Time-of-flight Secondary Ion Mass Spectrometry Research Articles

Lithium Self-Diffusion in a Polymer Electrolyte for Solid-State Batteries: ToF-SIMS/ssNMR Correlative Characterization and Modeling Based on Lithium Isotopic Labeling.

Manufacturers aim to commercialize efficient and safe batteries by finding new strategies. Solid-state electrolytes can be seen as an opportunity to develop batteries with a high energy density. They allow the use of lithium foil as the anode, increasing the energy density. Also, they are composed of nonflammable materials making them safer than liquid electrolytes. However, to enhance the electrochemical performances of forthcoming solid-state lithium metal batteries, phenomena governing ionic conductivity have yet to be mastered in such devices. Lithium isotopic tracing was successfully used in previous works to further understand lithium ion transport mechanisms in batteries. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and 6/7Li high-resolution solid-state nuclear magnetic resonance (ssNMR) spectroscopy are two complementary techniques probing local and global scale, respectively. Both techniques can distinguish lithium isotopes. Here, four polymer membranes were elaborated with the same lithium concentration, but with various isotopic enrichments from 7.6 to 95.4% of 6Li. The selected material was a poly(ethylene oxide) (PEO) membrane containing lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) as lithium salt. They are widely studied in the lithium battery field. First, reliable ToF-SIMS and ssNMR methodologies were validated in light of the converging results. They led to accurate determination of lithium isotopic abundance of polymer membranes with a 1 or a 2% uncertainty, respectively. Then, the developed methodologies were applied to characterize lithium self-diffusion in a polymer membrane. Furthermore, numerical simulations based on a two-dimensional diffusion model compared with ToF-SIMS analyses allowed us to extract a lithium self-diffusion coefficient of 1.6 × 10-12 m2·s-1 at 60 °C, which complements other published values. The robust methodologies described in this work can be extended to various applications and materials. They stand as powerful strategies to better understand lithium ionic transport, especially in multiphase materials, for example, in hybrid solid-state electrolytes.

High resolution imaging and analysis of extracellular vesicles using mass spectral imaging and machine learning

AbstractExtracellular vesicles (EVs) are potentially useful biomarkers for disease detection and monitoring. Development of a label‐free technique for imaging and distinguishing small volumes of EVs from different cell types and cell states would be of great value. Here, we have designed a method to explore the chemical changes in EVs associated with neuroinflammation using Time‐of‐Flight Secondary Ion Mass spectrometry (ToF‐SIMS) and machine learning (ML). Mass spectral imaging was able to identify and differentiate EVs released by microglia following lipopolysaccharide (LPS) stimulation compared to a control group. This process requires a much smaller sample size (1 µL) than other molecular analysis methods (up to 50 µL). Conspicuously, we saw a reduction in free cysteine thiols (a marker of cellular oxidative stress associated with neuroinflammation) in EVs from microglial cells treated with LPS, consistent with the reduced cellular free thiol levels measured experimentally. This validates the synergistic combination of ToF‐SIMS and ML as a sensitive and valuable technique for collecting and analysing molecular data from EVs at high resolution.

Stable cycling of LiNi0.9Co0.05Mn0.05O2/lithium metal batteries enabled by synergistic tuning the surface stability of cathode/anode

Ni-rich layered oxides (LiNi0.9Co0.05Mn0.05O2) show great potential in long-range and low-cost lithium-ion batteries. However, due to the high surface sensitivity, their practical application is hindered by interfacial instability with electrolytes under high voltage for long cyclic life. Herein, by combining both first-principle calculations and time-of-flight secondary ion mass spectrometry (TOF-SIMS), a novel surface fluorinated reconstruction (SFR) mechanism is proposed to improve the interfacial stability under high voltage, which could effectively regulate the surface fluoride species to desensitize the LiNi0.9Co0.05Mn0.05O2 interface. We demonstrate here that by tuning the ratio of fluoride species, the LiNi0.9Co0.05Mn0.05O2/Li battery could achieve excellent long-term and high voltage performance (163.5 mA h g−1 at 0.5 C for 300 cycles under 4.4 V), while the controlled sample decayed to 125.4 mA h g−1 after 300 cycles. Moreover, the favorable cross-talk effect induced by SFR further facilitates the incorporation of suitable amounts of Ni ions into the construction of stable solid electrolyte interface (SEI) layer for anode surface. Therefore, the ultra-long cycling stability under high voltage can be achieved by the robust cathode/electrolyte and Li/electrolyte interfaces, which results in excellent interfacial stability after long cycling. This work provides new insights into the surface design of cathode materials and improves the stability of the electrode-electrode interface under high voltage.

