Static Secondary Ion Mass Spectrometry Research Articles

Best practices for performing quantitative TOF-SIMS analyses

Despite its reputation for being nonquantitative, the TOF-SIMS technique is quite capable of providing quantifiable results. Static and near static SIMS measurements are never chaotic (that is subject to large changes due to small variations in the sample), and the instruments can be well controlled to provide highly reproducible results. These results can be replicated by different teams using similar instruments and even reproduced via correlation studies with data from substantially different tools. It is true that absolute concentrations cannot be calculated but must be derived via the use of standards produced by other techniques. Where accuracy (the correctness of the results) is what is needed, this is the approach that must be taken. Furthermore, the results can be nonlinear (especially when the differences in the surfaces being measured are at the atomic percent range and larger, a result of the “matrix effect”) and in these cases, enough standards must be obtained to determine the shape of the function that relates the SIMS results to actual quantities. In most cases, however, relative quantification obtained with sufficient precision (sufficiently narrow distribution of results on identical samples) is most important and key to the ability to evaluate and improve materials and processes. For relative comparisons, TOF-SIMS is usually an excellent analytical method. As with any technique as sophisticated as TOF-SIMS, attention to detail is required to obtain the reproducibility of which the technique is capable. This paper describes many of the details to which an analyst needs to attend to successfully produce repeatable and, therefore, quantifiable results via TOF-SIMS.

Secondary Ion Mass Spectral Imaging of Metals and Alloys.

Secondary Ion Mass Spectrometry (SIMS) is an outstanding technique for Mass Spectral Imaging (MSI) due to its notable advantages, including high sensitivity, selectivity, and high dynamic range. As a result, SIMS has been employed across many domains of science. In this review, we provide an in-depth overview of the fundamental principles underlying SIMS, followed by an account of the recent development of SIMS instruments. The review encompasses various applications of specific SIMS instruments, notably static SIMS with time-of-flight SIMS (ToF-SIMS) as a widely used platform and dynamic SIMS with Nano SIMS and large geometry SIMS as successful instruments. We particularly focus on SIMS utility in microanalysis and imaging of metals and alloys as materials of interest. Additionally, we discuss the challenges in big SIMS data analysis and give examples of machine leaning (ML) and Artificial Intelligence (AI) for effective MSI data analysis. Finally, we recommend the outlook of SIMS development. It is anticipated that in situ and operando SIMS has the potential to significantly enhance the investigation of metals and alloys by enabling real-time examinations of material surfaces and interfaces during dynamic transformations.

Comparison study of mouse brain tissue by using ToF-SIMS within static limits and hybrid SIMS beyond static limits (dynamic mode).

In the study of degenerative brain diseases, changes in lipids, the main component of neurons, are particularly important because they are used as indicators of pathological changes. One method for the sensitive measurement of biomolecules, especially lipids, is time-of-flight secondary ion mass spectrometry (ToF-SIMS) using pulsed argon cluster ions. In this study, biomolecules including various lipids present in normal mouse brain tissue were measured using ToF-SIMS equipped with pulsed argon cluster primary ions. Based on the ToF-SIMS measurement results, hybrid SIMS (OrbiSIMS), which is a ToF-SIMS system with the addition of an orbitrap mass analyzer, was used to directly identify the biomolecules by the region in the real tissue samples. For this, the results of ToF-SIMS, which measured the tissue samples from a single mouse brain within static limits, were compared with those from OrbiSIMS measured beyond the static limits in terms of the differences in molecular profiling. From this analysis, two types of positive and negative ions were selected for identification, with the OrbiSIMS MS/MS results indicating that the positive ions were glycerophosphocholine and the negative ions were glycerophosphoinositol and sulfatide, a sphingolipid. Then, to confirm the identification of the molecular candidates, lipids were extracted from mirror image tissue samples, and LC-MS/MS also using an orbitrap mass analyzer was performed. As a result, the direct identification of molecular candidate groups distributed in particular regions of the tissue samples via OrbiSIMS was found to be consistent with the identification results by LC-MS/MS for extracted samples.

