Static Secondary Ion Mass Spectrometry Analysis Research Articles

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.

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.

Reduction of Matrix Effects in Polystyrene/Poly(methylene methacrylate) Blends by Metal-Assisted Secondary Ion Mass Spectrometry

Secondary ion mass spectrometry (SIMS) is a very surface sensitive analysis technique with low detection limits. The main drawback of SIMS is its inherent incapability of providing quantitative information about sample compositions due to the frequent occurrence of ionization- and sputter-induced matrix effects. Metal-assisted SIMS (MetA-SIMS) is an experimental approach that consists in covering an organic sample with a minute amount of a noble metal prior to a static SIMS analysis, the main objective being an increase of the characteristic secondary ion intensities. We show in this article that MetA-SIMS is also a simple and efficient tool for reducing matrix effects in a set of polymer blend samples containing different relative concentrations polystyrene (PS) and poly(methylene methacrylate) (PMMA). These findings can be explained by diffusion processes leading to a sample surface configuration consisting of individual polymer chains embedded in a common Ag matrix.

Primary ion fluence dependence in time-of-flight SIMS of self-assembled monolayer of alkyl thiol molecules on Au(1 1 1)—Discussion of static limit

The nondestructive nature of static secondary ion mass spectrometry (SIMS) in the context of studies of self-assembled monolayers (SAMs) of organic molecules has been examined by measuring the primary ion fluence dependence of secondary ion signals with two well-known SAMs, C 18H 37SH on Au(1 1 1) and C 18H 37PO 3H 2 on freshly cleaved mica. This SIMS analysis is challenging because the bonding nature is delicate and the areal molecular density is less than 10 15 cm −2. In SIMS, it is prevalently assumed that if the primary ion fluence is confined to not more than 1 × 10 12 cm −2, all secondary ion signals should not change by more than 10% and the practically defined static condition is satisfied. Our results from time-of-flight SIMS with the common primary ions of Bi 3 +, Bi + and Ar +, indicate that this prevalent static assumption fails for both model SAMs. The SIMS results from the phosphyl case, which have been recently published, consistently display the evidence of bombardment-induced damage. In comparison, the thiol case presented here shows much more complex primary ion fluence dependence of SIMS signals. It is therefore concluded that practical static analysis should use primary ion fluence not more than 1 × 10 11 cm −2 or should simply record and report the effects of primary ion fluence.

Time-of-flight SIMS analysis of polypropylene films modified by flame treatments using isotopically labeled methane fuel

The surface of polypropylene (PP) film was oxidized by exposure to a flame fueled by isotopically labeled methane (CD4). The isotopic sensitivity of static secondary ion mass spectrometry (SIMS) was then used to gain new insights into the mechanism of flame treatment. SIMS analysis indicated that much of the oxidation of PP occurring in fuel-lean flames is not deuterated, while for PP treated in fuel-rich flames, some of the affixed oxygen is deuterated. These observations imply that O2 is the primary source of affixed surface oxygen in fuel-lean flame treatments, but that OH may be a significant source of affixed oxygen in fuel-rich flame treatments. Hydroxyl radicals are primarily responsible for hydrogen abstraction in fuel-lean flames, while H is the primary active gasphase species in fuel-rich flames. SIMS also detected trace quantities of oxidized nitrogen groups affixed to the flame-treated PP.

In Situ Temperature-Time Effect on MetA-S-SIMS

Metal-assisted (MetA) static secondary ion mass spectrometry (S-SIMS) is one of several ion yield enhancing methods developed for S-SIMS in the last decades. MetA-S-SIMS uses a very thin coating of gold or silver on the sample. Earlier experiments revealed dependence of the ion yield enhancement on the applied metal, the nature of the studied sample, the time after metallization, and the heating temperature (ex situ, i.e., under atmospheric pressure). This paper reports on the effects of time and temperature when samples are heated to temperatures between 30 and 80 degrees C inside the S-SIMS vacuum chamber (in situ). Thick layers of poly(vinylbutyral-co-vinylalcohol-co-vinylacetate) (PVB) containing dihydroxybenzophenone (DHBPh) were coated with a nm-thin-layer of gold. The S-SIMS analysis was performed over a period of several hours while samples were kept at a constant elevated temperature. Compared to ex situ heating in an oven, heating in the analysis chamber provided more rapid signal enhancement, but the magnitude of the enhancement was less (by a factor of two). Furthermore, additional experiments on ex situ heated samples revealed that storage of samples with enhanced ion yields at -8 degrees C is not sufficient to "stabilize" the enhancement. A steep decrease of the ion yields was observed as a function of time after 2.5 h.

