bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic properties of Strandberg anions: A DFT study of [X2Mo5O23]n−, (X = PV, SVI, AsV, SeVI), and [(RP)2Mo5O21]4− (R = H, CH3, C2H5)
Authors: Yan Li‐Kai , Su Zhong‐Min , Tan Ke , Zhang Min , Qu Lun‐Yu , Wang Rong‐Shun 
Published: May 2005

AbstractThe electronic properties of the anions mentioned in the title polyanions were calculated by means of Density Functional Theory (DFT). The redox properties and the basicity of the external oxygen sites of those polyanions were analyzed. The results show that the redox properties of Strandberg anions depend on the nature of heteroatom X. The organic group bonded to the heteroatom modifies the redox property of the cluster. The oxygen basicities of the polyanions were analyzed by virtue of molecular electrostatic potential (MEP). The MEP distribution suggests that the most basic centers are triple‐bridging oxygen atoms, one of which is shared with two metal atoms and one heteroatom X in [P2Mo5O23]6− and [As2Mo5O23]6−. In [(RP)2Mo5O21]4−, the triple‐bridging oxygen atoms and the double‐bridging oxygen atoms bonded to two Mo atoms identified as the most basic centers. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Theoretical study of helical structure caused by chirality of cysteine dimer
Authors: Liu Shu‐Zhen , Wang Hong‐Qi , Zhou Zheng‐Yu , Dong Xiu‐Li , Gong Xiao‐Li 
Published: May 2005

AbstractIn this work we report a theoretical study of the helix structure and chiral discrimination on the interactions between the chiral cysteine–cysteine. Two reasonable geometries on the potential energy hypersurface of the cysteine–cysteine system are considered with the global minimum. Accurate geometric structures, relative stabilities, harmonic vibrational frequencies, and infrared (IR) intensities were investigated. To take into account the water solvation effect, the Onsager model within the self‐consistent reaction field (SCRF) method and the polarized continuum (PCM) method were used to evaluate the interaction energy, ΔGsolv at the same level employed in the gas phase. The results indicate that the polarity of the solvent plays an important role in the structures and relative stabilities of different isomers. Computational results indicate that the global minimum should be conformer I regardless of whether in the gas phase or in aqueous solution, which differs from previous theoretical reports. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Yuri Alexeev, Theresa L. Windus, Chang‐Guo Zhan, David A. Dixon, Erratum to “Accurate heats of formation and acidities for H3PO4, H2SO4, and H2CO3 from ab initio electronic structure calculations,” International Journal of Quantum Chemistry (2005) 102(5) 775–784
Authors: Alexeev Yuri , Windus Theresa L. , Zhan Chang‐Guo , Dixon David A. 
Published: May 2005

AbstractThe original article to which this Erratum refers was published in International Journal of Quantum Chemistry (2005) 102(5) 775–784
XPS study of ethyl xanthate adsorbed onto cuprous sulphide
Authors: Mielczarski Jerzy , Suoninen Eero 
Published: May 2005

AbstractAdsorption of xanthate ions from an aqueous solution of potassium ethyl xanthate onto the surface of synthetic polycrystalline chalcocite (Cu2S) samples has been studied by measuring the XPS lines Cu 2p3/2, O 1s, C 1s and S 2p from samples exposed for different times to the xanthate solution. The analysis takes into account the attenuation of the signals, arising from the composition of the sample surface and the orientation of the adsorbed species. The adsorption mechanism is found to consist of a relatively rapid formation of a well‐oriented monolayer of xanthate ions followed by a slow growth of a disordered cuprous xanthate molecules on top of this layer. This mechanism seems to be common for the adsorption of xanthate on many different substrates.
Quantification of preferential sputtering and contamination overlayer effects in AES sputter profiling
Authors: Hofmann S. , Sanz J. M. 
Published: May 2005

AbstractA model calculation is presented for the quantitative evaluation of AES sputtering profiles of thin layers in the case of preferential sputtering and a contamination overlayer. The model is based on the statistical contribution to depth resolution, the escape depth effect correction and the preferential sputtering model of Ho et al. (1976). Applications to measured AES sputtering profiles of the anodic oxides Ta2O5 and Nb2O5 allow the determination of the thickness and the oxygen content of the contamination overlayer.
Study of the fiber/matrix interface in a SiC reinforced titanium alloy using a high resolution field emission Auger microprobe
Authors: Dudek H. J. , Larson L. A. , Browning R. 
Published: May 2005

