Depth Profiles Research Articles

Quantitative characterization of occupational sites of implanted P atoms in diamond

The authors implanted P atoms at 50 and 140-keV energies with respective fluences of 1×1014 and 2×1014/cm2 into diamond thin films synthesized by chemical vapor deposition on the type-Ib diamond substrate formed by high-pressure and high-temperature conditions. The occupational sites of implanted P atoms were determined in each processing stage of P implantation, ion-beam-induced epitaxial crystallization (IBIEC) annealing by 3-MeV-Ne2+ ion irradiation at 750°C, and thermal annealing at 850°C in vacuum, by quantitatively comparing the random and channeling yields in Rutherford backscattering (RBS) measurements. In the analysis of RBS spectra, simulated distributions were fitted to the experimentally obtained spectra and we quantitatively identified the occupational sites and ratio of implanted P atoms. In addition, we investigated the diffusion phenomenon of implanted P atoms during annealing processes from the depth profile of scattered He ions. Consequently, the averaged occupational ratio in the substitutional lattice site was stably recorded around 50%. From the depth profile in the RBS spectra, thermal diffusion of implanted P atoms was clearly observed during the last thermal annealing after MeV-IBIEC annealing. We finally discuss the potentials of the MeV-IBIEC irradiation at relatively low temperatures applying to useful and credible annealing methods for electrical activation as well as recovery of damaged crystallinity.

The Li battery digital twin – Combining 4D modelling, electro-chemistry, neutron, and ion-beam techniques

Knowledge driven materials and component design is key for improving the performance of Li-ion batteries and solving the remaining hurdles for next-generation battery concepts like all-solid-state batteries. While the spatial and time dependent distribution of Li would help elucidating performance bottlenecks and degradation phenomena, only a few analysis techniques are available, due to the unique nature of Li, especially as Li+-ion. In fact, only two non-destructive techniques with good time resolution can combine spatial information with absolute quantification of Li, one being Neutron Depth Profiling (NDP), the other Ion-Beam-Analysis (IBA). While both exploit nuclear processes, the information gained is complementary. NDP provides high depth resolution, but only limited lateral resolution, whereas IBA has high lateral, but only limited depth resolution. In this study, we benchmark both techniques for the first time using a set of Li-battery test-samples and show the strengths and synergies of both techniques. The derived information regarding the depth dependent Li-concentration is then used to validate a microstructure resolved continuum model of charge, discharge, and relaxation behavior of the cells and electro-chemical analysis. This fundamental work demonstrates a new route to optimize Li batteries on material and component level by combining advanced characterization and digital twin modelling.

Uncovering sources, distribution, and seasonal patterns of trace element deposition: the elemental puzzle of the western Himalayas.

The transport and deposition of atmospheric pollutants in the Himalayas have a adverse impact on the climate, cryosphere, ecosystem, and monsoon patterns. Unfortunately, there is a insufficiency of data on trace element concentrations and behaviors in the high-altitude Himalayan region, leading to limited research in this area. This study presents a comprehensive and detailed comprehension of trace element deposition, its spatial distribution, seasonal variations, and anthropogenic signals in the high-altitude Kashmir region of the Western Himalayas. Our investigation involved the analysis of 10 trace elements (Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in glacier ice, snow pits, surface snow, and rainwater collected at various sites including Kolahoi, Thajwas, Pahalgam (Greater Himalayan ranges), and Kongdori and Shopian (Pir Panjal Ranges) during 2021.The study reveals distinct ranges of concentrations for the trace elements at different sampling sites. Our analysis of trace element concentration depth profiles in snow pits reveals seasonal fluctuations during the deposition year. The highest concentrations were found in the autumn(below 20cm) and summer (top layer), compared to the winter concentration (10-20cm). The high enrichment factors (EFs) suggest the severity of human-induced trace metal deposition in the western Himalayan region, relative to surrounding regions. Surprisingly, the concentrations and EFs of trace elements showed seasonal contradictions, with lower concentration values and higher EFs during the non-monsoon season and vice versa. A source apportionment analysis using the positive matrix factorization (PMF) technique identified five sources of trace element deposition in the region, including crustal sources (32.33%), coal combustion (15.62%), biomass burning (17.63%), traffic emission (18.8%), and industrial sources (15.6%). Additionally, the study incorporated backward trajectories coupled with δ18O using the NOAA HYSPLIT model to estimate moisture sources in the region, which suggests atmospheric pollutants predominately deposited from the large-scale atmospheric circulation from westerlies (75%) during non-monsoon season. These findings underscore the urgent need for enhanced monitoring and research efforts in the future.