Improving the Stability of Li Metal Anode/Solid Electrolyte Interfaces via an Li3PO4 Intermediate Layer: An Investigation of Surface Chemistry and Electronic Band Structure

Recently, researchers are extensively developing next-generation batteries, including all-solid-state batteries (ASSBs), to meet the increasing demand for electric vehicles (EVs) and renewable energy storage. Li metal has been considered an ideal anode material due to its high theoretical capacity and low redox potential. However, it is highly reactive and severe side reactions occur at the interface between Li metal anode and solid electrolytes (SEs), significantly affecting battery performance. Therefore, Li metal anodes have not yet been commercialized. To obtain a chemically stable Li metal anode, the authors examined the side reactions at the interface between the Li metal anode and oxide-type SE using surface analysis techniques such as time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low-energy inverse photoelectron spectroscopy (LEIPS). In this paper, we present the results of interface analysis between Li metal anode/SE and discuss how to obtain a stable Li metal anode.

Regulating ethane and ethylene synthesis by proton corridor microenvironment for CO2 electrolysis

Electrocatalytic reduction of carbon dioxide is one of the most effective strategies to achieve carbon neutrality and energy sustainability. Although high-value multi-carbon products have been widely studied, limited electrocatalysts have been reported for the selective conversion of ethane. More importantly, the factors tuning the selectivity between ethane and ethylene have not been clarified. Here, Zn@Cu nanowire arrays (Zn@Cu-NWAs) catalyst is proposed to stimulate the maintenance of efficient CO2-to-C2H6 conversion at high current densities. Meanwhile, in order to investigate the factors affecting the interconversion between ethane and ethylene, the counterpart catalyst that facilitates C–C coupling to ethylene was also synthesized. Time-of-flight secondary-ion mass spectroscopy (TOF-SIMS), in-situ Raman spectroscopy, and simulation results show that Zn@Cu-NWAs can provide a localized proton corridor environment for the formation of ethane, accelerating the further proton-coupled CO2 reduction reaction (CO2RR) kinetics. Hence, this catalyst delivered an ethane Faraday efficiency of over 65% at −1.14 V vs. RHE with a total current density of 142.3 mA/cm2. This work provides a new perspective on regulating the local microenvironment to modify the selectivity of multi-carbon products.

Exploiting Mass Spectrometry to Unlock the Mechanism of Nanoparticle-Induced Inflammasome Activation.

Nanoparticles (NPs) elicit sterile inflammation, but the underlying signaling pathways are poorly understood. Here, we report that human monocytes are particularly vulnerable to amorphous silica NPs, as evidenced by single-cell-based analysis of peripheral blood mononuclear cells using cytometry by time-of-flight (CyToF), while silane modification of the NPs mitigated their toxicity. Using human THP-1 cells as a model, we observed cellular internalization of silica NPs by nanoscale secondary ion mass spectrometry (nanoSIMS) and this was confirmed by transmission electron microscopy. Lipid droplet accumulation was also noted in the exposed cells. Furthermore, time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed specific changes in plasma membrane lipids, including phosphatidylcholine (PC) in silica NP-exposed cells, and subsequent studies suggested that lysophosphatidylcholine (LPC) acts as a cell autonomous signal for inflammasome activation in the absence of priming with a microbial ligand. Moreover, we found that silica NPs elicited NLRP3 inflammasome activation in monocytes, whereas cell death transpired through a non-apoptotic, lipid peroxidation-dependent mechanism. Together, these data further our understanding of the mechanism of sterile inflammation.