AbstractUsing a high‐resolution Auger microprobe the chemical structure of the interface in a SiC reinforced titanium alloy has been examined. Only two phases, TiC and Ti5Si3, are identified in the interface. A TiC layer next to the SiC fiber was proven to form a diffusion barrier for titanium. The results aid in the understanding of the fiber surface degradation process during sample production and suggests processes for the further development of these composites.
Analysis of the Auger KLL spectra of carbon by the pattern recognition method
Authors: Lesiak B. , Mrozek P. , Jabloński A. , Jóźwik A. 
Published: May 2005

AbstractThe carbon KLL spectra were analysed using the pattern recognition methods. The standard spectra were recorded for (i) surface tungsten carbide, (ii) bulk tungsten carbide, (iii) graphite and (iv) amorphous carbon. The set of these spectra was a basis for the process of recognition. The careful analysis of the set of standard spectra made possible construction of several procedures (classifiers) for recognizing the chemical form of carbon corresponding to a given spectrum. The KLL spectra of carbonaceous residue growing on nickel foil were analysed using all the developed classifiers. At the early stages of growth the carbidic form of carbon was recognized, followed by the graphitic form at further stages. This result agrees with observations reported in the literature.
Distribution analysis of carbon and sulphur in CVD‐Al2O3‐layers by SIMS using Cs+ primary ions
Authors: Wilhartitz P. , Grasserbauer M. , Altena H. , Lux B. 
Published: May 2005

AbstractSecondary ion mass spectrometry was used to determine the carbon and sulphur content of aluminium oxide layers. Information about the lateral distribution was gained using ion imaging. For the characterization of the depth distribution, sputter profiling with high mass resolution was applied. Carbon was found to form a network structure within the aluminium oxide layer but carbides could not be detected. Evaluation of atomic and molecular ion patterns were used for speciation of carbon. Practical sensitivity factors were determined and used for semiquantitative evaluation of the depth profiles. The sputter rate of aluminium oxide and the ionisation probabilities of oxygen and aluminium were calculated.
Effects of the alloying elements Ti, Nb, Mo and V on the grain boundary segregation of P in iron and steels
Authors: Grabke H. J. , Möller R. , Erhart H. , Brenner S. S. 
Published: May 2005

AbstractInvestigations have been performed on the effects of the alloying elements Ti, Nb, Mo and V on the grain boundary segregation of phosphorous in iron and steels. The methods are AES analysis of grain boundaries on intergranular fracture faces and field‐ion microscopy and mass spectrometry (atomprobe). The elements Ti and Nb show strong interaction with P, keeping P in the grain and decreasing its grain boundary segregation. In the alloys and steels containing carbon, Ti and Nb react under formation of carbides, therefore with increasing C content the grain boundary segregation of P increases. For stoichiometric ratio Ti/C and Nb/C the segregation reaches a maximum; at higher carbon contents C displaces P from the grain boundaries. Some interfacial segregation of P is observed at or near the ferrite/carbide interface in the case of TiC, leading to a decrease of grain boundary segregation. The same effect applies for Mo2C but not for NbC. In contrast to Ti and Nb there is no direct interaction of Mo and P, which is also in contradiction to previous assumptions on the role of molybdenum in the temper embrittlement of low alloy steels.
Application of XPS to the surface analysis of yeast cells
Authors: Amory D. E. , Genet M. J. , Rouxhet P. G. 
Published: May 2005

