bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of pretreatment on a platinized tin oxide catalyst used for low‐temperature Co oxidation
Authors: Drawdy Jean E. , Hoflund Gar B. , Gardner Steven D. , Yngvadottir Eva , Schryer David R. 
Published: May 2005

AbstractA commercial platinized tin oxide catalyst used for low‐temperature CO oxidation has been characterized using ion scattering spectroscopy, Auger electron spectroscopy and electron spectroscopy for chemical analysis before and after reduction in 40 Torr of CO for 1 h at various temperatures in the range 75–175°C. The reduction results in loss of surface oxygen, formation of metallic tin, conversion of platinum oxides to PtOSn and Pt(OH)2 and a small amount of metallic Pt which alloys with the tin. These results should be useful in understanding how the pretreatment temperature affects the catalytic activity of platinized tin oxide toward CO oxidation.
XPS intensities and binding energy shifts as metal dispersion parameters in Ni/SiO2 catalysts
Authors: Gonzalez‐Elipe A. R. , Munuera G. , Espinos J. P. 
Published: May 2005

AbstractA set of Ni/SiO2 catalysts with metal loadings between 1 and 8% by weight has been prepared by several methods. Metal dispersions have been determined by H2 chemisorption and x‐ray line broadening analysis, giving metal particle sizes from ∼30 to 250 Å.XPS analysis of the samples has been recorded after reduction in situ and the data correlated with the metal loading and metal dispersion. When comparing the Ni 2p intensities, a good relationship has been obtained with metal surface concentration, showing the existence of two well‐defined set of catalysts with particles of quite different sizes. However, a single linear relationship is obtained for all the samples when the Ni 2p binding energies are plotted against the metal dispersion calculated from H2 chemisorption. The origin of the binding energy shift and its relation with metal dispersion is discussed.
FTIR study of nickel and copper oxidation: Theoretical approach and experience
Authors: Machefert J. M. , Le Calvar M. , Lenglet M. 
Published: May 2005

AbstractThe behaviour of the specular reflectance of several oxides on metals (Cr2O3 on Cr, Cu2O on Cu) has been studied theoretically and experimentally in the infrared region. Theoretical and experimental are in accordance with each other. The results obtained on pure metals are applied to the sudy of 80 Ni‐20 Cr and 55 Cu‐45 Ni alloys in order to identify the oxides grown on the oxides grown on the surface during thermal oxidation.
A general and simple approach for the determination of energy analyser transmission functions
Authors: Carrazza José , León Vladimir 
Published: May 2005

AbstractThe transimmison function of energy analyzer LHS‐11 from Leybold‐Heraeus has been obtained from the dependence of the signal intensity on the instrument pass energy (Ep) at a given kinetic energy of the incident electrons (Ek).For the energy analyzer, the transmission function has been expressed by the equation

A slight dependence of the exponent n on Ek is observed, and it has been fitted by the equation

This is a very general characterization of the transmission that gives its analytical description in the whole XPS range for a given set of operational parameters, such as slit dimensions, sample size and sample position.From the transmission function obtained and using reported values of the photoionization cross‐sections, two sets of XPS sensitivity factor for several elements have been calculated. With these factors, the surface concentrations of a multi‐element sample have been determined with good agreement between the values after Mg and AI Kα excitation. These results suggest that corrections due to variations in the transmission function with Ek can improve the accuracy of the calculated sensitivity factors.
X‐ray photoelectron spectroscopic studies of the bonding of phenyl sulfides to copper
Authors: Beecher James F. 
Published: May 2005

AbstractThe chemisorption and bonding of different phenyl sulfides with copper have been studied by x‐ray photoelectron spectroscopy (XPS). Volatile phenyl sulfides were employed: phenyl mercaptan, diphenyl sulfide and diphenyl disulfide. The reactions were conducted in an evacuated chamber adjacent to the analytical chamber of the XPS spectrometer so that the oxidation state of the copper could be controlled.Chemisorption and bonding depend both upon the phenyl sulfide species and the oxidation state of copper. The mercaptan reacts with copper in either state; oxygen is displaced from the oxidized copper surface and copper phenyl mercaptide is formed. Phenyl sulfide does not react with copper metal but displaces oxygen from the oxidized copper, along with the formation of a mercaptide. Diphenyl disulfide forms a mercaptide with unoxidized copper but does not react with oxidized copper. Some evidence for the formation of another unknown sulfide species is found in the reaction of diphenyl disulfide with copper.
Periodic variations in the nitrogen KLL Auger intensity from interstitial nitride films
Authors: Dawson Peter T. 
Published: May 2005

