ~8.3 MPa and an elongation at break of ~107%. The incorporation of silicon dioxide (20 wt%) enhances the composite’s rigidity, yielding a Young's modulus of ~0.94 GPa. Furthermore, these polysulfides display excellent adhesion strength on various substrates, such as aluminum (~7.0 MPa), walnut (~9.6 MPa), and steel (~11.0 MPa), with substantial retention of adhesion strength (~3.3 MPa on steel) at −196 °C. The straightforward synthetic process, combined with the accessibility of the triaziridine crosslinker, emphasizes the potential for further innovations in sulfur polymer chemistry.

Inverse Vulcanization of Aziridines: Enhancing Polysulfides for Superior Mechanical Strength and Adhesive Performance.

This study introduces a novel approach to inverse vulcanization by utilizing a commercially available triaziridine crosslinker as an alternative to conventional olefin-based crosslinkers. The model reactions reveal a self-catalyzed ring-opening of "unactivated" aziridine with elemental sulfur, forming oligosulfide-functionalized diamines. The triaziridine-derived polysulfides exhibit impressive mechanical properties, achieving a maximum stress of ~8.3 MPa and an elongation at break of ~107%. The incorporation of silicon dioxide (20 wt%) enhances the composite's rigidity, yielding a Young's modulus of ~0.94 GPa. Furthermore, these polysulfides display excellent adhesion strength on various substrates, such as aluminum (~7.0 MPa), walnut (~9.6 MPa), and steel (~11.0 MPa), with substantial retention of adhesion strength (~3.3 MPa on steel) at -196 °C. The straightforward synthetic process, combined with the accessibility of the triaziridine crosslinker, emphasizes the potential for further innovations in sulfur polymer chemistry.

Eco-Pozzolans as Raw Material for Sustainable Construction Industry: Comparative Evaluation of Reactivity Through Direct and Indirect Methods

A solution to reduce the consumption of raw materials and the generation of greenhouse gases is the partial replacement of clinker (the main constituent of cement) with supplementary cementitious materials. This study aimed to compare the reactivity of ten supplementary cementitious materials—synthetic/commercial ones and those from industrial and agricultural waste (eco-pozzolans). The characterization of the raw materials was carried out using X-ray fluorescence, the loss on ignition, X-ray diffraction, and the determination of the amorphous silica content and particle size distribution. The pozzolanicity assessment was carried out using the Frattini test (direct method) and electrical conductivity and pH tests (indirect method), with the latter presenting greater sensitivity and precision, enabling us to classify the pozzolan reactivity. Although synthetic/commercial pozzolans have higher silica content, the eco-pozzolans showed excellent reactivity results, thus indicating their use as sustainable pozzolans, presenting characteristics that enhance the performance of cement matrices and reduce the environmental impacts of production. Nyasil and rice leaf ash were the pozzolans that presented the greatest reactivity among those studied. The obtained results suggest that using industrial/agricultural waste like reactive pozzolans can help to mitigate the adverse impacts of cement production, address natural resource shortages, and promote a circular economy.

DNA adsorption monitoring with interdigital open-gate junction field effect transistor for DNA storage applications: MD modeling, design, and experimental results

This paper introduces a novel portable sensing platform designed to explore the intricate interaction between DNA molecules and silicon dioxide (SiO2) coated on a field effect transistor (FET), bearing profound implications for a spectrum of life science applications, particularly DNA storage. In-silico molecular dynamic (MD) simulations are employed to gain insights into the effects of DNA on the FET surface's potential under extreme conditions of dehydration of double-stranded DNA (dsDNA), verifying its capacity to generate surface charge when dehydrated due to the evaporation of droplets. The platform is comprised of a backgated interdigital open gate junction FET (ID-OGJFET) fabricated through an innovative electronic sensing platform foundry and accompanied by an electronic interface system incorporated with a fluidic sample holder that reads the surface charge on the sensor induced by negatively charged nucleotides in dsDNA and single-stranded DNA (ssDNA). This novel ID-OGJFET sensor coated with native SiO2 enables a direct-on-channel sensing area of >16 mm2 without top gate extension for the target application, working at low back gate voltage (<0.4 V) for adsorption analysis in the dry mode. Our study involves designing, synthesizing, and introducing DNA sequences onto the chip surface at various concentrations. This paper presents and discusses experimental results that align with MD simulations, elucidating the impact of DNA's intrinsic charge on the chip's surface under extreme dehydration conditions. These findings pave the way for developing a portable charge-sensitive DNA monitoring system, particularly in the emerging physical storage of DNA.

