SIMS Method Research Articles

Origin of garnet megacrysts from kimberlites

The asthenospheric source is commonly accepted for the genetic interpretation of minerals in megacryst assemblages from kimberlites and deformed lherzolites. Both assemblages are regarded as highest temperature and high-pressure formations in the mantle [1‐5]. According to [1, 2, 6], minerals of the megacryst assemblage are products of fractional crystallization of the asthenospheric melt. At the same time, the problem of close association of the formation of megacrysts and deformed lherzolites is discussed in [6], in which the lithospheric origin of deformed peridotites is suggested and evidence of refertilization of the lower lithosphere by asthenospheric melts is presented. All these problems remain to be solved and require further investigations. In this communication, we discuss data on the major oxide and REE contents in garnet megacrysts from kimberlites of the Mir pipe (Malobotuobinsk field); the Udachnaya, Dal’nyaya, and Zarnitsa pipes (Daldyn field); the Zapolyarnaya, Novinka, Komsomol’skaya‐ Magnitnaya pipes (Verkhnemunsk field) in the Yakutian province; and the Grib pipe in the Arkhangel’sk province; and garnets from xenoliths of deformed peridotites in the Udachnaya-Vostochnaya pipe. Our aim was to characterize the REE patterns in garnets from the deformed lherzolites and megacrysts, to establish the geochemical evolution of melts in equilibrium with these minerals, and to discuss their possible origin. The xenoliths and megacrysts were examined in detail under an optic microscope. The cores and marginal zones of garnet grains were analyzed for major oxides on a JXA-33 (Jeol) microprobe at the Institute of Geochemistry, Irkutsk. The trace element contents were determined with the SIMS method on a Cameca IMS ion probe at the Institute of Microelectronics and Informatics, Russian Academy of Sciences (Yaroslavl), using the technique described in [7]. The latter method provided measurements accurate to 10‐15% for concentrations of >0.1 ppm and 40‐50% at concentrations of <0.1 ppm.

Investigation of Mn‐dimers formation in silicon by SIMS method

AbstractIt has been theoretically predicted that manganese atoms in silicon matrix tend to form dimers which can show both ferro‐ and antiferromagnetic properties. One might expect that the significant part of such dimers (N‐mers) should be spattered as cluster ions while SIMS measurement. We have investigated samples of silicon wafers implanted with manganese ions and annealed. In the solid solution the probability of the situation when N doped atoms are nearest neighbours is proportional to Nth power of concentration. However, if in the solution the process of enhancement of neighbouring impurity atoms number takes place, the cluster ion signal should exceed the power law. We have verified the validity of this statement in ion implanted solutions of B and Mn in silicon. SIMS measurements in annealed samples show that the profile of Mn2 and Mn3 ions essentially exceed respectively the square and the cube of manganese concentration. Quantitative estimation shows that in the annealed sample at some depths manganese dimers contain about 10% of total Mn atoms. The connection between the obtained profiles and magnetic measurements is discussed. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Au agglomerates observed in the out-diffusion process of supersaturated high-temperature substitutional Au in Si

Out-diffusion profiles of supersaturated substitutional Au in Si annealed at 900 °C for 90 h have been measured by SIMS and ICTS methods over a distance of 80 μm from the specimen surface. The tendency of the profile of total Au atoms measured by SIMS and that of electrically active substitutional Au measured by ICTS agrees well, but the very small regions containing high-concentration of Au atoms, 3 × 1022 cm−3, are observed sporadically at the distance deeper than 10 μm from the surface by SIMS method. The size of the high-concentration region is estimated to be about 20 nm and its density is about 2 × 1010 cm−3. The small agglomerates contain 105–107 Au atoms and many of them contain about 2 × 105 atoms. The observed agglomerate is a new agglomeration of Au in Si. The state of the agglomeration (namely, precipitates of Au, agglomeration of substitutional Au in Si, or a new state) is not clear by SIMS measurement.

