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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Determination of the oxide scale growth mechanism using 18O-tracer experiments in combination with Transmission Electron Microscopy and nanoscale Secondary Ion Mass Spectrometry

Highlights: • {sup 18}O-tracer experiments to determine oxide scale growth mechanism on a Fe-Cr alloy. • Cr{sub 2}O{sub 3} scale growth primarily by means of metal outwards diffusion in air at 850 °C • nanoSIMS mapping on TEM lamella more accurate than SIMS sputter depth profiling • nanoSIMS mapping on TEM lamella reveal information about local oxide growth. • Strong local variation of oxide scale growth - Abstract: Two-stage {sup 18}O{sub 2}/{sup 16}O{sub 2} exposures can be used to investigate the effect that alloying elements, secondary phases, or surface treatments have on the high temperature oxidation behaviour of certain materials. During subsequent exposures to {sup 16}O{sub 2}- and {sup 18}O{sub 2}-rich atmospheres, {sup 16}O- and {sup 18}O-rich layers are formed. Analysis of the layers using Secondary Ion Mass Spectrometry (SIMS) depth profiling allows for conclusions to be drawn about the oxide scale growth mechanism. The conclusions are, however, not entirely unambiguous due to the limited lateral resolution of the technology. Rough surface topography and the thickness variation of the oxide scale over the analysed volume add to the ambiguity of the findings. In this study, an Fe-20%Cr alloy was exposed to both {sup 18}O- and {sup 16}O-rich environments at 850 °C. Two methods were used to analyse the thermally grown Cr{sub 2}O{sub 3} scale: (1) traditional SIMS depth profiling and (2) preparation of a cross-sectional lamellae for Transmission Electron Microscopy (TEM), which, subsequently, was analysed in a NanoSIMS. The NanoSIMS {sup 16}O and {sup 18}O elemental maps were then superimposed on the TEM image. In comparison with traditional SIMS depth profiling, the nanoSIMS elemental maps reveal detailed information about local oxide growth in different parts of an oxide scale. Moreover, a clear {sup 16}O/{sup 18}O interface can be seen in the nanoSIMS maps, which is not the case in the sputter depth profiles. The findings of this study show that the aforementioned issues associated with sputter depth profiling can be eliminated by mapping a cross-section of an oxide scale using high resolution nanoSIMS.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A rapid and convenient method for the preparation of thermochromic VO{sub 2} thin films

Highlights: • A simple and efficient route has been developed for the preparation of VO{sub 2} thin films. • VO{sub 2} films annealed at high enough crystallization temperature were obtained and analyzed. • Excellent optical modulation both in the visible and near-infrared region has been achieved in the prepared VO{sub 2} film. - Abstract: The annealing temperature for the preparation of VO{sub 2} films with sputtering method have always been applied in the range of 300–500 °C. Herein, a simple and efficient route has been developed for the preparation of VO{sub 2} thin films through the thermal oxidation of sputtered vanadium film at 585 °C. Structural, morphological, elemental analysis and thermochromic properties of synthesized VO{sub 2} films are reported. Different from the traditional sputtered VO{sub 2} films, large change of transmittance has been found in the visible region during phase transition. The present work shows the feasibility to fabricate reliably reproduced high quality VO{sub 2} films with reversible phase transition and excellent optical modulation both in the visible and near-infrared region.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Self-supported Zn/Si core-shell arrays as advanced electrodes for lithium ion batteries

Graphical abstract: Zn/Si core-shell arrays prepared by combined hydrothermal plus sputtering method show good performance with high specific capacity and excellent cycling stability. - Highlights: • Construct Zn/Si core-shell arrays via sputtering. • The Zn/Si core-shell arrays show high capacity and good cycles. • Core-shell arrays is favorable for fast ion/electron transfer. - Abstract: Silicon is considered as the most promising substitute for the commercial graphite anode of lithium ion batteries (LIBs) due to its high capacity and low working voltage. In this work, we realize the rational combination between Zn nanorods and Si forming self-supported Zn/Si core-shell arrays with the aid of hydrothermal and sputtering methods. Amorphous Si layer is well coated on the backbone of Zn nanorods with diameters of 70–80 nm. As a preliminary test, the Zn/Si core-shell arrays are used as the anode of LIBs and demonstrated with a high initial reversible capacity of 2795 mAh g{sup −1} at 0.1C, good high-rate capability with 1985 mAh g{sup −1} at 1C and stable cycling life. The good performance is due to the highly conductive Zn nanorod network and porous core-shell structure providing good mechanical support and fast transport of ions/electrons.