AbstractTransition metal nitride films have been prepared by reaction of ammonia gas at 300 Torr pressure with nine different transition metals at high temperatures in the range 900–1200°C. The films produced were typically microns thick and could therefore be characterized by x‐ray diffraction, in addition to Auger electron spectroscopy and scanning electron microscopy. Strong periodic variations in the intensity of the nitrogen KLL Auger emission have been observed from the nitrides of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W. The measured nitrogen signal was observed to decrease within each group, and also across each period. These results are discussed with reference to matrix effects in the Auger emission and the stability and structure of the interstitial nitrides.
Surface treatment of aluminum and titanium: From basic research to production failure analysis
Authors: Davis Guy D. 
Published: May 2005

AbstractHigh‐performance adhesive bonds require clean, microscopically rough adherend surfaces that are compatible with the adhesive or primer. Such surface allow wetting by the polymer and a complete filling of the pores of ‘nooks and crannies’. The resulting mechanical bonds supplement or supplant the chemical bonds present. For durability in aggressive environments, aluminum bonds that are exposed to high humidity also require hydration‐resistant oxide surfaces. Such hydration resistance is inherent in some surfaces, e.g. phosphoric acid‐anodized surfaces, and can be high temperatures, such bonds require oxide‐free surfaces when exposed to temperatures above 300°C. These surfaces can be formed by plasma spraying a metallic powder coating onto the titanium alloy. Although preparation of high‐quality surfaces and bonds is achieved readily in the laboratory, occasional failures are observed in the manufacturing environment owing to, for example, contamination, pH or temperature variations. These processing problems can prevent wetting of the surface or can destroy the microrough morphology. A basic understanding of the mechanisms involved in the production of appropriate surfaces and their resulting adhesive bonds and in their degradation is critical to the evaluation of the failures and their remedy.
Pretreatments of improve the adhesion of electrodeposits on aluminium
Authors: Monteiro F. J. , Barbosa M. A. , Ross D. H. , Gabe D. R. 
Published: May 2005

AbstractAluminium is generally regarded as a metal that is difficult to plate. By using a pretreatment sequence, which includes immersion in a zincate solution, it is possible to electroplate aluminium successfully, although adhesion levels are not always very high. Zincate solutions modified by the addition of various ions have been shown to promote adhesion. Using one such solution, an investigation has been carried out as to how, by modifying the pretreatment sequence, the adhesion on electrodeposits on aluminium can be improved. Such modifications included varying the etch procedures and using the so‐called double dip technique. Some of the factors giving rise to the improved adhesion of electrodeposits have been investigated by SEM, AES, SIMS, ESCA, EPMA and AAS.
AES/GDS characterization of thin oxide films on FeCr sheet steels
Authors: Suzuki S. , Suzuki K. 
Published: May 2005

AbstractThin oxide films on four kinds of commercial sheet were characterized with Auger electron spectroscopy (AES) and glow discharge optical emission spectroscopy (GDS). Enrichment of alloying elements was noticed in the thin oxide films formed in air. The depth profiles obtained by AES with ion sputtering showed that enrichment of chromium occurred at the interface between the oxide and the matrix. It was difficult with AES to obtain the profiles of silicon and manganese because of overlap of their peaks with the iron peaks on the spectrum. On the other hand, with GDS, silicon and manganese could be analysed quantitatively in thin films that are <0.05 μm thick.
Facts and artefacts in the characterization of Si/SiGe multiayers with SIMS
Authors: Zalm P. C. , Vriezema C. J. , Gravesteijn D. J. , van de Walle G. F. A. , de Boer W. B. 
Published: May 2005