Surface Analysis by Secondary Ion Mass Spectrometry (SIMS): Principles and Applications from Swiss laboratories

Secondary Ion Mass Spectrometry (SIMS) extracts chemical, elemental, or isotopic information about a localized area of a solid target by performing mass spectrometry on secondary ions sputtered from its surface by the impact of a beam of charged particles. This primary beam sputters ionized atoms and small molecules (as well as many neutral particles) from the upper few nanometers of the sample surface. The physical basis of SIMS has been applied to a large range of applications utilizing instruments optimized with different types of mass analyzer, either dynamic SIMS with a double focusing mass spectrometer or static SIMS with a Time of Flight (TOF) analyzer. Here, we present a short review of the principles and major applications of three different SIMS instruments located in Switzerland.

Sputtering, Cluster Primary Ions and Static SIMS

Sputtering using cluster primary ion beams is very important for the future development of static SIMS and the SIMS depth profiling of organic layers. However, different results from different laboratories may be confusing. Analytical models have an important function for enabling the prediction of behaviour for practical analysis. Sigmund's model for sputtering, often used in surface analysis, is helpful and accurate in the linear cascade regime. However, for cluster sputtering this is no longer the case and spike effects need evaluation. Evidence will be presented of the spike model validity for clusters of up to more than 10 atoms over 3 orders of magnitude in sputtering yield. Using data from one primary ion, extremely good descriptions of measurements reported with other primary ions can then be achieved. This theory is then used to evaluate the molecular ion yield behaviour of interest in the static SIMS of organics. This leads to universal dependencies for the de-protonated molecular ion yields, relating all primary ions, both single atom and cluster, which are illustrated by experimental data over 5 decades of emission intensity. This formulation permits the prediction of the (M-H)- secondary ion yield for different, or new, primary ion sources. It is shown how further gains are predicted. For analysing materials, raising the molecular secondary ion yield is extremely helpful but it is the ratio of this yield to the disappearance cross-section (the efficiency) that is critical. The relation of the damage and disappearance cross sections is formulated. Data are evaluated and a description is given to show how these cross sections are related and to provide a further universal relation for the efficiency/yield dependence of all cluster ions.

Evidence for new enantiospecific interaction force in chiral biomolecules

Evidence for new enantiospecific interaction force in chiral biomolecules

Structural Behavior and Spin-State Features of BaAl2O4 Scaled through Tuned Co3+ Doping.

Pure and Co3+-doped BaAl2O4 [Ba(Al1-xCox)2O4, x = 0, 0.0077, 0.0379] powder samples were prepared by a facile hydrothermal route. Elemental analyses by static secondary ion mass spectrometry (SIMS), X-ray absorption spectroscopy (XAS) measurements at the Co K-edge, and X-ray diffraction studies were fully correlated, thus addressing a complete description of the structural complexity of Co3+-doped BaAl2O4 powder. Powder X-ray diffraction (PXRD) patterns indicated that prepared samples were nanocrystalline with a hexagonal P63 symmetry. The X-ray absorption near-edge structure (XANES) measurements revealed the presence of cobalt in a +3 oxidation state, while the rarely documented, tetrahedral symmetry around Co3+ was extracted from the extended X-ray absorption fine structure (EXAFS) oscillation patterns. Rietveld structure refinements showed that Co3+ preferentially substitutes Al3+ at tetrahedral Al3 sites of the BaAl2O4 host lattice, whereas the (Al3)O4 tetrahedra remain rather regular with Co3+-O distances ranging from 1.73(9) to 1.74(9) Å. The underlying magneto-structural features were unraveled through axial and rhombic zero-field splitting (ZFS) terms. The increased substitution of Al3+ by Co3+ at Al3 sites leads to an increase of the axial ZFS terms in Co3+-doped BaAl2O4 powder from 10.8 to 26.3 K, whereas the rhombic ZFS parameters across the series change in the range from 2.7 to 10.4 K, showing a considerable increase of anisotropy together with the values of the anisotropic g-tensor components flowing from 1.7 to 2.5. We defined the line between the Co3+ doping limit and influenced magneto-structural characteristics, thus enabling the design of strategy to control the ZFS terms' contributions to magnetic anisotropy within Co3+-doped BaAl2O4 powder.