36 MATERIALS SCIENCE↗
DOE OSTI2019

First measurement of S/XB values of Re I visible emission lines

A spectroscopic parameter, so called S/XB (the number of ionization events per photon or inverse photon efficiency), is experimentally determined for Re I visible emission lines (488.9, 527.1, and 527.6 nm) at an electron temperature range of ~2–8 eV in the PISCES-B linear plasma device. Our standard mass loss method was applied, where a pure Re sample was sputtered by Ar plasma. In addition, a new alloy method was developed, where a W-3.3 at% Re alloy sample was used. In the new method, the sputtered flux ratio of Re and W atoms is assumed to be the same as the elemental composition because of the very similar sputtering yields. In this work, good agreement in measured Re I S/XB values is obtained between the standard mass loss and new alloy methods.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Evaluation of silicon carbide as a divertor armor material in DIII-D H-mode discharges

Silicon carbide (SiC) represents a promising but largely untested plasma-facing material (PFM) for next-step fusion devices. In this work, an analytic mixed-material erosion model is developed by calculating the physical (via SDTrimSP) and chemical (via empirical scalings) sputtering yield from SiC, Si, and C. The Si content in the near-surface SiC layer is predicted to increase during D plasma bombardment due to more efficient physical and chemical sputtering of C relative to Si. Silicon erosion from SiC thereby occurs primarily from sputtering of the enriched Si layer, rather than directly from the SiC itself. SiC coatings on ATJ graphite, manufactured via chemical vapor deposition, were exposed to repeated H-mode plasma discharges in the DIII-D tokamak to test this model. The qualitative trends from analytic modeling are reproduced by the experimental measurements, obtained via spectroscopic inference using the S/XB method. Quantitatively the model slightly under-predicts measured erosion rates, which is attributed to uncertainties in the ion impact angle distribution, as well as the effect of edge-localized modes. After exposure, minimal changes to the macroscopic or microscopic surface morphology of the SiC coatings were observed. Compositional analysis reveals Si enrichment of about 10%, in line with expectations from the erosion model. Extrapolating to a DEMO-type device, an order-of-magnitude decrease in impurity sourcing, and up to a factor of 2 decrease in impurity radiation, is expected with SiC walls, relative to graphite, if low C plasma impurity content can be achieved. Furthermore, these favorable erosion properties motivate further investigations of SiC as a low-Z, non-metallic PFM.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

The Formation of Hollow Lead Structures on the Surface of PbSe Films Treated in Argon Plasma

Conditions for ion sputtering of a PbSe/CaF{sub 2}/Si(111) epitaxial system in high-density inductively coupled plasma of high-frequency low-pressure discharge in argon have been established that ensure the formation of submicron-sized hollow lead structures on a lead-selenide surface. The surface was plasma-treated for time periods within 60–240 s at low energy (20–30 eV) of Ar{sup +} ions, which is close to their sputtering threshold energy. The properties of the obtained material were studied by the techniques of scanning electron microscopy and energy-dispersive X-ray microanalysis. It is shown that the characteristic size, shape, and density of surface structures can be varied within broad limits depending on the time of plasma treatment and temperature of the material surface. Physical processes responsible for the formation of hollow lead structures under the proposed conditions of plasma sputtering are considered.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

High-Efficiency and Low-Carbon Energy Storage and Power Generation System for Electric Aviation