Static secondary ion mass spectrometry (S-SIMS) in advanced textile research: Study of additives in polypropylene (PP) films

The development of novel PP textiles requires materials of which the surface has well defined hydrophilic properties, for instance, by the use of additives before extrusion and drawing. The feasibility of static secondary ion mass spectrometry (S-SIMS) to provide detailed information on the molecular surface composition of materials in the form of 30 μm thick films has been explored. Extensive charge build-up during S-SIMS analysis prevents direct characterisation of such materials. Several methods have been used to circumvent the problem. Specifically, deposition of gold over the entire surface and pressing a slot grid into the material allow the commercial hydrophilic additive in PP to be detected. While the slot grid preserves the pristine surface composition, mass spectra from gold-coated samples reflect the occurrence of redistribution artefacts.

Static SIMS analysis of carbonate on basic alkali‐bearing surfaces

AbstractCarbonate is a somewhat enigmatic anion in static secondary ion mass spectrometry (SIMS) because abundant ions containing intact CO32− are not detected when analyzing alkaline‐earth carbonate minerals common to the geochemical environment. In contrast, carbonate can be observed as an adduct ion when it is bound with alkali cations. In this study, carbonate was detected as the adduct Na2CO3·Na+ in the spectra of sodium carbonate, bicarbonate, hydroxide, oxalate, formate and nitrite and to a lesser extent nitrate. The appearance of the adduct Na2CO3·Na+ on hydroxide, oxalate, formate and nitrite surfaces was interpreted in terms of these basic surfaces fixing CO2 from the ambient atmosphere. The low abundance of Na2CO3·Na+ in the static SIMS spectrum of sodium nitrate, compared with a significantly higher abundance in salts having stronger conjugate bases, suggested that the basicity of the conjugate anions correlated with aggressive CO2 fixation; however, the appearance of Na2CO3·Na+ could not be explained simply in terms of solution basicity constants. The oxide molecular ion Na2O+ and adducts NaOH·Na+ and Na2O·Na+ also constituted part of the carbonate spectral signature, and were observed in spectra from all the salts studied. In addition to the carbonate and oxide ions, a low‐abundance oxalate ion series was observed that had the general formula Na2−xHxC2O4·Na+, where 0 < x < 2. Oxalate adsorption from the laboratory atmosphere was demonstrated but the oxalate ion series also was likely to be formed from reductive coupling occurring during the static SIMS bombardment event. The remarkable spectral similarity observed when comparing the sodium salts indicated that their surfaces shared common chemical speciation and that the chemistry of the surfaces was very different from the bulk of the particle. Copyright © 2003 John Wiley & Sons, Ltd.

Application of atomic and molecular primary ions for TOF–SIMS analysis of additive containing polymer surfaces

The influence of primary ion mass and composition on secondary ion emission of the additive Irganox 1010 ( m=1176 u) in polyethylene was investigated. O +, Ar +, Xe +, O 2 +, CO 2 +, SF 5 +, C 7H 7 +, C 10H 8 +, C 6F 6 +, and C 10F 8 + with a total energy of 11 keV were used as primary ions under static secondary ion mass spectrometry (SIMS) conditions. Positive and negative molecular secondary ions characterizing the additive were determined and their yields were evaluated. For all characteristic secondary ions we found a strong yield enhancement with increasing mass for atomic primary ions and increasing number of constituents for molecular primary ions. This yield enhancement is saturated once the molecular primary ion is made of more than six heavy atoms. In addition this yield increase depends on the mass and structure of the considered secondary ion. We did not find any evidence for an influence of the chemical composition of the applied molecular primary ions on the secondary ion emission when static SIMS conditions were met. The improved imaging capabilities of molecular primary ions was demonstrated by comparing focused Ar + and SF 5 + primary ion beams when mapping characteristic secondary ion emission from a structured additive containing polypropylene surface.

