Surface Depth Profiling Research Articles

Characterizing the marine iodine cycle and its relationship to ocean deoxygenation in an Earth system model

Abstract. Iodine (I) abundance in marine carbonates (measured as an elemental ratio with calcium, I / Ca) is of broad interest as a proxy for local/regional ocean redox. This connection arises because the speciation of iodine in seawater, the balance between iodate (IO3-) and iodide (I−), is sensitive to the prevalence of oxic vs. anoxic conditions. However, although I / Ca ratios are increasingly commonly being measured in ancient carbonate samples, a fully quantitative interpretation of this proxy requires the availability of a mechanistic interpretative framework for the marine iodine cycle that can account for the extent and intensity of ocean deoxygenation in the past. Here we present and evaluate a representation of marine iodine cycling embedded in an Earth system model (“cGENIE”) against both modern and paleo-observations. In this framework, we account for IO3- uptake and release of I− through the biological pump, the reduction in ambient IO3- to I− in the water column, and the re-oxidation of I− to IO3-. We develop and test a variety of different plausible mechanisms for iodine reduction and oxidation transformation and contrast model projections against an updated compilation of observed dissolved IO3- and I− concentrations in the present-day ocean. By optimizing the parameters controlling previously proposed mechanisms involved in marine iodine cycling, we find that we can obtain broad matches to observed iodine speciation gradients in zonal surface distribution, depth profiles, and oxygen-deficient zones (ODZs). However, we also identify alternative, equally well performing mechanisms which assume a more explicit mechanistic link between iodine transformation and environment – an ambiguity that highlights the need for more process-based studies on modern marine iodine cycling. Finally, to help distinguish between competing representations of the marine iodine cycle and because our ultimate motivation is to further our ability to reconstruct ocean oxygenation in the geological past, we conducted “plausibility tests” of different model schemes against available I / Ca measurements made on Cretaceous carbonates – a time of substantially depleted ocean oxygen availability compared to modern and hence a strong test of our model. Overall, the simultaneous broad match we can achieve between modeled iodine speciation and modern observations, and between forward proxy modeled I / Ca and geological elemental ratios, supports the application of our Earth system modeling in simulating the marine iodine cycle to help interpret and constrain the redox evolution of past oceans.

Enhancing Counterfeit Banknote Analysis: Case Studies Using TOF-SIMS

Counterfeiting banknotes poses a significant threat to economies worldwide, particularly in developing countries where cash transactions remain predominant. Despite advancements in security features, counterfeiters continue to adapt, necessitating more sophisticated analysis methods. Time of flight Secondary Ion Mass Spectrometry (TOF-SIMS) offers a powerful approach to surface chemical imaging and depth profiling of counterfeit currencies. Real cases of five different counterfeit Lebanese banknotes are studied, using TOF-SIMS to address specific questions regarding the composition and placement of replicated security features, gaining insights into counterfeit banknote production and the raw materials used. The findings provide essential information to decision-makers at the national bank, supporting the design of future currencies through the selection of security features best suited to the local market, thereby enhancing protection against financial fraud..

Surface composition and depth profile analysis of sulphate and chloride-based trivalent chromium electrodeposits using X-ray photoelectron spectroscopy

ABSTRACT This study investigated the colour and corrosion resistance of a commercial sulphate-based versus a chloride-based trivalent chromium electrodeposit, as well as the effects of post-treatment in a hexavalent chromium passivate solution. Surface composition and depth profiles were analysed using X-ray Photoelectron Spectroscopy (XPS). The factors influencing the appearance and corrosion performance in a Russian Mud Test are discussed.

Study of surface structure and interfacial effects on optical and magnetic properties of un-doped and Si-doped hematite films

Thermal evaporation technique has been used to synthesize the α-Fe2O3 (hematite) and Si-doped hematite films on three different substrates (SiO2/Si, Al2O3 and quartz). The post-deposition heat treatment at 800 °C has further improved the crystalline nature of the films. Rutherford backscattering spectroscopy has provided information for surface elemental composition and depth profile. Raman spectra have supported the formation of rhombohedral phase and inter-layer diffusion between substrate and films. The x-ray photoelectron spectroscopy has confirmed the mixed-valence oxidation states for Fe ions and +4 state for the Si ions in Si-doped hematite films. The optical reflectance spectra in the UV–Visible region indicated contributions from the films and film-substrate interface. The Si-doping has enhanced soft ferromagnetic properties in the hematite film with noticeable decrease of the magnetic coercivity and increase of the magnetic moment. The films showed blocking of magnetization at lower temperatures, typically below 125 K, and a wide thermomagnetic irreversibility between zero-field cooled and field cooled magnetization curves. The modified surface chemical structure, ferromagnetism and optical properties in the Si doped hematite films promise their potential applications in spintronics.

