Nuclear Reaction Analysis Research Articles

Measuring H2O concentrations in olivine by secondary ion mass spectrometry: Challenges and paths forward

Abstract Trace concentrations of H2O in olivine strongly affect diverse mantle and magmatic processes. H2O in olivine has been difficult to accurately quantify due to challenges in sample preparation and measurement, as well as significant uncertainties in standard calibrations. Here we directly compare secondary-ion mass spectrometry (SIMS) measurements of the olivine standards of Bell et al. (2003, hereafter Bell03) and Withers et al. (2012, hereafter Withers12) upon which most SIMS and Fourier transform infrared (FTIR) spectroscopy analyses are based. In the same SIMS session, we find that the olivine standards from the two studies are offset by ~50%, forming lines of different slope when comparing SIMS measurements to the independent nuclear reaction analysis (NRA) in Bell03 and elastic recoil detection analysis (ERDA) in Withers12. This offset is similar to the ~40% offset that exists in the FTIR absorption coefficients determined by those two studies, and points to the NRAERDA data as the cause for the offset more than different IR absorption characteristics of the different olivines. We find that the Withers12 olivine standards form the most precise calibration line, and that the measured Bell03 olivine standards have issues of reproducibility and accuracy due to the presence of hydrous inclusions (as documented previously by Mosenfelder et al. 2011). Owing to the limited availability of the Withers12 olivine standards, however, we recommend using orthopyroxene standards (Kumamoto et al. 2017) to calibrate H2O in olivine by SIMS due to similar calibration slopes. We revise the reference values of current orthopyroxene standards to account for uncertainties in the Bell et al. (1995) manometry data. With these revised values, the orthopyroxene calibration line is within 12% of the Withers12 olivine line, which is within the long-term uncertainty of the SIMS olivine measurements. We apply our SIMS calibration protocol to revise estimates of the partition coefficients for H2O between olivine and melt, resulting in a value of 0.0009 ± 0.0003 at pressures ~0.2–2 GPa. This brings into closer agreement between the partition coefficients determined from experimental studies and those based on natural studies of olivine-hosted melt inclusions.

Comparative study on quantitative carbon content mapping in archaeological ferrous metals with laser-induced plasma spectroscopy (LIBS) and nuclear reaction analysis (NRA) for 3D representation by LIBS

The carbon content distribution of ferrous archaeological artefacts in a quantitative way allows us to understand the nature of the materials. Our previous works have ever proved that the use of laser-induced breakdown spectroscopy (LIBS) could be an efficient method to solve problems of in situ analysis and offer a high spatial resolution. To assess the ability of this quantification in an absolute way the carbon quantification by LIBS is compared in this paper with the nuclear reaction analysis (NRA), one of the ion beam analysis (IBA) techniques generated by a deuterium ion beam. The IBA analysis has specific advantages, especially in terms of precision and non-destructiveness. A validation study is also presented on quantitative carbon content mapping in archaeological ferrous metals with LIBS and deuterium ion beam analysis. The application of LIBS quantitative mapping on different structures of archaeological pieces shows that the carbon content distribution can be well determined, demonstrating the 2D mapping capabilities of the laser techniques. With the help of LIBS stratigraphic analysis, a 3D deeper insight on microscale features presents a heterogeneity, induced better understanding of material organization at the microscale.

Deuterium retention and removal in liquid lithium determined by in situ NRA in Magnum-PSI

