Analysis of the antitarnish film on a tin surface by x-ray photoelectron spectroscopy and Auger electron spectroscopy

A corrosion-resistant complex film formed in ethylenediaminetetra(methylidenephosphonic acid) (EDTMP) solution was determined by x-ray photoelectron spectroscopy and Auger electron spectroscopy to consist of 48.0% O, 11.7% Sn, 7.7% N, 22.1% C and 10.5% P. From the differences in the binding energies of Sn, N and O before and after film formation and the RPO^2?₃ and SnN vibrations in the Raman spectrum of the film, it was deduced that N and O in EDTMP were coordinated with Sn in the film.     

X-ray photoelectron spectra and Auger studies of the surface oxidation of cobalt

Surface oxidation of Co has been investigated at different temperatures in the 300–600 K range at oxygen exposures upto 10⁶ L by XPES and AES techniques. In the XPES, both the valence band and core level bands have been employed to monitor the oxidation while in the AES, metal Auger intensity ratios as well as O(KLL)/Co(L₂₃M₄₅M₄₅) ratios have been examined. Only CoO is formed on the surface at high oxygen exposures at and above 500 K. Communication No. 62 from the Solid State and Structural Chemistry Unit.     

State of the Cu electrode surface studied by X-ray photoelectron and Auger spectroscopies

Annealing of the copper plate in flame was found (by XPS and X-ray Auger spectroscopy) to enrich the surface copper layers in oxygen in the forms of Cu₂O and adsorbed oxygen. The changes in the surface layers of the copper cathode due to annealing can be the origin of the earlier found enhancement of its activity in the electrocatalytic hydrogenation of citral and trans-2-allyl-6-R-1,2,3,6-tetrahydropyridines (R = Me, All, Ph). This method of the copper electrode pre-treatment provides its long durability, an insignificant decrease in the electrocatalytic activity in time, and the reproducibility of the electrocatalytic hydrogenation of unsaturated organic compounds.     

Quantitative surface analysis by Auger and x-ray photoelectron spectroscopy

Recent developments in quantitative surface analysis by Auger (AES) and x-ray photoelectron (XPS) spectroscopies are reviewed and problems relating to a more accurate quantitative interpretation of AES/XPS experimental data are discussed. Special attention is paid to consideration of elementary physical processes involved and influence of multiple scattering effects on signal line intensities. In particular, the major features of core-shell ionization by electron impact, Auger transitions and photoionization are considered qualitatively and rigorous approaches used to calculate the respective transition probabilities are analysed. It is shown that, in amorphous and polycrystalline targets, incoherent scattering of primary and signal Auger and photoelectrons can be described by solving analytically a kinetic equation with appropriate boundary conditions. The analytical results for the angular and energy distribution, the mean escape depth, and the escape probability as a function of depth of origin of signal electrons as well as that for the backscattering factor in AES are in good agreement with the corresponding Mote Carlo simulation data. Methods for inelastic background subtraction, surface composition determination and depth-profile reconstructions by angle-resolved AES/XPS are discussed. Examples of novel techniques based on x-ray induced photoemission are considered.     

Copper passivity and its breakdown in sodium bicarbonate solutions: A scanning electron microscopy and x-ray photoelectron and auger spectroscopy study

Effect of bicarbonate ions on the copper passivity and its local breakdown is studied by cyclic voltammetry, Auger spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy. Comparing data for solutions with various sodium bicarbonate concentrations shows copper to undergo pitting in 0.02 M NaHCO₃, whereas it remains stably passive in 0.10 M NaHCO₃. Independent studies suggest that carbonates play a protective role in stabilization of the oxide-hydroxide passive film on copper.     

X-ray photoelectron spectroscopy of boron compounds

The results of X-ray photoelectron (XPS) studies of boron compounds (predominantly boron hydrides and their derivatives — 49 compounds) are presented. The results are analyzed to form a representative set of XPS data for the boron element.     

Analysis of PPMMA films from oxygen plasma using X-ray photoelectron spectroscopy

Plasma polymerized methyl methacrylate (PPMMA) films have been synthesised on silicon substrates in RF glow discharge using oxygen plasma. The electron beam delineation sensitivity of the PPMMA films has been studied systematically by varying oxygen and monomer flow rates. X-ray photoelectron spectroscopy (XPS) analysis clearly illustrates how C/O ratio in the films determines the properties of PPMMA films as electron beam resist. © 1994 John Wiley & Sons, Inc.     