Use of Laser Texture Scanner to Control Quality of Chip Seal Construction

Chip seal is a pavement surface treatment, consisting of a combination of asphalt binder or emulsion and a layer of aggregate compacted on top of a pavement substrate. Raveling and bleeding are the two major distresses that affect the performance of chip seals. Studies have shown that these distresses can be related to the embedment depth, among a few factors. Embedment depth is the depth that rock is lodged into binder and is a key parameter that significantly affects the performance of chip seals. Currently, embedment depth is evaluated by pulling out the rock from the binder (often by a plier) and visually estimating the percentage of embedment. However, this method is subjective and does not provide accurate and reliable results. This study evaluated the use of laser texture scanner as quality control of chip seal construction. The mean profile depth (MPD), which is inversely related to percent embedment in the field, was measured and used to correlate with chip seal performance for raveling and bleeding. It was found that MPD is sensitive to compaction efforts of chip seals. The shoulder MPD value of chip seals after sweeping should be at a minimum of 0.150 in. to prevent bleeding from happening for the traffic volume experienced by the selected field project. When MPD in the wheelpath drops below 0.05 in., bleeding has occurred. More field experiments are needed to cover different construction practices and conditions to validate the findings from this study.

Effect of the One-to-Many Relationship between the Depth and Spectral Profile on Shallow Water Depth Inversion Based on Sentinel-2 Data

In shallow water, Sentinel-2 multispectral imagery has only four visible bands and limited quantization levels, which easily leads to the occurrence of the same spectral profile but different depth (SSPBDD) phenomenon, resulting in a one-to-many relationship between water depth and spectral profile. Investigating the impact of this relationship on water depth inversion models is the main objective of this paper. The Stumpf model and three machine learning models (Random Forest, Support Vector Machine, and Mixture Density Network) are employed, and the performance of these models is analysed based on the spatial distribution of the training dataset and the input information composition of these models. The results show that the root mean square errors (RMSEs) of the depth inversion of Random Forest and Support Vector Machine are significantly affected by the spatial distribution of the training dataset, while minimal effects are observed for the Stumpf model and the Mixture Density Network model. The SSPBDD phenomenon is widespread in Sentinel-2 images at all depths, particularly between 5 m and 15 m, with most of the depth maximum difference of the SSPBDD pixels ranging from 0 to 5 m. The SSPBDDs phenomenon can significantly reduce the inversion accuracy of any model. The number and the depth maximum difference of the SSPBDDs pixels are the main influencing factors. However, by increasing the visible spectral information and the spatial neighbourhood information in the input layer of machine learning models, the inversion accuracy and stability of the models can be improved to a certain extent. Among the models, the Mixture Density Network achieves the best inversion accuracy and stability.

Depth‐resolved historical painting study with minimal microsampling, illustrated with a newly discovered Botticelli workshop painting

AbstractA painting from the Botticelli workshop has been studied after its recent discovery, with an innovative and noninvasive approach combining two‐ dimensional scanning macro‐x‐ray fluorescence imaging (MA‐XRF) and a laboratory‐based depth‐resolved site‐selective confocal micro‐x‐ray fluorescence (CXRF) device. These analyses were supported by measurements on cross‐sections taken from the artwork using scanning electron microscopy coupled with an energy‐dispersive x‐ray system. The aims of this study are to confirm the painting's attribution and authentication, find characteristic markers and features, understand the artist's technique, materials used, and palette, and all of it while reducing sampling. The analyzing approach used combines imaging and site‐selective techniques while avoiding, reducing and replacing sampling without compromising the results. Chemical maps of the painting were obtained by MA‐XRF and enabled the identification of zones, colors, and chemical elements of interest alongside with a first assumption on the pigments used. Depth profiles were then performed in precise areas and colors using CXRF, allowing to evidence overlaying paint layers and obtain a more complete 3D vision of the painting. Contrasting the findings using this new methodology with the traditionally employed analysis process involving microsampling allowed us to determine the accuracy and veracity of our conclusions.