In this work, Li-filled 3D-printed porous tungsten samples were exposed to deuterium (D) plasma in Magnum-PSI with a wide ion flux from 4 × 1022 to 1.5 × 1024 m−2 s−1 and with a corresponding wide temperature range from below Li melting point (180.5 °C) to above Li deuteride (LiD) melting point (∼690 °C). The formation, decomposition and melting of LiD have been directly observed in the experiment via infra-red thermometry and visually post-mortem while still in vacuo, and correlated to the D retained content. The LiD formation was characterized by a solid precipitate layer formed on the surface with high emissivity (0.6–0.9) characterized by a blue or dark blue color after exposure. The melting of Li–LiD layer was found to occur close to the temperature predicted by Li–LiD phase diagram. In situ nuclear reaction analysis (NRA) was applied to perform the measurement of D retained in Li samples immediately after exposure without breaking the vacuum. D depth profiles were determined by NRA, in which the highest D concentration (15–45 at.%) was found in the top several micrometers and decreases with depth to low levels (<5%) within 5–30 μm. No pure LiD layer was found on the sample surfaces, however a D concentration close to 50 at.% was observed on a Li-D co-deposited layer on the clamping ring in some cases. The experiments also indicate that the D retained increases with increasing temperature until ∼500 °C. At temperatures beyond ∼500 °C the dissociation of LiD starts to dominate and the deuterium retention started to decrease. Overall, D retained fraction for all cases was found to be below ∼2%, which is significantly different from literatures where full uptake has been suggested. A 1D reaction–diffusion (RD) model based on D diffusion and chemical reactions with Li has been built. D depth profiles from the RD modelling can roughly match that from NRA measurement and a low D retained fraction below ∼2% was also indicated by the model. The model can also help explain the relationship between D retained and the surface temperature and fluence. After D plasma exposure, either helium or H plasma was utilized to remove the retained D in Li and both were proved to be effective and the removal efficiency can be as high as 96% above 420 °C.

Oxygen diffusion coefficient and characterization of leachant in UO2 corrosion studied by new methods

UO2 corrosion is a key issue in the study of the safe storage of spent nuclear fuel (SNF). In this work, corrosion experiments were performed on UO2 samples exposed to 18O labelled water during 290 days at room conditions, thereafter a complete analysis of the solid and leachant (labelled water) allow us obtaining new data and exploring new methods.Thus, a new application of the Nuclear Reaction Analysis (NRA), as a simple and low-cost approach, has been developed to estimate the oxidized layer thickness and the diffusion coefficient of oxygen through the oxidized layer. These results were verified by comparison with the ones obtained by traditional Secondary Ion Mass Spectrometry (SIMS).The diffusion coefficient obtained is two orders of magnitude larger than the scarce published ones at room temperature, highlighting the great effect of the composition of the oxidized layer due to the UO2 corrosion on this parameter. In addition, the water used in the corrosion experiments (leachant) has been analyzed by Raman spectroscopy, being the main purpose for the in situ analysis.The data obtained in this study bring out the great ability (higher than expected) of the oxygen to break through the oxidized layer which could endanger the SNF pellet integrity.Besides, this work shows new methods for analyzing corrosion experiments which can be used to obtain new data for completing the database.

Effect of noble-gas bubbles on deuterium trapping behavior in argon pre-implanted stainless steel

Ion implantation technique and nuclear reaction analysis were used to study the trapping behavior of deuterium by radiation defects in 316 austenitic stainless steel. Defect structure with a different ratio of displacement per atom (dpa) to argon gaseous impurity along with a depth has been formed by pre-irradiation of SS316 with 1.4 MeV argon ions. The deuterium migration between layers containing various defect types served as an indicator of traps strength. Computational evaluation of deuterium trapping process within the framework of the diffusion-trapping model has shown that gas-bubbles associated traps turn out to be a strongest deuterium traps with a binding energy of 0.74 eV. Other irradiation-induced defect types have a weaker effect on deuterium retention in austenitic steel. Experimental observations and calculation results are discussed with respect to the possibility of molecular hydrogen formation in radiation-induced nanovoids under operating conditions of water-cooled reactor internals.

Quantitative light element analysis: Complementary IBA methods for H to O detection using an external proton beam

A new setup for quantitative light element analysis of thin films using a 2.50–2.72 MeV external proton beam under atmospheric conditions is described. This setup simultaneously performs backscattering spectrometry (BS) and p-p coincidence elastic recoil detection analysis (C-ERDA) in transmission. BS utilizes a highly non-Rutherford cross-section for profiling of e.g. C, N and O whereas C-ERDA is used to measure H concentration profiles in foils of up to 12.5 μm in thickness. To validate the method, thin Ti layers are deposited on 200 nm Si3N4 membranes and loaded with H. The method shows an expected increase of H concentration in the films with longer loading times. Nuclear reaction analysis (NRA) for Li detection in LiMn2O4 samples is undertaken to test the possibility of using complementary proton scattering techniques simultaneously. A Li depth resolution of around 250 nm can be achieved. Radiation damage to Mylar and Kapton films is investigated and the radiation resistance of Kapton demonstrated.