AbstractA number of Si/Si1−x Gex heterostructures, grown by molecular beam epitaxy (MBE) and vapour phase epitaxy (VPE), were examined with secondary ion mass spectrometry (SIMS). A variety of experimental conditions was employed, limited to positive secondary ions and moderate to excellent depth resolution. The most elaborate results were obtained for O2 + primary ion bombardment at energies of 2–8 keV. These demonstrate (for x < 0.4): (1) a minimal erosion rate variation with germanium content x; (2) the near‐absence of matrix effects, i.e. x dependence, of the secondary ion yields for impurities like B, Ga, Sn, Sb and others; (3) an approximately concentration‐independent sensitivity for germanium. Furthermore, a surface‐energy‐difference‐driven, Ge‐segregation mechanism operative during MBE growth is discussed. This phenomenon is just one manifestation of the fundamentally different processes during MBE and VPE. Such processes may be responsible for the fact that interfaces in MBE samples, as obtained with SIMS, are loss abrupt than for VPE material. A simple explanation in terms of an inferior substrate‐cleaning procedure cannot be ruled out, however.
Noval detection scheme for the analysis of hydrogen and helium by secondary ion mass spectrometry
Authors: Gnaser H. , Oechsner H. 
Published: May 2005

AbstractFor the analysis of hydrogen and helium in solids and thin films by secondary ion mass spectrometry, the use of Cs+ primary ions in conjunction with the detection of HCs+ and HeCs+ molecular ions is proposed. For both species, detection limits of the order of 1019 atoms cm−3 are obtained at sputter removal retes of ∼1 nm s−1. A relative depth resolution of ∼2% is demonstrated for hydrogenated amorphous Is layers on single‐crystal Si. In these specimens, the HCs+ intensities scale linearly with the hydrogen concentrations cH in the range investigated (cH < 20at.%); hence, a quantitative evaluation of the H content appears possible by means of a single standard.
Structure of the adsorbed ethyl xanthate monolayer on copper
Authors: Laajalehto K. 
Published: May 2005

AbstractXPS intensity calculations from completely oriented and randomly oriented ethyl xanthate on copper have been made as a function of electron take‐off angle. Corresponding experiments also were carried out using the variable‐angle XPS (VAXPS) method. The results show that the completely oriented ethyl xanthate layer model at a certain stage of adsorption seems to be valid, as originally proposed by Mielczarski et al. However, there are systematic errors in the calculations, which are mainly due to uncertainties in calculated electron mean free paths and absolute values of parameters characterizing the assumed adsorption layer structure.
Analytical expression describing the attenuation of Auger electrons and photoelectrons in solids
Authors: Werner W. S. M. , Gries W. H. , Störi H. 
Published: May 2005

AbstractThe attenuation of Auger electrons and photoelectrons in solids as described by the so‐called depth distribution function (DDF), has been studied by means of a Monte Carlo simulation of electron transport in matter. Elastic scattering plays a significant role in the model. Based on the results of a large number of simulations, an empirically derived analytical expression for the DDF is proposed that includes the effects of elastic scattering. As part of this analytical DDF, a new attenuation parameter (AP) is introduced, which being a material constant independent of emission angle and layer thickness, can assume a central role in quantitative AES and XPS. The proposed AP as well as the general validity of the results is discussed. Most importantly, a simple relationship between the most significant quantities governing the transport of electrons in transport of electrons in solids, i.e. the inelastic mean free path (IMFP), the total mean free path (TEMP) and the attenuation parameter, was derived from the results. By a single Monte Carlo simulation, the AP can be determined. The DDF for different experimental geometries, film thicknesses, etc. can then be determined analytically.
Quantitative surface chemical analysis of AuCu alloys with XPS
Authors: Yoshitake M. , Yoshihara K. 
Published: May 2005

