Showing papers on "Silicon oxide published in 2020"

Laser-Induced Silicon Oxide for Anode-Free Lithium Metal Batteries.

Abstract: The development of a rechargeable Li metal anode (LMA) is an important milestone for improved battery technology. Practical issues hindering LMAs are the formation of Li dendrites and inactive Li during plating and stripping processes, which can cause short circuits, thermal runaway, and low coulombic efficiency (CE). Here, the use of a laser-induced silicon oxide (LI-SiOx ) layer derived from a commercial adhesive tape to improve the reversibility of Li metal batteries (LMBs) is studied. The silicone-based adhesive of the tape is converted by a commercial infrared laser into a homogeneous porous SiOx layer deposited directly over the current collector. The coating results in superior performance by suppressing the formation of Li dendrites and inactive Li and presenting higher average CE of 99.3% (2.0 mAh cm-2 at 2.0 mA cm-2 ) compared to bare electrodes. The thickness and morphology of the deposited Li is investigated, revealing a different mechanism of Li deposition on coated electrodes. The laser coating affords a method that is fast and avoids the use of toxic organic solvents and extensive drying times. The improved performance with the SiOx coating is demonstrated in LMB with a zero-excess ("anode-free") configuration where a 100% improved performance is verified.

A Polymer/Carbon-Nanotube Ink as a Boron-Dopant/Inorganic-Passivation Free Carrier Selective Contact for Silicon Solar Cells with over 21% Efficiency

Abstract: Traditional silicon solar cells extract holes and achieve interface passivation with the use of a boron dopant and dielectric thin films such as silicon oxide or hydrogenated amorphous silicon. Without these two key components, few technologies have realized power conversion efficiencies above 20%. Here, a carbon nanotube ink is spin coated directly onto a silicon wafer to serve simultaneously as a hole extraction layer, but also to passivate interfacial defects. This enables a low‐cost fabrication process that is absent of vacuum equipment and high‐temperatures. Power conversion efficiencies of 21.4% on an device area of 4.8 cm$^{2}$ and 20% on an industrial size (245.71 cm$^{2}$) wafer are obtained. Additionally, the high quality of this passivated carrier selective contact affords a fill factor of 82%, which is a record for silicon solar cells with dopant‐free contacts. The combination of low‐dimensional materials with an organic passivation is a new strategy to high performance photovoltaics.

Surface SiO2 Thickness Controls Uniform-to-Localized Transition in Lithiation of Silicon Anodes for Lithium-Ion Batteries.

Abstract: Silicon is a promising anode material for lithium-ion batteries because of its high capacity, but its widespread adoption has been hampered by a low cycle life arising from mechanical failure and t...

Hollow-structure engineering of a silicon-carbon anode for ultra-stable lithium-ion batteries

Abstract: Silicon has received much attention due to its high theoretical capacity as the electrode of lithium-ion batteries (LIBs). However, the poor stability caused by the volume expansion problem affects the cycle life of batteries, thus severely limiting the application of the silicon anode. In the present work, we engineered silicon nanotubes with hollow-structure to accommodate the volume expansion of silicon and improve the electrochemical stability of lithium ion batteries. Hollow silicon nanotubes were in situ synthesized on carbon cloth (HSiNTs/CC) by reducing silicon oxide and corroding zinc oxide nanorod templates and directly used as the anode of lithium-ion batteries without any binders or conductive additives. The results of electrochemical measurements indicated that HSiNTs/CC exhibits superior LIB performance with excellent cycling stability and good rate capability. At a current density of 100 mA g-1, a reversible capacity of 1420 mA h g-1 was achieved and the fabricated LIB could retain 93.7% of the initial capacity after 100 cycles. Even at a decoupled current density of 1000 mA g-1, the LIB still possesses a capacity of 1026 mA h g-1 and 98.3% capacity retention after 100 cycles. The results demonstrated that the thin hollow structures were well suited to accommodate the volume expansion of silicon and improve the stability of the HSiNTs/CC anode during the lithiation-delithiation cycles, which shines some light on the reasonable design and preparation of silicon anodes for ultra-stable lithium-ion batteries.

