bluuebunny/crossref_metadata_2025_split huggingface dataset:
XPS study of mixed cerium–terbium orthophosphate catalysts
Authors: Pemba‐Mabiala J. M. , Lenzi M. , Lenzi J. , Lebugle A. 
Published: December 2004

AbstractMonazite structure‐type solid solutions of cerium and terbium orthophosphates Ce1−xTbxPO4, with 0 < x < 1, were prepared by coprecipitation followed by calcination at 800°C for 2 h. They were used as catalysts for the oxidative dehydrogenation of ethylbenzene.The compounds Ce0.9Tb0.1PO4 and Ce0.7Tb0.3PO4, which give the maximum yield of styrene, were studied by XPS before and after catalysis. The binding energies were determined with carbon contamination as a reference (level 1s). Quantitative analysis was performed by using the limit compounds CePO4 and TbPO4 as standards. The surface composition before catalysis is slightly different from the bulk composition, whereas no significant variation of binding energies is observed. After catalysis, an important broadening of the peaks and a decrease of the (Ce + Tb)/P ratio appears. The decomposition of the P 2p and O 1s peaks allows us to show the formation of pyrophosphate at the catalyst surface. The formation of this phase during the catalytic reaction is connected to the mechanism of the surface reaction.
XPS analytical characterization of amorphous alloys: Fe70Cr10P13C7
Authors: De Filippo D. , Rossi A. , Elsener B. , Virtanen S. 
Published: December 2004

AbstractA qualitative and semiquantitative XPS analysis of the surface films formed on the amorphous Fe70Cr10P13C7alloy in the as‐received state after rapid quenching, after mechanical abrasion and after anodic passivation at +500 mV SCE in 1 N HCl was performed. A method for simulataneous evaluation of the thickness of the oxide layer and its composition is proposed.The results clearly show that oxidized phosphorus is incorporated in the outer layer of the passive film formed after anodic polarization at +500 mV SCE, in agreement with the model of the bipolar cation‐selective passive film proposed to explain the outstanding corrosion resistance of the alloy tested.
Depth profiling resonance ionization mass spectrometry of Be‐doped, layered III–V compound semiconductors
Authors: Downey S. W. , Emerson A. B. , Kopf R. F. , Kuo J. M. 
Published: December 2004

AbstractThe accumulation of Be at the interfaces of p‐type (NBe = 2 × 1019 cm−3) GaAs/AlAs and InGaAs/InAlAs structures grown by molecular beam epitaxy (MBE) is detected by depth profiling resonance ionization mass spectrometry (DPRIMS). These results help to interpret secondary ionization mass spectrometry (SIMS) matrix effects at interfaces. The magnitude of the effect depends upon the layer sequence. DPRIMS of heterojunction bipolar transistor (HBT) structures, made of GaAs and AlGaAs layers, show transient SIMS matrix effects from layers spaced 10.0 nm apart. Mass interferences in the Be profile of the HBT structure is precluded with DPRIMS. Therefore, this method allows more accurate interpretation of dopant profiles in these types of structures.
Surface segregation of substrate element on metal films in film/substrate combinations with Nb, Ti and Cu
Authors: Yoshitake M. , Yoshihara K. 
Published: December 2004

AbstractThe surface segregation of the substrate element on metal film by diffusion through the film was studied. Six film/substrate couples—Nb/Ti, Ti/Nb, Cu/Nb, Nb/Cu, Cu/Ti and Ti/Cu—deposited by rf magnetron sputtering were applied to investigate segregation behaviour, as well as Nb/Ti and Ti/Nb deposited by electron beam. The segregation behaviour of the substrate element by diffusion through the films was monitored at the film surface by AES. For Nb/Ti, Cu/Nb, Cu/Ti and Ti/Cu, the substrate element segregated on the film surface by diffusing through the film with a diffusion coefficient much larger than that corresponding to volume diffusion in the bulk. The segregation of Cu on Ti film was affected by an exposure of 2.6 × 10−6 Pa oxygen during heating. The activation energy for this diffusion was ∼60% of that in the bulk and the diffusion path seems to be the grain boundaries. The occurrence of this segregation via grain boundary diffusion did not depend on the film preparation process. From these results, the driving force of the segregation via grain boundary diffusion may be the decrease process. From these results, the driving force of the segregation via grain boundary diffusion may be the decrease of the surface free energy of film by the segregation of substrate element on grain boundaries and surfaces of films.
Analysis of polymer surfaces by SIMS: Part 15. Oxygen‐functionalized aliphatic homopolymers
Authors: Chilkoti Ashutosh , Ratner Buddy D. , Briggs David 
Published: December 2004