AbstractThe work of VAMAS‐SCA project no. 25 is reported. The project was an XPS round robin with thgree different compositions of AuCu alloys (Au 25 at.%,–Cu 75 at.%, Au 50 at.%–Cu 50 at.%, Au 75 at.%–Cu 50 at.%.). These alloys were alson the subject of an earlier AES round robin ( VASMAS‐SCA project no. 17). Pure gold and pure copper was used as the standard materials. By using peak areas of the Au 4f doublet and Cu 2p3/2 for the calculation, the effects of measurement conditions and data processing on quantification were examined. The reliability of quantification by three methods, namely the ‘relative sensitivity factors’ method, the ‘pure metals as standard materials’ method and the ‘alloy as standard material’ method, was compared. It is concluded that measurement conditions such as photoelectron emission angle and energy resolution did not affect quantification and that there was no effect of the different background subtraction methods on quantification. With the ‘alloy as standard material’ method, variations of the measured surface concentrations were the smallest, namely ∼2–6%.
Static secondary ion mass spectroscopic investigations of deuterated poly (ethylene terephthalate)
Authors: Ramsden William D. 
Published: May 2005

AbstractThe positive and negative ion static SIMS spectra of poly(ethylene terephthalate) (PET) deuterium labeled on either the ethylene glycol units or the terephthalate units were obtained and compared to those of unlabeled PET. These data confirm the ion structure assignments previously reported and allow the assignment of the origins and structures of most of the remaining peaks. The majority of the ions derive logically from the PET structure. A major mode of fragmentation f the PET chains is shown to be the break‐up of ester linkages to produce a carboxylic acid and a vinyl ester. This involves predominate transfer of a hydrogen atom from the glycol unit to the newly formed acid group. Minor, but interesting, ions have been detected which result form the recombination of fragments. These ions have structures not directly derived from the original polymer backbone and may add to the difficulties involved in analyzing the static SIMS spectra of ‘unknown’ surfaces as they suggest atomic connectivities which are not present on the original surface.
AES: Accurate intensity calibration of electron spectrometers—results of a BCR interlaboratory comparison co‐sponsored by the VAMAS SCA TWP
Authors: Seah M. P. , Smith G. C. 
Published: May 2005

AbstractAn interlaboratory study of the calibration of the intensity scales of Auger electron spectrometers has been completed. Thirty‐eight respondees have completed intensity measurements using pre‐calibrated reference materials of Cu, Ag and Au in either the direct or differential modes. The reference material calibrations, made at NPL, involve the recording of true spectra under defined conditions using the metrology spectrometer, in which all instrumental contributions to intensity have been accurately clibrated. The ratio of the spectral intensity form the respondee to that derived at NPL gives the intensity–energy response function of the respondee's instrument. In the direct mode this function may be calibrated at 1 eV intervals from 10 to 2500 eV using any one of the reference materials. By using all three materials it is shown that the average repeatability of the calibrations for the 38 respondees is better than 3% over the energy range 10–2500 eV, improving to < 2% over the range 100–1000eV. The mot serious unknown parameter that has given rise to uncertainty in the intensity function in the past has been the channel electron multiplier ditector efficiency. It is shown here that this term behaves as predicted theoretically and, if ignored, can lead to a factor of two error in intensity. With the present calibration the errors should be reduced to 2% for spectrometers in which there is little internal scattering. In the differential mode twelve peaks are used to define the intensity‐energy calibration. This calibration is less accurate than that in the direct mode and, at the present time, a one‐standard deviation uncertainty of ∼11% is more appropriate. In both modes a loss of intensity owing to multiplier overloading may cause severe errors in the high‐energy peaks.
Impurity migration during SIMS depth profiling
Authors: Vriezema C. J. , Zalm P. C. 
Published: May 2005

AbstractAmong the many processes that affect the accuracy of sputter depth profiling, ion beam‐induced segregation (IBIS) may result in impurity relocations over many micrometres. The most devastating IBIS mechanism of distribution disruption is known to become operative when certain impurities in silicon are profiled under oxide‐forming measurement conditions. Here, we forward evidence that in this particular manifestation of IBIS the bild‐up of an electric field across an insulating surface layer provides an important driving force. Migration towards as well as away from the bombarded surface is observed whenever negative or positive charging conditions are applied. This behaviour has only been observed for elements with a tendency to become singly positively charged ions. In the absence of an electric field, a smaller segregation effect of Group Ia elements away form the surface is shown. Occurrence of this effect for the Group Ia and not for the other elements is indicative of a possible influence of the thermodynamic differences. Further aspects of this field‐induced migration are discussed on the basis of extensive experiments in which the role of the concentration of segregating impurity and the mobility of the impurity in the insulating layer is investigated.A justification of the methodology adopted is provided. Earlier attempts to explain this particular form of IBIS are examined critically.
Study of concentration‐dependent dielectric properties of n‐type GaAs using variable angle spectroscopic ellipsometry
Authors: Snyder Paul G. , Xiong Yi‐Ming 
Published: May 2005