Diagnostic accuracy of contrast-enhanced computed tomography in assessing bone invasion in patients with oral squamous cell carcinoma

ObjectivesThis study aimed to evaluate the diagnostic accuracy of contrast-enhanced computed tomography (CT) in detecting bone invasion in oral squamous cell carcinoma (OSCC) patients and to explore clinicopathological factors associated with its reliability.Materials and methods417 patients underwent preoperative contrast-enhanced CT followed by radical surgery. The presence or absence of bone invasion served as the outcome variable, with histopathologic examination of the resection specimen considered the gold standard. Statistical analyses, comprising correlation analyses and the determination of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), were conducted.ResultsCT exhibited 76.85% sensitivity, 82.20% specificity, 47.14% PPV, and 89.67% NPV. False-positive and false-negative rates were 11.27% and 5.99%, respectively. Artifacts affected assessment in 44 patients, but not in those with bone invasion. Tumor size, depth of invasion (DOI), tumor localization at the upper jaw, lymphatic invasion, and perineural invasion correlated with incorrect identification of bone invasion (Chi-square, p < 0.05).ConclusionsDespite utilizing thin-section CT, notable false-positive and false-negative results persisted. Patients with T3 tumors, DOI ≥ 10 mm, or upper jaw tumors are at higher risk for misidentification of bone invasion. Combining multiple methods may enhance diagnostic accuracy, and the integration of artificial intelligence or tracking electrolyte disturbances by tumor depth profiling shows promise for further assessment of bone invasion before histopathology.Clinical relevanceSurgeons should consider these insights when planning tumor resection. Supplementary imaging may be warranted in cases with high risk factors for misidentification. Further methodological advancements are crucial for enhancing diagnostic precision.

Application of handheld/portable spectroscopic tools to the identification, inner stratigraphy and mapping of archaeological metal artefacts

Field handheld/portable instrumentations, such as in-situ geochemical analyzers, have the potential to assist efficiently targeted geochemical archaeometry campaigns in detecting and quantifying specific elements. Non-destructive portable energy dispersive x-ray fluorescence and micro-destructive handheld laser-induced breakdown spectroscopy (LIBS) instrumentation were utilized to investigate the elemental composition, internal stratigraphy by depth profiling and microscale compositional mapping of five copper and two iron alloy artefacts collected from various ancient graves in the Minervino Murge area, Apulia, Italy. The primary elements identified by both techniques included Cu, Sn and Pb in copper alloys, and Fe with minor amounts of Cu and Pb in iron alloys. Furthermore, the elements Al, Ca, Si, Mg, Na and K, mostly originated from soil contamination, and the trace elements Sb, Ni and Zn were detected. The satisfactory performance of both techniques was assessed by their capacity to provide reproducible elemental composition data. Finally, the depth profile and mapping achieved by LIBS contributed to understanding the metal processing and history of the objects studied, so confirming both techniques to be robust analytical tools in outdoor archaeology and archaeometry campaigns.

A Dielectric MXene-Induced Self-Built Electric Field in Polymer Electrolyte Triggering Fast Lithium-Ion Transport and High-Voltage Cycling Stability.

Quasi-solid polymer electrolyte (QPE) lithium (Li)-metal battery holds significant promise in the application of high-energy-density batteries, yet it suffers from low ionic conductivity and poor oxidation stability. Herein, a novel self-built electric field (SBEF) strategy is proposed to enhance Li+ transportation and accelerate the degradation dynamics of carbon-fluorine bond cleavage in LiTFSI by optimizing the termination of MXene. Among them, the SBEF induced by dielectric Nb4C3F2 MXene effectively constructs highly conductive LiF-enriched SEI and CEI stable interfaces, moreover, enhances the electrochemical performance of the QPE. The related Li-ion transfer mechanism and dual-reinforced stable interface are thoroughly investigated using ab initio molecular dynamics, COMSOL, XPS depth profiling, and ToF-SIMS. This comprehensive approach results in a high conductivity of 1.34 mS cm-1, leading to a small polarization of approximately 25 mV for Li//Li symmetric cell after 6000 h. Furthermore, it enables a prolonged cycle life at a high voltage of up to 4.6 V. Overall, this work not only broadens the application of MXene for QPE but also inspires the great potential of the self-built electric field in QPE-based high-voltage batteries.