Optimization of Time-of-Flight Secondary Ion Mass Spectrometry for Analysis of Porous Transport Layers

As we move towards commercialization of the proton exchange membrane water electrolyzers (PEMWEs), fundamental understandings of individual components and their integration with focus on material composition and its correlation to performance and lifetime of electrolysis cell operation is of significant importance. Porous Transport Layers (PTLs) increase overpotential of the cell when the titanium passivates, i.e. develops a titanium oxide surface layer of a certain thickness. To prevent this passivation, platinum group metal coatings are typically applied to the PTL, but this adds significant costs.This presentation will cover recent developments in characterization of PTL coatings and PTL-coating interfaces using Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) in correlation with Scanning Transmission Electron Microscopy and Energy Dispersive X-ray Spectroscopy (STEM-EDS) analysis. Although this technique is extremely beneficial, ToF-SIMS is typically applied to flat substrates and therefore has been mainly utilized in other scientific fields such as the thin film industry. This talk will discuss method validation and optimization that has been conducted for PTL analysis to allow its characterization by ToF-SIMS. Topics include understanding parameters and limitation of using SIMS on these morphologically challenging samples, as well as looking at elemental and species identification, and applying depth profiling to gauge information on coating and oxide thickness and their consistency. Correlations between real and flat substrates prepared under similar conditions are made, allowing standardization of depth profiling for future analysis of a wider variety of samples.

Using Focused Ion Beam Time-of-Flight Secondary Ion Mass Spectrometry to Depth Profile Nanoparticles in Polymer Nanocomposites.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a versatile surface-sensitive technique for characterizing both hard and soft matter. Its chemical and molecular specificity, high spatial resolution, and superior sensitivity make it an ideal method for depth profiling polymeric systems, including those comprised of both inorganic and organic constituents (i.e., polymer nanocomposites, PNCs). To best utilize ToF-SIMS for characterizing PNCs, experimental conditions must be optimized to minimize challenges such as the matrix effect and charge accumulation. Toward that end, we have successfully used ToF-SIMS with a Xe+ focused ion beam to depth profile silica nanoparticles grafted with poly(methyl methacrylate) (PMMA-NP) in a poly(styrene-ran-acrylonitrile) matrix film by selecting conditions that address charge compensation and the primary incident beam angles. By tracking the sputtered Si+ species and fitting the resultant concentration profile, the diffusion coefficient of PMMA-NP was determined to be D = 2.4 × 10-14 cm2/s. This value of D lies between that measured using Rutherford backscattering spectrometry (6.4 × 10-14 cm2/s) and the value predicted by the Stokes-Einstein model (2.5 × 10-15 cm2/s). With carefully tuned experimental parameters, ToF-SIMS holds great potential for quantitatively characterizing the nanoparticles at the surfaces and interfaces within PNC materials as well as soft matter in general.

Study of Li-Si Alloy Composition for Anode Materials in Sulfide-Based All-Solid-State-Batteries

Lithium alloys are promising anode materials with high specific capacity for all-solid-state-batteries (ASSBs). In this study, ASSBs were fabricated by consisting of Li-Si alloy anode, sulfide electrolytes and sulfur composite cathode. During discharge-charge cycles, changes in polarization resistance in the anode and cathode were separately traced using three-electrode system of an embedded Indium reference electrode in ASSBs. As de-alloying and alloying in Li-Si anode, Li distribution and phase changes were investigated using x-ray diffraction, optical microscopy and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMs). A half-cell was fabricated by using Indium foil as a counter electrode to study the Li ion diffusion coefficient in Galvanostatic Intermittent Titration Technique(GITT). It is observed that Li composition (22:5 ~ 1:1) in Li-Si alloy anode affected the chemo-mechanical stability and volume expansion behavior in ASSBs, which were associated with the redox behavior of sulfide solid electrolyte.