Low-frequency plasma activation of nylon 6

In the study reported in this paper, a series of reproducible conditions were employed to uniformly functionalize nylon 6 surfaces using a commercially available, low-frequency (40 kHz), low-pressure plasma system, utilizing oxygen plasma as a reactive gas. Initially, the plasma-treated samples were investigated using static contact angle measurements, showing a progressive increase in wettability with increasing plasma activation time between 10 and 40 s. Such an increase in wettability (and therefore increase in adhesive capabilities of the surfaces) was attributed to the creation of surface C-OH, C=O, and COOH groups. These surface-chemical modifications were characterized using x-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS). Surface radical densities were also shown to increase following plasma activation, having been quantified using a radical scavenging method based on the molecule 2,2-diphenyl-1-picrylhydrazyl (DPPH). The samples were imaged and analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), to confirm that there had been no detectable alteration to the surface roughness or morphology. Additionally, the “hydrophobic recovery” or “ageing” of the activated polymer samples, post-plasma treatment, was also investigated in terms of wettability and surface-chemistry, with the wettability of the sample surfaces decreasing over time due to a reduction in surface-oxygen concentration.

An investigation of the beam damage effect on in situ liquid secondary ion mass spectrometry analysis.

During in situ liquid secondary ion mass spectrometry (SIMS) analysis, the primary ion beam is normally scanned on a very small area to collect signals with high ion doses (1014 to 1016 ions/cm2 ). As a result, beam damage may become a concern when compared with the static limit of SIMS analysis, in which the dose is normally less than 1012 ions/cm2 . Therefore, a comparison of ion yields in in situ liquid SIMS analysis versus traditional static SIMS analysis of corresponding dry samples is of great interest. In this study, a dipalmitoylphosphatidylcholine (DPPC) liposome solution was used as a model system. Both liquid sample and dry sample were examined. Secondary ion yields using three primary ion species (Bi+ , Bi3+ and Bi3++ ) with various beam currents were investigated. Usable ion yields for both positive and negative characteristic signals (including molecular ions and characteristic fragment ions) were achievable based on optimized experimental conditions for in situ liquid SIMS analysis. The ion yield of the key DPPC molecular ion was comparable to that of traditional static SIMS, and unexpected low fragmentation was observed. The flexible structure of the liquid plays an important role for these observations. Therefore, beam damage may not be a concern in in situ liquid SIMS analysis if proper experimental conditions are used.

Graphene Enhanced Secondary Ion Mass Spectrometry (GESIMS)

The following invention - Graphene Enhanced Secondary Ion Mass Spectrometry - (pending European patent application no. EP 16461554.4) is related to a method of analysing a solid substrate by means of Secondary Ion Mass Spectrometry (SIMS). It comprises the steps of providing a graphene layer over the substrate surface and analysing ejected secondary anions through mass spectrometry analysis. The graphene layer acts as a kind of filament that emits a lot of secondary electrons during the experiment which significantly increases the negative ionization probability and thus the intensity of the SIMS signal can be more than two orders of magnitude higher than that of a similar sample without graphene. The method is particularly useful for the analysis of surfaces, 2D materials and ultra-thin films. The intensity of dopants and contamination signals can be enhanced up to 35 times, which approaches the detection limit of ~1015atoms/cm3, otherwise unreachable in a standard static SIMS analysis.

Relative Stability of Thiolate and Selenolate SAMs on Ag(111) Substrate Studied by Static SIMS. Oscillation in Stability of Consecutive Chemical Bonds

The stability of chemical bonds at the molecule–metal interface is of fundamental importance for a majority of applications based on organic materials. It remains, however, extremely difficult to determine this stability using experimental and theoretical methods. A detailed analysis of the static SIMS (S-SIMS) data obtained for the homologous series of thiolate- and selenolate-based self-assembled monolayers (SAMs) on the Ag(111) substrate reveals positional oscillations in the stability of consecutive chemical bonds in the vicinity of the molecule–metal interface. The observed oscillations are much more pronounced compared to recently reported analogous data for the Au(111) substrate, which confirms the universal nature of this phenomenon and its strong dependence on the type of molecule binding atom (S or Se) and the substrate (Ag or Au). Importantly, such an analysis has not been conducted to date using any other technique, and this study not only reveals the universal mechanisms of molecule–metal int...