Effect of Silane Treated Silicon (IV) Oxide Nanoparticle Addition on Mechanical, Impact Damage and Drilling Characteristics of Kenaf Fibre-Reinforced Epoxy Composite

Abstract: In this present research mechanical, impact damage and drilling characteristics of silane-treated silicon (IV) oxide particle dispersed kenaf natural fibre-reinforced epoxy hybrid composites has been studied. The principal aim of this work is explicit the role and need of silicon (IV) oxide nano particle in epoxy matrix along with kenaf fibre and benefit of silane treatment on reinforcements in mechanical, impact damage resistance and drilling characteristics. Nano silicon (IV) oxide particle of size 20 nm and kenaf fibre of 450 GSM were used to make composites with silane-treated form. Kenaf natural fibre of 50 vol.% and silicon oxide particles of 0.5, 1.0 & 2.0 vol.% were used for making hybrid composites. The maximum tensile, flexural and impact strength of 172 MPa, 255 MPa and 6.45 J was observed for composite contain 50 vol.% of fibre and 2.0 vol.% of silicon oxide. Similarly the silane treated composite designation of EKS3 gives very low impact damage on comparing with other composite designations. The drilling characteristics of hybrid composite proved that the addition of nano silicon (IV) oxide and silane-treated kenaf fibre reinforced epoxy composite maintains high dimensional stability, lower friction penetration, lower thermal affected zone and lower tool wear compare than other composites.

Atomic layer deposition of lithium-nickel-silicon oxide cathode material for thin-film lithium-ion batteries.

Abstract: Lithium nickelate (LiNiO2) and materials based on it are attractive positive electrode materials for lithium-ion batteries, owing to their large capacity. In this paper, the results of atomic layer deposition (ALD) of lithium–nickel–silicon oxide thin films using lithium hexamethyldisilazide (LiHMDS) and bis(cyclopentadienyl) nickel (II) (NiCp2) as precursors and remote oxygen plasma as a counter-reagent are reported. Two approaches were studied: ALD using supercycles and ALD of the multilayered structure of lithium oxide, lithium nickel oxide, and nickel oxides followed by annealing. The prepared films were studied by scanning electron microscopy, spectral ellipsometry, X-ray diffraction, X-ray reflectivity, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected-area electron diffraction. The pulse ratio of LiHMDS/Ni(Cp)2 precursors in one supercycle ranged from 1/1 to 1/10. Silicon was observed in the deposited films, and after annealing, crystalline Li2SiO3 and Li2Si2O5 were formed at 800 °C. Annealing of the multilayered sample caused the partial formation of LiNiO2. The obtained cathode materials possessed electrochemical activity comparable with the results for other thin-film cathodes.

Microscopic Observation of Solid Electrolyte Interphase Bilayer Inversion on Silicon Oxide

Abstract: Silicon has been investigated in recent years as an alloying anode material to enhance gravimetric energy density in lithium-ion batteries. While recent developments have suggested that silicon oxi...

A combination of hierarchical pore and buffering layer construction for ultrastable nanocluster Si/SiO x anode

Abstract: Porous Si can be synthesized from diverse silica (SiO2) via magnesiothermic reduction technology and widely employed as potential anode material in lithium ion batteries. However, concerns regarding the influence of residual silicon oxide (SiOx) component on resulted Si anode after reduction are still lacked. In this work, we intentionally fabricate a cauliflower-like silicon/silicon oxide (CF-Si/SiOx) particles from highly porous SiO2 spheres through insufficient magnesiothermic reduction, where residual SiOx component and internal space play an important role in preventing the structural deformation of secondary bulk and restraining the expansion of Si phase. Moreover, the hierarchically structured CF-Si/SiOx exhibits uniformly-dispersed channels, which can improve ion transport and accommodate large volume expansion, simultaneously. As a result, the CF-Si/SiOx-700 anode shows excellent electrochemical performance with a specific capacity of ~1,400 mA·h·g−1 and a capacity retention of 98% after 100 cycles at the current of 0.2 A·g−1.