Nanostructuring, fractal characterization and wettability of ion irradiated Au thin films and their thickness effect

This study proposes a method for modifying the wettability of Au thin films of thicknesses 5 nm and 10 nm on Si substrates using 8 keV Ne ion beam irradiation at different fluences, thereby enabling surface wettability adjustment at the nano-scale and its thickness dependence. This advancement would be highly beneficial for applications such as high-resolution printing and nano-biotechnology. The contact angle of the irradiated region for the 5 nm thin film changed from hydrophobic to hydrophilic with increasing ion dosage, whereas for the 10 nm thin film, it changed from hydrophilic to hydrophobic under the same conditions. Fractal analysis was performed on pristine and ion beam modified surfaces to investigate the underlying nano-structuring process, with reported values for average roughness (Ra), Hurst exponent (H), fractal dimension (Df), contact angle (CA), and wettability at different ion dosages. Atomic Force Microscopy and Rutherford Backscattering Spectroscopy were used to examine surface roughness and depth profile. The process of sputtering becomes crucial when the ion range approaches the thickness of thin films, with the sputter yield showing dependence on the thickness of thin films at different ion fluence levels. Monte Carlo simulations SRIM/TRIM and TRIDYN were used for comparison with the experimental results, with TRIDYN taking into account dynamic changes in the target's morphology and composition.

Quantitative aspects of ToF-SIMS analysis of metals and alloys in a UHV, O2 and H2 atmosphere

Although secondary ion mass spectrometry (SIMS) is a versatile method used in the fields of surface analysis, depth profiling and elemental and molecular mapping, it also lacks quantification capabilities. The main reason for this is the matrix effect, which influences the ionization yield of secondary ions with respect to the substrate from which the analyzed compounds originate. There are several approaches to reduce the matrix effect, and gas flooding is one of the easiest methods to apply. In this work, we have investigated the possibilities of the ToF-SIMS method for the quantification of selected metals and alloys containing these metals in different ratios by reducing the matrix effect in the presence of different atmospheres. The measurements were performed in the ultra-high vacuum (UHV) environment, H2 and O2 atmospheres. H2 flooding shows the most significant improvements compared to the UHV analysis, while O2 is also promising but has some limitations. Improvements are most evident for the transition metals Ti, Cr, Fe, Co and Ni employed in our study, while the p-block elements such as Al and Si do not change so extensively. The deviations from the true atomic ratios of selected transition metals in different alloys reach a maximum of only 46 % when analyzed in the H2 atmosphere. In contrast, these values are 66 and 228 % for the O2 atmosphere and UHV environment, respectively. Our results suggest that gas adsorption and consequent formation of a new matrix on the surface, especially in the case of hydrogen, reduces the differences between the different chemical environments and electronic structures of the surface. In this way, the quantitative aspects of the SIMS method can be improved.

Modification of AgNP-Decorated PET: A Promising Strategy for Preparation of AgNP-Filled Nuclear Pores in Polymer Membranes.

Polymer-based membranes represent an irreplaceable group of materials that can be applied in a wide range of key industrial areas, from packaging to high-end technologies. Increased selectivity to transport properties or the possibility of controlling membrane permeability by external stimuli represents a key issue in current material research. In this work, we present an unconventional approach with the introduction of silver nanoparticles (AgNPs) into membrane pores, by immobilising them onto the surface of polyethyleneterephthalate (PET) foil with subsequent physical modification by means of laser and plasma radiation prior to membrane preparation. Our results showed that the surface characteristics of AgNP-decorated PET (surface morphology, AgNP content, and depth profile) affected the distribution and concentration of AgNPs in subsequent ion-track membranes. We believe that the presented approach affecting the redistribution of AgNPs in the polymer volume may open up new possibilities for the preparation of metal nanoparticle-filled polymeric membranes. The presence of AgNPs on the pore walls can facilitate the grafting of stimuli-responsive molecules onto these active sites and may contribute to the development of intelligent membranes with controllable transport properties.

