bluuebunny/crossref_metadata_2025 huggingface dataset:
XPS characterization of biocompatible hydroxyapatite–polymer coatings
Authors: Casaletto M. P. , Kaciulis S. , Mattogno G. , Mezzi A. , Ambrosio L. , Branda F.
Published: October 2002

Hydroxyapatite coatings on polymeric substrates have been prepared by treating samples of poly(methyl methacrylate) (PMMA) and poly(2‐hydroxyethyl methacrylate) with a biomimetic method and by producing a mechanical mixture of polymers (PMMA and poly(butylmethyl methacrylate) and hydroxyapatite (1 : 1). The surface chemical composition of the samples has been studied by using X‐ray photoelectron spectroscopy. Both the reference polymers and the hydroxyapatite coatings have been analyzed. The surface modifications induced by interaction of the coatings with osteoblast cells have been studied as a function of the exposure time, after in vitro treatment for 7, 15 and 21 days. Quantitative XPS analysis enabled us to compare the quality of the samples and the different response to the in vitro treatment. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of thin Co/ZrO2 catalytic films by XPS, SEM and SAM
Authors: Stefanov P. , Atanasova G. , Robinson K. , Julbe A. , Guizard C. , O'Hara P. , Marinova Ts.
Published: October 2002

Thin Co/ZrO2 and Co/S‐ZrO2 catalytic films for hydrocarbon‐selective catalytic reduction (HC‐SCR) of NOx were prepared and characterized by means of XPS, SEM and scanning Auger microscopy (SAM). Zirconia was deposited on a fibrous inconel support (Bekaert) by the sol–gel method. Cobalt was deposited on pure and pre‐sulphated zirconia films by impregnation with a 6% CoCl2 solution. The photoelectron spectra indicated that cobalt was present mainly in the Co2+ state in the form of CoO‐like species. The SEM/SAM results showed homogeneous distribution and a smaller size of the Co particles deposited on pre‐sulphated zirconia compared with cobalt deposited on pure zirconia. The results indicated that sulphating of zirconia improved the dispersion of cobalt on the surface, which is a prerequisite for a good SCR performance. Copyright © 2002 John Wiley & Sons, Ltd.
Combined TPD and FTIR studies of Co/ZrO2 catalysts: determination of the cobalt dispersion
Authors: Hadjiivanov K. , Panayotov D. , Avreyska V. , Tsyntsarski B. , Klissurski D. , Marinova Ts.
Published: October 2002

Adsorption of NO on cobalt catalysts supported on zirconia and sulphated zirconia results in the formation of three main types of species: Zr4+(SO42−)‐NO and Zr4+(NO3−)‐NO nitrosyls (infrared band at 1940‐1906 cm−1), which are of low stability (temperature‐programmed desorption maximum at 55–80°C); Co2+(NO)2 geminal nitrosyls (set of bands at 1903‐1868 and 1814‐1777 cm−1) characterized by temperature‐programmed desorption maxima at 90–100°C; and linear Con+‐NO species (1942‐1858 cm−1) desorbing at 120–140°C. On the basis of the results obtained, a simple temperature‐programmed desorption technique for determination of the cobalt dispersion is developed. Copyright © 2002 John Wiley & Sons, Ltd.
Infrared investigation of the transformation of NO over supported Pt‐ and Rh‐based three‐way catalysts
Authors: Granger P. , Praliaud H. , Billy J. , Leclercq L. , Leclercq G.
Published: October 2002

The adsorption of NO and its reaction with CO have been investigated on Pt/Al2O3 and Rh/Al2O3 by in situ infrared spectroscopy. Different spectroscopic features have been observed on Rh and Pt after NO exposure at various temperatures, mainly related to the build up of positively, neutral and negatively charged NO species on Rh, with neutral NO species predominating on Pt. The formation of Rh‐NO+ and gem‐dicarbonyl species RhI(CO)2 during the adsorption of NO and the CO + NO reaction has been associated mainly with surface Rh oxidation at low temperature. On the other hand, the reductive properties of CO prevail above 250°C leading to the disappearance of the gem‐dicarbonyl structure. These infrared observations have been discussed on the basis of previous kinetic observations. Copyright © 2002 John Wiley & Sons, Ltd.
Angle‐resolved XPS analysis of molybdenum and tungsten in passive films on stainless steel PVD alloys
Authors: Olsson C.‐O. A. , Mathieu H.‐J. , Landolt D.
Published: October 2002

Passive films on physical vapour deposited alloys, based on 304L with additions of 20 at.% of molybdenum and tungsten, were studied with angle‐resolved XPS. The samples were anodically polarized in a sulphate solution to potentials in the low and high passive region, respectively. In the low passive region, the Mo spectrum contained a strong contribution of Mo(IV) hydroxide. In the high passive region, higher fractions of hexavalent species were found; W(VI) gave a stronger contribution than Mo(VI), as can be understood by the lower solubility of the W(VI) salts. Contributions to tetravalent molybdenum were found to consist of oxide (MoO2) as well as oxyhydroxide compounds. For tungsten, the dominating tetravalent contribution was WO2. Copyright © 2002 John Wiley & Sons, Ltd.
Oxidation of stainless steel under dry and aqueous conditions: oxidation behaviour and composition
Authors: Wambach J. , Wokaun A. , Hiltpold A.
Published: October 2002