Deuterium and beryllium depth profiles into the W-coated JET divertor tiles after ITER-like wall campaigns

A number of 35 samples cored from JET divertor tiles exposed to JET plasmas in ILW1 (ITER Like Wall – first campaign), ILW2, ILW1 + ILW2 and ILW3 campaigns were analyzed using the Glow Discharge Optical Emission Spectrometry (GDOES) technique. The depth profiles of the elements contained in the surface layer of the tiles (W, Mo, Be, C, O and D) have been quantitatively determined up to a depth of 30–60 μm.The upper zone of Tile 3 (the lower vertical zone of the inner divertor) seems to be an erosion zone as it was demonstrated with a Mo marker layer in the ILW1 campaign. By increasing the input energy in the following campaigns this erosion did not increase, but it almost disappeared, probably due to significant amounts of Be that were transported from the main chamber and deposited on that area. The Be concentration increased in the upper zone of Tile3 in ILW2 and ILW3 by a factor of about 5 in comparison with the ILW1 campaign. It looks like the Be layer protects the tile surface from erosion.Depending on the amount of Be deposited on specific areas of the W-coated CFC (Carbon Fiber Composite) tiles, two mechanisms of D retention were identified. If the peak concentration of Be is less than ∼4.5 at.% D is mainly trapped into the defects of the W/Mo structure including W/Mo and Mo/C interfaces. When the peak concentration of Be exceeds ∼4.5 at.%, D is mainly retained in the Be deposits. The GDOES results were correlated with SEM analyses performed on the GDOES crater flanks and with the TDS (Thermal Desorption Spectroscopy), results obtained with the same samples after GDOES analyses. They are in good agreement with the corresponding results obtained by other authors using NRA (Nuclear Reaction Analysis), SIMS (Secondary Ion Mass Spectrometry) and TDS.

Influence of thin surface oxide films on hydrogen isotope release from ion-irradiated tungsten

We studied the influence of thin, electro-chemically grown tungsten (W) surface oxide films on hydrogen isotope release from W. As deuterium (D) reservoir underneath the oxide, we used a defect-rich, ion-irradiated W layer that was filled with D prior to oxidation. Several oxide films with thicknesses between 5 and 100 nm were studied and compared with tungsten with a natural oxide film. The release of D through the oxide film was analyzed with thermal desorption spectroscopy (TDS). The depth-resolved concentration profiles of D in the sample were measured with nuclear reaction analysis at all experimental steps. Changes of the morphology of the oxide film due to the release of D were investigated with scanning electron microscopy (SEM).In TDS studies, we found that the thin oxide films significantly influence the release behavior of D from W. The first D release peak (at 560 K) is shifted towards higher temperature (or later times) with increasing oxide thickness. This indicates that the oxide film acts as both a D reservoir and a transport barrier that delays D release at temperatures above 475 K. At this temperature, D also starts to interact chemically with the oxide film and is released not only as HD or D2 but also in the form of heavy water (HDO and D2O). Above 700 K, D is released only in form of heavy water as long as enough oxide is available. Accordingly, SEM images after TDS show a strong modification of the oxide film. For film thicknesses of 5–10 nm, all oxide is removed from the surface and smooth metallic W remains. For 15 nm, the surface is still partially covered by oxide islands with several micrometer of metallic W between them. From the fact that D is still only released as heavy water at high temperatures, we conclude that the mobility of D atoms at the surface is very high. Even D atoms that surface far from an oxide island apparently travel along the surface to form an O-D group at the W oxide before they recombine with another D atom to form water.Our results indicate that the oxide film becomes relevant for the D release during TDS if the ratio of O atoms on the surface to D atoms in the sample is larger than 5–10 %. Consequently, even the natural oxide film (1–2 nm) that forms on W upon contact with air may significantly influence the D release spectra from TDS for experiments with low D retention.