A Dielectric MXene‐Induced Self‐Built Electric Field in Polymer Electrolyte Triggering Fast Lithium‐Ion Transport and High‐Voltage Cycling Stability

AbstractQuasi‐solid polymer electrolyte (QPE) lithium (Li)‐metal battery holds significant promise in the application of high‐energy‐density batteries, yet it suffers from low ionic conductivity and poor oxidation stability. Herein, a novel self‐built electric field (SBEF) strategy is proposed to enhance Li+ transportation and accelerate the degradation dynamics of carbon‐fluorine bond cleavage in LiTFSI by optimizing the termination of MXene. Among them, the SBEF induced by dielectric Nb4C3F2 MXene effectively constructs highly conductive LiF‐enriched SEI and CEI stable interfaces, moreover, enhances the electrochemical performance of the QPE. The related Li‐ion transfer mechanism and dual‐reinforced stable interface are thoroughly investigated using ab initio molecular dynamics, COMSOL, XPS depth profiling, and ToF‐SIMS. This comprehensive approach results in a high conductivity of 1.34 mS cm−1, leading to a small polarization of approximately 25 mV for Li//Li symmetric cell after 6000 h. Furthermore, it enables a prolonged cycle life at a high voltage of up to 4.6 V. Overall, this work not only broadens the application of MXene for QPE but also inspires the great potential of the self‐built electric field in QPE‐based high‐voltage batteries.

Exploring microstructural evolution, nitrogen depth profile, and dry wear performance in 31CrMoV9 steel through combined severe shot peening and plasma nitriding

The present study investigates the influence of severe shot peening (SSP) on the plasma nitriding behavior and sliding wear performance of 31CrMoV9 steel. Initially, the steel was austenitized at 880 °C, followed by oil quenching, and tempering at 520 °C for one hour. These samples were shot peened using high-carbon steel shots, resulting in an enhancement in surface hardness up to 447 HV, gradually converging to the initial martensitic hardness after 140 µm depth. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) scrutinized the initial and surface treated martensitic samples. Afterward, the plasma nitriding treatments were carried out at temperatures of 400 °C, 450 °C, and 500 °C for 8 hours in a 30% N2 + 70% H2 atmosphere and 300 Pa pressure. Microhardness testing, SEM, XRD, and glow-discharge optical emission spectroscopy (GDOES) evaluated both plasma nitrided (PN) and severe shot peened/plasma nitrided (SSP-PN) samples. Cross-sectional SEM observations revealed compound layer thicknesses of approximately 2.8 µm, 5.0 µm, and 6.3 µm for PN samples at 400 °C, 450 °C, and 500 °C, respectively. SSP-PN samples exhibited a substantial increase — roughly 71%, 44%, and 33% increase, respectively, compared to PN samples. GDOES analysis supported this trend and indicated enhanced nitrogen diffusion depth, particularly evident in SSP-PN samples at consistent temperatures. The XRD results showed the stability of Fe4N, Fe2–3N, and CrN phases at all three nitriding temperatures. Furthermore, the intensity of these phases increases with temperature and is augmented by the application of the SSP. Microhardness measurements indicated hardness escalation: from 775 HV to 980 HV at 400 °C, 932 HV to 1096 HV at 450 °C, and 1011 HV to 1205 HV at 500 °C due to SSP. Finally, the wear performance was investigated between the non-nitrided, SSP, PN, SSP-PN, samples. Initially, SSP led to decreased wear performance up to 500 m, followed by improved behavior up to 1500 m. At 400 °C, the SSP-PN sample exhibited a 12% lower wear rate than PN. At 450 °C and 1500 m, the SSP-PN sample displayed a 24% reduction, while at 500 °C, it showed a 27% reduction compared to PN. SEM observations indicated abrasion as the primary wear mechanism across all samples. The overall results indicated a significant similarity in the nitrogen depth profile, hardness depth, and wear performance between the SSP-PN sample at 450 °C and the PN sample at 500 °C. The fact suggested a potential reduction of approximately 50 °C in the typical plasma nitriding temperature for 31CrMoV9 steel as a result of the SSP process.