Reconciliation of total particulate organic carbon and nitrogen measurements determined using contrasting methods in the North Pacific Ocean as part of the NASA EXPORTS field campaign

Measurements of particulate organic carbon (POC) are critical for understanding the ocean carbon cycle, including biogenic particle formation and removal processes, and for constraining models of carbon cycling at local, regional, and global scales. Despite the importance and ubiquity of POC measurements, discrepancies in methods across platforms and users, necessary to accommodate a multitude of needs and logistical constraints, commonly result in disparate results. Considerations of filter type and pore size, sample volume, collection method, and contamination sources underscore the potential for dissimilar measurements of the same variable assessed using similar and different approaches. During the NASA EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) 2018 field campaign in the North Pacific Ocean, multiple methodologies and sampling approaches for determining POC were applied, including surface inline flow-through systems and depth profiles using Niskin bottles, in situ pumps, and Marine Snow Catchers. A comparison of results from each approach and platform often resulted in significant differences. Supporting measurements, however, provided the means to normalize results across datasets. Using knowledge of contrasting protocols and synchronous or near-synchronous measurements of associated environmental variables, we were able to reconcile dataset differences to account for undersampling of some particle types and sizes, possible sample contamination and blank corrections. These efforts resulted in measurement agreement between initially contrasting datasets and insights on long-acknowledged but rarely resolved discrepancies among contrasting methods for assessing POC concentrations in the ocean.

Fundamentals of thin film depth profiling by glow discharge optical emission spectroscopy

Glow discharge optical emission spectroscopy (GDOES) is a useful technique for qualitative plasma characterization. It also enables depth profiling of solid materials upon exposure of samples to energetic positively charged ions from gaseous plasma, providing specifics of both surface- and gas-phase collision phenomena that are considered. The early stages of developing GDOES useful for the determination of surface composition and depth profiling of solid materials are reviewed and analyzed, stressing the contribution of early authors. The advantages as well as drawbacks of the GDOES technique are presented and discussed. The recent applications of this technique for depth profiling of various materials are presented, and the directions for constructing a laboratory-scale device are provided.

LIBS characterization of the Frascati Tokamak Upgrade (FTU) limiter tiles after the experimental campaign with fusion plasma

In this work we present the results of the LIBS surface mapping and depth profiling of the Frascati Tokamak Upgrade (FTU) tiles of the poloidal limiter, made of a Molybdenum alloy (TZM) and removed from the reactor after its last experimental campaign with fusion plasma (late 2019). The measurements were performed by using a spectrometer array that covers the range 200–780 nm and a high-resolution spectrometer (0.1 Å at 500 nm) covering a spectral window of 10 nm. By applying a depth profiling procedure, the contamination of the tiles by B, Ca, Cr, Fe, K, Li, Mn, Mo, Ni, Ti was observed in their surface layers. Contamination with H, O, N was instead observed in deeper layers after some laser shots. B was attributed by the preliminary boronization procedure of the first wall (FW), carried out with deuterated diborane (D2B6), although D was not detected on the surface. Li was detected as deposited layer coming from previous experiments with liquid metals limiters in FTU. Ca and K are believed to come from the manipulation of the tiles after FTU decommissioning or as residual impurities of the deposited together with Li. H, O and N, from exposure of the tiles to the environmental gases, Mo and Ti were detected as main constituents of the tiles but also as eroded material during exposure to fusion plasma. Cr, Fe, Mn and Ni as eroded materials from the vacuum vessel (VV). In all cases, the surface concentration and thickness of the contaminated layer strongly varies across the TZM tile, showing a tendency of major impurity accumulations in areas more distant from the reactor's equatorial section.