Quantitative Lithiation Depth Profiling in Silicon Containing Anodes Investigated by Ion Beam Analysis

The localisation and quantitative analysis of lithium (Li) in battery materials, components, and full cells are scientifically highly relevant, yet challenging tasks. The methodical developments of MeV ion beam analysis (IBA) presented here open up new possibilities for simultaneous elemental quantification and localisation of light and heavy elements in Li and other batteries. It describes the technical prerequisites and limitations of using IBA to analyse and solve current challenges with the example of Li-ion and solid-state battery-related research and development. Here, nuclear reaction analysis and Rutherford backscattering spectrometry can provide spatial resolutions down to 70 nm and 1% accuracy. To demonstrate the new insights to be gained by IBA, SiOx-containing graphite anodes are lithiated to six states-of-charge (SoC) between 0–50%. The quantitative Li depth profiling of the anodes shows a linear increase of the Li concentration with SoC and a match of injected and detected Li-ions. This unambiguously proofs the electrochemical activity of Si. Already at 50% SoC, we derive C/Li = 5.4 (&lt; LiC6) when neglecting Si, proving a relevant uptake of Li by the 8 atom % Si (C/Si ≈ 9) in the anode with Li/Si ≤ 1.8 in this case. Extrapolations to full lithiation show a maximum of Li/Si = 1.04 ± 0.05. The analysis reveals all element concentrations are constant over the anode thickness of 44 µm, except for a ~6-µm-thick separator-side surface layer. Here, the Li and Si concentrations are a factor 1.23 higher compared to the bulk for all SoC, indicating preferential Li binding to SiOx. These insights are so far not accessible with conventional analysis methods and are a first important step towards in-depth knowledge of quantitative Li distributions on the component level and a further application of IBA in the battery community.

Absence of midgap states due to excess electrons donated by adsorbed hydrogen on the anatase TiO2(101) surface

Hydrogen is involved in various important chemical processes on metal-oxide surfaces. Due to its electron-donating character, hydrogen tends to form polaronic states, where the electron is spatially separated from the proton, which exerts significant impact on the electronic properties of metal-oxide surfaces. By individually probing the proton with nuclear reaction analysis and the electron with ultraviolet photoelectron spectroscopy and in combination with density functional theory calculations, we clarify the electronic state of hydrogen on the anatase ${\mathrm{TiO}}_{2}(101)$ surface. Hydrogen is found to adsorb with a saturation coverage of $0.48\ifmmode\pm\else\textpm\fi{}0.12$ monolayers, donating an excess electron to the substrate without forming a midgap state, which is in contrast to the behavior of oxygen vacancies.

Reduced defect recovery in self-ion damaged W due to simultaneous deuterium exposure during annealing

Deuterium (D) plasma exposure during annealing of self-ion damaged tungsten (W) is shown to exhibit reduced defect recovery when compared to annealing without D plasma exposure. In these experiments, samples were first damaged with 20 MeV W ions. Next, samples were annealed either with or without simultaneous D2 plasma exposure. The simultaneous annealed samples were first decorated by D2 plasma at 383 K prior to ramping up to an annealing temperature of 473, 573, 673, or 773 K and held for 1 h with concurrent plasma exposure. The vacuum annealed samples each had a corresponding temperature history but without D2 plasma treatment. Finally, all samples were exposed to D2 plasma at 383 K to decorate any remaining defects. Nuclear reaction analysis and thermal desorption spectroscopy (TDS) shows that the simultaneous plasma-exposed and annealed samples exhibited virtually no defect recovery at annealing temperatures of up to 673 K, and had higher D retention than found in the vacuum annealed samples. TDS results indicate that only the lowest detrapping energy defects recover at an 773 K anneal for the simultaneous plasma annealed samples, while the vacuum annealed samples showed defect recovery at all anneal temperatures. This experiment clearly demonstrates that D occupied defects can significantly reduce or eliminate defect annealing in W, and is consistent with the existence of synergistic plasma exposure/displacement damage effects in fusion-energy relevant plasma facing materials.

The synergies between displacement damage creation and hydrogen presence: the effect of D ion energy and flux

In this work the synergism between displacement damage creation and presence of hydrogen isotopes was studied. Tungsten samples were irradiated by 10.8 MeV W ions with or without the presence of D ions with two different energies of 300 eV/D and 1000 eV/D and different temperatures. In order to compare the results obtained with different exposure parameters the samples were afterwards additionally exposed to D ions at 450 K to populate the created defects. By increasing the W irradiation time, ion flux and energy, the increase of D concentration and D retention was observed as measured by nuclear reaction analysis and thermal desorption spectroscopy. By fitting the D depth profiles and D desorption spectra by the rate equation code MHIMS-R we could see that additional fill-levels were populated with higher flux and ion energy which ends up in higher final D concentration and retention as compared to experiments with lower D flux and energy.