This report summarizes the work performed by University of California San Diego (UCSD) – Honeywell Aerospace (Honeywell) team for the U.S. Department of Energy/Advanced Research Projects Agency-Energy (DOE/ARPA-E) under Phase 1 (April 2021 – October 2023) project, Cooperative Agreement DE-AR0001347 entitled “High-Efficiency and Low-Carbon Energy Storage and Power Generation System for Electric Aviation”. The main objective of this project is to develop and demonstrate an energy storage and power generation (ESPG) system operating on bio liquid natural gas (LNG) for electric aviation applications. The ESPG system concept in this project is a fuel cell, battery, and gas turbine hybrid system that incorporates an innovative solid oxide fuel cell (SOFC) technology. This SOFC technology has two main novel elements: (i) a lightweight and compact stack architecture that consists of cells and cell modules in electrical parallel and series connections (the module design) and (ii) exceptionally high performance, direct methane thin-film cells on porous substrate made by sputtering deposition process. This fuel cell has the specific power and volumetric power density suitable for electric aviation applications. Based on the current status of the SOFC technology, the Phase 1 work focused on the following activities: (i) ESPG System Modeling – to design and optimize an aircraft SOFC-based ESPG system concept that met the performance, weight and cost targets; (ii) Cell Material Development and Scaleup – to demonstrate scalability of the sputtering process for manufacture of thin-film SOFC cells of practical sizes, confirm the exceptional performance of sputtered cells, improve cell stability and durability for operation with hydrogen and methane fuel, and develop a suitable electrically conducting porous substrate to replace the current non-conducting ceramic substrate; (iii) Stack Development – to design and manufacture stack components for the stack architecture, evaluate and select a suitable sealant, and build and operate multi-cell stacks to demonstrate stack operation, and (iv) Technology to Market – to develop business models and commercialization plans, conduct various market and technology analysis and estimate SOFC and ESPG system costs.

25 ENERGY STORAGE↗
DOE OSTI2019

Effect of Ti Doping on the Crystallography, Phase, Surface/interface Structure and Optical Band Gap of Ga2O3 Thin Films

The effect of titanium (Ti) doping on the crystal structure, phase, surface/interface chemistry, microstructure and optical band gap of gallium oxide (Ga2O3) (GTO) films is reported. The Ti content was varied from 0 to * 5 at% in cosputtering, using Ga2O3 ceramic and Ti metal targets, deposited GTO films produced. The sputtering power to the Ti target was varied in the range of 0–100 W, while keeping the sputtering power to Ga2O3 constant at 100 W, to produce GTO films with 0–5 at% Ti. The Ti-incorporation-induced effects were significant for the crystal structure, phase, surface/interface chemistry and morphology, which in turn induce changes in the band gap. The high-resolution core-level X-ray photoelectron spectroscopy (XPS) analyses confirm that the Ga ions exist as Ga3? in both intrinsic Ga oxide and GTO films. However, XPS data reveal the formation of Ga2O3–TiO2 films with the presence of Ti4? ions with increasing Ti sputtering power, i.e., higher Ti contents in GTO. Evidence for the formation of nanocrystalline Ga2O3–TiO2 films was also found in the structural analyses performed using electron microscopy and grazing incidence X-ray diffraction. Significant band gap reduction (Eg * 0.9 eV) occurs in GTO films with increasing Ti dopant concentration from 0 to 5 at%. A correlation between the Ti dopant concentration, surface/interface chemistry, microstructure and band gap of GTO films is established.

Manandhar, Sandeep↗
DOE OSTI2024

Exploring the relationship between deposition method, microstructure, and performance of Nb/Si-based superconducting coplanar waveguide resonators

Superconducting quantum circuits (SQC) are one of the most promising hardware platforms for quantum computing, yet their performance is currently limited by the presence of various structural defects inside the circuit's structure. Despite impressive progress in the past decade, a precise understanding of the origin of these defects from various fabrication processes and their impact on coherence is still lacking. Here, in this study, we performed a comprehensive investigation on the microstructure, superconductivity, and resonator quality factor of Nb films deposited by high-power impulse magnetron sputtering (HiPIMS) and direct current (DC) magnetron sputtering. A suite of characterization techniques, including electron microscopy with spectroscopy, secondary ion mass spectrometry, magneto-optical microscopy, and pump-probe reflectivity spectroscopy is used. We reveal that niobium (Nb) resonators fabricated using HiPIMS exhibit a smaller average grain size, thicker surface oxide with larger thickness variations (rougher surface), and a thicker amorphous Nb/Si interface layer compared to samples deposited by DC sputtering. We identified that the amorphous Nb oxides (mainly located at the Nb surface and along the grain boundaries) and Nb-Si amorphous layers (at the Nb/Si interface) are major and potential sources of two-level system (TLS), while off-stochiometric oxides and suboxides of Nb close to the surface, crystalline defects (i.e., dislocations at grain boundary, point defects introduced during deposition) are main contributors of non-TLS sources. Our findings clarify the relationship between different defects and coherence loss mechanisms, highlighting the importance of material microstructure control on performance optimization in SQC.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Fabrication of porous transport electrodes: Development of quantitative approach for quality control