Corrosion behavior of a compositionally complex alloy utilizing simultaneous Al, Cr, and Ti passivation

The corrosion behavior of the Al0.3Cr0.5Fe2Mn0.25Mo0.15Ni1.5Ti0.3 compositionally complex dual-phase alloy was explored in a variety of electrolytes. Comparable corrosion resistance to 316L stainless steel and Ni-Cr binaries was observed in NaCl despite lower Cr concentrations. Individual elemental fates during corrosion were identified by combinations of in-situ atomic emission spectroelectrochemistry and ex-situ X-ray photoelectron spectroscopy with high-resolution surface analysis and depth profiling. A potentiostatically grown passive film was enriched in Al(III), Cr(III), Ti(IV), and Mo(VI). Al-Ti and Cr-Ti layers were suggested but significant Al, Cr, and Ti mixing was present. Proposed benefits of Al-Cr-Ti coexistence are addressed.

Chronology, duration, and periodicity of linear enamel hypoplasia at the late Iron Age site Non Ban Jak, Thailand: A quantitative microscopic analysis

We provide the first application of a quantitative microscopic approach that does not rely on the presence of perikymata for the identification and comprehensive analysis of linear enamel hypoplasia (LEH) to a large archaeological sample from Southeast Asia. Additionally, we introduce MicroPolySharp, a new computer program that automates the assessment of these stress episodes, and we present new dental crown width/height ratios for the region.Enamel surface depth profiles were measured from epoxy dental replicas generated from 48 individuals using a confocal microscope. The identification and analysis of LEH episodes was undertaken using MicroPolySharp, which combines three recently published methods specifically suited to worn archaeological samples. Ten parameters were examined: frequency, prevalence, episode duration, stress duration, recovery duration, age at first onset, age at last onset, total growth disruption, proportion of available enamel affected, and periodicity.Results revealed a high prevalence of LEH: 97.92 % (47/48) individuals affected. LEH frequency averaged 2.5 episodes per individual (range = 1 to 4 episodes). The chronology of episodes averaged 3.66 years (range = 1.4 to 5.5 years). The age of earliest episode occurrence averaged 3.1 years (range = 1.4 to 4.2 years). While the age of last episode averaged 4.3 years (range = 2.9 to 5.5 years). Duration of growth disruptions (stress + recovery) averaged 103 days (range = 27 to 269 days). Consistent with other studies, the average duration of the stress portion of episodes was 56 days (range = 9 days to 6.4 months) while the duration of the recovery portion averaged 47 days (range = 8 days to 5 months). The total amount of growth disruption for individuals averaged 263 days (range = 87 to 543 days). The proportion of available crown height affected by growth disruption averaged 21 % (range = 6 % to 42 %), while LEH periodicity for the sample averaged 8.6 months (range = 2.4–23 months). Stress and recovery durations, along with age at first episode, were the most sensitive and useful parameters for discerning differences between the subgroups of interest. Finally, the effects of any amount of variable crown height wear within the study group was found to have a significant confounding effect on all aspects of LEH results and interpretation if not properly controlled. Given the high prevalence, all individuals were, for the most part, equally affected. Future analysis of samples from the periods prior to and leading up to the Late Iron Age from nearby sites will be required to provide much needed context to the high levels of systemic stress observed at Non Ban Jak.

Hard x-ray angle-resolved photoemission from a buried high-mobility electron system

Novel two-dimensional electron systems at the interfaces and surfaces of transition-metal oxides recently have attracted much attention as they display tunable, intriguing properties that can be exploited in future electronic devices. Here we show that a high-mobility quasi-two-dimensional electron system with strong spin-orbit coupling can be induced at the surface of a KTaO$_3$ (001) crystal by pulsed laser deposition of a disordered LaAlO$_3$ film. The momentum-resolved electronic structure of the buried electron system is mapped out by hard x-ray angle-resolved photoelectron spectroscopy. From a comparison to calculations it is found that the band structure deviates from that of electron-doped bulk KTaO$_3$ due to the confinement to the interface. Nevertheless, the Fermi surface appears to be clearly three-dimensional. From the $k$ broadening of the Fermi surface and core-level depth profiling we estimate the extension of the electron system to be at least 1 nm but not much larger than 2 nm, respectively.