Characterization of Sr2Fe1,5Mo0,5O6-δ Based Solid Oxide Electrolysis Cells

Hydrogen electrodes of solid oxide electrolysis cells (SOEC) are typically made of Ni-YSZ cermet. Despite having excellent catalytic activity Ni-based electrodes suffer from poor redox stability and Ni volatility [1]. Sr2Fe1,5Mo0,5O6-δ (SFM) mixed ionic- and electric conducting (MIEC) double perovskite has been proposed as promising hydrogen electrode material for solid oxide electrolysis cells (SOEC) because of its excellent catalytic properties and good conductivity. In this study SOEC single cells were prepared using SFM hydrogen electrode and (La0,6Sr0,4)0,99Co0,96Ti0,04O3-δ (LSCT) as well as (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) air electrodes [2, 3].Studied cells were prepared using 19 mm 10Sc1CeSZ electrolyte substrates. Screen printed 6 μm thick Ce0.9Gd0.1O1.95 (GDC) layer was applied to both sides of the cell to prevent formation of insulating SrZrO3 layer. GDC layer was sintered to the electrolyte at 1300°C for 5h. SFM or 50%SFM/50%GDC electrode layer with 0,52cm2 surface area was screen printed to the GDC layer and was sintered at 1200°C and at 1150°C to optimize electrode composition and thermal treatment program of electrode. Afterwards LSCT or LSCF oxygen electrodes were screen printed to the other side of the cell and sintered at 1100°C for 2 h. Finally, cells were characterized using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and time-of flight secondary ion mass spectrometry (TOF-SIMS).Impedance spectroscopy analysis showed that cells with 50%SFM/50%GDC hydrogen electrode sintered at 1150°C and LSCT oxygen electrode had highest current densities, reaching 1,59 A/cm2 at 1,5V and 850°C with 67,5% water in hydrogen electrode compartment. However, stability of the cells needs to be further investigated. With TOF-SIMS analysis it became apparent that Sr is moving through GDC intermediate layer and poorly conducting phases are formed in the GDC/10Sc1CeSZ boundary.[1] C. Singhal, K. Kendall (Eds.), High-Temperature Solid Oxide Fuel Cells: Fundamentals, Design and Applications, Elsevier, Oxford, 2003.[2]Bernadet, C. Moncasi, M. Torell, A. Tarancon, High-performing electrolyte-supported symmetrical solid oxide electrolysis cells operating under steamelectrolysis and co-electrolysis modes, Int. J. Hydrogen Energy 45 (2020)14208–14217[3]Sanna, W. Zhang, P. Costamagna, P. HoltappelsSynthesis and electrochemical characterization of electrospun nanofiber cathodes for intermediate- temperature solid oxide fuel cells Int. J. Hydrog. Energy (2020), pp. 1-14

Nitrogen isotope marker experiments in austenitic stainless steel for identification of trapping/detrapping processes at different temperatures

Expanded austenite – austenitic stainless steel containing a colossal amount of nitrogen in solid solution – is still some kind of conundrum with the nitrogen atom transport from the surface into the bulk being enhanced for higher nitrogen content. At the same time, atomic ordering due to an enhanced affinity between chromium and nitrogen is observed.Here, nitrogen transport experiments are performed at different temperatures using 14N and 15N as isotopic tracers. The depth distribution of each of these isotopes as well as the total nitrogen content is investigated with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and glow discharge optical emission spectroscopy (GDOES), respectively. In parallel, phase information is obtained using in situ X-ray diffraction (XRD) during nitriding (for time-resolved data) and during sputter depth profiling (for depth-resolved data).During nitriding, no delayed transport of nitrogen, i.e. trapping, is observed for the expanded austenite. However, as soon as CrN precipitates are formed, nitrogen trapping is a dominant factor with an almost perfect correlation between precipitation and trapping. Cluster ion analysis in SIMS confirms this effect with the abundance of Cr2+ ions significantly increased compared to FeCr+ ions in the presence of precipitation. As nitrogen transport and CrN formation occur in parallel at higher temperatures, further experiments to separate the CrN formation at higher temperatures from the nitrogen transport at lower temperatures have been performed.

Complex intestinal and hepatic in vitro barrier models reveal information on uptake and impact of micro-, submicro- and nanoplastics