Focus on test, measurement, and materials

Focus on test, measurement, and materials

Chemical Analysis of Plasma‐treated Organic Surfaces and Plasma Polymers by Secondary Ion Mass Spectrometry

This feature article is focused on the application of secondary ion mass spectrometry (time‐of‐flight SIMS) to the chemical and structural study of plasma‐treated organic surfaces and plasma polymer films. After a brief historical perspective and a presentation of the recent developments of SIMS, illustrative case studies involving plasma‐treated polymer surfaces and plasma polymers are presented. Beyond surface analysis by static SIMS, we show the potential of molecular depth‐profiling by low‐energy Cs+ ions and large Arn+ clusters for the in‐depth chemical characterization of plasma‐modified samples. Together with SIMS data processing by multivariate analysis, molecular depth‐profiling could provide a step change for the analysis of films treated or polymerized with plasmas.

Static secondary ion mass spectrometry investigation of corrosion inhibitor Irgamet®39 on copper surfaces treated in power transformer insulating oil

Static secondary ion mass spectrometry was used to study the corrosion inhibitor Irgamet®39 on the surface of copper treated in insulating oils and the effect of temperature changes, by means of temperature programmed desorption experiments under vacuum, on metal coverage. Four commercial oils, both corrosive and non-corrosive, showed no significant influence on the stability of the tolyltriazole layer and the energy of its main desorption event from copper was calculated around 100kJmol−1. Finally, an example of ion imaging as diagnostic tool to track the distribution of corrosion inhibitor and by-products in decommissioned or failed power transformers is described.

Active sites and mechanisms for direct oxidation of benzene to phenol over carbon catalysts.

The direct oxidation of benzene to phenol with H2 O2 as the oxidizer, which is regarded as an environmentally friendly process, can be efficiently catalyzed by carbon catalysts. However, the detailed roles of carbon catalysts, especially what is the active site, are still a topic of debate controversy. Herein, we present a fundamental consideration of possible mechanisms for this oxidation reaction by using small molecular model catalysts, Raman spectra, static secondary ion mass spectroscopy (SIMS), DFT calculations, quasi in situ ATR-IR and UV spectra. Our study indicates that the defects, being favorable for the formation of active oxygen species, are the active sites for this oxidation reaction. Furthermore, one type of active defect, namely the armchair configuration defect was successfully identified.

Hydroxylation of the silica in microfabricated thin layer chromatography plates as probed by time-of-flight secondary ion mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy

Microfabricated silica thin layer chromatography (TLC) plates have previously been prepared on patterned carbon nanotube forests. The high temperatures used in their fabrication reduce the number of hydroxyl groups on their surfaces. Fortunately, silica can be rehydroxylated. In diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), a silanol peak below 3740 cm−1 indicates a well-hydroxylated silica surface that is fit for chromatography. Hydroxylations of our materials with HF are so effective that it is not possible to discern the position of this peak. In contrast, this signal is discernable when the plates are treated with NH4OH. To find a more convenient method for studying the surfaces of TLC plates, time-of-flight secondary ion mass spectroscopy (ToF-SIMS) was considered. ToF-SIMS is advantageous because multiple microfabricated TLC plates must be scraped to obtain enough silica for one DRIFT analysis, while static SIMS can be performed on very small regions (500 × 500 µm2 or less) of individual plates. Ratios of the SiOH+ and Si+ ToF-SIMS signals for microfabricated TLC plates correlated well with ~3740 cm−1 silanol peaks from DRIFT. Thus, SIMS allows direct analysis of all of our treated and untreated plates, including those hydroxylated with HF. The best hydroxylation condition for HF, which was better than any studied for NH4OH, was around 150 ppm at room temperature. The best hydroxylation condition for NH4OH was 50 °C for 72 h. ToF-SIMS versus DRIFT results of commercial TLC plates were also obtained and evaluated. Copyright © 2014 John Wiley & Sons, Ltd.