AbstractYeast cells, Saccharomyces cerevisiae and carlsbergensis, have been analysed by XPS.A preparation and analysis procedure was developed in order to minimize contamination and re‐arrangements of the cell surface. The use of an external standard of silica permitted the absolute surface concentrations to be estimated and the influences of sample preparation procedure on surface roughness and chemical composition of the cell surface to be evaluated separately. The selected procedure consisted of washing the cells in distilled water, freezing a pellet in liquid nitrogen, freeze‐drying at 268 K, mounting the obtained powder in a trough and pressing the surface.Repeated analyses on a given yeast strain enable the variances linked to the main steps of the preparation procedure for each surface element to be evaluated; thereby, confidence intervals can be given for any small set of XPS data. Freeze‐drying is the main source of variation and samples which have to be compared should be freeze‐dried together. The reproducibility of the surface concentration decreases in the order C, O, N, P and is much better for the N/P ratio than for N or P alone.The neutrality of the XPS preparation and analysis procedure towards the yeast cell surface is supported by the correlation obtained for ten yeast strains between the surface N/P ratio (dehydrated state) and the electrophoretic mobility at pH 4 (hydrated state). This gives confidence in the ability of XPS to investigate a biological surface. The surface specificity of XPS is illustrated by the very low O/C (0.39) and N/C (0.1) concentration ratios which denote a high proportion of lipids at the cell surface (60–70%), in contrast with the low proportion in the whole cell wall (8%).
XPS analysis of oxides
Authors: Paparazzo E. 
Published: May 2005

AbstractThe principal scope of this work is to explore the capacity of XPS spectroscopy in the characterization of oxides through consideration of O 1s spectra. Several examples of oxides, analysed both separately and in the form of mechanical mixtures, are reviewed. The quantitative aspects involved in the XPS analysis of oxide mixtures were studied by use of an approach based on intensity ratio measurements of the single O 1s components.Results obtained in the mixtures are utilized for establishing the presence, or otherwise, of a single oxidic phase at real interfaces of iron‐alumina systems, metallurgical coatings, and glasses.
Sample preparation effects in the surface analysis of V/Ti alloys
Authors: Dawson P. T. , Hu M. P. 
Published: May 2005

AbstractThe surface composition of V–21% Ti alloy as revealed by Auger electron spectroscopy becomes depleted in Ti on bombardment with 2‐kV argon ions. Alloy composition changes by preferential sputtering are frequently observed, but what is surprising in this case is that a steady‐state composition is not achieved until after ca. 8 h of sputtering. Experience with other alloy systems has been that steady state is attained in minutes; furthermore, it is difficult to conceive an atomic process which would account for such slow composition changes. The alloys was prepared by monoarc co‐melting of the pure metals, slicing with a slow‐speed diamond saw and mechanical polishing down to 1 μ diamond. The polishing damage will extend several micrometres below the sample surface, which is consistent with the thickness of sample removed by 8 h of ion bombardment. A possible model is provided by radiation induced segregation, where the defects created by ion bombardment of the alloy annihilate at both external and internal surfaces associated with polish damage. At the beginning of the sputtering, the internal surface provides the dominant sink, whereas after the polish damage has been entirely removed this is provided by the external ‘analysed’ surface. This interpretation was tested by preannealing a freshly polished specimen to remove the polish damage before sputtering. In this case, the steady‐state composition was attained in minutes, as predicted by the model. One final question concerns the absence of such effects in other systems, e.g. W/Mo, Cr/Mo. The answer can probably be found in the different room temperature mobilities of the ion‐bombardment‐induced defects in such refractory alloys when compared with V/Ti. This is supported by the composition changes observed on ‘room temperature annealing’ when bombardment of V/Ti is stopped, an effect never observed in the refractory alloys.
Electron‐stimulated desorption, secondary emission and charging of ionic crystals
Authors: Atabaev B. G. , Besedina E. A. , Kareev M. S. , Dzabbarganov R. 
Published: May 2005

AbstractNegative and positive charging of ionic monocrystals (KCl, NaCl, Al2O3, MgO, SiO2 and LiH) under low‐energy electron irradiation is investigated by AES and mass spectrometry. Secondary emission and electron‐stimulated desorption negative ions of LiH data are presented. The mass spectra of sputtered neutrals post‐ionized into negative ions, and their ionization coefficients on the auxiliary target with a low work function, are presented. A phenomenological model of charging of dielectrics that depends on defect formation and secondary emission properties under low‐energy electron irradiation is presented.
Surface analysis to study the improvements of silicon nitride/gallium arsenide interface properties
Authors: Cassette S. , Plais F. , Olivier J. 
Published: May 2005