Plastic particles are found almost ubiquitously in the environment and can get ingested orally by humans. We have used food-relevant microplastics (2 µm polylactic acid), submicroplastics (250 nm polylactic acid and 366 nm melamine formaldehyde resin) and nanoplastics (25 nm polymethylmethacrylate) to study material- and size-dependent uptake and transport across the human intestinal barrier and liver. Therefore, different Transwell™-based in vitro (co-)culture models were used: Differentiated Caco-2 cells mimicking the intestinal enterocyte monolayer, an M-cell model complementing the Caco-2 monoculture with antigen uptake-specialized cells, a mucus model complementing the barrier with an intestinal mucus layer, and an intestinal-liver co-culture combining differentiated Caco-2 cells with differentiated HepaRG cells. Using these complex barrier models, uptake and transport of particles were analyzed based on the fluorescence of the particles using confocal microscopy and a fluorescence-based quantification method. Additionally, the results were verified by Time-of-Flight - Secondary Ion Mass Spectrometry (ToF-SIMS) analysis. Furthermore, an effect screening at the mRNA level was done to investigate oxidative stress response, inflammation and changes to xenobiotic metabolism in intestinal and hepatic cells after exposure to plastic particles. Oxidative stress and inflammation were additionally analyzed using a flow-cytometric assay for reactive oxygen species and cytokine measurements. The results reveal a noteworthy uptake into and transport of microplastic and submicroplastic particles across the intestinal epithelium. Particularly, we show a pronounced uptake of particles into liver cells after crossing of the intestinal epithelium, using the intestinal-liver co-culture. The particles evoke some alterations in xenobiotic metabolism, but did not cause increased oxidative stress or inflammatory response on protein level. Taken together, these complex barrier models can be applied on micro-, submicro- and nanoplastics and reveal information in particle uptake, transport and cellular impact.

Advancements in ToF-SIMS imaging for life sciences.

In the last 2 decades, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) has gained significant prominence as a powerful imaging technique in the field of life sciences. This comprehensive review provides an in-depth overview of recent advancements in ToF-SIMS instrument technology and its applications in metabolomics, lipidomics, and single-cell analysis. We highlight the use of ToF-SIMS imaging for studying lipid distribution, composition, and interactions in cells and tissues, and discuss its application in metabolomics, including the analysis of metabolic pathways. Furthermore, we review recent progress in single-cell analysis using ToF-SIMS, focusing on sample preparation techniques, in situ investigation for subcellular distribution of drugs, and interactions between drug molecules and biological targets. The high spatial resolution and potential for multimodal analysis of ToF-SIMS make it a promising tool for unraveling the complex molecular landscape of biological systems. We also discuss future prospects and potential advancements of ToF-SIMS in the research of life sciences, with the expectation of a significant impact in the field.

Enhancing Ion Signals and Improving Matrix Selection in Time-of-Flight Secondary Ion Mass Spectrometry with Microvolume Expansion Using Large Argon Clusters.

The molecular environment has an important impact on the ionization mechanism in time-of-flight secondary ion mass spectrometry (ToF-SIMS). In complex samples, desorption/ionization, and thus the detection of a molecular signal, can be hampered by molecular entanglement, ionization-suppressive neighbors, or even an unfavorable sample substrate. Here, a method called microvolume expansion is developed to overcome these negative effects. Large argon clusters are able to transfer biomolecules from a target to a collector in vacuum. In this study, argon gas cluster ion beams (Arn+-GCIB with n centered around 3000 or 5000) are used to expand a microvolume from the sample to a collector, which is a material ideally enhancing the ionization yield. The collector is then analyzed using a liquid metal ion gun. The signal amplification factor corresponding to the expansion of phosphatidylcholine (PC) lipid on collectors partially covered with acidic matrices was evaluated as an initial proof of concept. In one experiment, the PC expansion on a pattern of four drop-casted matrix-assisted laser desorption/ionization matrices led to the selection of α-cyano-4-hydroxycinnamic (CHCA) as the optimal candidate for cationic PC detection. The ion signal is increased by at least three orders of magnitude when PC was expanded using 10 keV Ar3000+ and Ar5000+ on a sublimated layer of CHCA. Finally, the expansion of the gray matter of a mouse on different materials (Si, Au-coated Si, CHCA, and polyethylene) was achieved with varying degrees of success, demonstrating the potential of the method to further analyze complex and fragile biological assemblies.

Understanding the Mechanism of Light-Induced Age-Related Decrease in Melanin Concentration in Retinal Pigment Epithelium Cells.