The oxidation of austenitic stainless steel (316Ti) under dry oxidation and under pressurized aqueous conditions, both at ∼300°C, was studied by applying XPS, depth profiling and x‐ray diffraction. After dry oxidation a relatively smooth surface was found, depleted of chromium, nickel and molybdenum and leaving behind nearly exclusively iron oxides. In the oxide layer chromium oxides were detected, followed by metallic nickel and molybdenum. The growth of the whole oxide layer follows a logarithmic growth law. Under aqueous conditions a rougher surface was found, with oxide layers being a factor of ≥10 thicker than under dry oxidation conditions. A greater variety of the oxides were found, e.g. chromium and nickel oxides and hydroxides are present in considerable amounts already at the sample surfaces. Again, molybdenum is first detected in the oxide layer. During the first 60 days of steel oxidation in pressurized water, the oxide layer formation follows a parabolic growth law. Copyright © 2002 John Wiley & Sons, Ltd.
Corrosion inhibition of Al 6061 T6/Al2O3p 10% (v/v) composite in 3.5% NaCl solution with addition of cerium (III) chloride
Authors: Traverso P. , Spiniello R. , Monaco L.
Published: October 2002

The effect of cerium on corrosion inhibition of Al 6061 T6/Al2O3p 10% (v/v) metal matrix composite in aerated 3.5% NaCl solution after different immersion times at room temperature and pressure was investigated.

Experimental tests were conducted at different inhibitor agent concentrations (0, 200, 1000 and 2000 ppm of cerium) and for exposure times ranging from 2 h to 30 days. Corrosion inhibition power evaluation and surface layer characterization have been carried out by electrochemical (polarization potentiodynamic curves and impedance measurements) and free corrosion tests followed by several instrumental analyses (optical microscopy, x‐ray photoelectron spectroscopy, scanning electron microscopy).

Electrochemical data have shown that cerium compounds offer a noticeable inhibition level against localized corrosion in all considered cases and that the maximum protective power against corrosion attack is evident when the inhibitor is added at a 200 ppm concentration. Surface analysis revealed chemical and morphological characteristics of the passive layer. In particular, a higher amount of inhibitor led to the formation of a surface film with a higher content of cerium but without homogeneous distribution. This behaviour decreased the protection power of the passive layer while increasing composite substrate corrosion tendency. Copyright © 2002 John Wiley & Sons, Ltd.
Use of ToF‐SIMS in the study of corrosion processes: Monel 400 steam generator tubing under CANDU start‐up conditions
Authors: Francis J. T. , Brennenstühl A. M. , Ramamurthy S. , McIntyre N. S.
Published: October 2002

This work explores the use of time‐of‐flight secondary ion mass spectrometry to characterize films on Monel 400 steam generator tubing that has been subjected to simulated CANDU reactor start‐up conditions. The results are compared with those obtained using more traditional techniques, including scanning Auger microscopy and x‐ray photoelectron spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative analysis of the plasmon loss intensities in x‐ray photoelectron spectra of magnesium
Authors: Kurth M. , Graat P. C. J.
Published: October 2002

X‐ray photoelectron spectra of free‐electron metals such as magnesium and aluminium contain pronounced electron energy‐loss peaks due to plasmon excitations. Part of the intensity contained in these plasmon peaks is of an intrinsic nature. In this work a procedure is presented that allows the determination of intrinsic and extrinsic contributions to the plasmon loss structure and accounts for possibly different electronic properties at the surface. It is based on the reconstruction of a spectrum by convolution of physically realistic functions for the x‐ray energy distribution, the core‐level main peak, the cross‐sections for plasmon excitation and instrumental broadening. The procedure has been applied to an Mg 2p spectrum, giving a total intrinsic plasmon contribution of 46% relative to the main peak intensity. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative analysis of low‐energy N2+ implantation in TiC using XPS and TRIM
Authors: Fuentes G. G. , Elizalde E. , Sanz J. M.
Published: October 2002

We have studied the implantation of 2 keV N2+ ions in TiC. Both the shape and binding energy of the different core levels, as well as their modification, have been analysed during the implantation process. In order to quantify the implantation steps as a function of the N2+ dose, we have used a Monte‐Carlo‐based TRIM code to simulate the implantation profile of the nitrogen ions, except for the absolute atomic concentration, which is then determined by making use of the usual equations for quantitative XPS.

We have derived the atomic concentration of implanted nitrogen atoms, i.e. N(z, DN), as a function of depth and the N2+ ion dose in terms of TRIM simulated in depth profiles and the usual equations for quantitative XPS analysis. Owing to the accumulation effect and the sputtering of the target surface, the static nitrogen profiles NN(z) derived by TRIM evolve to an erf(z) distribution with increasing ion dose DN. A proper analysis of the Ti 2p, C 1s and N 1s peaks also allows different species to be distinguished and their distribution in depth. Copyright © 2002 John Wiley & Sons, Ltd.
Factors determining preferential sputtering in InGaAs system: angle‐resolved small‐area XPS investigation
Authors: Padeletti G. , Ingo G. M.
Published: October 2002

Different Ar+ energies (2 and 5 keV) were used to sputter (100) Ga0.73In0.27 As material at room temperature and under liquid nitrogen cooling. The preferential sputtering phenomena related to the different ion energies used have been investigated. Using angle‐resolved small‐area x‐ray photoelectron spectroscopy (AR‐SA‐XPS), chemical composition variations of the sputtered surface have been put in evidence. The results show an indium depletion on the outermost Ga0.73In0.27 As layer operating at room temperature. Indeed, even though indium and arsenic depletion is observed under liquid nitrogen cooling, the AR‐SA‐XPS results show that the effect is lower with respect to the surfaces sputtered at room temperature. These results are discussed in the framework of models proposed for explaining preferential sputtering phenomena. Copyright © 2002 John Wiley & Sons, Ltd.
Surface alteration of plagioclase during acid dissolution
Authors: Seyama Haruhiko , Kinoshita Kaoru , Soma Mitsuyuki
Published: October 2002

