Secondary Mass Spectrometer Research Articles

Presolar Grains as Probes of Supernova Nucleosynthesis.

We provide an overview of the isotopic signatures of presolar supernova grains, specifically focusing on 44Ti-containing grains with robustly inferred supernova origins and their implications for nucleosynthesis and mixing mechanisms in supernovae. Recent technique advancements have enabled the differentiation between radiogenic (from 44Ti decay) and nonradiogenic 44Ca excesses in presolar grains, made possible by enhanced spatial resolution of Ca-Ti isotope analyses with the Cameca NanoSIMS (Nano-scale Secondary Ion Mass Spectrometer) instrument. Within the context of presolar supernova grain data, we discuss (i) the production of 44Ti in supernovae and the impact of interstellar medium heterogeneities on the galactic chemical evolution of 44Ca/40Ca, (ii) the nucleosynthesis processes of neutron bursts and explosive H-burning in Type II supernovae, and (iii) challenges in identifying the progenitor supernovae for 54Cr-rich presolar nanospinel grains. Drawing on constraints and insights derived from presolar supernova grain data, we also provide an overview of our current understanding of the roles played by various supernova types- including Type II, Type Ia, and electron capture supernovae- in accounting for the diverse array of nucleosynthetic isotopic variations identified in bulk meteorites and meteoritic components. We briefly overview the potential mechanisms that have been proposed to explain these nucleosynthetic variations by describing the transport and distribution of presolar dust carriers in the protoplanetary disk. We highlight existing controversies in the interpretation of presolar grain data and meteoritic nucleosynthetic isotopic variations, while also outlining potential directions for future research.

Effects of AlOx Sub‐Oxide Layer on Conductance Training of Passive Memristor for Neuromorphic Computing

AbstractMemristors are recognized as crucial devices for the hardware implementation of neuromorphic computing. The conductance training process of memristors has a direct impact on the performance of neuromorphic computing. However, memristor breakdown and conductance decay still hinder the precise training process of neural networks based on passive memristor. Here, AlOx/LiNbO3 (LN) memristors are designed by inserting a AlOx sub‐oxide layer between the single‐crystalline LN thin film with oxygen vacancies (OVs) and Pt layer. Under the same training conditions, lower conductance and self‐compliance current effects are observed in AlOx/LN memristor. Slight spontaneous decay of conductance is achieved after the removal of the external stimulation. To explore the effects of AlOx sub‐oxide layer on the prevention of device breakdown and suppression of conductance decay, the memristive mechanism of devices with and without AlOx layer is revealed via time‐of‐flight secondary ion mass spectrometer (ToF‐SIMS). It is reasonable to believe that the AlOx inserting layer in memristors can serve as a self‐compliance current layer to inhibit device breakdown and provide the OVs reservoir to suppress conductance decay. These results offer new possibilities and theoretical grounds for achieving more reliable and precise conductance training of passive memristors.

Orbi‐SIMS Mediated Metabolomics Analysis of Pathogenic Tissue up to Cellular Resolution

AbstractTumors have a complex metabolism that differs from most metabolic processes in healthy tissues. It is highly dynamic and driven by the tumor cells themselves, as well as by the non‐transformed stromal infiltrates and immune components. Each of these cell populations has a distinct metabolism that depends on both their cellular state and the availability of nutrients. Consequently, to fully understand the individual metabolic states of all tumor‐forming cells, correlative mass spectrometric imaging (MSI) up to cellular resolution with minimal metabolite shift needs to be achieved. By using a secondary ion mass spectrometer (SIMS) equipped with an Orbitrap mass analyzer, we present a workflow to image primary murine tumor tissues up to cellular resolution and correlate these ion images with post acquisition immunofluorescence or histological staining. In a murine breast cancer model, we could identify metabolic profiles that clearly distinguish tumor tissue from stromal cells and immune infiltrates. We demonstrate the robustness of the classification by applying the same profiles to an independent murine model of lung cancer, which is accurately segmented by histological traits. Our pipeline allows metabolic segmentation with simultaneous cell identification, which in the future will enable the design of subpopulation‐targeted metabolic interventions for therapeutic purposes.