Polyether-segmented nylon hemodialysis membrane. VII. Studies on surface structures of various poly(ethylene oxide)-segmented nylon membranes

The relationships of the surface morphologies to the surface chemical compositions in poly(ethylene oxide)-segmented nylon (PEO–Ny) membranes prepared by the phase-inversion method were studied using scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and static secondary ion mass spectrometry (SSIMS). The PEO–Ny's used were high semicrystalline PEO-segmented polyiminosebacoyliminohexamethylene (PEO–Ny610), low semicrystalline PEO-segmented poly(iminosebacoylimino-m-xylylene) (PEO–NyM10), and amorphous PEO- segmented poly(iminoisophthaloyliminomethylene-1,3-cyclohexylenemethylene) (PEO–NyBI). SEM observation showed that the surfaces of the PEO–Ny610 and PEO–NyM10 membranes were composed of crystalline spherulite and that the PEO–NyBI membrane surface had a nodular structure. ESCA analysis exhibited the enrichment of the PEO segment at the surfaces of the PEO–Ny610 and PEO–NyM10 membranes. On the other hand, the enrichment of the Ny segment was observed in the case of the PEO–NyBI membrane. SSIMS analysis revealed that the outermost surfaces of the PEO–Ny membranes except the PEO–NyBI membrane were almost covered with the PEO segment. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 517–528, 2000

Mechanistic study of metalorganic chemical vapor deposition of (Ba,Sr)TiO3 thin films

The metalorganic precursor chemistry was studied on Pt(111) surfaces in a O162 and O182 backgrounds. Using temperature programmed desorption (TPD) and static secondary ion mass spectrometry (SIMS). The precursor chemistry of Sr(thd)2 was found to be different on oxide covered Pt(111) surface as compared to the clean Pt(111) surface. In an oxygen ambient, TPD showed at least four different reaction processes which involved the removal of carbon from the precursor ligands on oxide covered Pt(111). In two of these, gas phase oxygen was incorporated into the oxidative products. In contrast, one carbon removing reaction was observed on the clean Pt(111) surface. Isotopic labeling experiments have also been carried out to understand the film-formation reactions in the metalorganic chemical vapor deposition of (Ba,Sr)TiO3 (BST) films. Time-of-flight SIMS and nuclear reaction analysis reveal that the oxygen in the BST films originates from both the gas phase oxidants (18O) and the precursor ligands (16O). The ligand substitution by gas phase O2 plays a more prominent role in the film formation at lower temperatures. On the other hand, the reactive oxygen radicals produced by microwave plasma involved more in breaking the O–C bonds than substituting the precursor ligands for the film formation. Use of the 50% O182–50% N2 16O2 mixture results in a reduction of O18 incorporation in the BST films, indicative of the direct involvement of N2O in the film-formation reactions. The mechanistic studies are essential for understanding the new BST precursors used in this study, and provide useful information to correlate the film microstructure, step coverage, and dielectric properties with the precursor properties.

Secondary Ion Mass Spectrometric Characterization of Nail Polishes and Paint Surfaces

A variety of paint and fingernail polish samples, which were visually similar, but had different chemical compositions and formulations, was analyzed using quadrupole static secondary ion mass spectrometry (SIMS). Coating distinction was easily achieved in many cases because of the presence of dominant ions derived from the components of the coating, which could be observed in the SIMS spectra. In other instances, coating distinction was difficult within a product line because of spectral complexity; for this reason and because of the large numbers of spectra generated in this study, multivariate statistical techniques were employed, which allowed the meaningful classification and comparison of spectra. Partial Least Squares (PLS) and Principal Component Analysis (PCA) were applied to quadrupole SIMS data. PCA showed distinct spectral differences between most spectral groups, and also emphasized the reproducibility of the SIMS spectra. When using PLS analysis, reasonably accurate coating identification was achieved with the data. Overall, the PLS model is more than 90% effective in identifying the spectrum of a particular coating, and nearly 100% effective at telling which coating components represented in the PLS models are not present in a spectrum. The level of spectral variation caused by sample bombardment in the SIMS analysis was investigated using Fourier transform infrared spectroscopy (FT-IR) and quadrupole static SIMS. Changes in the FT-IR spectra were observed and were most likely a result of a number of factors involving the static SIMS analysis. However, the bulk of the sample is unaltered and may be used for further testing.