To examine the dissolution mechanism of silicate minerals in acidic solution, XPS was applied to plagioclase samples (Na0.5Ca0.5Al1.5Si2.5O8) treated with 5 × 10−2, 5 × 10−4 or 5 × 10−6 mol l−1 H2SO4 for 3 h, 1 day and 1 week. The atomic abundances of Na, Ca and Al relative to Si in the surface layer of acid‐leached (5 × 10−2 mol l−1 H2SO4) plagioclase decreased with increasing reaction time. The Si 2s and O 1s photoelectron spectra were shifted to higher binding energies during dissolution, and their binding energies were comparable to those of quartz after treatment for 1 week. From the preferential leaching of Na, Ca and Al, and the chemical shifts of the Si 2s and O 1s spectra, the formation of hydrous silicon dioxide on the mineral surface was deduced. The surface chemical composition of plagioclase changed in the same manner during dissolution by H2SO4 at a low concentration (5 × 10−4 mol l−1), although the magnitude of the decrease in surface concentrations of Na, Ca and Al was lower, suggesting the formation of a thinner altered surface layer. In addition, Al was less depleted than Na or Ca. Thus Na and Ca are more susceptible to acid leaching than Al. However, after dissolution in 5 × 10−6 mol l−1 H2SO4, the relative surface abundance of Al was slightly higher than that of the untreated sample. Surface enrichment in Al is probably associated with the formation of hydrous oxides of Si and Al. Copyright © 2002 John Wiley & Sons, Ltd.
XPS study of the reaction of chromium (VI) with mackinawite (FeS)
Authors: Boursiquot Sophie , Mullet Martine , Ehrhardt Jean‐Jacques
Published: October 2002

In this study, the ability of mackinawite (FeS) to reduce Cr(VI) was investigated as a function of the initial aqueous Cr(VI) concentration (1 × 10−4–5 × 10−3 M) at pH 5 and fixed ionic strength under a nitrogen atmosphere. X‐ray photoelectron spectroscopy was used to characterize the surface after reaction and to identify the oxidation products. Aqueous Cr(VI) concentration removed from solution was determined using the diphenylcarbazide colorimetric method. Mackinawite was found to act as an efficient Cr(VI) removal material. Surface analysis revealed that all detectable chromium occurred as Cr(III), even at the highest initial Cr(VI) concentration. Strong attenuation of the Fe 2p and S 2p signals from mackinawite counterbalanced the increase of the Cr 2p and O 1s levels when the initial Cr(VI) concentration increased. Clear evidence for the oxidation of Fe(II) to Fe(III), as well as hydroxylation of the surface, was provided by the Fe 2p and O 1s levels, respectively. Furthermore, the S 2p level indicated that S(‐II) was the main component, whatever the initial Cr(VI) concentration, with small amounts of polysulphides and elemental sulphur at the surface. These observations at pH 5 show that the mechanism of removal of Cr(VI) is through the reduction of Cr(VI) to Cr(III) and results in the formation of oxidation products such as Cr(OH)3 and/or FexCr(1−x)(OH)3 precipitates at the reacted mackinawite surface. Copyright © 2002 John Wiley & Sons, Ltd.
Investigation of planktonic foraminifera with ToF‐SIMS
Authors: Crone C. , Vering G. , Hönisch B. , Bijma J. , Arlinghaus H. F.
Published: October 2002

Various oceanic sediment properties deliver useful information for reconstructing environmental parameters of the past. Those properties that are closely related to environmental parameters are called ‘proxies’. They are measurable descriptors for desired (but unobservable) variables. Among others, promising advances were made in the field of boron isotopes in foraminiferal shells as a palaeo‐pH recorder. The isotope ratios are typically measured with thermal ionization mass spectrometry, which requires ∼200 shells to achieve high accuracy. We have investigated the possibility of using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) for imaging single foraminiferal shells and determining their elemental and isotopic distribution. The data show that ToF‐SIMS is a useful technique for determining their elemental distribution and for measuring boron isotopic ratios with high precision in a single foraminiferal shell. The use of well‐characterized standards for calibration as well as appropriate surface cleaning procedures for foraminiferal shells should improve data accuracy. Furthermore, the data imply that the parallel detection of all masses would simplify the establishment of new proxies. Copyright © 2002 John Wiley & Sons, Ltd.
ToF‐SIMS mapping of dialkylphthalate and bisphenol‐A adsorbed on small particles
Authors: Ono N. , Sakamoto T. , Owari M. , Nihei Y.
Published: October 2002

Small environmental particles are believed to act as carriers of endocrine disrupters so it is very important to establish techniques for analysing such harmful organic species adsorbed on small particles.

The authors examined the applicability of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) for analysis of endocrine‐disrupting chemicals adsorbed on individual small particles in order to evaluate the technique as an environmental analytical tool. Di(2‐ethylhexyl)phthalate (DEHP), dioctylphthalate (DOP) and 2,2‐bis(4‐hydroxyphenyl)propane (bisphenol‐A or BPA) were used as model compounds. All of them are suspected to be endocrine‐disrupting chemicals.

First, about one monolayer of each compound was adsorbed on a flat substrate instead of particles, and the mass spectra were measured. Next, DEHP or BPA was adsorbed on 6.8 µm silica particles and ToF‐SIMS spectral mapping was performed. From each spectral map, ToF‐SIMS spectra from a single particle area were extracted.