Comparison experiment on the sputtering of EUROFER, RUSFER and CLAM steels by deuterium ions

In this work, the RAFM steels EUROFER, RUSFER and CLAM, along with a reference pure Fe sample, were all exposed to the same source of deuterium and analyzed using the same techniques, allowing a direct comparison of the experimental results. A 200 eV/D mass-selected deuterium ion beam at the SIESTA facility was used to bombard the samples to a fluence of 5 × 1024 Dm−2 at 450 K. The surface morphology of the samples was investigated with Scanning Electron Microscopy. The sputter yield of the samples was determined by weight-loss measurements and confirmed by measurements of the eroded depth. The near-surface enrichment of W and Ta was investigated via Energy-dispersive X-ray spectroscopy, X-ray Photoelectron Spectroscopy and Rutherford Backscattering Spectrometry. Grain-orientation-dependent sputtering was studied with Confocal Laser Scanning Microscopy and Electron Backscatter Diffraction. Lastly, Nuclear Reaction Analysis and Thermal Desorption Spectrometry were employed to analyze deuterium retention in all the samples. The erosion behavior of all three steels under deuterium bombardment was confirmed to be similar. The measured sputter yield was comparable for all three steels, and significantly lower than that of pure Fe. Likewise, all steels develop a needle-like surface morphology under the given exposure conditions and a W- and Ta-enriched layer in the range of few nanometers, while the Fe sample remained smooth. Retained deuterium amounts were also comparable among the steel samples, and were overall larger than the retention measured for the pure Fe sample.

Review on the thickness measurement of ultrathin oxide films by mutual calibration method

Mutual calibration was suggested as a method to determine the absolute thickness of ultrathin oxide films. It was motivated from the large offset values in the reported thicknesses in the Consultative Committee for Amount of Substance (CCQM) pilot study P‐38 for the thickness measurement of SiO2 films on Si(100) and Si(111) substrates in 2004. Large offset values from 0.5 to 1.0 nm were reported in the thicknesses by ellipsometry, X‐ray reflectometry (XRR), medium‐energy ion scattering spectrometry (MEIS), Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), and transmission electron microscopy (TEM). However, the offset value for the thicknesses by X‐ray photoelectron spectroscopy (XPS) was close to zero (−0.013 nm). From these results, the mutual calibration method was reported for the thickness measurement of SiO2 films on Si(100) by combination of TEM and XPS. The mutual calibration method has been applied for the thickness measurements of hetero oxide films such as Al2O3 and HfO2. Recently, the effect of surface contamination was reported to be critical to the thickness measurement of HfO2 films by XPS. On the other hand, MEIS was proved to be a powerful zero offset method which is not affected by the surface contamination. As a result, the reference thicknesses in the CCQM pilot study P‐190 for the thickness measurement of HfO2 films on Si(100) substrate were determined by mutual calibration method from the average XRR data and MEIS analysis. Conclusively, the thicknesses of ultrathin oxide films can be traceably certified by mutual calibration method and most thickness measurement methods can be calibrated from the certified thicknesses.

Measuring in situ CO2 and H2O in apatite via ATR-FTIR

We present a new approach to determine in situ CO2 and H2O concentrations in apatite via attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Absolute carbon and hydrogen measurements by nuclear reaction analysis (NRA) and elastic recoil detection (ERD) are used to calibrate ATR-FTIR spectra of CO2 and H2O in apatite. We show that CO2 and H2O contents in apatite can be determined via linear equations (r2 > 0.99) using the integrated area of CO2 and H2O IR absorption bands. The main benefits of this new approach are that ATR-FTIR analyses are non-destructive and can be conducted on polished sample material surfaces with a spatial resolution of ~ 35 μm. Furthermore, the wavenumber of the phosphate IR absorption band can be used to determine the crystallographic orientation of apatite, which allows for accurate quantification of CO2 and H2O in randomly orientated apatite grains. The limit of quantification of H2O in apatite is ~ 400 ppm and ~ 100 ppm for CO2. Via two examples, one from a carbonatite and one from a metasedimentary rock, we show that this new technique opens up new possibilities for determining volatile concentrations and behavior in a wide range of hydrothermal, igneous, and metamorphic systems.