It is known that during the process of aging, there is a significant decrease in the number of melanosomes in the retinal pigment epithelium (RPE) cells in the human eye. Melanosomes act as screening pigments in RPE cells and are fundamentally important for protection against the free radicals generated by light. A loss or change in the quality of melanin in melanosomes can lead to the development of senile pathologies and aggravation in the development of various retinal diseases. We have previously shown that the interaction between melanin melanosomes and superoxide radicals results in oxidative degradation with the formation of water-soluble fluorescent products. In the present study, we show, using fluorescence analysis, HPLC, and mass spectrometry, that visible light irradiation on melanolipofuscin granules isolated from RPE cells in the human eye results in the formation of water-soluble fluorescent products from oxidative degradation of melanin, which was in contrast to lipofuscin granules and melanosomes irradiation. The formation of these products occurs as a result of the oxidative degradation of melanin by superoxide radicals, which are generated by the lipofuscin part of the melanolipofuscin granule. We identified these products both in the composition of melanolipofuscin granules irradiated with visible light and in the composition of melanosomes that were not irradiated but were, instead, oxidized by superoxide radicals. In the melanolipofuscin granules irradiated by visible light, ions that could be associated with melanin oxidative degradation products were identified by applying the principal component analysis of the time-of-flight secondary ion mass spectrometry (ToF-SIMS) data. Degradation of the intact melanosomes by visible light is also possible; however, this requires significantly higher irradiation intensities than for melanolipofuscin granules. It is concluded that the decrease in the concentration of melanin in RPE cells in the human eye with age is due to its oxidative degradation by reactive oxygen species generated by lipofuscin, as part of the melanolipofuscin granules, under the action of light.

Savinin Triggers Programmed Cell Death of Ray Parenchyma Cells in Heartwood Formation of Taiwania cryptomerioides Hayata.

The purpose of this study was to investigate the relationship between lignan biosynthesis and programmed cell death (PCD) of ray parenchyma cells during the heartwood formation of Taiwania (Taiwania cryptomerioides Hayata). Since the PCD of ray parenchyma cells and the synthesis of lignans are the two main processes involved in the formation of heartwood, both of which need to be completed through gene regulation. Based on the results of genomics and bioinformatics analysis, that the PCD of tracheids are induced by genotoxic, and the PCD of ray parenchyma cells is induced by biological factors, such as fungi, bacteria, and viruses, which could induce oxidative stress. According to the results of time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis, lignans are produced in ray parenchyma cells, and the accumulation of savinin and its downstream lignans might be the cause of PCD in ray parenchyma cells. An in vitro experiment further confirmed that the accumulation of savinin could cause protoplasts of Taiwania's xylem to produce taiwanin A, which is the marker of heartwood formation in Taiwania. Resulting in an increase in reactive oxygen species (ROS) content, which could induce oxidative stress in ray parenchyma cells and potentially lead to PCD. Based on these findings, we conclude that accumulation of savinin could be induced PCD of ray parenchyma cells in heartwood formation in Taiwania.

Investigation of atomic-scale decorations on mixed conducting oxides via time-of-flight secondary ion mass spectrometry (ToF-SIMS)

Sub-nanometer modifications of mixed ionic electronic conducting (MIEC) materials, like the perovskite La0.6Sr0.4CoO3-δ (LSC), represent a promising approach to improving their oxygen exchange kinetics and degradation stability. The complex interactions between decoration layers and the host material are still not fully understood and are a subject of current research. Under these circumstances, a novel approach using time-of-flight secondary ion mass spectrometry (ToF-SIMS) was developed to gain deeper insight into the electronic and chemical interactions of LSC with different oxidic decorations. The investigated samples were prepared by pulsed laser deposition (PLD) on YSZ single crystals, starting with a 100 nm thin LSC layer, which was then modified by sub-nm decorations of CaO, TiO2, and SnO2 (nominally 0.05–0.5 nm) on top. By using ToF-SIMS with a sampling depth of 1–2 nm, it was possible to extract information simultaneously on the decoration layer and the host oxide. Significant differences in secondary ion (SI) intensities of the host material LSC were found that can be attributed to the formation of surface-near dipoles as a consequence of the acidic or basic nature of the decoration oxide. Further, relative stoichiometric variations of the La+, Sr+, and Co+ signals depending on the decoration oxide were observed, suggesting different preferential decoration sites on the LSC surface.