Quantitative analysis of trace levels of surface contamination by X‐ray photoelectron spectroscopy. Part II: Systematic uncertainties and absolute quantification

We discuss analyses of trace levels of surface contamination using X‐ray photoelectron spectroscopy (XPS). The problem of quantifying common sources of statistical and systematic uncertainties for these measurements is formulated in terms of the needs of extreme ultraviolet lithography, but the results and conclusions are applicable to a broad range of XPS applications. We quantify the systematic uncertainties introduced by particular cases of overlapping peaks on different substrate structures by simulating measured spectra with the National Institute of Standards and Technology Database for the Simulation of Electron Spectra for Surface Analysis (SESSA). One example demonstrates that the relative atomic concentrations of trace elements such as S, P, and halogens on a Ru surface could be dramatically overestimated if the fitting of the overlapping Ru 3d and C 1s peaks excludes the contribution from carbon. We also show how spectra generated by SESSA can be compared with measured spectra to determine absolute amounts of surface impurities on layered samples of the type used for extreme ultraviolet lithography. We provide estimates of the total uncertainty for such measurements by considering the systematic limitations of SESSA and the statistical uncertainties of the measurements. The same procedure can be employed for other multilayered materials. Finally, we describe two approaches for converting XPS detection limits for an elemental impurity in an elemental matrix to the corresponding detection limits for the impurity as a thin film on the surface of the matrix material.     

Quantitative analysis of trace levels of surface contamination by X‐ray photoelectron spectroscopy. Part I: Statistical uncertainty near the detection limit

We discuss the problem of quantifying common sources of statistical uncertainties for analyses of trace levels of surface contamination by using X‐ray photoelectron spectroscopy. We examine the propagation of error for peak‐area measurements by using common forms of linear and polynomial background subtraction including the correlation of points used to determine both background and peak areas. This correlation has been neglected in previous analyses, but we show that it contributes significantly to the peak‐area uncertainty near the detection limit. We introduce the concept of relative background subtraction variance (RBSV) that quantifies the uncertainty introduced by the method of background determination relative to the uncertainty of the background area itself. The uncertainties of the peak area and atomic concentration and of the detection limit are expressed using the RBSV, which separates the contributions from the acquisition parameters, the background‐determination method, and the properties of the measured spectrum. These results are then combined to find acquisition strategies that minimize the total measurement time needed to achieve a desired detection limit or atomic‐percentage uncertainty for a particular trace element. Minimization of data‐acquisition time is important for samples that are sensitive to X‐ray dose and also for laboratories that need to optimize throughput.     

Interlaboratory study comparing analyses of simulated angle‐resolved X‐ray photoelectron spectroscopy data

An interlaboratory study has been conducted to determine the following: (i) the similarities and differences of film thicknesses and composition profiles obtained from analyses of simulated angle‐resolved X‐ray photoelectron spectroscopy (ARXPS) data by different analysts using different algorithms for data analysis, and (ii) the effects of two assumptions commonly made in data‐analysis algorithms for ARXPS on derived film thicknesses and composition profiles. The analyzed data were generated by the National Institute of Standards and Technology Database for the Simulation of Electron Spectra for Surface Analysis, (SESSA) which provides a simple way to study the influence of the aforementioned effects on compositional depth profile reconstruction. Sets of simulated ARXPS data were produced for thin films of SiO₂, SiON, HfO₂, and HfON of varying thicknesses on a Si substrate. For some HfON films, the N concentration varied with depth. Eleven groups participated in the round robin study. The majority (eight) employed a commercial ARXPS instrument in which the angular distribution is measured for a fixed sample geometry, in contrast to conventional ARXPS in which the sample is tilted for angular variation. The average deviations between the reported average depth, film thickness, and amount of material typically varied between 20% and 30% but were considerably larger, between 30% and 80%, for some cases. The average errors were generally larger for simulations that included elastic scattering and the finite analyzer‐acceptance angle (realistic conditions) than those for simulations that neglected elastic scattering and the finite analyzer‐acceptance angle (simplified conditions). The retrieved N depth profiles were quantitatively different from the true depth profiles and showed substantial variability among the group of members who used the same instrument and analysis software. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantitative surface analysis performed with an imaging photoelectron spectrometer

The paper gives an outline of the basic principle of our imaging technique for XPS. The advantage of the concept is its excellent applicability to quantitative pixel information. This idea is verified by two examples which are representative for routine problems in XPS. These are quantitative surface analysis and determination of overlayer thicknesses. A lateral resolution of at least 0.2 mm is achieved and thus a pixel size of 0.2 mm × 0.2 mm can be quantified automatically by means of numerical algorithms without need of reference samples.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Donor-acceptor properties of isonitriles studied by photoelectron spectroscopy and electron transmission spectroscopy