Machine learning for efficient grazing-exit x-ray absorption near edge structure spectroscopy analysis: Bayesian optimization approach

In materials science, traditional techniques for analyzing layered structures are essential for obtaining information about local structure, electronic properties and chemical states. While valuable, these methods often require high vacuum environments and have limited depth profiling capabilities. The grazing exit x-ray absorption near-edge structure (GE-XANES) technique addresses these limitations by providing depth-resolved insight at ambient conditions, facilitating in situ material analysis without special sample preparation. However, GE-XANES is limited by long data acquisition times, which hinders its practicality for various applications. To overcome this, we have incorporated Bayesian optimization (BO) into the GE-XANES data acquisition process. This innovative approach potentially reduces measurement time by a factor of 50. We have used a standard GE-XANES experiment, which serve as reference, to validate the effectiveness and accuracy of the BO-informed experimental setup. Our results show that this optimized approach maintains data quality while significantly improving efficiency, making GE-XANES more accessible to a wider range of materials science applications.

Combined different luminescence dating approaches on fluvial gravel deposits from the southern upper Rhine graben

In recent years, luminescence dating has witnessed significant advancements to overcome its traditional boundaries. However, methodological challenges persist when dating high-energy fluvial gravel deposits in proglacial settings, because partial bleaching and the scarcity of sand lenses complicate luminescence age estimation through conventional approaches. To address these issues, using rock surfaces of large clasts may overcome the limited availability of sand layers in some deposits and allow clast specific assessment of luminescence signal resetting at the time of deposition through the analyses of bleaching profiles. The Hartheim gravel pit in the southern Upper Rhine Graben of southwest Germany features a sedimentary succession deposited by distal braided river meltwater streams reworked during the late Pleistocene. Different luminescence approaches have been applied to sand lenses, the sandy matrix of gravel deposits and crystalline cobbles. Quartz optically stimulated luminescence (OSL) ages range between ∼19 and 22 ka, which represents the time just after the last glaciation maximum in the region. The OSL ages of the sandy matrix of ∼24–27 ka are in an agreement with the previous estimates, as these are from a stratigraphic lower position. However, post-IR infrared stimulated luminescence (pIRIR) ages of sand layer and sandy matrix both are some 3–6 ka older than the OSL ages, despite being internally very consistent. Luminescence depth profiles show that the signal was deeply reset in some cobbles, whereas in others only the IRSL signal in the surface layer appears to have been reset. The cobble IRSL ages show a relatively large spread, and it remains uncertain, if this is caused by incomplete bleaching or it reflects dosimetric issues. Nevertheless, overall, our results underscore the potential of rock surface luminescence dating to date fluvial deposits from the Upper Rhine Graben and similar settings.

Electrically active defects induced by thermal oxidation and post-oxidation annealing of n-type 4H-SiC

In this work, we have performed a detailed study of the defects created in the bulk of 4H-SiC after thermal oxidation and post oxidation annealing using deep level transient spectroscopy and minority carrier transient spectroscopy (MCTS). The study reveals the formation of several shallow and deep level majority carrier traps in the bandgap. The ON1 (EC−0.85 eV), ON2a (EC−1.05 eV), and ON2b (Ec−1.17 eV) levels are the most dominant and are observed across all the samples (EC denotes the conduction band edge). Three shallow levels Ti(k) (EC−0.17 eV), E0.23 (EC−0.23 eV), and C1/2 (EC−0.36/0.39 eV) are observed in the samples. For most of the majority carrier defects, the highest concentration is observed after an NO anneal at 1300°C. This behavior is sustained in the depth profile measurements where the defect concentration after the NO anneal at 1300°C is significantly higher than for the rest of the samples. The origin of most of the majority carrier defects has been attributed to C interstitial injection from the interface during thermal oxidation and annealing. MCTS measurements reveal two prominent minority carrier traps, labeled O0.17 (EV+0.17 eV) and B (EV+0.28 eV), where the concentration of O0.17 is independent of annealing parameters while the concentration of the B level increases after the NO anneal (EV denotes the valence band edge). Furthermore, the depth profiles of the defects are used to evaluate their diffusion parameters by solving the diffusion equation to fit the experimental profiles. The defect concentrations decay exponentially with depth, which evidences that the defects were created at or near the SiO2–SiC interface and migrate toward the bulk during oxidation and post-oxidation annealing.