Experimental and numerical study of submonolayer sputter deposition of polystyrene fragments on silver for the storing matter technique.

In static secondary ion mass spectrometry (SIMS), quantification and high ionization probabilities are difficult to obtain. The Storing Matter technique has been developed to circumvent these issues and has already been applied to deposit inorganic and organic samples. For organic samples, the effect of fragmentation during sputter deposition and changing coverage on time-of-flight (TOF)-SIMS mass spectra has not been investigated. In this work, polystyrene (PS) was sputter deposited on silver using an argon ion beam in order to investigate these parameters and to get a better control of the whole process. For this purpose, we introduce a multitechnique characterization approach for the submonolayer deposition of PS. Experimental methods (TOF-SIMS, X-ray photoelectron spectroscopy (XPS)) were used in combination with simulations (density functional theory (DFT) calculations) in order to obtain information about the molecular and structural changes and the interactions of organic matter with the metal surface. Alterations of the PS surface and PS sputter deposit as a function of surface coverage and Ar(+) ion fluence are addressed. A major finding is that this approach can be used to identify surface reactions between different fragments on the collector surface. Indeed, in the dynamic regime, the ratio of large to small fragments is increasing although the fragmentation during the sputter deposition should lead to increasingly smaller fragments. Hence, for Storing Matter, the coverage on the collector must be kept low in order to minimize the reactions between fragments and to preserve the information on the original sample.

Fragmentation of polystyrene during sputter deposition in the storing matter instrument

The storing matter technique has been developed to get easier quantification in secondary ion mass spectrometry (SIMS) by decoupling the sputtering step from the analysis step. First, the matter is deposited in the submonolayer range on a collector that is analysed next by SIMS. Most work on the storing matter technique has been carried out for inorganic samples. The technique has also been applied successfully to organic samples. In this work, the fragmentation of polystyrene (PS) molecule deposited on silver (Ag) during storing matter deposition is investigated using static SIMS analysis with Bi3+ clusters. The fragmentation of PS at different coverages is studied by calculating the ratios of large‐to‐small peak intensities of fingerprint spectra. These ratios are compared with those obtained previously by the storing matter technique using Ar+ as analysis beam in time‐of‐flight‐SIMS. Different degrees of fragmentation are observed with varying coverage, suggesting different sticking factors of fragments on the collector. Compared with Bi3+, the Ar+ projectile produces a higher amount of large fragments and is found to be better suited for the analysis of PS deposits on silver collectors. In both situations, C7H7+ is the major fragment in the mass spectra. Copyright © 2014 John Wiley & Sons, Ltd.

SIMS—A precursor and partner to contemporary mass spectrometry

Significant events driving the development of SIMS over the last 50 years are reviewed. The discussion includes recollections of dynamic and static SIMS from the 1970s, of the emergence of TOF–SIMS during the 1980s and of the incorporation of cluster ion bombardment during most recent times. Advances in theoretical understanding of the sputtering phenomenon and of the ionization process that accompanied these advances are also included. Many early discoveries were focused upon the stimulated desorption of organic and bioorganic molecules, first via static SIMS and next via fast atom bombardment, that were important precursor experiments to modern day mass spectrometry. Today, submicron molecule-specific imaging and molecular depth profiling represent unique aspects of SIMS experiments. Developments that led to the optimization of these modalities are also emphasized in the review. In general, the characteristics of SIMS that make it a contemporary partner to modern day mass spectrometry are highlighted.

Surface characterization and stability of an epoxy resin surface modified with polyamines grafted on polydopamine

This paper reports on polydopamine and polyamine surface modifications of an etched epoxy cresol novolac (ECN) resin using the ‘grafting to’ method. Three different polyamines are used for the grafting reactions: branched polyethyleneimine (B-PEI), linear polyethyleneimine (L-PEI) and diethylenetriamine (DETA). These modifications are compared to control materials prepared via direct deposition of polyamines. The stability of the modifications toward a concentrated hydrochloric acid (HCl) environment is evaluated. The modified surfaces are characterized with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and time-of-flight static secondary ion mass spectroscopy (TOF-S-SIMS).