This work focuses on porous transport electrodes (PTEs), which integrate the anodic catalyst with the adjacent Ti porous transport layer (PTL). Challenges in catalyst deposition on PTLs, particularly at low loadings, motivated this study to evaluate various fabrication methods and characterization approaches. This work investigated Pt-treated PTLs coated with Ir-based catalysts using several common methods, including airbrush coating, rod coating, ultrasonic spray coating, electrodeposition, and sputter deposition, with catalyst loadings ranging from 2.9 to 0.1 mg/cm 2 , providing the opportunity for comparisons across a large set of samples produced by different methods. Two widely accessible characterization techniques: X-ray computed tomography (XCT) and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) were explored. Initial evaluation of selected samples with XCT provided qualitative insights into catalyst distribution, however comprehensive quantitative analysis was limited. SEM-EDS enabled detailed information on the catalyst distribution both qualitatively and quantitatively using two metrics. Atomic and surface area % ratios of Pt:Ir and Ti:Ir revealed trends in catalyst loading and losses into the PTL pores, as well as evaluating the homogeneity of catalyst coatings. The analysis demonstrated that ultrasonic spray coating, electrodeposition, and sputter coating produced the most homogeneous coatings, with minimal catalyst losses observed for electrodeposition and sputter coating. By adapting common techniques with novel, standardized methodologies, this work establishes a universally applicable framework for cross-study comparison of PTEs. The SEM-EDS approach provides a practical, accessible tool for PTE characterization and contributes a reference dataset supporting both research development and rapid quality control.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Study of synergistic effects and compositional dependence of hydrogen evolution reaction on MoxNiy alloy thin films in alkaline media

In this paper hydrogen evolution reaction (HER) on the molybdenum-nickel thin films has been studied. The Mo x Ni y thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A change in the crystal structure of the samples prepared at different temperatures was observed. The structure of the samples prepared at 25 °C are bcc or amorphous. The structure of alloys sputtered at 800 °C changed to fcc. Tafel plots were constructed for each Mo x Ni y alloy sample. The mechanism of HER was determined from Tafel slope analysis. Values of charge transfer resistance were also determined by impedance spectroscopy. The compositional dependence of activity and the stability of Mo x Ni y thin films in 1 M NaOH were determined by cycling and chronoamperometry. Our results demonstrate that Mo x Ni y thin films prepared at 800 °C show significantly improved activity compared to pure Mo and Ni metals. On the other hand, Mo x Ni y thin films sputtered at 25°C do not show increased activity in comparison to pure Ni metal. Furthermore, this points to a synergistic effect between fcc Mo and fcc Ni in thin films sputtered at elevated temperatures. Mo 63 Ni 67 thin films alloy prepared at 800 °C shows the best values of catalytic activity for HER from all investigated compositions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Sensitivity of WallDYN material migration modeling to uncertainties in mixed-material surface binding energies