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.

Design of Silica-Cobalt Composite Microporous Structures with Dispersed Carbon Particles for Highly Permselective Gas Separation Membranes.

Metal-doped silica membranes, fabricated via the sol-gel technique using metal nitrates, hold promise for high-temperature separation processes, such as H2 separation in steam reforming reactions. However, controlling the status of the doped metal is challenging and often leads to defect formation owing to the aggregation of metal oxides. In this study, we designed a uniform carbon-Co-SiO2 ceramic membrane using a one-pot sol-gel method with copolymerization, employing tetraethoxysilane and cobalt acetylacetone(III) (Co-(acac)3) as precursors. Organic chelate ligands within the amorphous silica network formed by the polymerization reaction were carbonized by calcination at 250-750 °C in an inert atmosphere. This approach suppressed defect formation and tailored the microporous structures to a wide range of separation systems. For example, the SiO2-Co-(acac)3 membrane calcined at 550 °C demonstrated a notable C3H6 permeance of 4.0 × 10-8 mol m-2 s-1 Pa-1 (GPU: 120), with a high C3H6/C3H8 selectivity of 46, attributed to the molecular sieving effect, whereas the membrane calcined at 650 °C exhibited a remarkable He permeance of 4.6 × 10-7 mol m-2 s-1 Pa-1 (GPU: 1400), with a high He/CH4 selectivity of 830. This study provides valuable insights into the development of defect-free carbon-cation-SiO2 ceramic membranes for a broad range of gas separation processes.

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.

Dairy sludge characteristics and its degradation during thermal treatment and thermal plasma treatment

ABSTRACT Thermal treatment and thermal plasma treatment processes of dairy sludge were conducted. The thermal treatment was undertaken at temperatures from 200 °C to 1000 °C to establish the chemical composition and thermal degradation of the sludge. These results served as a foundation for interpreting the properties of the vitreous slag obtained from the sludge treated in the DC-transferred arc plasma reactor. The dairy sludge is characterised by a high volatile matter but also presents substantial ash content, with primary elements such as Al, P, Si, Ca, and Fe. The characterisations of the samples were made employing techniques like X-ray fluorescence, X-ray diffraction analysis (XRD), FT-IR spectrometry, Thermogravimetric analysis, and Differential Scanning Calorimetry. The results highlight the degradation of primary milk components like lactose, casein protein, and milk fat, with distinct differential thermogravimetric peaks at 230, 316, and 479 °C. As the temperature of thermal treatments approached 1000°C, silicon dioxide, calcium silicon, dicalcium silicate, and hydroxyapatite were identified in XRD spectra. Plasma-treated sludge features various oxide crystalline structures, including Al2O3, CaO(Al2O3)6, CaO(Al2O3)2, Ca2Al(AlSi)O7, KFeO2, and ZrO1.98. FTIR analysis of sludge identifies a complex organic composition presenting alkanes, amines, amides, hydroxyl groups, and metallic and semi-metallic oxide bond absorption. The FTIR results suggest the degradation of organic compounds and retention of phosphorous and aluminum bonds, especially after 600 °C. The vitreous slag from plasma treatment exhibits distinct composition characteristics without organic compound, presenting a vitreous and metallic/ceramic matrix. This research underscores the potential of thermal plasma treatments to neutralise dairy sludge.

Ice-grain impact on a rough amorphous silica surface

Using molecular dynamics simulation, we analyze the collision between a water-ice grain and a silica surface. Both a flat and porous surfaces are studied. We find that the presence of pores in the silica sample and the induced roughness of the silica surface significantly influence the collision outcome. The presence of pores on the surface increases the contact area of the colliding grain with the silica sample, and consequently also the number of reaction products, i.e., water dissociation products and silanol groups formed at the silica surface. The effect is maximum if the pore size is of the order of the grain radius. In addition, the presence of pores on the surface allows for the penetration of water molecules under the surface, molecule ejection from the colliding ice grain is enhanced, and dissipation of the collision energy into the sample is hindered.