The ToF‐SIMS spectra from actual environmental particles, which adsorb many different kinds of compounds together, are expected to be very much complicated. It seems almost impossible to identify all the compounds. However, if a few expected compounds show strong and characteristic fragment peaks, ToF‐SIMS might be a very powerful tool to analyse the distribution of the compounds. In the study of the fate of endocrine‐disrupting chemicals, very important information such as the relationship between the compound and its carrier particles will be obtained from ToF‐SIMS analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Study of long‐term corrosion layers grown on high‐tin leaded bronzes by means of the combined use of GDOES and SEM + EDS
Authors: Ingo G. M. , Angelini E. , Bultrini G. , Calliari I. , Dabala M. , De Caro T.
Published: October 2002

Glow discharge optical emission spectrometry (GDOES) and scanning electron microscopy + energy‐dispersive spectrometry (SEM + EDS) are used for studying the microchemistry of the long‐term corrosion products, i.e. the patina, on archaeological high‐tin leaded bronzes used by Romans, most likely as mirrors. The results show that via GDOES it is possible to obtain reliable and detailed elemental composition–depth profiles for the corrosion products of the patina and for the bulk chemical composition of the bronzes that are in good agreement with the microchemical features obtained via SEM + EDS. The results provide good insight into the corrosion layers, showing copper and lead selective corrosion and depletion phenomena leading to the formation of a complex microchemical structure and, further, showing clearly the interaction between the inorganic and organic constituents of the soil, such as iron, silicon and phosphorus, in contact with the corrosion products grown on the bronzes. Finally, the results show that GDOES, with its ability of routine and rapid analysis of layers of thickness up to 150 µm, in combination with SEM + EDS, has significant potential in studies of the corrosion products for the restoration and conservation of ancient high‐tin leaded bronzes. Copyright © 2002 John Wiley & Sons, Ltd.
X‐ray mapping of microstructures in hardmetals and cermets
Authors: Wollein B. , Bohn M. , Lengauer W.
Published: October 2002

Hardmetals and cermets are alloys with a complicated microstructure of hard‐phase constituents such as WC, TiC, TiN,… and its combinations. A variety of microstructural constituents can form in these alloys, which define their performance to a large extent. Some hard‐phase particles occur in a core‐and‐rim type structure in which the element concentration differs substantially between the core and the rim. In order to investigate the microstructural features of hardmetals and cermets in detail, model alloys in the form of diffusion couples were prepared. X‐ray investigations using state‐of‐the‐art wavelength‐dispersive x‐ray mapping procedures implemented on a Cameca SX 50 microprobe were performed for all the elements, both light and heavy, occurring in these alloys. Line coincidences were treated by comparison with chemically analysed standards and by subtracting interfering radiations.

After 1008 h, W‐rich rims were found around Ti‐rich cores inside the Ti(C,N) phase of the Ti(C,N)/(Ti,W)C diffusion couple. The thickness of these rims did not change with time. When W was substituted by Mo it was observed that the well‐known core–rim structure is built by diffusion of Mo into the Ti(C,N) grains. But with time the Mo diffuses into the core of the Ti(C,N) phase and homogenizes, showing that the core–rim structure is not stable. Copyright © 2002 John Wiley & Sons, Ltd.
Application of AFM in microscopy and fabrication of micro/nanostructures
Authors: Lopour F. , Kalousek R. , Škoda D. , Spousta J. , Matějka F. , Šikola T.
Published: October 2002

In the paper atomic force microscopy (AFM) studies of microstructures made by ion beams on Si and Au surfaces and by AFM local anodic oxidation on Ti thin films is presented. By using the AFM technique, etching limits of inert atoms in the production of silicon and silver grids were found. It was proved that the height of Ti oxide lines fabricated by AFM increases linearly with the voltage between a tip and a sample. On the other hand, the half‐width of the lines did not depend linearly on this voltage. The results are useful for experiments in the fabrication of nanoelectronic devices (e.g. single‐electron transistors). Copyright © 2002 John Wiley & Sons, Ltd.
A new method of thin gate SiO2 reliability characterization
Authors: Liu Hongxia , Hao Yue
Published: October 2002

Time‐dependent dielectric breakdown (TDDB) of thin gate oxides is an important reliability issue of MOS integrated circuits. Breakdown characteristics of thin gate oxides are measured under constant voltage stress (CVS). Effects of the gate voltage and gate oxide area on charge to breakdown Qbd are discussed. The experimental results show that Qbd is not a constant; Qbd depends on both the gate oxide area and stress voltage and cannot act as the breakdown criterion over a wider stress range. Based on experimental results, a novel empirical power law is proposed to characterize thin gate oxide reliability and the correlated parameters are fitted. The empirical power law has been used in extrapolations to obtain Qbd for an arbitrary oxide area and gate voltage. Extrapolated results are in good agreement with those measured at constant voltage, so it is a useful tool for predicting thin gate oxide reliability. Copyright © 2002 John Wiley & Sons, Ltd.
Structure of Gd2O3 films epitaxially grown on GaAs(100) and GaN(0001) surfaces
Authors: Flückiger T. , Erbudak M. , Hensch A. , Weisskopf Y. , Hong M. , Kortan A. R.
Published: October 2002