Local atomic structure of Cu(In x Ga1−x )Se2 (x = 0.25, 0.5, and 0.75) systems for solar cells

The local atomic structure of thin surface layers of crystalline quasi-binary Cu(In x Ga1−x )Se2 solid solutions was studied by SIMS and EXAFS techniques. The SIMS method showed that the elemental composition of the sample changes most significantly in thin layers at a depth of 5–10 nm; in deeper layers, the component concentrations correspond to the bulk values. The EXAFS method in the x-ray fluorescence mode showed that the results obtained are in agreement with the assumption that quaternary crystalline quasi-binary Cu(In x Ga1−x )Se2 solid solutions exhibit local disorder while average long-range order is detected from x-ray diffraction data.

SIMS as a subnanometer probe: A new tool for chemical profile analysis of grafted molecules

The complexity of modern engineered surfaces requires the development of very powerful methods to analyze and characterize them. We demonstrate that it is possible to obtain chemical information about the skeleton of organic molecules constituting SAMs grafted on a silicon surface by using a new type of SIMS method. A profile can be achieved by the investigation of the temporal variation of secondary ion intensities that correspond to the fractional parts of the molecule constituting the SAMs. The equivalent ablation rate is less than 0.5 nm/min.

Secondary ion mass spectrometry of [formula omitted] molecular ion complexes

Excellent detection sensitivity, high dynamic range and good depth resolution make the SIMS technique extremely powerful for the analysis of surfaces and interfaces. However, a serious problem in SIMS analysis is its “matrix effect” that hinders the quantification of a certain species in a sample and consequently, probing the composition of surfaces or interfaces by SIMS is greatly hindered. Appropriate corrective measures are therefore, needed to calibrate the secondary ion currents into respective concentrations for accurate compositional analysis. Working in the MCs+-SIMS mode (M – element to be analyzed, Cs+ – bombarding ions) can circumvent the matrix effect. The quantitative potential of the MCs+-SIMS method is understood by assuming that an MCs+ ion is generated by the combination of a secondary neutral M0 atom with a re-sputtered Cs+ ion in the near-surface region. The emission process for the species M0 is thus decoupled from the subsequent MCs+ ion formation process, in analogy with the ion formation in secondary neutral mass spectrometry (SNMS), resulting in a drastic decrease in matrix effect. Although this technique has found its applicability in direct quantification, it generally suffers from a low useful yield. In such cases, detection of MCsn+ (n=2,3,…) molecular ions offers a better sensitivity as the yields of such molecular ion complexes have often been found higher than that of MCs+ ions. This is true in most of the cases where the elements are strongly electronegative with respect to cesium. Several works have been reported on the emission of MCsn+ molecular ions in the SIMS process, but a complete understanding on the formation mechanism of these ion complexes is still lacking. The kinetic energy distributions of secondary MCsn+ molecular ion complexes has been found to be an effective approach to estimate the local instantaneous surface work function changes under various surface exposure conditions, thereby enabling one to elucidate on the probable formation mechanisms of these molecular complexes from their emission dynamics. The present paper addresses a brief review on the MCsn+ molecular ion complexes that are emitted in the SIMS process, including various phenomenological approaches on the subject.

A-Si Capping SIMS for shallow dopant profiles

Capping a sample surface using amorphous-Si (a-Si) prior to SIMS analysis is a common method for improving ultra-shallow boron depth profiling, however, details of the limitations of a-Si capping have not been thoroughly investigated. In this study we have investigated the problems and/or limitations of a-Si capping method when applied to SIMS. Capping Si layers were grown using Si evaporation in UHV (∼2×10 −8 Pa) at less than 100 °C during growth. Using this a-Si capping SIMS method we have successfully measured shallow depth profiles for ultra-shallow B and P.