XPS investigation of 5N purity Al thin foils for MEMS devices

Thin Al foils are promising materials for applications in devices of microelectromechanical systems (MEMS). In this work, three foils of high purity (5N) Al with different thickness (10, 50, and 125 μm) were analyzed by means of X‐ray photoelectron spectroscopy (XPS), before and after annealing (720 K for 30 min). XPS surface analysis and depth profiling of chemical composition were performed to investigate the distribution of Al oxide. Electron energy loss spectroscopy (EELS) measurements were also carried out in order to identify the plasmon losses and chemical state of Al. The loss peaks in the 5N‐Al thin foils were compared with those of an Al foil of commercial purity (99.95 wt%). The thickness of the oxide layer on the sample surface of all the samples is not constant and oxide is thicker in the samples of high purity than in those of commercial quality. Moreover, the thinnest foils of 5N‐Al (10 μm) exhibit the thinnest oxide layer. These findings have been discussed by considering the size effect, that is, mechanical properties of thin foils are improving as the thickness decreases. The complex morphology of the metal‐oxide interface may contribute to enhance the mechanical performances of Al foils with a thickness below ~50 μm, because the free dislocations pile up against the interface which represents an obstacle for their motion hindering plastic deformation. Obtained results suggest that Al foils to be used in MEMS devices should be of high purity and annealed to get a surface completely covered by the oxide layer.

Effects of mineral surface silanization and bitumen coating on its filtration from an aqueous slurry

The effects of residual bitumen on oil sands tailings filtration have rarely been examined. In the present work, the filtration of bitumen-coated minerals, including quartz, rutile, kaolinite, and montmorillonite, was studied. Bitumen-coated quartz was compared with silanized quartz to decouple the effects of surface hydrophobicity and adsorbed bitumen layer on filtration. The minerals were treated in bitumen-toluene solutions with different bitumen concentrations. The treated minerals were subjected to vaccum filtration and their wettability was measured by sessile drop contact angle method. It was found that the filtration rate of silanized quartz was linearly correlated with contact angle. It was also observed that at low bitumen concentration, the contact angle and filtration rate of all tested minerals were increased. However, at high bitumen concentration, the filtration rates were reduced drastically despite the high contact angle. CHNS elemental analyses, and X-ray photoelectron spectroscopy surface composition and depth profile analyses showed that the minerals had higher C, N, S contents and thicker bitumen layer when they were treated at higher bitumen concentration. It was hypothesized that under the pressure gradient during filtration, the thick and patchy bitumen coating layers could inter-penetrate when the mineral particles were pushed together, to form a inter-locked film to close off the pores in the filter cake. Indeed, mineral-bitumen aggregates were observed by X-ray microscope/nanoCT imaging of the filter cake. It was concluded that a thin layer of bitumen coating helped filtration due to the induced hydrophobicity, but a thick (and patchy) bitumen coating impeded filtration.

Quantum microscopy based on Hong–Ou–Mandel interference

Hong-Ou-Mandel (HOM) interference, the bunching of indistinguishable photons at a beam splitter, is a staple of quantum optics and lies at the heart of many quantum sensing approaches and recent optical quantum computers. Here, we report a full-field, scan-free, quantum imaging technique that exploits HOM interference to reconstruct the surface depth profile of transparent samples. We demonstrate the ability to retrieve images with micrometre-scale depth features with a photon flux as small as 7 photon pairs per frame. Using a single photon avalanche diode camera we measure both the bunched and anti-bunched photon-pair distributions at the HOM interferometer output which are combined to provide a lower-noise image of the sample. This approach demonstrates the possibility of HOM microscopy as a tool for label-free imaging of transparent samples in the very low photon regime.

Hydrogeology of alpine lakes in the Northern Calcareous Alps: a comparative study on the role of groundwater in Filblingsee and Eibensee