Deuterium retention in MeV ion-irradiated beryllium

Beryllium , as the material of choice for the ITER first wall, will be subject to high energy neutrons during the operation of the fusion device. Such irradiation will create displacement damage in the crystal lattice , which is known to influence hydrogen isotope retention, e.g. in iron and tungsten . In our study, we irradiated beryllium samples with high-energy oxygen ions up to various dpa levels (0.01 dpa, 0.1 dpa, and 1 dpa) and subsequently exposed the samples to deuterium plasma at 370 K and 573 K. The amount of retained deuterium was measured by thermal desorption spectroscopy and nuclear reaction analysis and was found to decrease by about 18% in the samples damaged up to 0.1 dpa compared to the undamaged ones. Further damaging up to 1 dpa did not show any additional effects on deuterium retention. Transmission electron microscopy was used to check for the existence of bubbles after plasma exposure.

Ion bombardment technique induced alterations in the surface chemical composition and shielding parameters of polymeric material

At present, ion beam technology is one powerful technique to improve the physico-chemical properties of polymeric material. In this work, ultra high molecular weight polyethylene samples were bombarded with 1 MeV He-ion beam at fluences ranging from 1×1013 to 5×1014 ions/cm2. The changes in the chemical composition of the treated layer caused by the ion beam were investigated. The hydrogen escapes due to the ion beam irradiations were measured by the nuclear reaction analysis (NRA) technique using the 1H(15N, αγ)12C reaction. The oxygen uptake has been studied by the Rutherford backscattering spectrometry (RBS) and Fourier transform infrared spectrometer (FTIR) techniques. The partial and total mass attenuation coefficients of photons at energies 81, 356, 511 and 1332 keV were estimated using the XCOM program (version 3.1). The obtained results showed that the hydrogen release was increasing with an increase in ion fluence. Moreover, important oxygen uptake of bombarded samples was also observed. These effects led to significant improvements in the surface characteristics of the treated materials such as changes in the shielding parameters. The changes in the mass attenuation coefficients (μ/ρ) were calculated relying on the incoming photon energies and the atomic concentrations of the elements that are present in the target material. The total atomic cross-sections and effective atomic numbers were calculated by using the data of the total mass attenuation coefficients. A decrease in both the total atomic cross-section and effective atomic numbers was noticed with an increase in the ion beam fluence.

Analysis of SEI Formation and Fast Charging on Lithium Loss in NMC/Graphite Cells

Fast charging of a Li-ion battery is a key requirement for the acceptance of electric vehicles. However, charging at high currents is known to accelerate battery degradation when not conducted in an appropriate operational window. One way to influence the viability of fast charging is to optimize the cell formation procedure. In this study, we investigated the effect of an accelerated formation protocol which was previously shown to benefit rate capability vs. a reference protocol [1]. We analyzed the effects of formation methods and charge rates on electrode surfaces with methods including Li nuclear reaction analysis (Li-NRA) [2,3,4] and secondary ion mass spectroscopy (SIMS) as well as electrochemical experiments using three-electrode cells.The two SEI formation methods were applied and then the NMC/graphite cells were cycled at charge rates of 1C, 3C, and 5C for 100 cycles. Normalized capacity retention and post-mortem electrode analysis revealed that performance degradation is not merely attributable to lithium aggregation at the graphite anode surface (as has been suggested previously), but also to accelerated cathode degradation. The correlations of formation methods and charge rates on capacity fading, resistance, and Li concentration depth profiles on the anode surfaces by Li-NRA and SIMS analyses point to a small, but nonetheless significant role of cell formation on long term performance.Two NRA methods, proton induced gamma ray emission (PIGE) and deuteron induced particle emission (DIPE), and SIMS were employed to quantify the prevalence of lithium at the anode interface. Each showed a dependence of lithium amount on the charge rate, and to a lesser extent the formation procedure, even if the capacity retention for the two fastest rates was similar after 100 cycles. Such physical results illustrate that though the aggregation of lithium at the anode surface is important, degradation of the cathode may play a greater role in sustained electrochemical function.Using a three-electrode cell, we also deconvoluted the resistance at each electrode and found that the DC resistance of the cathode was more correlated with an observed increase in full cell resistance than that of the anode. We observed that aggregation of lithium at the anode under accelerated charging conditions alters the amount of reversible lithium inventory and thus the operating potential range of the cathode, yielding greater degradation.[1] B. K. Antonopoulos, C. Stock, F. Maglia, H. E. Hoster, Electrochim. Acta, 269 (2018), 331-339.[2] A. Schulz, D. DeRosa, S. Higashiya, M. Rane-Fondacaro, H. Bakhru, P. Haldar, J. Energy Storage 14 (2017), 106-111.[3] A. Schulz, D. DeRosa, S. Higashiya, M. Rane-Fondacaro, H. Bakhru, P. Haldar, J. Power Sources 360 (2017), 129-135.[4] M. Chebuske, S. Higashiya, S. Flottman, H. Bakhru, B. Antonopoulos, O. Paschos, F. S. Gittleson and H. Efstathiadis, Chem. Commun. 56 (2020), 14665–14668.