AbstractIt has been shown that NH3, plasma treatment of GaAs surfaces before deposition of plasma‐enhanced chemical vapour deposited silicon nitride significantly improves the SiNH/GaAs interface properties. The decrease of surface state density together with the increase of Fermi level excursion in the energy gap are correlated with chemical spectroscopic measurements.
Standard reference spectra for XPS and AES: Their derivation, validation and use
Authors: Smith G. C. , Seah M. P. 
Published: May 2005

AbstractA principal requirement for quantitative AES and XPS is the ability to measure true spectral intensities. In order to achieve this we have developed a fully instrumented electron spectrometer to measure absolute intensities for AES and XPS. The spectra contain no distortion due to the energy dependencies of the analyser transmission or the detector efficiency, and therefore provide the true spectrum n(E) with a known uncertainty. In addition, the intensity scale is known accurately in terms of electrons detected per unit of incident flux. The experimental methods and theoretical basis used in the determination of standard reference spectra are discussed, and results are presented for both Auger electron and x‐ray photoelectron spectroscopies. AES or XPS spectra of NPL reference materials taken on any user's instrument, with the appropriate conditions, may be compared with the true spectra derived here to calibrate the energy dependence of that particular instrument's intensity scale. In this way, all instruments may be calibrated absolutely to an accuracy of ±2%.
Back‐scattering and X‐ray‐induced correction factors for AES of thin overlayers: Influence on lateral resolution
Authors: Valamontes E. , Nassiopoulos A. G. , Glezos N. 
Published: May 2005

AbstractSome results on Monte‐Carlo calculations of back‐scattering and x‐ray‐induced correction factors for AES on thin overlayers have been given in a previous paper. In this work, further results are given concerning both correction factors and the lateral resolution in the primary beam energy range 5–60 keV. The x‐ray‐induced correction factors include both characteristic and continuous x‐rays created in the bulk by the primary electron beam or by back‐scattered electrons that contribute to the creation of Auger electrons within the film on their way out of the sample. The contribution of continuous x‐rays, negligible at low primary beam energies, is found to be important at energies of >20 keV. The influence of back‐scattering on the lateral resolution in the primary beam energy range 20–60 keV has also been studied.
Influence of nickel on the behaviour of superferritic 290 Mo alloys in sulphuric and hydrochloric acid media: XPS, AES and electrochemical studies
Authors: Traisnel M. , Elachab M. , Gengembre L. , Leroy J. M. 
Published: May 2005

AbstractImpedance and potentiodynamic polarization measurements show that the addition of nickel to superferritic 290 Mo alloys improves their resistance to the corrosion process in sulphuric acid and plays a disastrous part in hydrochloric acid. The chemical composition, thickness and depth profile of the passivating layers obtained in sulphuric acid are determined by using XPS and AES. In the anodic polarization domain, chromium oxide is the major component of the passivating layers and the addition of nickel increases its segregation slightly. In the cathodic polarization domain, the addition of nickel leads to passivating layers that are clearly more developed. Chromium oxide is no longer the major component, and an important segregation of molybdenum oxide and, to a lesser extent, nickel oxide towards the uppermost layer is observed.
Surface analysis of uranyl fluoride layers with a glow discharge lamp
Authors: Nel J. T. , Stander C. M. , Böhmer R. G. 
Published: May 2005

AbstractSurface analysis with a Grimm‐type glow discharge lamp was used to analyse uranyl fluoride layers that had formed on a nickel sufbstrate after exposure to UF6. Narrow‐band optical filters were used to isolate the intensities of three fluorine emission lines. An in‐depth profile of layer composition was obtained.
Surface characterization of coated powders: Al2O3SiO2‐coated TiO2
Authors: Johansson Leena‐Sisko , Losoi Tuomo 
Published: May 2005

