Secondary Ion Mass Spectrometry Analysis Research Articles

Growth of phosphorus-doped ZnTe thin films by molecular beam epitaxy using InP as the dopant source

P-doped ZnTe thin films were grown by MBE on ZnTe (100) substrates using InP as the P source under various InP fluxes. Secondary ion mass spectroscopy (SIMS) analyses showed that the P concentration in ZnTe thin films increased with increasing InP flux, although In atoms were also incorporated in the films. To suppress In incorporation, the outlet of the InP cell was modified by mounting a cap and a plate with small holes. As a result, In incorporation was significantly suppressed, resulting in an In concentration three orders of magnitude lower, as confirmed by SIMS, although the P concentration also decreased by almost one order of magnitude compared with the case without a cap. An acceptor-bound exciton (Ia) peak was observed at around 2.36 eV in the P-doped ZnTe thin film grown with a cap, and the Ia intensity increased after annealing, indicating the activation of P acceptors.

Back to the basics of time-of-flight secondary ion mass spectrometry data analysis of bio-related samples. II. Data processing and display.

This is the second half of a two-part Tutorial on the basics of the time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of bio-related samples. Part I of this Tutorial series covers planning for a ToF-SIMS experiment, preparing and shipping samples, and collecting ToF-SIMS data. This Tutorial aims at helping the ToF-SIMS user to process, display, and interpret ToF-SIMS data. ToF-SIMS provides detailed chemical information about surfaces but comes with a steep learning. The purpose of this Tutorial is to provide the reader with a solid foundation in the ToF-SIMS data analysis.

Compositional changes by SIMS and XPS analyses on fresh and aged Roman-like glass

This study reports important analytical evidence of an unusual non-uniform element distribution in the superficial layers of glass matrices (from few nm up to 1 µm). The unforeseen observation was made on silica-soda-lime glass mock-ups before and after their artificial ageing, using secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS) surface analysis techniques. The analyses showed a marked non-homogeneous element distribution at the glass surface. The results indicated a very low concentration of Na at the surface up to a depth of around 500 nm below the surface, where its concentration increases reaching a plateau. In addition, the profile distribution of H in the first 200 nm of the pristine glass surface indicated a diffusion of hydrogen from the surrounding environment to the glass network. Additional modifications during the glass ageing process related to external factors (such as temperature and humidity) were also identified in relation to sodium atoms, with atoms on the glass surface showing a different chemical state from those in the bulk. This study confirms that glass composition as well as glass alteration are non-homogeneous locally supporting the importance of studying glass surface as region of interaction with surrounding environment.

Contribution of ammonia in xanthates adsorption onto copper oxide mineral surface in high-alkaline solution

Ammonia is a useful modifier for enhancing surface sulfurization in copper oxide ore flotation using xanthate as a collector. However, its potential role in the reaction of sulfhydryl collector with sulfurized copper oxide mineral in a complex pulp has been neglected. This work investigates the contribution of ammonia to xanthate adsorption on the sulfurized malachite surface, independent of its effect on sulfurization. Zeta potential measurements indicate that NH3·H2O increases the surface potential of malachite and enhances the proximity of xanthate to the malachite surface in a strong-alkaline solution. Adsorption tests and time-of-flight secondary ion mass spectrometry analysis demonstrate that NH3·H2O can increase the xanthate adsorption density. Spectroscopic analysis reveals copper(I) xanthate and dixanthogen as the primary xanthate products, with their quantities increasing upon NH3·H2O treatment. Thermodynamic analysis of the reaction of malachite, HS−, and xanthate to form copper(I) xanthate and dixanthogen shows that NH3·H2O treatment enhances the stability of the reaction compared to its absence. Thus, NH3·H2O treatment increased the recovery of sulfurized malachite by over 10%. This study offers a comprehensive understanding of ammonia modification for enhancing sulfurization–xanthate flotation of copper oxide minerals and provides a scientific basis for developing high-efficiency collectors.