Study of enhanced magnetron sputtering process of NiO by using flow modulation of oxygen

We present the pulsed de magnetron sputtering method in which a nickel target is sputtered in a mixture of argon and reactive oxygen gas. The flow modulation of oxygen is proposed to enhance the deposition process in the preparation of the oxide films. The flow rate of oxygen is modulated periodically in time and during deposition when oxygen flows is cut off to remove the oxide formed on the target. A modulated deposition process was monitored directly by optical emission spectroscopy, measuring the deposition rate and the partial pressure. The effect of the different oxygen flow, which was changed periodically, changes with time on the target potential and the deposition rate were investigated. The variations of the Ni/O atomic ratios in NiO films were revealed by SIMS method.

Comparative measurements of acceptor concentration at the growth and nucleation side of microwave plasma CVD polycrystalline diamond films

Comparative studies of the electrical and optical properties of the growth and nucleation surfaces of free-standing boron-doped polycrystalline diamond films were performed. The diamond films, approximately 0.4 mm thick, were grown in a microwave plasma chemical vapor deposition (MPCVD) reactor. Capacitance–voltage measurements at electrolytic and solid-state contacts, charge-based deep-level transient spectroscopy and IR absorption measurements were used to determine the parameters of the electrically and optically active intrinsic and boron-induced defects in the diamond films. The total boron concentration was obtained by a SIMS method. In the diamond bulk adjacent to the nucleation side, consisting of submicron-sized grains, the concentrations of both the intrinsic and boron-induced acceptor defects were found to be approximately one order of magnitude higher than those near the growth surface, which is coarse-grained. This difference is tentatively attributed to the elevated concentration of crystal lattice defects near the nucleation surface, which, in addition to boron atoms, play the role of acceptors in diamond. Our experimental data (electrical and optical) show that these additional acceptors are mainly localized near the nucleation side of the thick boron-doped MPCVD diamond films.

Effect of crystal structure on the electrochemical behaviour of synthetic semiconductor diamond: Comparison of growth and a nucleation surfaces of a coarse-grained polycrystalline film

Comparative studies of the electrochemical behaviour of the growth and nucleation surfaces of a free-standing boron-doped polycrystalline diamond film grown in a microwave plasma CVD reactor are performed. The uncompensated acceptor concentration in diamond is determined from the electrochemical impedance (Mott–Schottky plots), uncompensated boron acceptor concentration from infrared absorption measurements, and the total boron concentration, by the SIMS method. In the diamond bulk adjacent to the nucleation surface, constituted from submicrometre-sized crystallites, both the boron concentration and the total acceptor concentration are found to be significantly higher than near the growth surface, where the film crystallinity is more perfect. This difference is tentatively attributed to the increased concentration of crystal lattice defects near the nucleation surface. These defects, in addition to boron atoms, play the role of acceptors in diamond.

Investigation of diffusion of magnesium in lithium fluoride crystals by the sims method

Using secondary ion mass spectroscopy, diffusion of magnesium impurity in lithium fluoride is investigated. A temperature dependence of the magnesium diffusion coefficients within the temperature interval 870–1073 K is established, which is described by an expression of the following type: D = 2.8·10–3·exp(–1.5/kT). Combining the data on self-diffusion of cations with the results of the ion conductivity measurements, estimation is made of the thermodynamic parameters characterizing the jump of a diffusant. The calculated frequencies of the impurity ion jump to the cation vacancy are reported.

Tracer solute diffusion of Nb, Zr, Cr, Fe, and Ni in γ-TiAl: effect of preferential site occupation

Solute diffusion of Nb, Zr, Fe, Cr, and Ni was measured in the phase γ-TiAl within a wide temperature interval. Both the SIMS method ( 93Nb, 58Fe, and 52Cr isotopes) and the radiotracer technique ( 95Nb, 95Zr, and 59Fe isotopes) were applied. Linear Arrhenius dependencies were found for Nb, Zr, and Cr diffusion, whereas Fe diffusion in TiAl revealed a substantially curved Arrhenius dependence similarly to Ti self-diffusion in this compound. The observed solute diffusion behavior is interpreted in terms of the preferential site occupation in the compound and by the interplay of the Ti sublattice diffusion mechanism and the intersublattice jumps of the solute atoms. Unlike in α 2-Ti 3Al, neither Fe diffusion nor Ni diffusion is extremely fast in γ-TiAl. This feature is explained by the different modes of forming solid solutions (substitutional or interstitial) in both compounds, which seems to be related to the different Ti atom arrangements around the interstitial octahedral sites in both compounds.