Use of Particle Induced X-Ray Emission (PIXE), Particle Induced Gamma–Ray Emission (PIGE), Energy Dispersive X-Ray Analysis (EDXRF) for Detecting Trace Elements in Soil Sample

This review paper provides a comprehensive overview of trace element analysis utilizing ion-atom interaction techniques, focusing on the principles, applications, and recent advancements in the field. Ion- atom interaction techniques, including Particle Induced X- Ray Emission (PIXE), Particle Induced Gamma–Ray Emission (PIGE), Energy Dispersive X-Ray Analysis (EDXRF), Rutherford backscattering spectroscopy (RBS), and ion beam analysis (IBA), offer unique capabilities for trace element analysis with high sensitivity and minimal sample preparation requirements. The paper begins by discussing the fundamental principles underlying ion-atom interaction techniques, such as the interaction of energetic ions with matter and the subsequent detection of emitted X-rays or backscattered particles. It explores the various analytical parameters that influence the sensitivity, resolution, and depth profiling capabilities of these techniques. Furthermore, the review highlights the diverse applications of ion-atom interaction techniques in fields such as environmental monitoring, forensic science, biomedical research, and materials science. It showcases how these techniques have been utilized to address specific analytical challenges, such as the detection of trace contaminants in environmental samples or the characterization of thin films and semiconductor materials.

Effect of Bias Potential on the Interface of a Solid Electrolyte and Electrode during XPS Depth Profiling Analysis.

Depth profiling is an essential method to investigate the physical and chemical properties of a solid electrolyte and electrolyte/electrode interface. In conventional depth profiling, various spectroscopic tools such as X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) are utilized to monitor the chemical states along with ion bombardment to etch a sample. Nevertheless, the ion bombardment during depth profiling results in an inevitable systematic error, i.e., the accumulation of mobile ions at the electrolyte/electrode interface, known as the ion pile-up phenomenon. Here, we propose a novel method using bias potential, the substrate-bias method, to prevent the ion pile-up phenomena during depth profiling of a solid electrolyte. When the positive bias potential is applied on the substrate (electrode), the number of accumulating ions at the electrolyte/electrode interface is significantly reduced. The in-depth XPS analysis with the biased electrode reveals not only the suppression of the ion pile-up phenomena but also the altered chemical states at the interfacial region between the electrolyte and electrode depending on the bias. The proposed substrate-bias method can be a good alternative scheme for an efficient yet precise depth profiling technique for a solid electrolyte.

In-situ Synchrotron x-ray photoelectron spectroscopy study of medium-temperature baking of niobium for SRF application

Abstract In order to determine optimal parameters of vacuum thermal processing of superconducting radiofrequency niobium cavities exhaustive information on the initial chemical state of niobium and its modification upon a vacuum heat treatment is required. In the present work the chemical composition of the niobium surface upon ultra-high vacuum baking at 200–400 °C similar to “medium-temperature baking” and “furnace baking” of cavities is explored in-situ by synchrotron X-ray photoelectron spectroscopy (XPS). Our findings imply that below the critical thickness of the Nb2O5 layer (≈ 1 nm) niobium starts to interact actively with surface impurities, such as carbon and phosphorus. By studying the kinetics of the native oxide reduction, the activation energy and the rate-constant relation have been determined and used for the calculation of the oxygen-concentration depth profiles. It has been established that the controlled diffusion of oxygen is realized at temperatures 200–300 °C, and the native-oxide layer represents an oxygen source, while at 400 °C the pentoxide is completely reduced and the doping level is determined by an ambient oxygen partial pressure. Fluorine (F to Nb atomic ratio is 0.2) after the buffered chemical polishing was found to be incorporated into the surface layer probed by XPS (≈ 4.6 nm), and its concentration increased during the low-temperature baking (F/Nb=0.35 at 230 °C) and depleted at higher temperatures (F/Nb=0.11 at 400 °C). Thus, the influence of fluorine on the performance of mid-T baked, nitrogen-doped and particularly mild-baked (120 °C/48 h) cavities must be considered. The possible role of fluorine in the educed Nb+5 → Nb+4 reaction under the impact of an X-ray beam at room temperature and during the thermal treatment is also discussed. The range of temperature and duration parameters of the thermal treatment at which the niobium surface would not be contaminated with impurities is determined.