Inert Gas Element as Active Infrared‐Absorption Source and Donor in Silicon for Forbidden‐Wavelength Sensing

AbstractIntrinsic silicon (Si) is forbidden for infrared (IR) sensing at the communication wavelength like 1.31 or 1.55 µm due to the well‐known bandgap limitation. In this work, an unexpected physical picture of using argon (Ar) is identified, which is usually inert to the surrounding chemical environment and used as a protective agent in semiconductor processing, to overcome the IR‐sensing‐forbidden problem in Si. Here, it is shown by an analysis of a dynamic secondary ion mass spectrometer that such a Si, when exposed to laser pulse in Ar gas, can contain a very high dose of Ar up to 1020 cm−3 even after 1300 days. First‐principles calculations, molecular dynamics, and Hall effect measurements reveal that, due to both steric and dynamic repulsions by Ar orbitals to Si dangling bonds, the Ar‐filled‐vacancy produces a much wider defect band inside the gap, which is not only responsible for strong infrared absorption, but also causes a significant increase in n‐type conductivity, both in line with experiments. The study proves that originally inert elements in fact can act as active impurities in semiconductors for advanced applications, which updates the current knowledge of defect physics.

Nano-Scale Secondary Ion Mass Spectrometry: A Paradigm Shift in Soil Science

Soils exhibit structural heterogeneity across diverse spatio-temporal scales, yielding myriad of microhabitats, highlighting the need for a nuanced understanding of the intricate interactions within the soil matrix. At the nanometer scale, the interplay among organic matter (OM), mineral particles, and microbiota intricately govern the long-term destiny of soil carbon (C), nutrient cycling, and the fate of both organic and inorganic pollutants. Notably, the sorption of soil organic matter (SOM) onto smaller clay particles and its entrapment in microaggregates further contribute to this complex dynamic. Understanding these processes depends on recognizing their scale-dependent nature, necessitating sophisticated techniques for investigation. Although various methods are employed across scales, the current set of techniques still lacks the requisite sensitivity and resolution for microscale data collection. To address this limitation, the adoption of novel microscopic and spectroscopic techniques capable of probing molecular, isotopic, and elemental patterns at the micro to nano scale becomes imperative. Among these cutting-edge methodologies, the nano-scale secondary ion mass spectrometer (NanoSIMS) emerges as a paradigm-shifting tool. Representing the latest evolution in ion microprobes, NanoSIMS seamlessly integrates high-resolution microscopy and isotopic analysis, maintaining unparalleled signal transmission and spatial resolution, reaching as fine as 50 nm. Its capabilities extend beyond conventional applications in science, as evidenced by recent breakthroughs in utilizing NanoSIMS to study biophysical interfaces in soils. This article underscores the pressing need to advance the incorporation of NanoSIMS as a pioneering instrumentation technique in soil studies. Furthering the implementation of this novel instrumentation technique in soil studies will pave avenues and aid in the advancement of future research.

Hf-W dating of zircon in mesosiderite with high-pressure sintered standard

New standard zircons applicable to in situ analysis of Hf/W ratio by Nanoscale secondary ion mass spectrometer (NanoSIMS) were prepared and applied to Hf-W dating of a differentiated meteorite classified as mesosiderite. The standard zircons were synthesized by high-pressure experiment from starting materials which were mixture of hafnium oxide, tungsten oxide and high-purity zircon powder. The mixed powders were stirred and pulverized by a high-energy ball mill. They were then sintered at 1000 °C and 6 GPa using multi-anvil apparatus. Homogeneity of Hf/W ratios of synthesized zircons was examined by SEM–EDS, EPMA, and Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS). Hf/W ratios of the same zircons were measured by a NanoSIMS with 2 nA oxygen primary beam and mass resolving power of 10,000. The relative sensitivity factor (RSF) of Hf/W ratio was determined by comparing zircon data measured by LA-ICPMS and NanoSIMS. Observed RSF (Hf/W) of zircon is 0.585 ± 0.180 (hereafter all error 2σ) consistent with 0.855 ± 0.468 of previous work within experimental error margin. The value is higher than observed RSF of glass matrix, 0.301 ± 0.062, and significantly higher than glass data of 0.21–0.22 in references. Based on the RSF, the Hf/W ratios of zircons extracted from mesosiderite “Asuka 882,023” were measured together with W isotopic compositions by NanoSIMS. Observed data in 180Hf/186W–182W/186W diagram are fitted by a straight line, yielding a slope (182Hf/180Hf) of 8.19 ± 3.50 × 10–6. This slope is converted into an absolute zircon Hf-W age of 4536.5+4.6–7.2 Ma using the age anchor of CV3 chondrite. This age agrees well with a reference value of 4532.0+11.4–20.8 Ma.