Doping effect in graphene-graphene oxide interlayer.

Abstract: Interlayer coupling in graphene-based van der Waals (vdW) heterostructures plays a key role in determining and modulating their physical properties. Hence, its influence on the optical and electronic properties cannot be overlooked in order to promote various next-generation applications in electronic and opto-electronic devices based on the low-dimensional materials. Herein, the optical and electrical properties of the vertically stacked large area heterostructure of the monolayer graphene transferred onto a monolayer graphene oxide film are investigated. An effective and stable p-doping property of this structure is shown by comparison to that of the graphene device fabricated on a silicon oxide substrate. Through Raman spectroscopy and density functional theory calculations of the charge transport characteristics, it is found that graphene is affected by sustainable p-doping effects induced from underneath graphene oxide even though they have weak interlayer interactions. This finding can facilitate the development of various fascinating graphene-based heterostructures and extend their practical applications in integrated devices with advanced functionalities.

Charge transport mechanism in the metal–nitride–oxide–silicon forming-free memristor structure

Abstract: Silicon oxide and silicon nitride are two key dielectrics in silicon devices. The advantage of Si3N4 over other dielectrics is that silicon nitride is compatible with silicon technology. It is required to study in detail the charge transport mechanism in a Si3N4-based memristor to further improve the cell element and to create a matrix of these elements. Despite many research activities carried out, the charge transport mechanism in Si3N4-based memristors is still unclear. Metal–nitride–oxide–silicon structures that exhibit memristor properties were obtained using low-pressure chemical vapor deposition at 700 °C. The fabricated metal–nitride–oxide–silicon memristor structure does not require a forming procedure. In addition, the metal–nitride–oxide–silicon memristor has a memory window of about five orders of magnitude. We found that the main charge transport mechanism in the metal–nitride–oxide–silicon memristor in a high resistive state is the model of space-charge-limited current with traps. In a low resistive state, the charge transport mechanism is described by the space-charge-limited current model with filled traps. Trap parameters were determined in the Si3N4-based memristor in the high resistive state.

Functionalized Silicon Electrodes in Electrochemistry.

Abstract: Avoiding the growth of SiOx has been an enduring task for the use of silicon as an electrode material in dynamic electrochemistry. This is because electrochemical assays become unstable when the Si...

Nanoasperity Adhesion of the Silicon Surface in Humid Air: The Roles of Surface Chemistry and Oxidized Layer Structures.

Abstract: The interfacial adhesion between silicon oxide surfaces is normally believed to be governed by the surface chemistry of the topmost surface affecting the water contact angle and hydrogen bonding interactions. In the case of a silicon wafer, the physical structure of the native oxide at the surface can vary drastically depending on the aging process; thus, not only the surface chemistry but also the history of surface treatment can also have a profound impact on nanoasperity adhesion. This study reports the effect of aging conditions (ambient air, liquid water, and liquid ethanol) on the nanoasperity adhesion behaviors of a silicon surface. When the silicon surface is kept in liquid alcohol, the surface remains hydrophobic, and adhesion in ambient air can be explained with the capillary effect of the liquid meniscus condensed around the annulus of the nanoasperity contact. When the silicon surface is oxidized in ambient air, the surface gradually becomes hydrophilic, and the strongly hydrogen-bonded water network of adsorbed water plays a dominant role in the nanoasperity interfacial adhesion force. When the silicon surface is aged in liquid water, the interfacial adhesion force measured in ambient air is significantly larger than the value predicted from the theoretical model based on the water contact angle and the hydrogen bonding interaction at the topmost surface. This is because the surface layer oxidized in liquid water is gel-like and thus can swell upon uptake of water from the humid air. To fully encompass all these behaviors, a solid-adsorbate-solid model predicting the adhesion force is developed by introducing a fitting parameter β, which can be adjusted depending on the adsorbed water structure and the swelling capacity of the oxidized surface layer.