Characterization of GaN structures for power electronics by secondary ion mass spectrometry and atomic force microscope approach

This scientific paper describes the chemical study of different Al2O3/GaN interfaces found in the new generation of high electron mobility transistors developed for power electronics applications. The stake for these interfaces is the limitation, ideally the absence of an oxidized gallium layer hampering the good electrical behavior of the semiconductor. These structures have been studied through time-of-flight secondary ion mass spectrometry (ToF-SIMS), magnetic SIMS (M-SIMS), and atomic force microscopy (AFM) analyses. Two structures were considered: a bilayer Al2O3 10 nm–GaOx 2 nm on GaN and a Al2O3 10 nm single layer deposited on preliminary etched GaN. The first sample was used as a dedicated reference sample where an actual gallium oxide layer was grown, whereas the second one was a technologically relevant structure. Several experimental conditions were compared for the ToF- and M-SIMS analyses; in particular, three angles of incidence for the primary Cs+ sputter beam (65°, 61°, 45°) were used, leading to diverse depth resolutions and roughnesses, as revealed by surface topography analysis provided by AFM. Among the different incidence angles, it was found that the best experimental conditions were those obtained by ToF-SIMS analysis with an incidence angle of 45°, generating the least roughness.

Developing TSV wet cleaning chemistry for quantum computing application

New 3D-integration routes for superconducting Josephson junction qubits include the development of an interposer die with through‑silicon vias (TSV) for vertical and compact interconnections. Since fluoropolymer dielectric residues remaining in the vias may be detrimental for subsequent processes or qubit functionality, they must be removed without damaging the structure or other materials. Therefore, we developed a new O2 plasma-free, selective and non-toxic wet cleaning solution that can remove both the fluoropolymer from the vias and the photoresist used for TSV patterning from the surface. Key formulation physico-chemical properties are discussed based on cleaning results obtained by scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS). Also discussed is evidence of the dissolution and removal of fluoropolymer formed during Bosch etching. Finally, SEM and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses confirm complete removal of fluoropolymer residue from the vias. These encouraging results confirm a viable, manufacturable one-step wet cleaning process for TSVs designed for 3D packaging of qubits and other applications.

Oxyanion Engineering Suppressed Iron Segregation in Nickel-Iron Catalysts Toward Stable Water Oxidation.

Nickel-iron catalysts represent an appealing platform for electrocatalytic oxygen evolution reaction (OER) in alkaline media because of their high adjustability in components and activity. However, their long-term stabilities under high current density still remain unsatisfactory due to undesirable Fe segregation. Herein, a nitrate ion (NO3 - ) tailored strategy is developed to mitigate Fe segregation, and thereby improve the OER stability of nickel-iron catalyst. X-ray absorption spectroscopy combined with theoretical calculations indicate that introducing Ni3 (NO3 )2 (OH)4 with stable NO3 - in the lattice is conducive to constructing the stable interface of FeOOH/Ni3 (NO3 )2 (OH)4 via the strong interaction between Fe and incorporated NO3 - . Time of flight secondary ion mass spectrometry and wavelet transformation analysis demonstrate that the NO3 - tailored nickel-iron catalyst greatly alleviates Fe segregation, exhibiting a considerably enhanced long-term stability with a six-fold improvement over FeOOH/Ni(OH)2 without NO3 - modification. This work represents a momentous step toward regulating Fe segregation for stabilizing the catalytic performances of nickel-iron catalysts.

The effects of chemistry variations on hot cracking susceptibility of Haynes® 282® for aerospace applications

Hot cracking susceptibility of Haynes® 282® with varying amount of C (0.05–0.09 wt%), Mn (0.03–0.12 wt%), Si (0.03–0.16), B (0.005–0.006 wt%) and Zr (0–0.01) are investigated. Synergistic role of C and B is found on solidification and heat affected zone (HAZ) liquation cracking susceptibility. High amount of C and B promote formation of eutectic constituents during final stages of solidification and promote crack healing by backfilling effect. When C and B are added in low amount the crack healing does not occur due to the absence of eutectic consituents therefore cracking extent increases. Thermodynamics simulations indicate C and B tie up to MC carbides and M3B2 borides during solidification. Scanning Electron Microscopy and Nanoscale secondary ion mass spectrometry analysis reveal C and B to be present both in solid solution and in form of precipitates to Ti-Mo rich carbides and Mo rich borides, respectively. In HAZ, these phases promote liquation cracking where cracking extent correlates to the amount carbides and borides. Lower C and B is found to reduce the liquation cracking in the HAZ. Furthermore, a high temperature homogenization heat treatment at 1190 °C excarbates the cracking by dissolving the borides and releasing B to the grain boundaries.

