bluuebunny/crossref_metadata_2025 huggingface dataset:
Addition theorems as three‐dimensional Taylor expansions. II.Bfunctions and other exponentially decaying functions
Authors: Weniger Ernst Joachim
Published: October 2002

Addition theorems can be constructed by doing three‐dimensional Taylor expansions according tof(r+r′)=exp (r′⋅∇)f(r). Since, however, one is normally interested in addition theorems of irreducible spherical tensors, the application of the translation operator in its Cartesian form exp (x′∂/∂x)exp (y′∂/∂y)exp (z′∂/∂z) would lead to enormous technical problems. A better alternative consists in using a series expansion for the translation operator exp (r′⋅∇) involving powers of the Laplacian ∇2and spherical tensor gradient operators\documentclass{article}\pagestyle{empty}\begin{document}$\mathcal{Y}^{m}_{\ell}(\nabla)$\end{document}, which are irreducible spherical tensors of ranks zero and ℓ, respectively (Santos, F. D. Nucl Phys A 1973, 212, 341). In this way, it is indeed possible to derive addition theorems by doing three‐dimensional Taylor expansions (Weniger, E. J. Int J Quantum Chem 2000, 76, 280). The application of the translation operator in its spherical form is particularly simple in the case ofBfunctions and leads to an addition theorem with a comparatively compact structure. Since other exponentially decaying functions like Slater‐type functions, bound‐state hydrogenic eigenfunctions, and other functions based on generalized Laguerre polynomials can be expressed by simple finite sums ofBfunctions, the addition theorems for these functions can be written down immediately. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Does digermane exhibit free rotation? A test of barrier theory
Authors: Goodman Lionel , Pophristic Vojislava , Wang Windy
Published: October 2002

Hartree–Fock/6‐311G(3df,2p) analysis of the digermane internal rotation barrier shows that at 300 K digermane is in large amplitude (∼40°) oscillation about the staggered equilibrium structure. Quantum superposition (hyperconjugation between the germanyl groups) is predicted to contribute less than half of the 0.8 kcal/mol barrier energy, but it is key to sufficiently rigidize the molecule to prevent free rotation. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Hermitian Fock matrix in the chemical Hamiltonian approach: Fulfilling Löwdin's prediction*
Authors: Mayer I.
Published: October 2002

Following a remark of Löwdin, a technique is developed permitting one to formulate the BSSE‐fee SCF equations of the chemical Hamiltonian approach (CHA) by using a Hermitian Fock matrix. Contrary to the usual CHA practice, the energy is also calculated with the means of the same Fock matrix. This scheme reproduces exactly the CHA–SCF results usually obtained by using a non‐Hermitian Fock matrix for computing the orbitals and a conventional Hermitian one for computing the energy. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Methoxyphenols—antioxidant principles in food plants and spices: Pulse radiolysis, EPR spectroscopy, and density functional theory calculations*
Authors: Bors Wolf , Kazazic Snjezana P. , Michel Christa , Kortenska Vessela D. , Stettmaier Kurt , Klasinc Leo
Published: October 2002

The phenoxyl radicals of several phenols and phenolic acids with o‐methoxy groups were generated by pulse‐radiolytic oxidation with azide radicals and their buildup and decay evaluated with kinetic spectroscopy. Structures of the phenoxyl radicals were obtained with EPR spectroscopy and the experimental isotropic coupling constants confirmed by hybrid density‐functional calculations with Becke's three parameter hybrid functional using the Lee, Yang, and Parr functional theory and a variety of basis sets, and with consideration of the solvent. While the calculations resulted in reasonable correlations with the experimental data, the apparent distinction in the stability of the various radicals seems to be primarily due to kinetic rather than electronic effects. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Molecular dynamics study on liquid 1‐octanol. Part 2. Water‐saturated 1‐octanol solution*
Authors: Fernandes de Oliveira César Augusto , Guimarães Cristiano Ruch Werneck , Bicca de Alencastro Ricardo
Published: October 2002

In medicinal chemistry, partition coefficients are extremely important thermodynamic properties as they may be related to drug transfer across biological membranes. We are currently interested in obtaining octanol/water relative partition coefficients (Δlog Po/w) by using the free‐energy perturbation (FEP) technique within the Discover program (version 2.9.7) of MSI. In this program, however, FEP calculations can only be performed if the all‐atom consistent‐valence force field (CVFF) is used. As a consequence, we have recently derived new parameters for the 1‐octanol nonbonded terms of CVFF, which reproduce relevant physicochemical properties of its liquid state [Oliveira, C. A. F.; Guimarães, C. R. W.; Bicca de Alencastro, R. Int J Quantum Chem 2000, 80, 999–1006]. Nevertheless, the experimental measurements of the octanol/water partition coefficients are always conducted using 1‐octanol that has first been saturated with water. Therefore, in this work, we are verifying if the combination of the CVFF water model with the new CVFF parameters, derived for liquid 1‐octanol, describes the solvent mixture adequately. The good agreement observed between our calculated physicochemical properties, using molecular dynamics simulations, and experimental values and other theoretical results gives support to our model. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Reactivity of the NS2/3(907–1206)ASK4protein with β‐mercaptoethanol studied by electrospray ion trap mass spectrometry
Authors: Orsatti Laura , Pallaoro Michele , Steinküler Christian , Orru' Stefania , Bonelli Fabio
Published: October 2002