Silicon-Based Anode of Lithium Ion Battery Made of Nano Silicon Flakes Partially Encapsulated by Silicon Dioxide

Abstract: Ubiquitous mobile electronic devices and rapidly increasing electric vehicles demand a better lithium ion battery (LIB) with a more durable and higher specific charge storage capacity than traditional graphite-based ones. Silicon is among the most promising active media since it exhibits ten times of a specific capacity. However, alloying with lithium by silicon and dissociation of the silicon-lithium alloys induce high volume changes and result in pulverization. The loss of electrical contacts by silicon with the current collector of the anode causes rapid capacity decay. We report improved anode cycling performance made of silicon flakes partially encapsulated by silicon dioxide and coated with conductive nanocarbon films and CNTs. The silicon dioxide surface layer on a silicon flake improves the physical integrity for a silicon-based anode. The exposed silicon surface provides a fast transport of lithium ions and electrons. CNTs and nanocarbon films provide electrical connections between silicon flakes and the current collector. We report a novel way of manufacturing silicon flakes partially covered by silicon dioxide through breaking oxidized silicon flakes into smaller pieces. Additionally, we demonstrate an improved cycling life and capacity retention compared to pristine silicon flakes and silicon flakes fully encapsulated by silicon dioxide. Nanocarbon coatings provide conduction channels and further improve the anode performance.

Alternating silicon oxy-nitride and silicon oxide stripe formation by nitric oxide (NO+) ion implantation

Abstract: We report nitric oxide ion (NO+) beam induced nanoscale pattern formation on Si (100) surface. The patterns are found to be structurally as well as chemically periodic. A highly reactive 14 keV NO+ beam is developed in an Electron Cyclotron Resonance ion beam system and implanted on Si (100) surface at oblique angles to form a periodic nano-ripple pattern with specific silicon oxide and silicon oxy-nitride enriched sectors with different dielectric constants. Well-defined ripple patterns start to form at comparatively lower ion fluences due to an additional instability generation by the chemical reaction of NO+ ions with silicon. The chemical shift of the Si 2p peak in the x-ray photoelectron spectroscopy study of an ion irradiated sample confirms the formation of silicon oxide and silicon oxy-nitride, whereas the local chemical nature of the ion induced ripple patterns, probed by electron energy loss spectroscopy, approves spatially resolved silicon oxide and silicon oxy-nitride stripe pattern formation. The ion modified layer thickness measured by cross-sectional transmission electron microscopy has an excellent agreement with Monte Carlo simulations. The optical sensitivity of an NO+ bombarded chemically patterned Si surface is also studied by UV–Visible spectroscopy. Formation mechanisms and potential applications of such nano-scale spatially graded materials are discussed.

Growth mechanism of highly oriented layered Sb2Te3 thin films on various materials

Abstract: Sb2Te3 is a layered material with outstanding properties leading to applications in interfacial phase change memories, spintronic and thermoelectric devices. For successful integration in devices, controlling the orientation of the atomic planes of Sb2Te3 deposited by sputtering on various materials used for electrodes and on dielectric layers is required. We have succeeded in depositing Sb2Te3 thin films (thickness in the range 10-100 nm) by sputtering in industrial deposition equipments on WSi, TiN, amorphous Si as well as on native and thermal silicon oxide layers. The structure and orientation of the films were studied by x-ray diffraction. The Sb and Te planes are found parallel to the substrate, whatever the nature of the bottom material, provided that the sputtering conditions avoid a Te deficiency in the deposited film. These results show that deposition of Sb2Te3 with out-of-plane orientation on silicon oxide is actually possible, in contrast with previous literature results. Scanning transmission electron microscopy images of the interface between the Sb2Te3 film and the bottom material allow to elucidate the growth mechanism. The formation of a surface layer containing a few Te planes on top of the bottom material is mandatory for the subsequent growth of an out-of-plane oriented Sb2Te3 film by van der Waals epitaxy.

Foundry-compatible thin film lithium niobate modulator with RF electrodes buried inside the silicon oxide layer of the SOI wafer.