AbstractThe positive and negative ion spectra from simple oxygen‐containing aliphatic homopolymers (i.e. ethers, ketones, carboxylates and backbone esters) are reported. Interpretation of the static SIMS fragmentation patterns of these polymers is shown to be related to the structure of the polymer, in particular its heterofunctionality. A systematic investigation of the atomic secondary anions that are ubiquitous to all organic polymers reveals that their relative yields are not devoid of chemical information, but appear to be related to polymer structure.
Remarks on the surface characterization of carbon fibres
Authors: Desimoni E. , Casella G. I. , Cataldi T. R. I. , Salvi A. M. , Rotunno T. , Di Croce E. 
Published: December 2004

AbstractThe characterization of carbon fibres by x‐ray photoelectron spectroscopy depends on several experimental and theoretical aspects that noticeably improve the accuracy of the analysis when properly taken into account. These aspects are briefly discussed in the light of the most representative literature available. Attention is focused on points that need a deeper understanding and suggestions are given about possible analysis strategies.
Structural properties of BN thin films obtained by plasma‐enhanced chemical vapour deposition
Authors: Montero I. , Galán L. , Osòrio S. P. , Martínez‐Duart J. M. , Perrière J. 
Published: December 2004

AbstractIn this work BN films have been deposited by the plasma‐enhanced chemical vapour deposition (PECVD) technique on p‐type (100) silicon substrates, using borazine and nitrogen as precursors. X‐ray photoelectron spectroscopy, infrared spectroscopy, x‐ray diffraction, nuclear reaction analysis and Rutherford backscattering spectroscopy were used to analyse the films. The results of quantitative XPS analysis indicate the formation of a thin surface layer (∼3 nm) of boron oxynitride, BNO0.3, over a bulk of nearly stoichiometric boron nitride, BN1.1. The presence of the hexagonal phase mixed with amorphous boron nitride was identified. Infrared and Rutherford backscattering spectroscopies combined with a liquid etching technique were used to determine the composition and structure across the film thickness. From these measurements we infer that the composition across the film is nearly constant but with a gradual transition from an amorphous structure close to the Si/BN1.1 interface to an hexagonal structure towards the outer layers. Thermal treatments of the boron nitride films up to a temperature of ∼1000°C in a nitrogen atmosphere resulted in a small decrease of both the B/N atomic concentration ratio and the refractive index of the film. The insulating characteristics of the boron nitride for application as an intermetal dielectric were also treated. The electrical conduction results can be interpreted in terms of a Schottky mechanism, which allows us to calculate the high‐frequency dielectric constant, εr = 3.2.
X‐ray photoemission spectroscopy and scanning Auger microscopy studies of a Roman lead pipe ‘fistula’
Authors: Paparazzo E. , Moretto L. , D'Amato Clotide , Palmieri A. 
Published: December 2004

AbstractWe report scanning Auger microscopy (SAM) and x‐ray photoemission spectroscopy (XPS) analysis of a Roman lead pipe ‘flstula’, the main emphasis being placed on the comparison between the surface and interface chemical composition of the joint and of the rest of the pipe. We find that the ‘tertiarium,’ a Pb–Sn alloy that the Romans used for soldering the joint, has a beneficial effect in limiting the formation of white lead, 2PbCO3·Pb(OH)2·Comparison measurements performed in the alloy and the pure separate metals show that tin markedly limits the ambient surface oxdation of lead. Conversely, tin is much more oxidized in the alloy than when analysed alone. Auger point spectra indicate that carbon is the main surface contaminant of the patina of the fistula, and Auger imaging is used to pinpoint, with a spatial resolution of ∼0.5 ∼m, the distribution of this element at the interface of a lead/tertiarium solder, performed according to the procedures described by Plinius. The diagnostic capability of Auger transitions of lead and tin for distinguishing between different phases is discussed on the basis of their chemical shifts and surface sensitivities.
Auger/LEED linear heating study of Sn and S bulk‐to‐surface diffusion in a Cu(111)(Sn, S) single crystal
Authors: Viljoen E. C. , Du Plessis J. 
Published: December 2004