Ion-trap SIMS analysis of pinacolyl methylphosphonic acid on soil

The minimum detection limit and semi-quantitative determination of surface coverages of pinacolyl methylphosphonic acid (PMPA) on soil by static secondary-ion mass spectrometry (SIMS) are reported. The soil was exposed to aqueous solutions of PMPA and then analyzed on an ion-trap SIMS instrument. Mass spectrometry/mass spectrometry was utilized to discriminate against the chemical background inherent in environmental samples (such as soil). The quasimolecular ion [PMPA − H] − at m/ z = 179 was trapped and then subsequently fragmented to form an ion at m/ z = 95, which is interpreted as a loss of the pinacolyl olefin (C 6H 12) to form the methylphosphonic acid anion. The product ion at m/ z = 95 was used to investigate the surface coverage of PMPA on the soil. The m/ z = 95 product-ion abundance was observed to be linearly related to the PMPA surface coverage between 2 and 0.002 monolayers. The minimum detection limit is estimated at 0.008 monolayer (approximately 12 pg mm −2, three standard deviations of the blank). These data were compared with analyses performed by using a quadrupole SIMS instrument, which indicates an improvement in sensitivity by the ion-trap SIMS of a factor of 250. The results of this study demonstrate that ion-trap SIMS is a facile approach for determination of phosphonates on soil.

Direct Surface Analysis of Pesticides on Soil, Leaves, Grass, and Stainless Steel by Static Secondary Ion Mass Spectrometry

Direct surface analyses by static secondary ion mass spectrometry (SIMS) were performed for the following pesticides adsorbed on dandelion leaves, grass, soil, and stainless steel samples: alachlor, atrazine, captan, carbofuran, chlorpyrifos, chlorsulfuron, chlorthal-dimethyl, cypermethrin, 2,4-D, diuron, glyphosate, malathion, methomyl, methyl arsonic acid, mocap, norflurazon, oxyfluorfen, paraquat, temik, and trifluralin. The purpose of this study was to evaluate static SIMS as a tool for pesticide analysis, principally for use in screening samples for pesticides. The advantage of direct surface analysis compared with conventional pesticide analysis methods is the elimination of sample pretreatment including extraction, which streamlines the analysis substantially; total analysis time for SIMS analysis was ca. 10 min/sample. Detection of 16 of the 20 pesticides on all four substrates was achieved. Of the remaining four pesticides, only one (trifluralin) was not detected on any of the samples. The minimum detectable quantity was determined for paraquat on soil in order to evaluate the efficacy of using SIMS as a screening tool. Paraquat was detected at 3 pg/mm2 (ca. 0.005 monolayers). The results of these studies suggest that SIMS is capable of direct surface detection of a range of pesticides, with low volatility, polar pesticides being the most easily detected.

Surface fluorination of polyethylene films by different CF 4 glow discharges: effects of frequency and electrode configuration

Polyethylene has been treated in a CF 4 plasma using parallel-plate electrodes at 13.56 MHz and an asymmetric configuration of electrodes both at 70 kHZ (low frequency) and 13.56 MHz (r.f.). The chemical species involved in the plasmas and subsequent surface modifications were characterized. Plasma analysis by optical emission spectroscopy indicated that discharges obtained with asymmetric electrodes had a higher energy than those in the diode reactor. In the former case, 70 kHz plasmas had a higher energy than at 13.56 MHz. Analysis of the surface properties showed that r.f. and low frequency plasmas do not have the same kinetics concerning the fluorination process. Low frequency plasmas enhanced fluorination for short treatment times ( t<1 s) with an increase in the surface wettability whereas, at 13.56 MHz, relative long treatment times ( t>1 s) yielded highly fluorinated substrates (F 1 s-to-C 1 s ratio, 1.4), hence decreasing the wettabilities of the treated surfaces. For equivalent long treatment times ( t>5 s) the fluorine uptake of the surface is higher in the diode reactor than in the 70 kHz reactor with asymmetric electrodes but is less than that obtained in the case of 13.56 MHz with the same reactor. The most efficient discharge is therefore the 13.56 MHz discharge with asymmetric electrodes. Static secondary-ion mass spectrometry analysis indicated a substantial fluorination of the substrates due to the substitution of H by F. No modification of the surface roughness was observed by scanning electron microscopy analysis. Rutherford backscattering spectroscopy measurements showed that fluorine diffuses through the polymeric matrix.