Static secondary ion mass spectrometry (S-SIMS) Part 1: methodology and structural interpretation

Static secondary ion mass spectrometry (S-SIMS) allows the chemical characterization of the constituents in the upper monomolecular layer of a solid sample. Within the range of micro-analytical methods, S-SIMS occupies a rather unique position in that it combines monolayer sensitivity with the capability to generate molecular information. In general, elemental ions, structural fragments, molecular and adduct ions are generated from both inorganic and organic molecules, including polymers. The chemical analysis of the upper monolayer makes S-SIMS especially suited to the study of the interface chemistry in a variety of materials. Polymer applications take an important place because S-SIMS allows a lot of information on these often intractable materials, e.g., identification, detection of surface functionalities, study of segregation of copolymer components and molecular weight (MW) distributions. In addition to the qualitative identification, S-SIMS allows high reproducibility and thereby permits quantitative studies with the aid of standards. Finally, S-SIMS offers imaging capabilities to visualize directly the distribution of given components within the upper surface layer of solids. Mapping with high lateral resolution is feasible for elemental ions and in favorable cases also for organic compounds. This review aims at a comprehensive coverage of the S-SIMS literature of the past decade. It comprises two parts, of which the first part deals with the more general aspects of the technique. It begins with a brief tutorial review of instrumentation, methodology and current concepts of ion formation. Particular attention is given to the link and difference with the matured dynamic SIMS method. Finally, imaging in S-SIMS is discussed. Application of S-SIMS to complex materials makes the interpretation of signals, in terms of the sample composition, intricate but crucial. Therefore, the features of inorganic and organic mass spectra are surveyed to assess the structure specificity and the kind of information obtainable. The second part of this review focuses on a variety of applications, primarily in the field of material sciences. Detailed studies on the surface chemistry of catalysts are discussed. The increasing importance of surface modification and tailoring to improve the interface properties has generated a wide range of applications. Examples from different technologies and industrial processes, such as semiconductors, paint, composite materials and corrosion protection of metals, are highlighted. Attention is devoted to the complementarity between S-SIMS and other micro-analytical surface techniques. The review aims at being of interest on the one hand to the S-SIMS users looking for interesting application areas and on the other hand, to the application chemists searching a method, potentially capable of yielding specific information for their material analysis problem. © 1999 John Wiley & Sons, Inc., Mass Spec Rev 18: 1–81, 1999

Static secondary ion mass spectrometry (S-SIMS) Part 1: methodology and structural interpretation