AbstractThe novel technique of linearly heating a sample to obtain both the pre‐exponential factor D0 and the activation energy E from a single run is applied to the Cu(111)(Sn, S) system. Using Auger electron spectroscopy the surface enrichment is measured as a function of time (temperature) and fitted with an integral expression containing the fit parameters D0 and E. The fit values at all heating rates agree excellently with published, our own experimental and conventional t1/2 values after temperature corrections.
XPS analysis of metal grain boundary surfaces
Authors: Hallam K. R. , Wild R. K. 
Published: December 2004

AbstractX‐ray photoelectron spectroscopy (XPS) can provide a quantitative analysis of the surface and determine the chemical state of elements present. However, until recently the spatial resolution has not been adequate to analyse small particles. As a result, Auger electron spectroscopy has been used to obtain elemental information where good spatial resolution is required. Analysis of grain boundary surfaces has therefore been restricted to this technique, with the result that no chemical‐state information has been obtained relating to the elements present on the grain boundary. This paper describes results in which grain boundary surfaces exposed in an imaging XPS instrument have been analysed using XPS. In particular, tin and phosphorus are shown to segregate to the grain boundary surface in the elemental state.
Monitoring the surface coverage of W/TiO2 catalysts by ion scattering spectroscopy
Authors: Fiedor Joseph N. , Houalla Marwan , Proctor Andrew , Hercules David M. 
Published: December 2004

AbstractA series of W/TiO2 catalysts was prepared by incipient wetness impregnation with W loadings varying from 1.64 to 28.4 wt.% WO3. The coverage of the TiO2 surface by W species was monitored by ion scattering spectroscopy (ISS). The results indicated that the W coverage increased from 21.6% for the 1.64 wt.% WO3/TiO2 catalyst to ∼85% for catalysts with W loadings ≥10.3 wt.% WO3. These values agreed with those predicted from monolayer‐like dispersion. The relatively constant coverage for W loadings > 10.3 wt.% WO3 was taken as an indication of multilayer or WO3 formation. These results were consistent with Raman and x‐ray photoelectron spectroscopy (XPS) data previously obtained in our laboratory.
X‐ray photoelectron spectroscopy investigation of pumice‐supported nickel catalysts
Authors: Venezia A. M. , Bertoncello R. , Deganello G. 
Published: December 2004

AbstractPumice‐supported nickel catalysts, prepared by the method of slow homogeneous precipitation with urea, were analysed by x‐ray photoelectron spectroscopy (XPS). By comparison with similarly prepared silica‐ and alumina‐supported nickel catalysts, a preferential interaction of Ni2+ with Al3+ of the support has been determined. A quantitative XPS analysis indicated large segregation of nickel to the surface. The treatment with H2 at 673 K and 1073 K produced a partial reduction of Ni+2 to Ni0. The extent of the reduction was largest at 1073 K and in this case the reduced Ni in the metallic phase was detectable by x‐ray diffraction. A decrease of the Ni 2p/Si 2p intensity ratio occurring in the lower temperature H2‐treated catalysts was attributed to diffusion of nickel as Ni2+, as a consequence of a solid‐state reaction between nickel ions and support oxides, whereas the decrease of the intensity ratio in the high‐temperature reduced catalysts was attributed to sintering of the nickel particles and to diffusion of nickel atoms interacting with oxygen vacancies of the support.
Interfacial layers formed during the moulding of nitrile butadiene rubber compounds: Influence of carboxylic acid residues on adhesion
Authors: Reeves L. A. , Kiroski D. , Packham D. E. 
Published: December 2004