Chemolithotrophic biosynthesis of organic carbon associated with volcanic ash in the Mariana Trough, Pacific Ocean

Volcanic ash is a major component of marine sediment, but its effect on the deep-sea carbon cycle remains enigmatic. Here, we analyzed mineralogical compositions and glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in submarine tuffs from the Mariana Trough, demonstrating a fraction of organic carbon associated with volcanic ash is produced in situ. This likely derives from chemolithotrophic communities supported by alteration of volcanic material. Tuff GDGTs are characterized by enrichment of branched GDGTs, as in chemolithotrophic communities. Scanning electron microscope, Raman spectrum and nano secondary ion mass spectrometry analysis demonstrates organic carbon exists around secondary heamatite veins in the altered mafic minerals, linking mineral alteration to chemolithotrophic biosynthesis. We estimate organic carbon production of between 0.7 − 3.7 × 1011 g if all the chemical energy produced by ash alteration was fully utilized by microorganisms. Therefore, the chemolithotrophic ecosystem maintained by ash alteration likely contributes considerably to organic carbon production in the seafloor.

The restriction of calcium influx in metaphase and post-metaphase stages of cell division revealed by imaging secondary ion mass spectrometry (SIMS).

A secondary ion mass spectrometry (SIMS)-based isotopic imaging technique of ion microscopy was used for observing calcium influx in single renal epithelial LLC-PK1 cells. The CAMECA IMS-3f SIMS instrument, used in the study, is capable of producing isotopic images of single cells at 500nm spatial resolution. Due to the high-vacuum requirements of the instrument the cells were prepared cryogenically with a freeze-fracture method and frozen freeze-dried cells were used for SIMS analysis. The influx of calcium was imaged directly by exposure of cells to 44 Ca stable isotope in the extracellular buffer for 10min. The 44 Ca influx was measured at mass 44 and the distribution of endogenous calcium at mass 40 (40 Ca) in the same cell. A direct comparison of interphase cells to cells undergoing division revealed that calcium influx is restricted in metaphase and post-metaphase stages of cell division. This restriction is lifted in late cytokinesis. The net influx of 44 Ca in 10min was approximately half under calcium influx restriction in comparison to interphase cells. Under calcium influx restriction the 44 Ca concentration was the same between the mitotic chromosome and the cytoplasm. These observations indicate that the endoplasmic reticulum (ER) calcium uptake is compromised under calcium influx restriction in cells undergoing division.

Pt‐Promoted In2O3 Reduction and Reconstruction at the Pt/In2O3 Interface in CO2 Hydrogenation Atmosphere

AbstractAs an essential path toward the elucidation of the reaction mechanism, the capture of the catalytically active phase and its evolution has been the primary goal of mechanistic studies. Here, the physicochemical properties on In2O3 (111) and Pt/In2O3 (111) thin film model catalysts were tracked in CO2 hydrogenation atmosphere under various pressures and temperatures by ambient pressure X‐ray photoelectron spectroscopy (APXPS). The redox behaviours of surface Pt and In2O3, the formation and interconversion of reaction intermediates, and the structural dynamics at the topmost surface, as a consequence of the outward diffusion of InOx species, nucleation of surface Pt nanostructures and the formation of PtInOx species, were captured and analyzed. The reconstruction at the Pt/In2O3 (111) interface was also observed by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and scanning electron microscopy (SEM) analysis. In‐situ spectroscopic and structural analysis on a well‐defined metal/metal‐oxide interface offers a powerful means to probe the mechanistic details of the heterogeneous processes.