Self-assembled layer as an effective way to block copper diffusion into epoxy

The reliability of copper/epoxy bonding is important for power semiconductors. It has been found that copper can diffuse into epoxy and accelerate epoxy decomposition at high temperatures, deteriorating reliability. We proposed a way to inhibit copper diffusion into epoxy by using self-assembled layers. Copper substrates with self-assembled layers on their surface were encapsulated with epoxy and placed at 200 °C for 1000 h. The diffusion of copper into epoxy was evaluated by XPS depth profiling, and the decomposition of epoxy was evaluated by ATR-FTIR. The results showed that self-assembled layers can effectively hinder copper diffusion into epoxy. The possible reason is that the existence of the self-assembled layer greatly reduces the formation of copper ions. Also, we found that the self-assembled layer survived the heating, implying its potential for practical power module applications.

Investigation of the X‐ray fluorescence technique in the characterization of Ni coatings applied to historical heritage studies

AbstractHistorical heritage pieces allow a better comprehension of the characteristics of different civilizations over time. The characterization of such pieces is of paramount importance for their preservation. Energy‐dispersive X‐ray fluorescence (EDXRF) is recommended for this application, mostly because it is non‐destructive and the equipment is portable. However, one of its limitations is the difficulty in separating the signal from the substrate and the coating of multilayered samples, as it does not provide depth resolution. This project investigates the application of EDXRF in the characterization of metallic coatings, in the context of historical heritage. The elemental concentration of electrodeposited Ni coatings onto carbon steel substrates was obtained from EDXRF analyses. The relationship between the layer thickness and the variation of the Kα/Kβ intensity ratio of nickel peaks was exploited and the thicknesses of the coatings were estimated through EDXRF measurements. For comparison, particle‐induced x‐ray emission spectroscopy and scanning electron microscopy of the cross‐section were employed, providing a depth profile of the coatings. The estimated thicknesses from EDXRF analysis were comparable to those observed in the microscopy images for thinner films (up to 8 μm). On the other hand, for thicker films, the thicknesses were underestimated, due to the technique's depth limit and matrix effects, as secondary absorption. Despite these limitations, EDXRF remains valuable for evaluating cultural heritage pieces, often providing sufficient information to address authenticity concerns or to guide restoration processes. A case study was also performed to apply the methodology discussed on historical metallic pieces.

On the short-term response of entrained air bubbles in the upper ocean: a case study in the north Adriatic Sea

Abstract. Air bubbles in the upper ocean are generated mainly by waves breaking at the air–sea interface. As such, after the waves break, entrained air bubbles evolve in the form of plumes in the turbulent flow, exchange gas with the surrounding water, and may eventually rise to the surface. To shed light on the short-term response of entrained bubbles in different stormy conditions and to assess the link between bubble plume penetration depth, mechanical and thermal forcings, and the air–sea transfer velocity of CO2, a field experiment was conducted from an oceanographic research tower in the north Adriatic Sea. Air bubble plumes were observed using high-resolution echosounder data from an upward-looking 1000 kHz sonar. The backscatter signal strength was sampled at a high resolution, 0.5 s in time and 2.5 cm along the vertical direction. Time series profiles of the bubble plume depth were established using a variable threshold procedure applied to the backscatter strength. The data show the occurrence of bubbles organized into vertical plume-like structures, drawn downwards by wave-generated turbulence and other near-surface circulations, and reaching the seabed at 17 m depth under strong forcing. We verify that bubble plumes adapt rapidly to wind and wave conditions and have depths that scale approximately linearly with wind speed. Scaling with the wind–wave Reynolds number is also proposed to account for the sea-state severity in the plume depth prediction. Results show a correlation between measured bubble depths and theoretical air–sea CO2 transfer velocity parametrized with wind-only and wind/wave formulations. Further, our measurements corroborate previous results suggesting that the sinking of newly formed cold-water masses helps bring bubbles to greater depths than those reached in stable conditions for the water column. The temperature difference between air and sea seems sufficient for describing this intensification at the leading order of magnitude. The results presented in this study are relevant for air–sea interaction studies and pave the way for progress in CO2 gas exchange formulations.