Enhancing the Efficiency and Stability of Tin-Lead Perovskite Solar Cells via Sodium Hydroxide Dedoping of PEDOT:PSS.

Tin-lead (Sn-Pb) perovskite solar cells (PSCs) have gained interest as candidates for the bottom cell of all-perovskite tandem solar cells due to their broad absorption of the solar spectrum. A notable challenge arises from the prevalent use of the hole transport layer, PEDOT:PSS, known for its inherently high doping level. This high doping level can lead to interfacial recombination, imposing a significant limitation on efficiency. Herein, NaOH is used to dedope PEDOT:PSS, with the aim of enhancing the efficiency of Sn-Pb PSCs. Secondary ion mass spectrometer profiles indicate that sodium ions diffuse into the perovskite layer, improving its crystallinity and enlarging its grains. Comprehensive evaluations, including photoluminescence and nanosecond transient absorption spectroscopy, confirm that dedoping significantly reduces interfacial recombination, resulting in an open-circuit voltage as high as 0.90V. Additionally, dedoping PEDOT:PSS leads to increased shunt resistance and high fill factor up to 0.81. As a result of these improvements, the power conversion efficiency is enhanced from 19.7% to 22.6%. Utilizing NaOH to dedope PEDOT:PSS also transitions its nature from acidic to basic, enhancing stability and exhibiting less than a 7% power conversion efficiency loss after 1176h of storage in N2 atmosphere.

Disequilibrium oxygen isotope distribution among aqueously altered minerals in Ryugu asteroid returned samples

AbstractOxygen 3‐isotope ratios of magnetite and carbonates in aqueously altered carbonaceous chondrites provide important clues to understanding the evolution of the fluid in the asteroidal parent bodies. We conducted oxygen 3‐isotope analyses of magnetite, dolomite, and breunnerite in two sections of asteroid Ryugu returned samples, A0058 and C0002, using a secondary ion mass spectrometer (SIMS). Magnetite was analyzed by using a lower primary ion energy that reduced instrumental biases due to the crystal orientation effect. We found two groups of magnetite data identified from the SIMS pit morphologies: (1) higher δ18O (from 3‰ to 7‰) and ∆17O (~2‰) with porous SIMS pits mostly from spherulitic magnetite, and (2) lower δ18O (~ −3‰) and variable ∆17O (0‰–2‰) mostly from euhedral magnetite. Dolomite and breunnerite analyses were conducted using multi‐collection Faraday cup detectors with precisions ≤0.3‰. The instrumental bias correction was applied based on carbonate compositions in two ways, using Fe and (Fe + Mn) contents, respectively, because Ryugu dolomite contains higher amounts of Mn than the terrestrial standard. Results of dolomite and breunnerite analyses show a narrow range of ∆17O; 0.0‰–0.3‰ for dolomite in A0058 and 0.2‰–0.8‰ for dolomite and breunnerite in C0002. The majority of breunnerite, including large ≥100 μm grains, show systematically lower δ18O (~21‰) than dolomite (25‰–30‰ and 23‰–27‰ depending on the instrumental bias corrections). The equilibrium temperatures between magnetite and dolomite from the coarse‐grained lithology in A0058 are calculated to be 51 ± 11°C and 78 ± 14°C, depending on the instrumental bias correction scheme for dolomite; a reliable temperature estimate would require a Mn‐bearing dolomite standard to evaluate the instrumental bias corrections, which is not currently available. These results indicate that the oxygen isotope ratios of aqueous fluids in the Ryugu parent asteroid were isotopically heterogeneous, either spatially, or temporary. Initial water ice accreted to the Ryugu parent body might have ∆17O > 2‰ that was melted and interacted with anhydrous solids with the initial ∆17O < 0‰. In the early stage of aqueous alteration, spherulitic magnetite and calcite formed from aqueous fluid with ∆17O ~ 2‰ that was produced by isotope exchange between water (∆17O > 2‰) and anhydrous solids (∆17O < 0‰). Dolomite and breunnerite, along with some magnetite, formed at the later stage of aqueous alteration under higher water‐to‐rock ratios where the oxygen isotope ratios were nearly at equilibrium between fluid and solid phases. Including literature data, δ18O of carbonates decreased in the order calcite, dolomite, and breunnerite, suggesting that the temperature of alteration might have increased with the degree of aqueous alteration.