Three-phase froth stability in hematite flotation using DDA as a collector

The effect of hematite and quartz with different particle sizes on the three-phase froth stability using dodecylamine (DDA) as a collector was investigated, and the mechanism of how quartz improves froth stability was explored. Microflotation experiment, three-phase froth stability experiment, froth morphology photography, pulp viscosity measurement, contact angle measurement, zeta potential measurement, time-of-flight secondary ion mass spectrometry analysis, and molecular dynamics simulation were conducted in this investigation. Results showed that flotation performance and froth stability were obviously different for minerals with different particle sizes. The froth half-life was remarkably higher in the presence of quartz particles compared with hematite particles, forming stickier froth, especially for quartz particle sizes below −18 μm. Fine quartz was found to be a key factor in improving the froth stability in hematite flotation using DDA as a collector. The high pulp viscosity, damping coefficient, and maximum capillary pressure resulting from quartz with low density, small size, and high concentration hindered liquid drainage and reduced the desorption probability of particles from the bubble surface, thereby preventing the coalescence of two adjacent bubbles. DDA was found to be more readily adsorbed on the quartz surface, leading to a higher adsorption capacity, better hydrophobicity, and increased distribution of counter ions at the interface. This condition reinforced the mutual repulsion force between liquid film surfaces and prevented further thinning of the liquid film, ultimately strengthening froth stability.

Molecular identification of wines using in situ liquid SIMS and PCA analysis.

Composition analysis in wine is gaining increasing attention because it can provide information about the wine quality, source, and nutrition. In this work, in situ liquid secondary ion mass spectrometry (SIMS) was applied to 14 representative wines, including six wines manufactured by a manufacturer in Washington State, United States, four Cabernet Sauvignon wines, and four Chardonnay wines from other different manufacturers and locations. In situ liquid SIMS has the unique advantage of simultaneously examining both organic and inorganic compositions from liquid samples. Principal component analysis (PCA) of SIMS spectra showed that red and white wines can be clearly differentiated according to their aromatic and oxygen-contained organic species. Furthermore, the identities of different wines, especially the same variety of wines, can be enforced with a combination of both organic and inorganic species. Meanwhile, in situ liquid SIMS is sample-friendly, so liquid samples can be directly analyzed without any prior sample dilution or separation. Taken together, we demonstrate the great potential of in situ liquid SIMS in applications related to the molecular investigation of various liquid samples in food science.

Preparation of wafer-scale highly conformalamorphous hafnium dioxide thin films by atomic layer deposition using a thermally stable boratabenzene ligand-containing hafnium precursor

In the present study, HfO2 thin films were fabricated via atomic layer deposition (ALD) using a novel heteroleptic metal organic precursor [tris (dimethylamino) dimethylaminoboratabenzene hafnium] [η6:η1-(C5H5BNMe2)Hf(NMe2)3; (BBHf)] along with O2 as the oxygen source at a range of growth temperatures (i.e., 150–350 °C). This novel precursor is a heteroleptic complex synthesized by the introduction of a boratabenzene ligand (BB) into the parent Hf metal sphere to achieve an enhanced thermal stability. In this system, O2 is used as a mild oxygen-containing reactant to replace the typically employed ozone (O3). Distinctive self-limiting deposition was established with a comparatively high growth per cycle value of 0.068 nm, and linear growth was observed as a function of the ALD cycle number. Thermal decomposition was not detected at or below 350 °C, thereby indicating the improved thermal stability compared to when frequently used Cp (cyclopentadienyl)-amide precursors are employed. Under the ALD deposition conditions employed herein (275 °C), a complete step coverage was achieved with a good conformality on high aspect ratio dual trenches [top and bottom widths = 40 and 15 nm, respectively, aspect ratio (AR) ≈ 6.3], and uniformity was obtained on the large planar substrate (15 cm diameter). Upon annealing at 700 °C, the as-grown film formed an amorphous structure with a slightly enhanced crystallinity, while annealing at 850 °C led to the generation of nanocrystalline HfO2 films with amorphous structures, as indicated by X-ray diffraction measurements. The as-grown films were determined to be slightly rich in oxygen compared to the stoichiometry of HfO2, although they also contained significant amounts of residual impurities, such as H, B, and C (∼6, 6, and 7 at.%, respectively), as confirmed by Rutherford backscattering spectrometry and elastic recoil detection analyses. The impurity levels were further reduced by increasing the growth temperature and by subsequent post-annealing, as evidenced by X-ray photoelectron spectroscopy and secondary-ion mass spectrometry analyses. Finally, ellipsometry analysis was performed to measure the optical properties of the prepared ALD-HfO2 thin films. It is expected that the described process may be of significance in the preparation of high-k films wherein thermally stable amorphous films with extremely conformal and uniform coatings are required to fabricate next-generation electronic devices.