Static secondary ion mass spectrometry (S-SIMS) allows the chemical characterization of the constituents in the upper monomolecular layer of a solid sample. Within the range of micro-analytical methods, S-SIMS occupies a rather unique position in that it combines monolayer sensitivity with the capability to generate molecular information. In general, elemental ions, structural fragments, molecular and adduct ions are generated from both inorganic and organic molecules, including polymers. The chemical analysis of the upper monolayer makes S-SIMS especially suited to the study of the interface chemistry in a variety of materials. Polymer applications take an important place because S-SIMS allows a lot of information on these often intractable materials, e.g., identification, detection of surface functionalities, study of segregation of copolymer components and molecular weight (MW) distributions. In addition to the qualitative identification, S-SIMS allows high reproducibility and thereby permits quantitative studies with the aid of standards. Finally, S-SIMS offers imaging capabilities to visualize directly the distribution of given components within the upper surface layer of solids. Mapping with high lateral resolution is feasible for elemental ions and in favorable cases also for organic compounds. This review aims at a comprehensive coverage of the S-SIMS literature of the past decade. It comprises two parts, of which the first part deals with the more general aspects of the technique. It begins with a brief tutorial review of instrumentation, methodology and current concepts of ion formation. Particular attention is given to the link and difference with the matured dynamic SIMS method. Finally, imaging in S-SIMS is discussed. Application of S-SIMS to complex materials makes the interpretation of signals, in terms of the sample composition, intricate but crucial. Therefore, the features of inorganic and organic mass spectra are surveyed to assess the structure specificity and the kind of information obtainable. The second part of this review focuses on a variety of applications, primarily in the field of material sciences. Detailed studies on the surface chemistry of catalysts are discussed. The increasing importance of surface modification and tailoring to improve the interface properties has generated a wide range of applications. Examples from different technologies and industrial processes, such as semiconductors, paint, composite materials and corrosion protection of metals, are highlighted. Attention is devoted to the complementarity between S-SIMS and other micro-analytical surface techniques. The review aims at being of interest on the one hand to the S-SIMS users looking for interesting application areas and on the other hand, to the application chemists searching a method, potentially capable of yielding specific information for their material analysis problem. © 1999 John Wiley & Sons, Inc., Mass Spec Rev 18: 1–81, 1999

Interaction of beryllium with molecular and ion deuterium. deuterium retention in the codeposited beryllium/deuterium layer

Abstract The study of the surface and bulk processes (retention, oxide layers effects, sputtering, implantation defects formation in the ion stopping region, codeposition) is very important for the prediction of the hydrogen isotopes inventory in the plasma facing materials (PFM). This work presents the results of the SIMS studies after gas phase saturation and implantation, preferential sputtering of the beryllium oxide films by the D+ and He+ ions, and the ERD measurements of the Be/D codeposition. The deuterium retention in beryllium after gas phase saturation (1 Pa, 575 K) and 5 keV D+ bombardment at temperature 375 K were studied by the SIMS method. The deuterium depth distribution is presented for the implantation case. Sputtering of the beryllium oxide films by the D+ and He+ ions was compared. The Be oxide films preferential is sputtered during the deuterium ions bombardment. Beryllium deposition to the glass plate was performed in a Penning discharge cell in pure D-Kr atmosphere and in the D-Kr g...

An Algorithm for Solving the Factorization Problem in Permutation Groups

The factorization problem in permutation groups is to represent an elementgof some permutation groupGas a word over a given setSof generators ofG. For practical purposes, the word should be as short as possible, but must not be minimal. Like many other problems in computational group theory, the problem can be solved from a strong generating set (SGS) and a base ofG. Different algorithms to compute an SGS and a base have been published. The classical algorithm is the Schreier–Sims method. However, for factorization an SGS is needed that has all its elements represented as words overS. The existing methods are not suitable, because they lead to an exponential growth of word lengths. This article presents a simple algorithm to solve the factorization problem. It is based on computing an SGS with elements represented by relatively short words over the generators.

SIMS: computation of a smooth invariant molecular surface

SIMS, a new method of calculating a smooth invariant molecular dot surface, is presented. The SIMS method generates the smooth molecular surface by rolling two probe spheres. A solvent probe sphere is rolled over the molecule and produces a Richards-Connolly molecular surface (MS), which envelops the solvent-excluded volume of the molecule. In deep crevices, Connolly's method of calculating the MS has two deficiencies. First, it produces self-intersecting parts of the molecular surface, which must be removed to obtain the correct MS. Second, the correct MS is not smooth, i.e., the direction of the normal vector of the MS is not continuous, and some points of the MS are singular. We present an exact method for removing self-intersecting parts and smoothing the singular regions of the MS. The singular MS is smoothed by rolling a smoothing probe sphere over the inward side of the singular MS. The MS in the vicinity of singularities is replaced with the reentrant surface of the smoothing probe sphere. The smoothing method does not disturb the topology of a singular MS, and the smooth MS is a better approximation of the dielectric border between high dielectric solvent and the low dielectric molecular interior. The SIMS method generates a smooth molecular dot surface, which has a quasi-uniform dot distribution in two orthogonal directions on the molecular surface, which is invariant with molecular rotation and stable under changes in the molecular conformation, and which can be used in a variety of implicit methods of modeling solvent effects. The SIMS program is faster than the Connolly MS program, and in a matter of seconds generates a smooth dot MS of a 200-residue protein. The program is available from the authors on request (see http:@femto.med.unc.edu/SIMS).