Abstract In the Northern Calcareous Alps (NCA) there are countless small lakes with small orographic catchments that are often located only slightly below the respective summit regions. On the one hand, the lakes are located in karstable aquifers and their existence is likely to be related to karstification. Then, they are expected to be directly connected to the karst water body. These lakes are classified as karst lakes. On the other hand, the alpine environment is also influenced by glacial processes and lakes might be related to glacial erosion and deposition. For these glacial lakes, the share of groundwater inflow and outflow is regarded as subordinate even within high permeable karst lithologies. Here we compare two alpine lakes of potentially different origin in the NCA in Salzburg with the aim to provide a basis for an aerial survey of the numerous small alpine lakes in the NCA region and their characterization using the guiding parameters elaborated here. We consider (a) the lake geometry, (b) potential inflow and outflow systems, and (c) physicochemical parameters and hydrochemistry of the Filblingsee and the Eibensee, both located in the Fuschlsee region. Filblingsee was initially considered as a typical karst lake and Eibensee as a moraine-dammed glacial lake. Some clear differences arise in lake geometry, which in the karst lake shows a nearly round surface and concentric depth profile, while the glacial lake is elongated in the direction of glacier flow and has the deepest areas just upstream of the moraine dam. Both lakes show very little to no surficial inflow. Inflow and outflow occur in groundwater in both cases but are not directly tied to a highly permeable karst system. The depth profiles of the field parameters of the two lakes differ only slightly and show a dominant groundwater inflow in mid-depth regions but no flow through at the lake bottom. Water chemistry in both lakes and their potential outflows correspond to the respective aquifer in terms of solution load. Filblingsee can be characterized as a hanging lake in a secondarily sealed doline, Eibensee lies in a glacially excavated depression sealed by glacial sediments. While the inflow and outflow conditions and the hydrochemistry of both lakes are very similar, the lake geometry is a clear distinguishing feature that can be attributed to the different genesis of the two lakes. This can therefore be used as a guiding parameter for the classification of the numerous small alpine lakes in the NCA.

Polymer Derived Ceramics based on SiAlOC glasses as novel protective coatings for ferritic steel

In this work, the potential of using Polymer Derived Ceramics based on SiAlOC glasses in the form of protective thin layers was demonstrated on Ferritic Stainless Steel (FSS) Crofer 22APU steel, an alloy often used for intermediate- and low-temperature Solid Oxide Fuel Cells (SOFC’s) interconnects. Microstructural features were investigated by the detailed analysis combining Electron Probe Micro Analysis (EPMA) and Raman Confocal imaging (surface imaging and depth profiling), which revealed the formation of Si-O-Cr bridges, believed to play a crucial role to slow down oxidation of the steel. Additionally, the positive role of aluminum introduced into the SiOC system, which enhances the suppression of the degradation by transport processes. The most crucial value of such findings is the formation of a flexible coating material (SiAlOC glasses) that may be applied on a wide range of FSSs increasing their heat resistance. The application of the combination of methods to determine both chemical (EPMA) and phase (Raman) composition of a multi-layered complex system is also demonstrated.

Development of an optical measurement system for surface depth measurements and study of focus effect on determination of steel inclusion content by EN-10247

Surface inspections are important in steelmaking processes to characterize the final product’s quality. We present a method to measure surface depth profile using laser scattering geometry. This technique is used to analyze the focus effect on microscopic analyses of steel inclusions using the EN-10247 standard. The results presented herein offer promising new perspectives for the metal manufacturing industry through cost-effective solutions that attain quasi in-line process inspection capabilities.

Using a Chloride-Free Magnesium Battery Electrolyte to Form a Robust Anode-Electrolyte Nanointerface.

Magnesium bis(hexamethyldisilazide) (Mg(HMDS)2)-based electrolytes are compelling candidates for rechargeable magnesium batteries due to their high compatibility with magnesium metal anode. However, the usual combination of Mg(HMDS)2 with chloride salts limits their practical application due to severe corrosion of cell components and low anodic stability. Herein, we report for the first time, a chloride-free Mg(HMDS)2-based electrolyte in 1,2-dimethoxyethane. By chemically controlling the moisture content using tetrabutylammonium borohydride as a moisture scavenger, the electrolyte demonstrates outstanding electrochemical performance in magnesium plating/stripping, with an average Coulombic efficiency of 98.3% over 150 cycles, and is noncorrosive to cell components. Surface analysis and depth profiling of the magnesium metal anode reveals the formation of a robust solid electrolyte interphase at the anode-electrolyte nanointerface, which allows magnesium plating/stripping to occur reversibly. The electrolyte also demonstrates good compatibility with a copper sulfide nanomaterial cathode, which exhibits a high initial discharge capacity of 261.5 mAh g-1.