Robust macroscale superlubricity of multiple base oils achieved on soft epoxy resin coatings

Reducing the friction of base oils to a superlubricity state is highly expected at engineering scale. However, it still is a great challenge for the most of viscous base oils to achieve superlubricity on the conventional tribopairs up to now. Here we report the strategy of solid-oil composited lubrication constructed with an ultra-smooth epoxy resin (EP) coating and base oils for achieving superlubricity. Especially, the frictional results showed that the proposed strategy in this study could be suitable for multiple base oils, including nonpolar and polar base oils as lubricants. The friction coefficient of steel/EP tribopair lubricated by the base oils containing hydroxyl group can be as low as 0.001. Meanwhile, the composited lubrication system did not undergo an obvious running-in stage to achieve the superlubricity state regardless of the type of base oils. The surface hydroxylation of the steel counter ball sliding against EP coating was observed by time-of-flight secondary ion mass spectrometer, even when lubricated by nonpolar base oils without hydroxyl group. This could be a critical factor for the base oils to achieve superlubricity. This finding provides a new and facile approach to realize robust superlubrication for different base oils at engineering scale.

Low‐Pressure Nitrocarburizing in Standard Vacuum Furnaces—Preliminary Studies

For the first time, low‐pressure nitrocarburizing process is performed in a minorly modified standard vacuum furnace on 16MnCr5 alloy steel samples. Ammonia and acetylene are used as a source of nitrogen and carbon, respectively. Lowering the pressure of the process ensures longer and more efficient ammonia dissociation. To prove the safety of the process, exhaust gases are investigated online using residual gas analyzer mass spectrometer, whereas reaction products deposited on the sample's surface are studied by means of time‐of‐flight secondary ion mass spectrometer. Possible reactions taking place in the atmosphere of the chamber are written down. In the results of conducted examinations, it is confirmed that no toxic gases are generated, and no cyanides and polycyclic aromatic hydrocarbons are formed during the process. Additionally, microstructure analysis of the cross sections of nitrocarburized sample is performed using scanning electron microscopy (SEM) and optical microscopy. It confirms the diffusion of nitrogen and carbon into the near surface layer. SEM/energy‐dispersive X‐ray spectroscopy analysis demonstrates precipitation of carbide and carbonitride, what is proved by X‐ray diffractometer and microhardness profile analysis. The presented low‐pressure nitrocarburizing results in an increase in hardness from about 200 to over 500 HV and the formation of an effective case depth of about 20 μm, after only 20 min of the process.

The Impact of Microstructure on Filament Growth at the Sodium Metal Anode in All‐Solid‐State Sodium Batteries

AbstractIn recent years, all‐solid‐state batteries (ASSBs) with metal anodes have witnessed significant developments due to their high energy and power density as well as their excellent safety record. While intergranular dendritic lithium growth in inorganic solid electrolytes (SEs) has been extensively studied for lithium ASSBs, comparable knowledge is missing for sodium‐based ASSBs. Therefore, polycrystalline Na‐β″‐alumina is employed as a SE model material to investigate the microstructural influence on sodium filament growth during deposition of sodium metal at the anode. The research focuses on the relationship between the microstructure, in particular grain boundary (GB) type and orientation, sodium filament growth, and sodium ion transport, utilizing in situ transmission electron microscopy (TEM) measurements in combination with crystal orientation analysis. The effect of the anisotropic sodium ion transport at/across GBs depending on the orientation of the sodium ion transport planes and the applied electric field on the current distribution and the position of sodium filament growth is explored. The in situ TEM analysis is validated by large field of view post‐mortem secondary ion mass spectrometer (SIMS) analysis, in which sodium filament growth within voids and along grain boundaries is observed, contributing to the sodium network formation potentially leading to failure of batteries.