Application of the SIMS Method in Studies of Cr Segregation in Cr‐Doped CoO: I, Aspects of Quantitative Analysis

Aspects of calibration of intensities of SIMS secondary ions vs concentration as well as sputtering time vs depth are considered for Cr‐doped CoO. Advantages and limitations of the SIMS method in quantitative analysis of segregation‐induced concentration profiles in oxide crystals are discussed. The studies indicate a substantial effect due to charging the surface during sputtering. The depth calibration was performed by using the Ta2O5/Ta system as a standard. Good depth resolution was revealed. The calibration dependence of Cr intensities on concentration is characterized by a wide scatter of data caused by charging the surface. Very good shape reproducibility of the intensity ratio vs depth profiles was revealed. Therefore, normalized intensity ratios can be used for calibration.

Application of the SIMS Method in Studies of Cr Segregation in Cr‐Doped CoO: II, Depth Profiles

Surface segregation‐induced depth profiles of Cr were determined for Cr‐doped CoO single crystals equilibrated at different temperatures (1373–1673 K) and oxygen partial pressures (102–105 Pa). It was shown that the shape of the depth profiles depends on both conditions of annealing and subsequent cooling procedure. It has been observed that during slow cooling of specimens from the condition of segregation equilibrium at elevated temperatures to the temperature of the experiment (room temperature), there is substantial change of the concentration profile involving desegregation of Cr (Cr diffusion from the surface to the bulk) resulting in its depletion. It has also been shown that the rate of the desegregation process (the process which results in a decrease of surface concentration) is slower than the lattice transport kinetics of Cr in CoO. It is concluded that the desegregation is rate‐controlled by the decomposition of a spinel‐type bidimensional surface structure which is formed at elevated temperatures as a result of Cr segregation.

Precise determination of the isotopic composition of potassium: Application to terrestrial rocks and lunar soils

We detail a method for the precise and accurate determination of isotopic variations in the 41 K 39 K ratio with a precision of ±0.5‰ (2 σ m). Purified potassium is chemically extracted from rocks, soils, minerals, or solutions by ion exchange chromatography. Complete chemical yields (>99.8%) are achieved in order to avoid laboratory-induced isotopic fractionations. The purified potassium is converted to a glass by melting with barium borate flux, and the resultant bead is mounted for ion probe analysis. The SIMS method utilized by the ion probe produces extremely stable K+ ion beams, with no measurable temporal variability in the isotope ratio. The instrumental fractionation is steady at about −4‰, and is corrected for by measurement of a standard. The measurement of gravimetrically prepared isotopic standards indicates that the method is accurate at the stated level of precision and free of egregious errors. Analysis of terrestrial samples including peridotite, basalts, granites, carbonatite, biotite schists, and seawater, indicate the complete absence of isotopic variations in δ41 1K among terrestrial materials at the 0.5%o level. Application to lunar soils and a regolith breccia confirms previously observed large isotopic fractionation effects (Garner et al., 1975a; Church et al., 1976). Some lunar soils, e.g., 14163, are shown to have large sample heterogeneity (≈7%o), while others, e.g., soils and a regolith breccia at several Apollo 15 sites (Station 7 9 ), are homogeneous at the level of analytical precision. The presence of potassium isotopic effects in bulk soils (up to +12.7‰ in this study) with magnitudes comparable to the Rayleigh fractionation factor (25‰) indicates that volatility during micrometeorite impact melting played a large role in lunar regolith formation. As much as 15% of the regolith potassium has been lost from the Moon, through the tenuous lunar atmosphere.