Some alkyl and aryl isonitriles, considered as CO analogue sigma-donor and pi-acceptor ligands in transition metal chemistry, were studied by means of HeI photoelectron spectroscopy and electron transmission spectroscopy, in order to evaluate their donor-acceptor properties from the measured ionization energies (IE) and vertical electron attachment energies (VAE). The investigated molecules were 2-propyl, 1-butyl, tert-butyl, 1-pentyl, cyclohexyl, 2,6-dimethylphenyl, 4-methoxyphenyl and 4-chorophenyl isonitrile. By interpreting the spectra on the basis of literature data and quantum chemical calculations, the spectral features associated with the molecular orbitals mainly involved in coordination and back-donation were identified. The results show that the IE (10.62-10.95 eV) of the sigma electron pair (n(c)) responsible for the sigma-donor capability is substantially lower than that of CO. The VAEs of the empty pi* orbitals involved in the d/pi* back-donation indicate that aryl isonitriles are better acceptors (VAE <0.3 eV) than their aliphatic counterparts (VAE >2.7 eV). In the case of aryl derivatives, the pi-donor ability could also play some role in metal-ligand bonding (IE 8.74-9.34 eV). Isonitrile coordination characteristics are also compared with those of CO, N(2) and CH(3)CN.     

Summary of ISO/TC 201 Standard: XX ISO 18118: 2004 – Surface chemical analysis – Auger electron spectroscopy and X‐ray photoelectron spectroscopy – Guide to the use of experimentally determined relative sensitivity factors for the quantitative analysis of homogeneous materials

ISO 18118 provides guidance on the measurement and use of experimentally determined relative sensitivity factors for the quantitative analysis of homogeneous materials by Auger electron spectroscopy (AES) and X‐ray photoelectron spectroscopy (XPS). This article provides a brief summary of this International Standard. Copyright © 2005 John Wiley & Sons, Ltd.     

Polypyrrole-coated poly(vinyl chloride) powder particles: surface chemical and morphological characterisation by means of X-ray photoelectron spectroscopy and scanning electron microscopy

Polypyrrole (PPy)-coated poly(vinyl chloride) (PVC) powder particles were prepared by the in situ chemical polymerisation of pyrrole in aqueous solutions in the presence of PVC powder particles. The PVC particles in suspension served as a hydrophobic substrate for the in situ polymerisation of pyrrole using iron chloride as the oxidising agent and sodium p-toluene sulfonate. In these conditions, tosylate-doped PPy (PPyTS) was obtained and chlorides were inserted as minor codoping species. In some cases, the pyrrole was polymerised after incubating the PVC particles with poly(N-vinyl pyrrolidone). Scanning electron microscope (SEM) micrographs showed that the PVC particles retained their initial, quasispherical shape after coating by PPy. At low magnification, the coated PVC particles appeared smooth, but at high magnification, they exhibited a decoration by elementary nanoparticles of about 200-nm size due to PPy bulk powder grains. Elemental analysis indicated a mass loading of PPy in the range 1–58% w/w. Specific surface analysis by X-ray photoelectron spectroscopy (XPS) resulted in the spectra of the PPy-coated PVC particles resembling those of bulk powder PPyTS even for low PPy mass loading. The surface fraction of PPy repeat units was found to vary in the 55–91% range. This result is consistent with the SEM observation of the PPy nanoparticles at the surface of PVC powder grains. However, despite the important loading of PPy, the XPS estimation of the overlayer thickness is in favour of a patchy coating rather than continuous coatings of PPy.     

X-ray photoelectron spectroscopy analysis of the surface composition of Azospirillum brasilense in relation to growth conditions

X-ray photoelectron spectroscopy (XPS) has been used to determine the surface chemical composition of the Gramnegative bacterium Azospirillum brasilense as a function of growth conditions. As opposed to growth in complex medium, growth in synthetic medium led to low reproducibility of XPS results, and did not show a significant variation of the cell surface composition as a function of culture time; moreover, the molecular composition obtained by modelling the XPS data was found to be generally poorer in proteins, and richer in polysaccharides and in hydrocarbon-like compounds. The direct correlation between the phosphate concentration and the concentration of carbon bound only to carbon and hydrogen, ---(C,H), indicated that hydrocarbon-like compounds detected at the surface of cells grown in synthetic medium are essentially phospholipids. The poor reproducibility of the XPS data obtained for cells grown in synthetic medium and the random observation of phospholipids at the outermost cell surface are not due to cell disruption or to migration of intracellular components during sample preparation; exposure of phospholipids at the cell surface reflects either actual variations of the composition of the native surface induced by nutrient limitation or reorganization of cell surface polymers upon freeze drying.     