The Effect of the Degree of Fluorination on the MOCVD Growth of Cobalt Oxide Thin Films using Co(II) Acetylacetonate Complexes

AbstractThe structurally related cobalt β‐diketonate complexes Co(acac)2, Co(acac)2 ⋅ TMEDA, Co(tfac)2 ⋅ TMEDA, and Co(hfac)2 ⋅ TMEDA (acac=2,4‐pentanedionate, tfac=1,1,1‐trifluoro‐2,4‐pentane‐dionate, hfac=1,1,1,5,5,5‐hexafluoro‐2,4‐pentane‐dionate, TMEDA=N,N,N′,N′‐tetramethylethylenediamine) were thermochemically (thermogravimetric analysis, differential scanning calorimetry) and spectroscopically (infrared, UV‐VIS and electron resonance spectroscopy) characterised and used as precursor for the MOCVD growth of cobalt monoxide (CoO) thin films. The influence of the degree of fluorination of the cobalt precursors on the morphology (scanning electron microscopy) and phase composition (X‐ray diffraction) of the CoO films is demonstrated. Carbon, nitrogen and fluorine impurities as a result of the thermal decomposition of the 2,4‐pentanedionate and tetraamine ligands in the films were identified by X‐ray photoelectron spectroscopy, time‐of‐flight secondary ion mass spectrometry, Rutherford backscattering spectrometry and nuclear reaction analysis. In addition, the influence of these contaminants on the electrocatalytically activity for the oxygen evolution reaction (OER) in alkaline media of the MOCVD grown CoO films is shown.

Systematic compositional analysis of sputter-deposited boron-containing thin films

Boron-containing materials exhibit a unique combination of ceramic and metallic properties that are sensitively dependent on their given chemical bonding and elemental compositions. However, determining the composition, let alone bonding, with sufficient accuracy is cumbersome with respect to boron, being a light element that bonds in various coordinations. Here, we report on the comprehensive compositional analysis of transition-metal diboride (TMBx) thin films (TM = Ti, Zr, and Hf) by energy-dispersive x-ray spectroscopy (EDX), x-ray photoelectron spectroscopy (XPS), time-of-flight elastic recoil detection analysis (ToF-ERDA), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA). The films are grown on Si and C substrates by dc magnetron sputtering from stoichiometric TMB2 targets and have hexagonal AlB2-type columnar structures. EDX considerably overestimates B/TM ratios, x, compared to the other techniques, particularly for ZrBx. The B concentrations obtained by XPS strongly depend on the energy of Ar+ ions used for removing surface oxides and contaminants prior to analyses and are more reliable for 0.5 keV Ar+. ToF-ERDA, RBS, and NRA yield consistent compositions in TiBx. They also prove TiBx and ZrBx films to be homogeneous with comparable B/TM ratios for each film. However, ToF-ERDA, employing a 36-MeV 127I8+ beam, exhibits challenges in depth resolution and quantification of HfBx due to plural and multiple scattering and associated energy loss straggling effects. Compared to ToF-ERDA, RBS (for the film grown on C substrates) and NRA provide more reliable B/Hf ratios. Overall, a combination of methods is recommended for accurately pinpointing the compositions of borides that contain heavy transition metals.