Secondary ion mass spectrometry quantification of boron distribution in an array of silicon nanowires

The development of non-planar structures such as arrays of nanowires (NWs), poses a significant challenge for dopant concentration determination. Techniques that can be readily used for 3D structures usually lack the desired sensitivity whereas secondary ion mass spectrometry (SIMS), known for its excellent detection limits, is designed to analyze flat samples. In this work, we overcome the limitation of standard SIMS approaches. NWs are covered with photoresist forming a flat surface. For high incident angle bombardment, the sputtering process becomes self-flattening, i.e. the ions collide with the sidewalls of the exposed tips of NWs at much lower angles and sputter them significantly faster. Thus, reliable information about the dopant distribution along the height of NWs can be obtained. The SIMS analysis can be performed on an array of 1000 x 1000 nanowires with a detection limit of about 5 x 1016 atoms/cm3 and a reasonable signal-to-noise ratio of about 10 dB.

An empirical calibration of the serpentine-water oxygen isotope fractionation at T = 25–100 °C

The ability to precisely constrain the physical–chemical conditions of serpentinization, such as temperature and fluid source, is limited by the accuracy of calibrations for oxygen isotope fractionation between serpentine and water – i.e., 1000 lnα(serpentine-water) – which disagree by up to 20‰ when extrapolated to T < 200 °C. In this study, we present a new empirical calibration of 1000 lnα(serpentine-water) aiming to improve applications of oxygen isotope geochemistry to very low-T serpentinization (T < 100 °C). We used the high-spatial resolution capabilities of Secondary Ion Mass Spectrometry (SIMS) to analyze oxygen isotope ratios in mineral pairs of calcite + serpentine, quartz + serpentine and talc + serpentine co-crystallized at scales ≤ 50 μm in six serpentinite samples from the Samail ophiolite (Oman). SIMS analysis shows that the mineral pairs are relatively homogenous in oxygen isotope ratios with variability in δ18O values ≤2‰ (2 s). Clumped isotope thermometry and petrological constraints indicate crystallization temperatures from 25 to 100 °C for the investigated samples. These independent constraints on temperature allowed us to derive 1000 lnα(serpentine-water) by combining Δ18O(quartz-serpentine), Δ18O(talc-serpentine) and Δ18O(calcite-serpentine) measured by SIMS in the investigated samples with Δ18O(quartz-water), Δ18O(talc-water) and Δ18O(calcite-water) calibrations available in the literature. Our empirical calibration of 1000 lnα(serpentine-water) = 1.04 ± 0.20 (2SE) × 106/T2 (T in K), from T = 25 to 100 °C, is within uncertainty of former high-temperature empirical calibrations extrapolated to T < 100 °C and matches experimental calibrations when extrapolated to T = 250 °C. The new serpentine-water calibration enables more accurate reconstructions of fluid-rock interactions occurring during low-temperature serpentinization processes in various tectonic settings.

Effect of boron carbide reinforcments on the PEO process of B4C/Al matrix composite

Plasma electrolytic oxidation (PEO) is an effective way to improve the thermal control property and service lifetime of the B4C/aluminum matrix composites (B4C/AMC) used in nuclear power field. The evolution process of B4C particles during the growth of PEO film was investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) morphology observation, secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS) chemical composition analysis. The results show that the B4C particles keep intact status but inhibit spark discharge in the initial oxidation stage, and then a few B4C particles are partly oxidized to small size and mixed into the film. After that, plenty of B4C particles are oxidized to B2O3 and solid C which escapes from the film as carbon oxide gas under strong spark discharge. The B4C particles disrupt the continuity of the film due to lack of sparking on their surface at the early stage of oxidation, but the film compactness is improved with decreasing B4C particles in the film under high oxidation voltage.