Atomically thin films of Gd2O3 grow on GaAs(100) in the cubic α‐Mn2O3 structure exposing the (110) surface. The film disorders upon brief sputtering with 1000 eV Ar+ ions for 10 s. Subsequent annealing of the sample at 700 K restores the crystalline structure, however, with fourfold symmetry. Core‐level binding energy shifts show that the chemical states of all four components change upon sputtering and change further upon annealing. This observation is consistent with breaking and subsequent restoring of the chemical bonds at the Gd2O3/GaAs interface during surface processes until a new compound is formed. The Gd2O3 films grown on GaN(111) are stabilized in the high‐temperature hexagonal phase exposing their sixfold symmetric surface. Secondary electron imaging patterns recorded during sequential sputtering reveal that there is a high degree of rotational alignment of crystallographic features at the Gd2O3/GaN interface. Copyright © 2002 John Wiley & Sons, Ltd.
Single‐crystal LiNbO3 surfaces processed in low‐temperature hydrogen plasma: XPS, REELS and AFM study
Authors: Turčičová H. , Zemek J. , Tóth J. , Drbohlav I.
Published: October 2002

Single crystals of lithium niobate, which is a widely used material in opto‐electronics, holography, surface acoustic wave devices, etc., have been processed in a low‐temperature plasma of radiofrequency discharge in hydrogen. The aim was to examine a new kind of surface modification of LiNbO3. The surface modification has been studied by XPS, reflection electron energy‐loss spectroscopy (REELS) and atomic force microscopy (AFM). The XPS study via the Nb 3d spectral lineshape revealed the plasma effect: a decomposition of the niobate structure and the appearance of niobium oxides. The subsequent REELS study performed at 4 keV electron energy showed a transfer of characteristic electron‐loss energies of relevant transitions. Oxygen and lithium escape from the surface and hydrogen is incorporated from the plasma, producing niobium hydride. The deterioration of the niobate unit cells is accompanied by an enhancement of conduction electrons. The subsequent thermal reoxidation in medical oxygen did not restore the original niobate structure. The surface morphology after the reoxidation is characterized by elongated 100 nm grains situated normally to the surface. The main constituents of this new top layers are niobium oxides Nb2O5 and NbO. The present results form part of a complex study of the plasma modification of lithium niobate. The plasma processing induces lattice defects that are similar to those of ion implantation or metal ion doping: the electrical and optical properties of the surface layer drastically differ from those of the bulk. Copyright © 2002 John Wiley & Sons, Ltd.
Quantification of oxide film thickness at the surface of aluminium using XPS
Authors: Alexander M. R. , Thompson G. E. , Zhou X. , Beamson G. , Fairley N.
Published: October 2002

Oxide films grown anodically at the surface of superpure aluminium are used as standards to assess the accuracy of the thickness (dXPS) determined using the Beer–Lambert treatment of the Al 2p metal and oxide peak intensities. For the fitting conditions employed, the value of dXPS is found to be very close to the true film thickness for films <10 nm thick, beyond which imprecise values are obtained. A surface layer of hydration is identified from the curve fitting of the O 1s core level, which would qualitatively account for the slight underestimate of film thickness provided by the expression for dXPS. The validity of the Al 2p fit may be determined through this correlation of thickness but requires first a quantitative assessment of the thickness and composition of the hydroxide‐rich layer. Copyright © 2002 John Wiley & Sons, Ltd.
Dynamic segregation during ferrite oxidation revealed by XPS
Authors: Domenichini B. , Amilain‐Basset K. , Bourgeois S.
Published: October 2002

Dynamic segregation phenomena were revealed by XPS during the oxidation of some ferrites (Fe2.5Ti0.5O4, Fe2.5Ni0.5O4, Fe2CrO4 and FeCr2O4). This kind of phenomenon induces, at a low temperature (below room temperature), drastic changes in the cationic composition of the most external layers. Dynamic segregation is a function of the cationic composition, the oxidation capability and the morphology of these ferrites. Although dynamic segregation seems to be a quite frequent phenomenon that often can be observed during ferrite oxidation, there are materials in existence where it does not appear, such as molybdenum ferrite. Copyright © 2002 John Wiley & Sons, Ltd.
Stabilization of polar solid oxide surfaces: competition between adsorption and reconstruction
Authors: Domenichini Bruno , Pataut Gaël , Bourgeois Sylvie
Published: October 2002

Multi‐cationic spinel compounds are solids that exhibit polar faces. X‐ray Photoelectron spectroscopy revealed the main phenomena allowing the stabilization of these faces, carried out as a function of the material treatment, particularly the cooling rate after thermal treatment at a high temperature (1200°C). This study showed that, whatever the cooling rate, each sample is subject to a significant hydroxylation that reduces the polarity. Nevertheless, it appears that the hydroxyl group content at the surface is a strong function of the cooling rate. Indeed, whereas quenched materials are subject to high levels of hydroxylation, slowly cooled samples are sparingly hydroxylated. This phenomenon corresponds to the fact that, during a slow cooling down, a change of the cationic composition in the topmost layers of the solids is able to occur, inducing a decrease of the polarity. Moreover, this segregation comes with a change of the grain surface morphology, leading to less polar faces. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of additives at polymer surfaces by ToF‐SIMS
Authors: Médard N. , Poleunis C. , Eynde X. Vanden , Bertrand P.
Published: October 2002

In order to test the possibility of additive concentration quantification based on SIMS data, model samples were prepared. Samples consisted of thin polymer layers deposited by spin coating from solutions containing controlled amounts of selected additives. After identification of the main characteristic additive peaks, the SIMS intensity measured on these samples was compared with the bulk additive concentration. Our results showed that for the Irgafos 168–Hostavin N30 mixtures a linear relationship was found between SIMS intensity ratio and bulk composition. Thus, no synergy effect was detected when these additives are mixed together. However, for Irgafos 168 in copolymer PETi no linearity was observed. The data, based either on relative intensity or on multivariate statistical analysis (principal component analysis), indicated a strong segregation of the additive at the surface, i.e. a possible synergy effect with the polymer matrix. Finally, it appears that the segregation effect depended greatly on the nature of the additive and the polymer because, for the same bulk concentration, copper phthalocyanine in PETi and Irgafos 168 or Irganox 1010 in atactic polypropylene were barely detected. Copyright © 2002 John Wiley & Sons, Ltd.
Surface chemical derivatization of plasma‐treated PET and PTFE
Authors: Markkula T. K. , Hunt J. A. , Pu F. R. , Williams R. L.
Published: October 2002