Effects of initial Cu grain size and impurity residues on the liquid phase reactions between molten solder and electroplated Cu

Copper (Cu) electroplating is a cost-effective and scalable technology used to fabricate interconnects/metallizations in microelectronic products. Liquid-phase soldering reactions between electroplated Cu and Sn-based alloys are essential for constructing heterogeneous joints for mechanical support and electrical conduction applications. In this study, three Cu electroplated layers with different grain sizes and impurity contents are fabricated by formulating additives in the plating solution. The Cu electroplated layers are reacted with molten Sn-3.5 wt% Ag alloy at 260 °C for 20–60 min to investigate the liquid phase reactions. Microstructural characterizations of the electroplated Cu layers and the Cu/solder/Cu joints are carried out using electron microscopy and X-ray diffraction processes. A time-of-flight secondary ion mass spectrometer is used to analyze the impurity contents in the Cu electroplated layers. The Cu/solder/Cu joints after liquid phase reactions are mechanically analyzed to measure the shear strength. The results show that the additive formulas affect the microstructural features and the impurity contents in the Cu electroplated layers. Electroplating of Cu with an ultrafine grain texture accompanies a high impurity content, and the solder joint constructed by the ultrafine-grained Cu exhibits a rapid liquid phase reaction and interfacial voiding propensity, leading to a low shear strength.

Comprehensive investigation of sputtering deposition pressure effects on a-InGaZnO Schottky diodes

The effects of Ar sputtering deposition pressure on the optical, structural, morphological, and electrical properties of amorphous InGaZnO thin films were investigated. The InGaZnO thin films, which have amorphous structures determined by grazing incidence x-ray diffraction, contained In, Ga, Zn, and O confirmed by secondary ion mass spectrometry method. Additionally, when the thicknesses of the deposited thin films are examined, it was seen that the profilometer measurement results of the crater formed by secondary ion mass spectrometer and scanning electron microscope measurement results are nearly similar, and it is approximately 100 nm. The surface roughness, obtained from Atomic Force Microscopy results, show that decreased up to a particular value with the increase of the working pressure, and then the surface roughness increased. The optical band gaps of the films were obtained in the range of 3.50 eV−3.58 eV via Tauc relation by using the Ultraviolet-Visible measurements carried out in the wavelength range of 200 nm−1100 nm. It was seen that the optical band gap was decreased with the increase in Ar pressure. The electrical properties of InGaZnO thin film-based Schottky diodes, such as the barrier height, ideality factor, saturation current, series resistance, and shunt resistance, have also been studied comprehensively. The electrical results showed that diode properties change with increasing deposition pressure.

Diffusion timescale conundrum in contact metamorphism: Oxygen isotope and trace element profiles in dolomite

Successful application of diffusion chronometry is based on detailed knowledge of diffusion parameters obtained from laboratory experiments, which also need to be upscaled to be applied to natural samples. While generally applicable, several examples of disagreement with other dating techniques and discrepancies with geological observations highlight the importance of validating diffusion parameters and their use to geochronologic application by testing them on samples from well-characterized geologic environments.The incomplete dissolution and reprecipitation reaction of dolomite associated with infiltration along grain boundaries of a fluid of magmatic origin in a contact metamorphic environment is the starting point of this study. The reaction produces dolomite rims, which are characterized by lower δ18O values (about 16‰) and slightly higher Fe (∼1000 ppm) and Mn (∼200 ppm) concentrations. The cores, in comparison, have no Fe and Mn and a δ18O value of about 30‰. This compositional and isotopic gradient led to chemical re-equilibration through diffusion at the reaction interface. We acquired oxygen isotope profiles using a secondary ion mass spectrometer (SIMS), with spot sizes as small as 3 µm, and iron and manganese profiles with a NanoSIMS and a beam diameter of about 240 nm. These profiles were then compared against cumulative theoretical diffusion distances calculated for a modeled time – temperature path of the contact aureole using the experimentally determined diffusion parameters for O, Fe and Mn in dolomite.The oxygen isotope profiles yielded diffusion distances of ca. 10 µm, corresponding to a formation temperature of about 550 °C, which is concordant with phase petrology and a timing for fluid infiltration at the onset of cooling of the contact aureole (i.e., non-isothermal evolution of the dolomite marbles). The Fe and Mn profiles were very sharp, with a diffusion length of about 150 nm. Such short diffusion length would be achieved at near-surface temperature and corresponding cooling timescale are several orders of magnitude smaller than those derived from the oxygen diffusion profiles. From the mineralogy and textures, a decoupling of the oxygen isotopes and Fe–Mn reaction interface can be ruled out, suggesting that the published diffusion parameters are not fully representative, either due to the experimental conditions or by the assumed diffusion mechanism of natural processes. This case study is not the first example in the literature where the diffusion rate of Fe and Mn in natural dolomite seems to be substantially slower than predicted by experiments. Thus, there is a need to re-assess the experimental diffusivities before Fe and Mn diffusion in dolomite can be reliably used to determine duration, cooling or heating paths of metamorphic processes.