The effect of calcium hypochlorite on the adsorption of diethyldithiocarbamate (DDTC) on the surface of molybdenite and bismuthinite

In this paper, the effect mechanism of calcium hypochlorite on the adsorption of the collector DDTC on the surface of molybdenite and bismuthinite was explored. The single mineral flotation test showed that calcium hypochlorite had significant inhibition on the flotation behavior of bismuthinite, but had no similar effect on that of molybdenite. The results of FT-IR spectra and contact angle measurement indicated that the collector DDTC was not able to adhere to the bismuthinite surface treated with calcium hypochlorite, but could adhere to the molybdenite surface treated with the same way. Synthesizing the results of electrochemical test, thermodynamic analysis, Raman spectra, and Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) test, it could be confirmed that calcium hypochlorite could react on the surface of bismuthinite and molybdenite, and the reaction on the bismuthinite surface first produced Bi3+ and Cl-, which continued to react in solution and finally formed BiOCl precipitation, while the reaction on the molybdenite surface formed soluble components, which dissolved into the solution. Therefore, the hydrophilic BiOCl precipitation covered the bismuthinite surface, hindering the adsorption of DDTC, while the soluble components produced on the molybdenite surface entered the solution without affecting its surface wettability and collector adsorption, which maybe was the root cause of the selective depression of calcium hypochlorite.

Thermal interdiffusion, microstructure and contact resistivity of NiOx/Ni/p+ poly-Si layer systems for perovskite/TOPCon tandem solar cells during annealing processes

In a recently published article (Lange et al., 2023) [1], we envisioned and discussed a tandem solar cell concept based on a perovskite/TOPCon architecture in p-i-n configuration, that utilizes a p+/n+ polycrystalline silicon (poly-Si) tunnel junction and NiOx as hole transport material of the perovskite top cell. A direct contact of NiOx to p+ poly-Si is inevitable in such a device. We investigated that junction and reported how the contact resistivity of the NiOx/p+ poly-Si junction can be improved by orders of magnitudes by intentionally inserting a nm-thin metallic Ni interlayer at that interface through the formation of nickel silicide.In this contribution, we present comprehensive data on layer stack morphology, composition and interdiffusion and the impact on the measured contact resistivity based on (scanning) transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) of model samples as well as the real contact structures. Diffusion and reaction processes in the NiOx/Ni/p+ poly-Si layer stack are investigated during the annealing in the temperature range between 100 °C and 500 °C for varying Ni interlayer thicknesses of 0, 1.0 and 2.0 nm. Furthermore, two NiOx syntheses routes are investigated: sputter deposition (s-NiOx) and a wet-chemical approach (wc-NiOx). We correlate the improvement of contact resistivity for both systems and temperatures <300 °C in regard to contacts without metallic Ni interlayer with the observation of pinhole formation within the SiOz. We have observed that annealing the Ag/s-NiOx junctions above 300 °C under ambient air leads to rectifying contacts and high contact resistivities due to excessive interdiffusion of Ni, O and Ag.

Investigation of Effects of Sulfuric Acid in Single Wafer Cleaning Process Using Isopropyl Alcohol

Isopropyl alcohol (IPA) was used in the drying process to remove the contamination after the wet cleaning process. Regardless of the types of chemical solutions, the IPA is more strictly controlled because it is used. However, when the IPA was exposed to low acid concentration, the IPA polymers were generated to the di-isopropyl ether, isopropyl acetate, and di-isopropoxy methane. And the pH of IPA rapidly changed by about 1.99 in ppm level concentration. Generated IPA polymers were adsorbed on the wafer surface. These polymers can occur defects, and the probability increases as the concentration increases. Scanning mobility particle sizer (SMPS) measurement system can be measured the impurity in IPA solution. The total impurity concentration was increased by the concentration of H2SO4 with the same results in both gas chromatography mass spectrometry (GCMS) and time of flight secondary ion mass spectrometry (ToF-SIMS). SMPS results can be correlated with the concentration of impurities. In this paper, IPA polymers were defined by acid contamination, and these polymers have affected the Si wafer surface. In addition, the SMPS measurement system was introduced for the detection of impurities in IPA solutions.