The WallDYN package has recently been applied to a number of tokamaks to self-consistently model the evolution of mixed-material plasma facing surfaces. A key component of the WallDYN model is the concentration-dependent surface sputtering rate, calculated using SDTRIM.SP. This modeled sputtering rate is strongly influenced by the surface binding energies (SBEs) of the constituent materials, which are well known for pure elements but often are poorly constrained for mixed-materials. This work examines the sensitivity of WallDYN surface evolution calculations to different models for mixed-material SBEs, focusing on the carbon/lithium/oxygen/deuterium system present in NSTX. A realistic plasma background is reconstructed from a high density, H-mode NSTX discharge, featuring an attached outer strike point with local density and temperature of 4 × 10 20 m -3 and 4 eV, respectively. It is found that various mixed-material SBE models lead to significant qualitative and quantitative changes in the surface evolution profile at the outer divertor, with the highest leverage parameter being the C-Li binding model. Uncertainties of order 50%, appearing on time scales relevant to tokamak experiments, highlight the importance of choosing an appropriate mixed-material sputtering representation when modeling the surface evolution of plasma facing components. Lastly, these results are generalized to other fusion-relevant materials with different ranges of SBEs.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

An analytical expression for ion velocities at the wall including the sheath electric field and surface biasing for erosion modeling at JET ILW

For simulation of plasma-facing component erosion in fusion experiments, an analytical expression for the ion velocity just before the surface impact including the local electric field and an optional surface biasing effect is suggested. Energy and angular impact distributions and the resulting effective sputtering yields were produced for several experimental scenarios at JET ILW mostly involving PFCs exposed to an oblique magnetic field. The analytic solution has been applied as an improvement to earlier ERO modelling of localized, Be outer limiter, RF-enhanced erosion, modulated by toggling of a remote, however magnetically connected ICRH antenna. The effective W sputtering yields due to D and Be ion impact in Type-I and Type-III ELMs and inter-ELM conditions were also estimated using the analytical approach and benchmarked by spectroscopy. The intra-ELM W sputtering flux increases almost 10 times in comparison to the inter-ELM flux.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Liquid lithium divertor analysis using coupled plasma material interaction model

A liquid lithium divertor can improve performance of future fusion devices by creating efficient power exhaust and improving the energy confinement via pumping of the hydrogen isotopes. In addition, significantly higher heat fluxes can be handled if controlled vapor shielding is used to redistribute the divertor heat flux over a wider area. Design and optimization of such a system calls for an analysis model which includes a strong two-way coupling between the plasma and divertor material. The incoming plasma heat and particle flux will affect the divertor surface temperature, which is a defining factor of the lithium evaporative and sputtered flux going into the plasma. Results of the coupled model based on the plasma edge code SOLPS-ITER and the computational fluid dynamics (CFD) code ANSYS-CFX will be presented for different configurations. An analytical slab flow model is used as a heat transfer boundary condition for SOLPS, defining particle flux from the wall via calculation of the surface temperature. At the final step, results of the SOLPS analysis are verified using a 3D CFD magnetohydrodynamics (MHD) analysis which uses heat and particle flux from SOLPS as a boundary condition. In addition to plasma heat flux, both analytical and CFD temperature models include several plasma material interaction effects, such as lithium evaporation, condensation and sputtering based on deuterium target flux. New adatom sputtering model based on the available experimental data is presented. Analytical model is expanded to include free surface axisymmetric configurations. Results of parametric studies of the divertor configurations with different lithium inlet temperature and velocity will be presented leading to the optimal design resulting in the lowest possible lithium contamination in the core.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Increased fracture depth range in controlled spalling of (100)-oriented germanium via electroplating

Controlled spalling in (100)-oriented germanium using a nickel stressor layer shows promise for semiconductor device exfoliation and kerfless wafering. Demonstrated spall depths of 7-60 um using DC sputtering to deposit the stressor layer are appropriate for the latter application but spall depths < 5 um may be required to minimize waste for device applications. This work investigates the effect of tuning both electroplating current density and electrolyte chemistry on the residual stress in the nickel and on the achievable spall depth range for the Ni/Ge system as a lower-cost, higher-throughput alternative to sputtering. By tuning current density and electrolyte phosphorous concentration, it is shown that electroplating can successfully span the same range of spalled thicknesses as has previously been demonstrated by sputtering and can reach sufficiently high stresses to enter a regime of thickness (<7 um) appropriate to minimize substrate consumption for device applications.