Toward Operando Structural, Chemical, and Electrochemical Analyses of Solid-State Batteries Using Correlative Secondary Ion Mass Spectrometry Imaging.

The global transition from fossil fuels to green energy underpins the need for efficient and reliable energy storage systems. Advanced analysis and characterization of battery materials is not only important to understand fundamental battery properties but also crucial for their continued development. A deep understanding of these systems is often difficult to obtain through only pre- and/or post-mortem analyses, with the full complexity of a battery being hidden in its operational state. Thus, we have developed an operando methodology to analyze solid-state batteries (SSBs) structurally as well as chemically before, during, and after cycling. The approach is based on a specially designed sample holder, which enables a variety of electrochemical experiments. Since the entire workflow is performed within a single focused ion beam scanning electron microscope equipped with an in-house developed magnetic sector secondary ion mass spectrometer, we are able to pause the cycling at any time, perform analysis, and then continue cycling. Microstructural analysis is performed via secondary electron imaging, and the chemical mapping is performed using the secondary ion mass spectrometer. In this proof-of-concept study, we were able to identify dendrites in a short-circuited symmetric cell and to chemically map dendritic structures. While this methodology focuses on SSBs, the approach can directly be adapted to different battery systems and beyond. Our technique clearly has an advantage over many alternatives for battery analysis as no transfer of samples between instruments is needed and a correlation between the microstructure, chemical composition, and electrochemical performance is obtained directly.

New Olivine Reference Materials for Secondary Ion Mass Spectrometry Oxygen Isotope Measurements

To accurately analyze the oxygen isotope of olivine using secondary ion mass spectrometry (SIMS), appropriate standard materials are required to calibrate for matrix effects caused by chemical composition differences between the samples and the standard materials. In this study, we investigated the homogeneity of oxygen isotopes in two natural olivine minerals using a secondary ion mass spectrometer to evaluate their potential as standard materials. The two minerals, JAY03-3 and JAY02-4, with forsterite contents of 99.3% and 99.6%, respectively, were evaluated for homogeneity in oxygen isotope composition. The recommended oxygen isotope values were characterized using CO2 laser fluorination, and the homogeneity was tested with in situ SIMS oxygen isotope measurements. Our results show that the δ18O value determined via CO2 laser fluorination for JAY03-3 is 16.37 ± 0.22‰ (2 s) and for JAY02-4 is 18.29 ± 0.28‰ (2 s). The precision of SIMS oxygen isotope measurements is 0.57‰ (2 s) for JAY03-3 and 0.70‰ (2 s) for JAY02-4. These two minerals have the potential to be used as standard materials for calibrating the oxygen isotope value of end-member forsterite during in situ analysis of SIMS oxygen isotope.

Development of High Throughput Microscope Mode Secondary Ion Mass Spectrometry Imaging

This paper describes the development and initial results from a secondary ion mass spectrometer coupled with microscope mode detection. Stigmatic ion microscope imaging enables us to decouple the primary ion (PI) beam focus from spatial resolution and is a promising route to attaining higher throughput for mass spectrometry imaging (MSI). Using a commercial C60+ PI beam source, we can defocus the PI beam to give uniform intensity across a 2.5 mm2 area. By coupling the beam with a position-sensitive spatial detector, we can achieve mass spectral imaging of positive and negative secondary ions (SIs), which we demonstrate using samples comprising metals and dyes. Our approach involves simultaneous desorption of ions across a large field of view, enabling mass spectral images to be recorded over an area of 2.5 mm2 in a matter of seconds. Our instrument can distinguish spatial features with a resolution of better than 20 μm, and has a mass resolution of >500 at 500 u. There is considerable scope to improve this, and through simulations we estimate the future performance of the instrument.