Surfaces of two widely used biomaterials—poly(tetrafluoroethylene) (PTFE) and poly(ethylene terephthalate) (PET)—have been modified using gas plasmas. The concentrations of hydroxyl, carboxyl, carbonyl and amine groups were analysed with chemical derivatization (CD), using different aldehyde, acetic anhydride, alcohol and hydrazine reagents, and SIMS. Quantification was done by comparing the CD/SIMS results with XPS atomic ratios. Ammonia helical resonator plasma (HRP) treatment was found to incorporate mainly amine and hydroxyl groups on both materials. Argon HRP treatment of PTFE and nitrogen capacitor plate plasma (CPP) treatment of PET were found to increase carboxylic functionalities. The double‐bonded oxygen of the ester group of the unmodified PET was attacked and transformed to other groups in the order ammoniaplasma > nitrogenHRP > nitrogen CPP, with carbonyl content being reduced to 2.6, 4.1, and 7.6 respectively from 13.5 groups per 100 carbon atoms of the untreated PET. Chemical derivatization greatly helped to distinguish between the functional groups on the plasma‐treated surfaces. The difference between the surface specificity of SIMS and XPS has been discussed in the light of these results. Copyright © 2002 John Wiley & Sons, Ltd.
Thiophene‐containing organometallic polymers studied by near‐edge x‐ray absorption spectroscopy
Authors: Polzonetti G. , Iucci G. , Altamura P. , Ferri A. , Paolucci G. , Goldoni A. , Parent Ph. , Laffon C. , Russo M.V.
Published: October 2002

A near‐edge x‐ray absorption fine structure (NEXAFS) spectroscopy investigation on the electronic structure of some novel π‐conjugated organometallic polymers is presented. The investigated materials consist of Pt and Pd(II) complex units linked together through σ‐bonded organic spacers of ethynyl‐thiophene type in a polymeric array.

The C K‐edge NEXAFS spectra were interpreted by comparison with literature data and with the spectra of reference samples. The linking between the thiophene rings and alkyne groups produces a splitting of the C 1s → π* peak observed in the spectra of the thiophene systems. Angle‐dependent measurements, performed at normal and grazing incidence of the linearly polarized photons, evidenced a preferential orientation of the polymer chains with an average tilt angle of 45° for the thiophene moieties. Copyright © 2002 John Wiley & Sons, Ltd.
Quantifying the cathodoluminescence generated in ZnS‐based phosphor powders
Authors: Greeff A. P. , Swart H. C.
Published: October 2002

Field emission displays (FEDs) are a possible alternative to other display technologies. They work similar to cathode ray tubes, but instead of an electron gun they have an array of tiny metallic tips acting as electron emitters. This array is situated in close proximity to the phosphor screen and produces light by a process of cathodoluminescence (CL). During prolonged electron beam irradiation a non‐luminescent ZnO layer forms on the irradiated surface of the ZnS phosphor powder. This is due to electron‐beam‐stimulated surface chemical reactions between the ZnS phosphor and water vapour present in the ultrahigh vacuum environment. The low‐energy electrons used in FEDs have a shallow penetration depth and, because the CL is dependent upon the energy loss in the ZnS bulk itself, growth of the ZnO layer significantly degrades the CL intensity. Energy loss profiles in the ZnS for different ZnO thicknesses were determined using Monte‐Carlo electron trajectory simulations. These profiles, along with photon absorption profiles, were used to determine a curve relating the normalized CL intensity to the ZnO thickness. It was compared with experimentally measured values obtained during CL degradation experiments on standard ZnS : Cu,Al,Au phosphor powders and ZnO thickness measurements with sputter depth profiling. Assuming the presence of a 20 nm thick diffusion interface between the ZnO layer and the ZnS bulk, the theoretical and experimental results agree well. Initially the interface represents the initial stages of oxidation, but after the oxide layer starts to grow as a uniform film it represents a physical interface formed due to diffusion processes. Copyright © 2002 John Wiley & Sons, Ltd.
Surface potential images of self‐assembled monolayers patterned by organosilanes: ab initio molecular orbital calculations
Authors: Saito N. , Hayashi K. , Sugimura H. , Takai O. , Nakagiri N.
Published: October 2002

Self‐assembled monolayers (SAMs) with different function terminal groups were prepared on substrates of n‐type silicon by chemical vapour deposition (CVD) from n‐octadecyltrimethoxysilane (ODS: H3C(CH2)17Si(OCH3)3), heptadecafluoro‐1,1,2,2‐tetrahydro‐decyl‐1‐trimethoxysilane (FAS: F3C(CF2)7 (CH2)2Si(OCH3)3), n‐(6‐aminohexyl)aminopropyltrimethoxysilane (AHAPS: H2N(CH2)6NH(CH2)3 Si(OCH3)3) and 4‐(chloromethyl)phenyltrimethoxysilane [CMPS: H2ClC(C6H4)Si(OCH3)3]. The sample surfaces covered with ODS‐SAM were irradiated under a reduced pressure of 10 Pa with vacuum ultraviolet (VUV) light through a photomask. Then, the irradiated areas with the ODS‐SAM removed were covered with another SAM by CVD. Surface potential images of the patterned areas were measured by Kelvin probe force microscopy (KPFM) and explained by ab initio molecular orbital (MO) calculations. The KPFM measurements showed that the surface potential contrasts of the FAS‐, AHAPS‐ and CMPS‐SAMs against the ODS‐SAM were about −170, +50 and −30 mV, respectively. The surface potentials as a function of area occupied by a molecule were predicted using the respective dipole moments perpendicular to substrates, which were obtained by the ab initio MO calculations. The predicted surface potentials of the FAS‐, CMPS‐ and AHAPS‐SAMs approximately agreed with the measured values at areas of about 1.5, 1.6 and 0.6 nm2 per molecule. The ab initio MO calculations also showed differences in surface potentials appearing due to the differences in Fermi levels of the respective SAMs. Copyright © 2002 John Wiley & Sons, Ltd.
XPS and theoretical studies of the electronic structure of FeX and NiX (X = Al, Si, P)
Authors: Shabanova I. N. , Mitrochin Y. S. , Terebova N. S. , Nebogatikov N. M.
Published: October 2002