AbstractThe aim of this study has been to find experimental strategies to characterize surface of coated powders. We have studied hydrous alumina + silica‐coated TiO2 pigments using different XPS methods, isoelectric points (ieps) and x‐ray fluorescence (XRF). We tested especially the applicability of a simple XPS analysis method introduced by Tourgaard et al.Coated TiO2 powders were analysed qualitatively with ieps, XPS surface concentrations, XPS depth profiling, and Ti 2p photoemission peak‐to‐background ratio D, The ratio D together with surface concentrations, was found to characterize well the quality of the coating. Differences in surface layers were affirmed also by ieps and XPS profiling.The asymptotic value of D for uncoated, uncontaminated TiO2 powder, interpolated from qualitative results, was ∼25 eV. This is within 25% of the predicted universal constant (25.2 eV) for transition metals and alloys.Coating layer thicknesses were calculated from XRF and XPS data, the latter assuming an exponential attenuation model with superficial carbon. Based on the value of D, Ti 2p photoelectron mean path lengths (R) also were calculated from the experimental equation by Tougaard. We found good correlation between the results from conventional XPS layer calculations and the Tougaard equation. The methods are independent of each other. Together, they seemed to give more reliable information on the non‐ideal powder surfaces studied than either of the methods alone.
Ion–solid interaction at low energies: Principles and application of quantitative ISS
Authors: Niehus Horst , Spitzl Ralf 
Published: May 2005

AbstractQuantitative surface analysis with low‐energy (500–5000 eV) ion scattering is known to be difficult, most often because of strong charge transfer and multiple scattering effects occurring during ion–surface interaction. In order to avoid neutralization problems, either alkali primary ions or noble gas ions in combination with the detection of all scattered particles was applied. Multiple scattering occurs predominantly at forward scattering and might confound the analysis. Backward scattering (i.e. 180° impact collision ion scattering) bypasses strongly the multiple scattering complication and has been used successfully for the analysis of a number of surface structures for metals, semiconductors and binary alloys. Quantitative surface structures were determined by comparison with computer simulations.
Testing epoxy composite surfaces for bondability
Authors: Parker Brenda M. , Waghorne Rex M. 
Published: May 2005

AbstractComposite surfaces before and after pretreatment for adhesive bonding have been examined by x‐ray photoelectron spectroscopy (XPS) and the extent of transfer of release agents or other contaminants from release agents, which also were analysed by XPS, was estimated. Composite surfaces were examined also by optically stimulated electron emission (OSEE). Surface analyses were correlated with the strengths of adhesive bonded joints. OSEE shows promise as a non‐destructive method for determining the bondability of epoxy resin matrix composites.
Modification of polypropylene surfaces by flame treatment
Authors: Sutherland I. , Brewis D. M. , Health R. J. , Sheng E. 
Published: May 2005

AbstractThe changes induced on the surface of polypropylene homopolymer following flame treatment have been studied. Surface compositions were determined using x‐ray photoelectron spectroscopy and compared to surface free energies estimated from contact angle measurements. The effect of air‐to‐gas ratio, total flow rate, contact time with the flame and the distance between the inner cone tip of the flame and the polymer have been investigated. Mild flame treatments were found to be effective in promoting the adhesion of polyurethane paints to the polypropylene. The adhesion between flame‐treated polypropylene and the paint film was assessed using a composite butt test and the measured bond strengths were found to be well in excess of those obtained using solvent wiping or chlorinated polyolefin primers.
Analysing coated powders with XPS
Authors: Johansson Leena‐Sisko 
Published: May 2005

AbstractThe goal for this study has been to show how different XPS analysis methods may be used in the characterization of coated powders. An inhomogeneous powder system serves also as an example of inhomogeneous uneven samples in general.The XPS methods discussed here are: elastic peak measurements and the layer calculations derived from them; depth profiling by sputtering or by verying the analysing angle; and analysis of both elastic and inelastic parts of an XPS peak by methods introduced by Tougaard et al. Correlations between the results from different XPS methods are also discussed.As an example, XPS methods were applied to the surface characterization of real coated TiO2 pigments. XPS results are also compared both with XRF bulk analysis and with each other.
Quantification of carbon in MOVPE‐grown AlAs on GaAs substrates using SIMS
Authors: Maydell E. A. , Fabian D. J. , Roberts J. S. 
Published: May 2005

AbstractConcentrations of carbon in layer of metal organic vapour phase epitaxy (MOVPE)‐grown AIAs on GaAs substrates were determined by SIMS using a Cs+ primary ion beam. The measurements demonstrate that by using an ultrahigh vacuum (UHV)VG quadrupole‐based SIMS instrument and thorough outgassing of samples, sputter etching conditions can be established that give C− signals unaffected by residual gas interference, while maintaining good depth resolution.