AbstractThe mould release of nitrile butadiene rubber is strongly influenced by residues from the polymer and compounding ingredients that form an interfacial layer during moulding. Carboxylic acid residues may comprise an important part of this layer. There are two potential sources of these: emulsifier residues in the base rubber and ‘stearic acid’ added during compounding. Generally the mould adhesion decreases as the carboxylic acid concentration increases, but residues from longer chain acids, such as stearic acid, reduce adhesion to a greater extent than do those from shorter chain acids such as lauric acid. Evidence from XPS and SIMS shows that residues from both can come to the interface, but rheological results indicate that the latter are less easily sheared and so are associated with higher mould sticking.
Influence of formulation chemistry on the locus of failure of adhesive joints
Authors: Taylor A. M. , McLean C. H. , Charlton M. , Watts J. F. 
Published: December 2004

AbstractThe durability of photocured resins adhered to ceramic substrates has been investigated. Monochromated XPS and time‐of‐flight SIMS were employed to determine the precise locus of failure in butt‐joints comprised of a photocured resin adhered to either a 96% pure, debased alumina substrate or single‐crystal silicon. Prolonged (> 14 days) immersion in water at 50°C resulted in cohesive failure, with 1–2 nm of polymer remaining on one of the ceramic substrates. An absence in the spectrum of any components attributable to characteristic groups from a major constituent of the polymer within this overlayer suggested the possibility that one of the minor resin components was aggregating at the organic/inorganic interface to produce an in situ weak boundary layer. The interactions of some of the organic molecules present in the formulation with the α‐alumina substrate were investigated using molecular modelling techniques to indicate the most favourable interactions with the substrate. Durability studies were also carried out on a reformulated photocured resin to investigate the effect of removal of the ethoxylated methacrylate monomer, suspected of being the principal organic component at the weak boundary layer, on both joint performance and locus of failure.
Use of matrix corrections in the calculation of surface composition of AgPd alloys in auger electron spectroscopy
Authors: Reniers F. 
Published: December 2004

AbstractThe surface segregation in binary alloys is often studied by Auger electron spectroscopy. However, the information obtained in the Auger spectra is representative of a region thicker than one monolayer. The Auger signal must be decomposed into the contributions of the different atomic layers. On the other hand, it is now well known that matrix correction factors must be used to relate the intensity of the Auger signal to the composition of the sample. As these two parameters are seldom put together in the treatment of Auger data, we tried to combine them for the study of the surface segregation in silver–palladium alloys. We calculated the matrix correction factors for AgPd alloys in the whole range of concentrations. The attenuation length corrections and the backscattering corrections were calculated on the basis of different models (Seah and Dench, Penn, Tanuma–Powell–Penn, Ichimura–Shimizu–Langeron, Reuter–Ichimura, etc.). The matrix corrections were compared to the Hall and Morabito approach and with previously published results. The matrix corrections were then introduced into a layer‐by‐layer model of interpretation of the Auger signal. While the surface composition calculated without matrix correction reveals silver enrichment relative to the bulk of the samples, the use of matrix corrections lead to an enrichment in silver that is strongly attenuated.
Combined atomic force‐, friction force‐ and local elasticity microscopy on ReS2 crystals: Surface topography and material contrast
Authors: Schimmel Th. , Friemelt K. , Lux‐Steiner M. , Bucher E. 
Published: December 2004

AbstractCrystal surfaces of the layered dichalcogenide semiconductor rehenium disulphide (ReS2) grown by the vapour‐phase transport technique were investigated by combined atomic force microscopy (AFM), lateral (friction) force microscopy (LFM) and force modulation (local elasticity) microscopy as well as scanning electron microscopy (SEM). The as‐grown crystals exhibit atomically flat surfaces, on which circular islands with a typical diameter of 0.3 μm and a height of 30–50 nm have grown. While AFM only yields the topographic information, the simultaneously recorded lateral force and force modulation images give a clear material contrast, showing that on the islands the lateral forces are higher and the local elasticity is lower than on the bare ReS2 surface. The dependence of both the topographic and the lateral force images on the scanning direction is investigated. The results indicate that during crystal growth a different material, presumably ReBr3, has segregated on the surface of the ReS2 crystals. It is demonstrated that AFM in combination with LFM and force modulation microscopy can provide information on the composition of heterogeneous samples as well as the local mechanical properties of the different components.
Atomic force microscopy investigation of argon‐bombarded InP: Effect of ion dose density
Authors: Demanet C. M. , Malherbe J. B. , van der Berg N. G. , Sankar Vijaya 
Published: December 2004