Enhancing the electron mobility in Si-doped (010) β-Ga2O3 films with low-temperature buffer layers

We demonstrate a new substrate cleaning and buffer growth scheme in β-Ga2O3 epitaxial thin films using metal–organic vapor phase epitaxy (MOVPE). For the channel structure, a low-temperature (LT, 600 °C) un-doped Ga2O3 buffer was grown, followed by a transition layer to a high-temperature (HT, 810 °C) Si-doped Ga2O3 channel layers without growth interruption. The (010) Ga2O3 Fe-doped substrate cleaning uses solvent cleaning, followed by additional hydrofluoric acid (49% in water) treatment for 30 min before the epilayer growth. This step is shown to compensate the parasitic Si channel at the epilayer–substrate interface that originates from the substrate polishing process or contamination from the ambient. From secondary ion mass spectroscopy (SIMS) analysis, the Si peak atomic density at the substrate interface is found to be several times lower than the Fe atomic density in the substrate—indicating full compensation. The elimination of the parasitic electron channel at the epi–substrate interface was also verified by electrical (capacitance–voltage profiling) measurements. In the LT-grown (600 °C) buffer layers, it is seen that the Fe forward decay tail from the substrate is very sharp, with a decay rate of ∼9 nm/dec. X-ray off-axis rocking curve ω-scans show very narrow full width at half maximum (FWHM) values, similar to the as-received substrates. These channels show record high electron mobility in the range of 196–85 cm2/V⋅s in unintentionally doped and Si-doped films in the doping range of 2 × 1016–1 × 1020 cm−3. Si delta-doped channels were also grown utilizing this substrate cleaning and the hybrid LT buffers. Record high electron Hall mobility of 110 cm2/V⋅s was measured for sheet charge density of 9.2 × 1012 cm−2. This substrate cleaning, combined with the LT buffer scheme, shows the potential of designing Si-doped β-Ga2O3 channels with exceptional transport properties for high-performance Ga2O3-based electron devices.

Influence of Lanthanum Precursor on the Activity of Nickel Catalysts in the Mixed-Methane Reforming Process.

This work investigated the influence of the catalytic support precursor on the activity of nickel catalysts 20%Ni/5%La2O3-95%Al2O3 in the mixed methane reforming process. The activity tests were carried out at a temperature of 750 °C. The research showed that the catalyst prepared from the precursor containing chloride exhibited very low conversions of methane and carbon dioxide. The poisoned catalyst system before and after the calcination process was subjected to Temperature Programmed Surface Reaction tests to determine whether the thermal treatment causes a decrease in the amount of chlorine in the system. To determine the decomposition temperature of the LaCl3 precursor and the nickel chloride NiCl2 compound, the samples were analyzed by Thermogravimetry. Finally, the catalytic samples were tested by Time-of-Flight Secondary Ion Mass Spectrometry analysis to confirm the presence of nickel-chlorine bonds on the surface of the catalytic system.

Effect of N doping on the microstructure and dry etch properties of amorphous carbon deposited with a DC sputtering system.

The importance of developing a hardmask with excellent performance, and physical and chemical properties to utilize in long-term etching is spotlighted due to the acceleration of development in high-density semiconductors. To develop such a hardmask, amorphous carbon hardmasks doped with various concentrations of N were fabricated with a DC magnetron sputtering system using varying inert gas (Ar to N2) ratios. In contrast to the expectation that doped nitrogen would block the permeation of fluorine and improve the etch resistance, as the nitrogen concentration increased, the selectivity of the doped amorphous carbon films decreased. To understand this degradation with increasing nitrogen concentration, systematic X-ray photoelectron spectroscopy (XPS), radial distribution function (RDF), and X-ray reflectometry (XRR) analyses were conducted. In this study, we found that as the amount of nitrogen increased, the density of the film decreased, and the amount of pyridinic and pyrrolic nitrogen bonds with low formation energy increased. In contrast, based on time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis of etched nitrogen-doped amorphous carbon films, the penetration depth of fluorine ions from the etchant decreased as the amount of nitrogen increased. Therefore, in order to develop an excellent hardmask using amorphous carbon, it is important to increase the density of the film and the nitrogen concentration in the film while lowering the ratio of pyrrolic N to pyridinic N, i.e., increasing the ratio of graphitic N.