Abstract: Ever-increasing complexity of communication systems demands the co-integration of electronics and photonics. But there are still some challenges associated with the integration of thin film lithium niobate (TFLN) electro-optic modulators with the standard and well-established silicon photonics. Current TFLN platforms are mostly not compatible with the silicon photonics foundry process due to the choice of substrate or complicated fabrication requirements, including silicon substrate removal and formation of radio-frequency (RF) electrodes on the top of the TFLN. Here, we report on a platform where all the optical and RF waveguiding structures are fabricated first, and then the TFLN is bonded on top of the silicon photonic chip as the only additional step. Hence, the need for substrate removal is eliminated, and except for the last step of TFLN bonding, its fabrication process is silicon foundry compatible and much more straightforward compared to other fabrication methods.

SiO2 Is Wasted Space in Single-Nanometer-Scale Silicon Nanoparticle-Based Composite Anodes for Li-Ion Electrochemical Energy Storage

Abstract: The electrode processing conditions of silicon-based composite anodes play a pivotal role in the resulting interfacial chemical speciation and, thus, the electrochemical cycling behavior of the ele...

Isolating p- and n-Doped Fingers With Intrinsic Poly-Si in Passivated Interdigitated Back Contact Silicon Solar Cells

Abstract: Polycrystalline silicon on silicon oxide (poly - Si/SiO x ) passivating contacts enable ultrahigh-efficiency interdigitated back contact silicon solar cells. To prevent shunt between n- and p-type-doped fingers, an insulating region is required between them. We evaluate the use of intrinsic poly - Si for this isolation region. Interdigitated fingers were formed by plasma deposition of doped hydrogenated amorphous silicon through mechanically aligned shadow masks on top of a full-area intrinsic hydrogenated amorphous silicon ( a -Si:H) layer. High-temperature annealing then crystallized the a- Si:H to poly - Si and drove in the dopants. Two mechanisms were identified which cause contamination of the intrinsic poly - Si gap during processing. During deposition of doped fingers, we show using secondary ion mass spectrometry and conductivity measurements that the intrinsic gap becomes contaminated by doped a- Si:H tails several nanometers thick to concentrations of ∼1020 cm−3. Another source of contamination occurs during high-temperature annealing, where dopants desorb from doped regions and readsorb onto intrinsic a- Si:H. Both pathways reduce the resistivity of the intrinsic gap from ∼105 to ∼10−1 Ω·cm. We show that plasma etching of the a- Si:H surface before crystallizing with a capping layer can eliminate the contamination of the intrinsic poly-Si, maintaining a resistivity of ∼105 Ω·cm. This demonstrates masked plasma deposition as a dopant patterning method for Si solar cells.

Low-Temperature Fabrication (≤150 °C) of High-Quality Sputtered Silicon Oxide Thin Film with Hydrogen Plasma Treatment

Abstract: Low-temperature fabrication of thin-film dielectrics is essential for various applications including flexible/stretchable electronics, monolithic three-dimensional integrated circuits, and large-ar...

Polyester-supported Chitosan-Poly(vinylidene fluoride)-Inorganic-Oxide-Nanoparticles Composites with Improved Flame Retardancy and Thermal Stability

Abstract: Polyester (PET) was pre-activated by atmospheric air plasma and coated by various inorganic oxide nanoparticles (MOx) such as titanium dioxide (TiO2), zinc oxide (ZnO), and silicon oxide (SiO2), using poly(vinylidene fluoride) (PVDF) and chitosan (CT) as binders. The resulting PET-PVDF-MOx-CT composites were thermally compressed and then characterized by scanning electron microscopy, Fourier infrared spectroscopy, thermal gravimetric analysis, and flame retardancy (FR) ability tests. PET modifications resulted in more thermally stable and less harmful composites with weaker hazardous gas release. This was explained in terms of structure compaction that blocks pyrolysis gas emissions. CT incorporation was found to reduce the material susceptibility to oxidation. This judicious procedure also allowed improving flame retardancy ability, by lengthening the combustion delay and slowing the flame propagation. Chitosan also turned out to contribute to a possible synergy with the other polymers present in the synthesized materials. These results provide valuable data that allow understanding the FR phenomena and envisaging low-cost high FR materials from biodegradable raw materials.