AbstractThe dielectric function ε spectra of Si‐doped n‐type GaAs crystals at room temperature (296 K) have been determined between 1.53 and 5.01 eV, using variable angle spectroscopic ellipsometry (VASE). Samples with carrier concentrations ranging from 4.6 × 1017 to 3.3 × 1018 cm−3 were measured. The effects of surface microscopic roughness, native oxide overlayer and the subsurface damage were mathematically removed with an appropriate multilayer model. The GaAs dielectric function spectra were modeled using the sum of seven harmonic oscillators, whose center energies, half‐widths and amplitudes were fitting parameters in the multilayer model. It was found that, as the doping level increased, the E1 and E1 + Δ1 peak structures near 3 eV in the ε2 spectrum broadened considerably more than the E0′ and E2 peak structures near 4.7 eV, while the amplitude of the E1 peak decreased with respect to that of the E1 + Δ1 peak. Other effects due to doping were a shift of the ε2 spectrum towards lower energies and a decrease in the amplitude of the E2 peak.
Low‐energy Auger electron spectroscopy of clean and oxidized Cu(100) and Fe/Cu(100) surfaces
Authors: Daas H. Den , Gijzeman O. L. J. , Geus J. W. 
Published: May 2005

AbstractThe background subtraction method for undifferentiated Auger spectra proposed by Peacock is shown to be reliable for the low‐energy Fe and Cu MVV peaks. This is illustrated by the good results obtained for spectra of clean and oxidized Cu(100), Cu(100) containing 0–5 monolayers of Fe and oxidized surfaces. This variety of surfaces made it possible to test the method on spectra with overlapping peaks of different heights and on spectra in which the peak shape changed.The spectra of the unoxidized Cu (100)/Fe surfaces could be described by weighted sums of the pure Cu and Fe MVV peaks. The background intensity at energies higher than the Cu peak could be used as an internal calibration factor for the spectra. These results are used to calculate the inelastic mean free paths for the Cu and Fe MVV electrons, which were 0.36 ± 0.07 and 0.44 ± 0.09 nm, respectively.For the oxidized surfaces the Fe (oxide) peak could be extracted by a simple subtraction of a pure Cu MVV peak. This Cu peak apparently did not change shape upon oxidation.
Preparation and surface characterization of silica‐supported ZrO2 catalysts; comparison of layered model systems with powder catalysts
Authors: De Jong A. M. , Eshelman L. M. , van IJzendoorn L. J. , Niemantsverdriet J. W. 
Published: May 2005

AbstractModel supports consisting of a thin layer of SiO2 on a silicon single crystal have been used to study ZrO2/SiO2/Si model systems made by the same wet chemical preparation methods as used in the preparation of technical catalysts. The results obtained with the models are in good agreement with those on ZrO2 catalysts on porous silica supports.
Energy dependence of UPS peak intensities of physisorbed SF6 layers: Influence of the IMFP
Authors: Klekamp A. , Umbach E. 
Published: May 2005

AbstractThe energy dependence of the electron inelastic mean free path (IMFP) or, more precisely, of the attenuation length (AL), λ(E), may drastically influence the relative intensities of valence peaks, even within the UPS He(II) spectrum of a single species. This is shown for the well‐characterized adsorbate system SF6 on Ni(111), for which five valence peaks are observed in a relatively small energy range of 8 eV. With He(II) radiation the kinetic energies of these peaks range between 23 and 31 eV, and their intensities vary by up to 60% for adsorbate layers of different thicknesses. This potentially confusing effect can be used to determine λ and its energy dependence in the low kinetic energy range (<35 eV). We find λ values between 3.5 and 7.5 monolayers; their energy dependence differs from that expected from the Seah and Dench equation.