For the stoichiometric compounds FeX and NiX (X = Si, Al, P) the x‐ray photoelectron spectra of valence bands are obtained and calculations of their electronic structure are carried out by the tight‐binding linear muffin‐tin orbital atomic sphere approximation method (TB‐LMTO‐ASA). A satisfactory agreement between the x‐ray photoelectron spectra and the calculated density‐of‐states curves is obtained. It is shown that with an increase of the second‐component p‐electrons, hybridization of d(metal) and p(X) electrons decreases, the probability of d–p resonance increases and the contribution of p(X) states near Ef increases. Copyright © 2002 John Wiley & Sons, Ltd.
Study by Monte‐Carlo simulation of resolution improvement by energy filtering in Bio‐TEM
Authors: Suga H. , Kouzuki T. , Shimizu R , Kotera M.
Published: October 2002

An electron microscope for observing biological samples at atmospheric pressure has been proposed. The major principle of the present instrument is that a biological sample is set in a conventional transmission electron microscope (TEM) beamline but it is isolated from a high vacuum by upper‐ and lower bulkheads. As indicated by an electron trajectory simulation, a clear image could be obtained if the bulkhead was 100 nm thick beryllium foil. In the present study, the feasibility of the image resolution improvement is examined by energy filtering of the transmitted electrons. Copyright © 2002 John Wiley & Sons, Ltd.
Influence of PMAA‐graft‐PEO copolymers on the formation of thin ZnO films from aqueous solutions
Authors: Hoffmann Rudolf , Fuchs Tobias , Niesen Thomas P. , Bill Joachim , Aldinger Fritz
Published: October 2002

The microstructure of ZnO thin films was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The ZnO films were deposited on bare silicon as well as on Si wafers modified with self‐assembled monolayers (SAMs) by the thermohydrolysis of zinc salts from aqueous solution with the addition of water‐soluble copolymers. The influence of polymethacrylic acid partially grafted with polyethylenoxide side‐chains on the morphology of the thin films was investigated.

X‐ray photoelectron spectroscopy (XPS) was carried out to determine the composition of the thin films. A comparison of the position of the O 1s peak in as‐deposited and annealed films suggests that the copolymer remains attached to the precipitated ZnO particles. After calcination at 723 K the copolymer is completely removed, yielding ZnO films with a thickness of ∼70 nm. Copyright © 2002 John Wiley & Sons, Ltd.
Compositional analysis of SiOxNy:H films by heavy‐ion ERDA: the problem of radiation damage
Authors: Bohne W. , Fuhs W. , Röhrich J. , Selle B. , Sieber I. , del Prado A. , San Andrés E. , Mártil I. , González‐Díaz G.
Published: October 2002

Films of SiOxNy:H were deposited at room temperature on Si substrates by the electron cyclotron resonance (ECR) plasma method. By varying the flow rates of the precursor gases SiH4, O2 and N2, the whole composition range between pure silicon oxide and nitride could be covered. Heavy‐ion elastic recoil detection analysis (HI‐ERDA) with a 150 MeV 86Kr ion beam and time‐of‐flight (ToF) mass separation was applied to determine the absolute atomic concentrations of all film components, including hydrogen. Additionally, the bonding configuration of the films was studied by infrared (IR) spectroscopy. Extended ion beam exposure was found to decrease the intensity of the N–H phonon band as well as the nitrogen and hydrogen concentrations. By storing the ion scattering data event by event and by recalculating a zero‐dose composition, this effect was taken into account. The corrected HI‐ERDA results revealed clear relations to the deposition parameters (e.g. the O2/SiH4 flow ratio). The hydrogen incorporated in the films turned out to be bonded predominantly to nitrogen. The damage effects were strongest in the medium composition range. They were found to scale with the relative concentration of SiO2N2‐type basic tetrahedrons, suggesting that this bonding configuration is most sensitive against irradiation during the HI‐ERDA measurement. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of lead–titanium–oxygen compounds by static SIMS
Authors: Aubriet Frédéric , Poleunis Claude , Bertrand Patrick
Published: October 2002

Pb–Ti–O thin films, lead titanate powder, lead monoxide, titanium dioxide and a stoichiometric PbO–TiO2 mixture were investigated by time‐of‐flight (ToF) SIMS. The nature of the numerous PbxOy+/−, TixOy+/− and PbxTix,Oy+/− ionic species generated by 15 keV Ga+ primary ion bombardment analysed by ToF‐SIMS allowed the identification of the involved metal–oxygen system. The detection of PbxTix,Oy+/− mixed metal ions was specific to lead titanate (film and powder). Indeed, these species were not observed when the PbO–TiO2 stoichiometric mixture was examined. Consequently, they allowed unambiguous molecular identification of the Pb–Ti–O investigated system. Copyright © 2002 John Wiley & Sons, Ltd.
Free‐electron metal alloys: a study by high‐energy XPS
Authors: Abel Marie‐Laure , Tsakiropoulos Panos , Watts John F. , Matthew James A. D.
Published: October 2002

In an extension of previous work on charge redistribution phenomena in aluminium transition metals alloys, high‐energy x‐ray photoelectron spectroscopy (XPS) was performed on alloys prepared with elements having sp‐dominated band structure, specifically aluminium, magnesium and silicon, and the alloys Al–2.5Mg, Al–25Mg, Al–10Si and Al–50Si have been investigated. This work was performed using an ESCA300 spectrometer fitted with a Cr Kβ source (hν = 5946.7 eV).