AbstractSamples of InP(100) n‐doped with S atoms to 4 × 1018 cm−3 and to 6 × 1018 cm−3 were bombarded with 0.5 and 5 keV argon ions. The angle of incidence of the 5 keV ions was 71° with respect to the sample normal and 41° for the 0.5 keV ions. The resulting topography development was investigated by means of atomic force microscopy (AFM) and transmission electron microscopy (TEM) of Cr–C replicas of the bombarded surfaces. There was a correlation between the AFM images and those from the TEM replicas. At the same magnification the AFM images showed more detail. The surface roughness in the AFM images and those from the TEM replicas. At the same magnification the AFM images showed more detail. The surface roughness in the AFM images was quantified using the software of the AFM instrument. In the range 5 × 1014−2 × 1018 Ar+ cm−2, there was a linear relationship between the roughness parameter and the logarithm of the ion dose density. This fact excludes a seeding sputter erosional theory for the explanation of the development of bombardment‐induced topography on InP. At the higher does densities, ripple formation was observed. The dose density dependence of average wavelength of the ripples did not correlate with the predictions of the Bradley–Harper theory.
Fast simulation of XPS and AES spectra by transformations of electron trajectories
Authors: Alkemade Paul F. A. 
Published: December 2004

AbstractA new Monte Carlo simulation model is presented for the calculation of XPS or AES spectra of homogeneous or near‐homogeneous solids. The model is at least one order of magnitude faster than conventional simulation models. The increase in computation efficiency is obtained by translations and rotations of simulated electron trajectories.Simulations have been applied to evaluate a number of models for inelastic and elastic scattering. In addition, a successful comparison is made between simulated and measured XPS spectra of Al and of Ag over a range of 600 eV.
Electronic structure of tin oxides: High‐resolution study of XPS and Auger spectra
Authors: Kövér L. , Kovács Zs. , Sanjinés R. , Moretti G. , Cserny I. , Margaritondo G. , Pálinkás J. , Adachi H. 
Published: December 2004

AbstractHigh‐resolution core and valence band photoemission as well as photoinduced Auger spectra of metallic Sn, polycrystalline SnO and SnO2 ((110) natural single‐crystal cassiterite and polycrystalline) samples were measured in order to give information on local electronic and geometric structures around the core‐ionized atoms and for providing data for facilitating quantitative analysis of systems containing these species. The SnO surfaces were obtained without the use of ion sputtering by using a special preparation procedure based on in vacuo surface scraping. The respective experimental valence band spectra could be utilized in quantitative analysis of layered tin oxide structures. Valence band spectral shapes are compared to spectra calculated by using a cluster‐type (DV‐Xα) MO model. From the Sn Auger parameter measurements, using a simple electrostatic model, the similarity of the initial‐state effects for the two oxides was deduced, while the oxygen Auger parameter values indicated large polarizability and the respective final‐state hole–hole repulsion energies were determined.
Realistic cluster approach for interpreting the valence band structure of phosphorus oxyanions
Authors: Cserny I. , Kövér L. , Némethy A. , Adachi H. , Tanaka I. , Sanjinés R. , Coluzza C. , Margaritondo G. 
Published: December 2004

AbstractThe electronic structures of different phosphates were studied by using the DV‐Xα cluster molecular orbital method. Experimental data on crystal structures from x‐ray diffraction measurements were used to set up realistic model clusters. Theoretical XPS valence band spectra obtained from the DV‐Xα calculations were compared to our high‐resolution XPS measurements on polycrystalline powder Li3PO4, Na3PO4, Na4P2O7 and (NaPO3)n samples. These new measurements made possible a more rigorous test of the theoretical approach and more reliable shape analysis than the previous set of data obtained by non‐monochromatized measurements combined with the resolution enhancement technique. Systematic study of different clusters showed that the cations around the PO4 cluster and the distortion of the PO4 tetrahedra due to the anisotropic crystal forces play only a minor role and their influence on the valence band spectra was found to be negligible. In the case of polyphosphates, considerable changes were found in the valence band spectra as a consequence of small changes in the bond angle of the P—O—P bridges. Our results, based on cluster parameters specific to the anhydrous crystals, are in good agreement with the experiments.