A X-ray photoelectron spectroscopy study of HDTMAB distribution within organoclays

X-ray photoelectron spectroscopy (XPS) in combination with X-ray diffraction (XRD) and high-resolution thermogravimetric analysis (HRTG) has been used to investigate the surfactant distribution within the organoclays prepared at different surfactant concentrations. This study demonstrates that the surfactant distribution within the organoclays depends strongly on the surfactant loadings. In the organoclays prepared at relative low surfactant concentrations, the surfactant cations mainly locate in the clay interlayer, whereas the surfactants occupy both the clay interlayer space and the interparticle pores in the organoclays prepared at high surfactant concentrations. This is in accordance with the dramatic pore volume decrease of organoclays compared to those of starting clays. XPS survey scans show that, at low surfactant concentration (<1.0 CEC), the ion exchange between Na⁺ and HDTMA⁺ is dominant, whereas both cations and ion pairs occur in the organoclays prepared at high concentrations (>1.0 CEC). High-resolution XPS spectra show that the modification of clay with surfactants has prominent influences on the binding energies of the atoms in both clays and surfactants, and nitrogen is the most sensitive to the surfactant distribution within the organoclays.     

Investigation of Ti/CuO interface by X-ray photoelectron spectroscopy and atomic force microscopy

The Ti/CuO interface has been studied by the techniques of X-ray photoelectron spectroscopy and atomic force microscopy. Thin films of titanium were deposited on a CuO substrate at room temperature by the e-beam technique. The photoelectron spectra of titanium and copper were found to exhibit significant chemical interaction at the interface. The titanium overlayer was observed to get oxidized to TiO₂, while the CuO was observed to get reduced to elemental copper. This chemical interaction was observed to occur until a thickness of 7 nm of the titanium overlayer. For thicknesses greater than this value, the presence of unreacted titanium in the sample was detected. Barrier characteristics at the Ti/CuO interface were also carried out for substrate temperatures of 300°C, 400°C, 500°C, and 600°C as a function of the titanium overlayer thickness. A linear trend in the barrier thickness of the overlayer was observed between 400°C and 600°C substrate temperatures. The atomic force microscopy micrographs of the unannealed samples depicted layer-by-layer growth of elemental titanium on copper. At the Ti/CuO interface in such samples, the micrographs exhibited island formation of TiO₂ corresponding to the Volmer-Weber growth model. This formation has been interpreted as the relaxation in the strain energy. The percentage coverage of the underlying substrate by the TiO₂ islands showed a linear trend for the thicknesses of the titanium overlayer investigated. The average size of these islands also showed a linear trend as a function of the thickness of the overlayer.     

Investigation of surface and thermogravimetric characteristics of carbon-coated iron nanopowder

Demand for high-density press and sinter components is increasing day by day. Of the different ways to improve the sinter density, the addition of nanopowder to the conventional micrometer-sized metal powder is an effective solution. The present investigation is aimed at studying the surface chemistry of iron nanopowder coated with graphitic carbon, which is intended to be mixed with the conventional iron powder. For this purpose, iron nanopowder in the size range of 30 nm to submicron (less than 1 micron) was investigated using thermogravimetry at different temperatures: 400°C, 600°C, 800°C, 1000°C, and 1350°C. The X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and high-resolution scanning electron microscopy (HR-SEM) were used for characterizing the powder as well as samples sintered at different temperatures. The presence of iron, oxygen, carbon, chromium, and zinc were observed on the surface of the nanopowder. Iron was present in oxide state, although a small metallic iron peak at 707 eV was also observed in the XPS spectra obtained from the surface indicating the oxide scale to be maximum of about 5 nm in thickness. For the sample treated at 600°C, presence of manganese was observed on the surface. Thermogravimetry results showed a two-step mass loss with a total mass loss of 4 wt.% when heated to 1350°C where the first step corresponds to the surface oxide reduction.     

利用X射线光电子能谱研究马家塔煤显微组分中氧的赋存形态

煤中氧的赋存形态是煤结构研究的重要内容,煤炭加工转化（如煤的热解、直接加氢液化等）也需要确实详尽的煤中氧赋存形态的数据信息。x射线光电子能谱法（x—ray Photoelectron Speetroscopy,XPS）是近年来新出现的最有效的元素分析方法之一,目前,已在化学、物理、生物等各个领域中得到广泛应用。1974年,XPS分析方法首次用于煤的研究,近年来,XPS成为研究煤中硫和氮存在形态的有效方法之一。许多学者在煤中无机矿物中碳、氧、硫的存在形态及XPS直接测定煤中有机硫等方面做过较多研究工作,但由于煤结构的复杂性、实验条件不尽相同以及煤中矿物的干扰等,以往的研究结果并不完全相同。     

X-ray emission and X-ray photoelectron studies of electron density distribution in Cu(II) complexes with 2-imidazoline nitroxides

Electron density distribution in Cu(II) complexes with 2-imidazoline nitroxides was investigated by X-ray emission and X-ray photoelectron spectroscopy. The structure of the highest occupied molecular orbital (HOMO) of the compounds is determined mainly by the interaction of the metal with the donor atoms of the ligands. Coordination of the nitroxide by the Cu(hfac)₂ acceptor matrix changes the shape of the CuL _α spectral line. The 3s X-ray photoelectron spectra provide evidence about the transfer of electron density to the copper atom in the complexes.