Examination of the final‐ and initial‐state Auger parameters shows that very little variation occurs in the alloys compared with pure elemental solids and that the values obtained are very close to being within experimental error. Examination of the plasmon energies and intensities, however, shows that the main variations are obtained for alloys forming a discrete phase upon alloying (intermetallic phase) as opposed to alloys forming solid solutions or those precipitating pure metallic phases on cooling. The Al–25Mg alloy contains the Al3Mg2 (β) phase. This phase contributes towards the variation of the effective cell volume of Mg and Al compared with the pure metals and is consistent with an increase and a decrease of their respective plasmon energies. Copyright © 2002 John Wiley & Sons, Ltd.
Passivity and its breakdown on stainless steels and alloys
Authors: Qiu J. H.
Published: October 2002

The service reliability of stainless steels and alloys is predominantly determined by the chemical stability of an ultrathin passive film on their surfaces. The thickness, composition and structure of such an ultrathin oxide film are all influenced by the alloy composition and the nature of the environments they are exposed to. Surface analysis of passive films formed on different grades of stainless steels under different conditions showed that chromium was significantly enriched in the surface film whereas nickel was not present in the oxidized state. Breakdown of passivity either due to mechanical damage or due to chemical attack often leads to localized corrosion in the form of pitting, crevice corrosion and stress corrosion cracking. This paper discusses the corrosion resistance characteristics of stainless steels and alloys in the context of surface film properties. Copyright © 2002 John Wiley & Sons, Ltd.
Nanoscale surface characterization of conducting and non‐conducting materials with STM and contact SFM: some problems and solutions
Authors: Zhdan Peter A.
Published: October 2002

Methods of scanning tunnelling microscopy (STM) and of contact scanning force microscopy (CSFM) are widely used in many academic and industrial laboratories for nanoscale surface characterization of conducting and insulating materials. These techniques allow for very high (atomic) resolution to be achieved in different environments—vacuum, air and liquids—not to mention their ability to evaluate quantitatively selected surface features, including statistical analysis of corrugations, which permits roughness parameters to be determined on the nano‐ and microscale. Many CSFM systems are used now in industrial research laboratories, quality assurance and control departments where precise surface feature dimensioning of roughness analysis is critical for product development or process control. Each STM and CSFM user comes up against these tasks regularly during his/her daily work, therefore thorough understanding of the main principles, advantages and limitations of specific operation modes is the basis for appropriate setting of the experiments and for interpretation of acquired STM and CSFM data.

Here, using a variety of experimental results obtained in our laboratory during the last few years for a number of different conducting and non‐conducting materials, some principal questions and problems related to the practical aspects of STM and CSFM are reviewed and discussed in detail: requirements for samples to be studied and their preparation for investigation, optimization of the experimental set‐up and acquisition parameters for different environments; and correct interpretation of the acquired experimental data. We hope that practical recommendations given in this paper will be useful to new users of STM and CSFM, introducing them to this field and helping in their experimental work, especially when studying ‘difficult’ samples. Copyright © 2002 John Wiley & Sons, Ltd.
Using in situ AFM to investigate corrosion and passivation of duplex stainless steels
Authors: Yang X. F. , Castle J. E.
Published: October 2002

This paper reports in situ atomic force microscopy (AFM) and SEM studies of the corrosion of duplex stainless steels. The results showed selective dissolution of the duplex structure, with one rapidly dissolving phase and one slowly dissolving phase. Electron probe microanalysis (EPMA) measurements showed that the weak phase contained more Cr and Mo and the resistance phase contained more Ni, which was used to assign these phases to ferrite and austenite, respectively. Copper deposition experiments showed that the resistant phase was more noble and acted as the cathode. The mode of dissolution was apparently modified after polarization of the steel in the passive range. Copyright © 2002 John Wiley & Sons, Ltd.
A practical approach for comparing means of two groups without equal variance assumption
Authors: Wang Hansheng , Chow Shein‐Chung
Published: October 2002

In this paper we consider two‐groups of i.i.d. normally distributed random variables (N(μx,σx2) and N(μy,σy2)) without assuming equal variance (σx2 = σy2). We propose a simple method for constructing confidence bounds based on Howe's approximation I. Its applications in parallel clinical trial (testing H0 : μx‐μy=0 versus H1 : μx‐μy<0) and parallel bioequivalence (BE) trial (testing H0:∣μx‐μy∣δ versus H1:∣μx‐μy∣<δ) are studied. Sample size calculation formulae for both cases are derived. Their performances are evaluated by simulation. Our study shows that the proposed procedure can control type I error satisfactorily compared with Cochran–Cox's and Satterthwaite's approximations while maintaining a relatively high power. The proposed approach is not only simple for constructing the confidence limit, but also provides a simple and accurate formula for sample size calculation. Copyright © 2002 John Wiley & Sons, Ltd.