14 SOLAR ENERGY↗
DOE OSTI2020

Three-Dimensional Mass Spectrometric Imaging of Biological Structures Using a Vacuum-Compatible Microfluidic Device

Three-dimensional (3D) molecular imaging of biological structures is important for a wide range of research. In recent decades, secondary ion mass spectrometry (SIMS) has been recognized as a powerful technique for both two-dimensional (2D) and 3D molecular imaging. Sample fixations (e. g., chemical fixation and cryogenic fixation methods) are necessary to adapt biological samples to the vacuum condition in the SIMS chamber, which has been demonstrated to be non-trivial and less controllable, thus limiting the wider application of SIMS on 3D molecular analysis of biological samples. Our group recently developed in situ liquid SIMS that offers great opportunities for the molecular study of various liquids and liquid interfaces. In this work, we demonstrate that a further development of the vacuum-compatible microfluidic device used in in situ liquid SIMS provides a convenient freeze-fixation of biological samples and leads to more controllable and convenient 3D molecular imaging. The special design of this new vacuum-compatible liquid chamber allows an easy determination of sputter rates of ice, which is critical for calibrating the depth scale of frozen biological samples. Sputter yield of a 20 keV Ar 1800 + ion on ice has been determined as 1500 (± 8%) water molecules per Ar 1800 + ion, consistent with our results from molecular dynamics simulations. Moreover, using the information of ice sputter yield, we successfully conduct 3D molecular imaging of frozen homogenized milk and observe network structures of interesting organic and inorganic species. Finally, taken together, our results will significantly benefit various research fields relying on 3D molecular imaging of biological structures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

High Useful Yield and Isotopic Analysis of Uranium by Resonance Ionization Mass Spectrometry

Useful yields from resonance ionization mass spectrometry can be extremely high compared to other mass spectrometry techniques, but uranium analysis shows strong matrix effects arising from the tendency of uranium to form strongly bound oxide molecules that do not dissociate appreciably on energetic ion bombardment. Here, we demonstrate a useful yield of 24% for metallic uranium. Modeling the laser ionization and ion transmission processes shows that the high useful yield is attributable to a high ion fraction achieved by resonance ionization. We quantify the reduction of uranium oxide surface layers by Ar + and Ga + sputtering. The useful yield for uranium atoms from a uranium dioxide matrix is 0.4% and rises to 2% when the surface is in sputter equilibrium with the ion beam. The lower useful yield from the oxide is almost entirely due to uranium oxide molecules reducing the neutral atom content of the sputtered flux. We also demonstrate rapid isotopic analysis of solid uranium oxide at a precision of <0.5% relative standard deviation using relatively broadband lasers to mitigate spectroscopic fractionation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Mechanical Properties and Chemical Reactivity of Li x SiO y Thin Films

Silicon (Si) is a commonly studied candidate material for next-generation anodes in Li-ion batteries. A native oxide SiO 2 on Si is often inevitable. However, it is not clear if this layer has a positive or negative effect on the battery performance. This understanding is complicated by the lack of knowledge about the physical properties of the SiO 2 lithiation products and by the convolution of chemical and electrochemical effects during the anode lithiation process. In this study, Li x SiO y thin films as model materials for lithiated SiO 2 were deposited by magnetron sputtering at ambient temperature, with the goal of (1) decoupling chemical reactivity from electrochemical reactivity and (2) evaluating the physical and electrochemical properties of Li x SiO y . X-ray photoemission spectroscopy analysis of the deposited thin films demonstrate that a composition close to previous experimental reports of lithiated native SiO 2 can be achieved through sputtering. Our density functional theory calculations also confirm that the possible phases formed by lithiating SiO 2 are very close to the measured film compositions. Scanning probe microscopy measurements show that the mechanical properties of the film are strongly dependent on lithium concentration, with a ductile behavior at a higher Li content and a brittle behavior at a lower Li content. The chemical reactivity of the thin films was investigated by measuring the AC impedance evolution, suggesting that Li x SiO y continuously reacts with the electrolyte, in part because of the high electronic conductivity of the film determined from solid-state impedance measurements. The electrochemical cycling data of the sputter-deposited Li x SiO y /Si films also suggest that Li x SiO y is not beneficial in stabilizing the Si anode surface during battery operation, despite its favorable mechanical properties.

14 SOLAR ENERGY↗