Surface fluorination of polyethylene films by different glow discharges. Effects of frequency and electrode configuration

Polyethylene has been treated in a CF4 plasma using two configurations for the electrodes: parallel-plate electrodes at 13.56 MHz, and a nonsymmetrical configuration of electrodes at 70 kHz. The chemical species involved in the plasmas and the subsequent surface modifications were characterized. Comparison of the emissions in the range 200-450 nm was made with optical emission spectroscopy. The excited radicals' CF2 bands and the CF+ broad continuum were detected and a comparison of their relative intensities indicated a more energetic aspect to the low-frequency discharge. This was confirmed by comparing the ratio of N2+/N2 in the two cases. Analysis of the surface properties by means of X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectrometry (SSIMS), and contact angle measurements showed rapid fluorination of the surface (t = 0.1 s) for the nonsymmetrical electrodes. Longer treatment times (up to 15 s) led to more fluorinated surfaces, thereby decreasing the wettability of the treated substrates; fluorine incorporation was, however, more significant at equivalent treatment times in the diode reactor. SSIMS analysis indicated the formation of more complex fluorine compounds with an increase in the treatment time with no notable modification other than replacement of H by F. Further increases in the treatment time for low-frequency treated samples in the nonsymmetrical configuration of electrodes caused an increase in the surface roughness, as observed by SEM (scanning electron microscopy) analysis. RBS (Rutherford backscattering spectroscopy) measurements showed that beyond 0.1 s, which corresponds to the time required for rapid fluorination, fluorine diffuses through the polymeric matrix and its concentration is enhanced with increasing treatment time.

Structure of the CO bond on supported Pd particles: influence of size and surface state

We have investigated the surface of supported palladium particles by static secondary ion mass spectrometry (SSIMS). Pd particles were grown in situ on alumi na (oxide layer and sapphire surfaces) and stabilized by heating treatment. The particle size, density and crystallographic structure were determined in previous studies by transmission electron microscopy and diffraction (TEM and TED). Various ionic species are detected by SSIMS analysis which makes it possible to characterize the CO absorbed layer: Pd n CO+ (n=1, 2) for molecular adsorption and Pd n C+ for CO dissociation. The size dependence of the bonding state of CO (linear, bridge, ...) was monitored by: PdCO+/σ n Pd n CO+ signal ratio over various size particles (mean diameter in the 2–9 nm range). Investigations were performed as a function of CO coverage (adsorption at room temperature) and also under CO dissociation conditions: heating under CO atmosphere or CO+O2 (catalysis). The data analysis shows that on clean Pd particles smaller than 3 nm the CO molecules give rise mainly to PdCO+ species. We have interpreted this result by the adsorption of CO on two palladium atoms, the carbon end being tightly bonded to a low coordination Pd atom and the oxygen end weakly bonded to a neighbour Pd atom. These couples of Pd atoms form the specific sites for CO dissociation, the density of which depends on the roughness of the particle surface.

Quantitative static secondary ion mass spectrometry of molecular ions from 1-.beta.-3,4-dihydroxyphenylalanine (L-dopa) and indolic derivatives

Traditionally, static secondary ion mass spectrometry (SIMS) is believed to yield qualitative information and very little quantitative information. A method to obtain quantitative molecular ion data from organic static SIMS analysis of L-DOPA and related compounds is presented. Linear calibration curves have been constructed by integrating the protonated molecular ion to silver ion peak area ratios over a known ion dosage and plotting versus the original sample concentration.

The surface chemical structure of poly(β-hydroxybutyrate) microparticles produced by solvent evaporation process

The surface chemistry of poly(β-hydroxybutyrate) particles produced by the solvent evaporation approach has been examined, before and after cleaning, by zetapotential measurements and static secondary ion mass spectrometry (SSIMS). The SSIMS analysis was able to detect the presence of the residual stabiliser (surfactant sodium dodecyl sulphate (SDS)) on the particle surface. The surface analysis showed that DS still predominates at the particle surface even after cleaning by dialysis and ultrafiltration methods. A significant reduction in DS surface content was seen after cleaning by gel permeation chromatography. The implications of these findings are discussed with reference to the particle production technique and the cleaning processes.