Effects of suppressors on the incorporation of impurities and microstructural evolution of electrodeposited Cu solder joints

BackgroundCopper (Cu) electrodeposition is a cost-effective and scalable technology commonly used to fabricate interconnects and heat sinks in microelectronic devices. Adding organic functional additives, such as suppressors, to plating solutions is crucial to achieve conformal microvia filling by Cu electroplating. However, codeposition of organic additives is inevitable and leads to reliability concerns regarding impurity residues in the Cu electrodeposited layer. MethodsIn this study, polyethylene glycol (PEG) at 8,000 g mol−1 and a triblock copolymer EPE (polyethylene oxide-polypropylene oxide-polyethylene oxide) at 2,900 g mol−1 are applied as suppressors and individually added to plating solutions to compare their suppression strength toward Cu deposition using galvanostatic measurements. Their adsorption/desorption behaviors on the Cu surface are theoretically analyzed based on the electronic distribution properties of the two suppressor molecules calculated by quantum chemical calculations. The impurity residues in the Cu layers are measured by a time-of-flight secondary ion mass spectrometer, and their effects on the joining reactions between tin (Sn) solder and Cu are investigated by observing the microstructural evolution in the Sn/Cu joints subjected to isothermal aging. Significant findingsEPE2900 outperforms PEG8000 in the suppression strength toward Cu deposition. Unlike PEG8000, which causes a high level of impurity incorporation, the impurity residues in the Cu layer constructed by EPE2900 are negligible. As a result, the Sn/Cu solder joint constructed by EPE2900 exhibits high microstructural stability free of the propagation of detrimental voids during isothermal aging at 200 °C. The better suppression efficacy and negligible impurity residues of EPE2900 can be rationalized based on quantum chemical calculations.

Compositional Variability of 2.0‐Ga Lunar Basalts at the Chang'e‐5 Landing Site

AbstractChina's Chang'e‐5 (CE‐5) mission successfully returned a total of 1.731 kg of lunar material from the north‐eastern Oceanus Procellarum region. Young (∼2.0 Ga) ages were reported from the CE‐5 basalts. However, there are controversies on whether they are low‐Ti or high‐Ti mare basalt type. Here, we report the results of a comprehensive petrographic, elemental, and Pb isotopic investigation on a 17.6 mg CE‐5 basalt clast (CE5C0000YJYX048). By combining high‐resolution X‐ray tomography of the clast and microbeam (scanning electron microscope SEM, electron probe microanalyzer EPMA) analyses of mineral grains peeled off the clast surface, we derived the bulk clast chemical composition with a very small sample consumption (i.e., <3 mg). The poikilitic clast has a bulk TiO2 content of 3.78 ± 1.01 wt%, which is representative of a low‐Ti basalt end‐member in the lunar mare basalts samples. Furthermore, the pyroxene in the studied clast is dominantly pigeonite, in contrast to other reported CE‐5 samples where augite is the dominant pyroxene mineralogy. Despite these compositional peculiarities, in situ secondary ion mass spectrometer dating yielded a Pb‐Pb age of 2,040 ± 22 Ma for the fragment, which is consistent with ages reported from other CE‐5. Based on the chemical and age data analyzed in this study, it can be concluded that the lunar basalts obtained from the CE‐5 mission originated from a low‐Ti mare basalt‐type source. The mineral composition of the mare basalt clast studied, which is dominated by pigeonite, fayalite, and anorthite, likely resulted from late‐stage magmatic crystallization when the magma was enriched in Fe.

Activation of Mg impurities in epitaxial p-GaN with rapid thermal annealing assisted supercritical fluid treatment

The activation of an Mg acceptor in p-GaN with rapid thermal annealing (RTA) assisted low-temperature supercritical fluid (SCF) treatment (RTA-A-SCF) was investigated. After RTA-A-SCF treatment, the luminescence band of the N vacancy in the PL spectra was significantly suppressed. An evident decrease in H concentration is also observed in secondary ion mass spectrometer measurements, it indicates an obvious decrease of Mg–H complexes in the p-GaN. In addition, the ohmic contacts have been well improved and the hole concentration has increased by an order of magnitude. The activation mechanism of RTA-A-SCF treatment was further analyzed by X-ray photoelectron spectroscopy.