The present work reports a mass spectrometric investigation of the NS2/3 protein, a protease from hepatitis C virus (HCV). During routine protein manipulation, in the presence of 100 mM β‐mercaptoethanol and under denatured conditions, the protein was unexpectedly modified at its cysteine residues, and the increased molecular weight corresponded to one molecule of β‐mercaptoethanol bound. The modified protein, once refolded, was found to be less active than the unmodified one. The aim of this work was to investigate whether the reactivity of cysteines with β‐mercaptoethanol involves one specific, highly reactive residue of the sequence, or if the modification is a random process. Liquid chromatography (LC) coupled on‐line with an electrospray ion trap mass spectrometer was used to identify the modification sites. It was found that five cysteines out of nine had reacted with β‐mercaptoethanol, none of them showing a significantly higher reactivity than the others. 95% of sequence coverage was obtained. Copyright © 2002 John Wiley & Sons, Ltd.
ART in‐well air stripping—An innovative technology succeeds where other technologies have failed
Authors: Odah Mohamed
Published: October 2002

Accelerated Remediation Technologies LLC (ART) developed a proprietary
(patent‐pending) effective remediation technology that is based on verified and established
concepts. The ART technology combines in‐situ air stripping, air sparging, soil vapor extraction, enhanced
bioremediation/oxidation, and Dynamic Subsurface CirculationTM in an innovative wellhead system.
The system is designed to accommodate a 4‐inch well and is cost‐effective when compared with other
remediation technologies. The air‐sparging component results in lifting the water table. This lifting of
the water in the well causes a net reduction in head at the well location. Vacuum pressure (the
vapor‐extraction component) is applied on top of the well point to extract vapor from the subsurface.
The negative pressure from the vacuum extraction results in water suction that creates additional water lifting
(mounding). A submersible pump is placed at the bottom of the well to recirculate water to the top for
downward discharge through a spray head. The water cascades down the interior of the well similar to what occurs
in an air‐stripping tower. Enhanced stripping via air sparging near the bottom of the well occurs
simultaneously. In essence, the well acts as a subsurface air‐stripping tower. The
pumped‐and‐stripped, highly oxygenated water flows down well annulus and over the
“mounded” water back in to the aquifer, which creates a circulation zone around the well to further
enhance cleanup.

The ART technology has been implemented at several sites nationwide, including industrial laundry facilities,
manufacturing plants, and service stations, and has achieved significant reductions in contaminant
concentrations. Specifically, a concentration of tetrachloroethene (PCE) decreased from 2,700 to 240
μg/l, in 13 days. In less than three months, the concentrations dropped further to 79 μg/l, which
is within the range of background levels. Other sites utilizing the technology have exhibited similar reduction
trends in complex subsurface environments. © 2002 Wiley Periodicals, Inc.
High‐temperature‐aging‐promoted Rh oxides on supported automotive exhaust catalysts
Authors: Suhonen S. , Hietikko M. , Polvinen R. , Valden M. , Laitinen R. , Kallinen K. , Härkönen M.
Published: October 2002

Thermal decomposition of noble metal oxide phases formed during aging in air on industrially manufactured γ‐Al2O3‐supported Rh catalysts was investigated. Some of the catalyst washcoats were modified by various stabilizers, promoters and oxygen storage components, such as La2O3, CeO2 and Ce–Zr mixed oxide. In order to investigate the effect of aging, stabilizers and manufacturing method on the thermal stability of the noble metal oxide phases formed, a stepwise thermal decomposition in high vacuum (pressure <10−7 Torr) was performed. X‐ray photoelectron spectroscopy (XPS) was used to observe the changes in chemical state after each annealing cycle. Our results show marked differences in the rate of reduction between different Rh catalysts. Disposition of the Rh oxides towards reduction was also investigated by exposing the catalysts to 400 mbar of H2 at 300°C for 30 min. After 3 h of aging in air at 1000°C an irreducible rhodium oxide, which was identified to be either Rh2O3 diffused into alumina or RhO2 in intimate contact with the alumina surface, was formed regardless of the Ce–Zr mixed‐oxide additive and manufacturing method of the catalyst. Copyright © 2002 John Wiley & Sons, Ltd.
Environmental application of surface reactivity analysis
Authors: Lamari Darkrim F. , Levesque D.
Published: October 2002

In order to use hydrogen gas as an energy vector, several possibilities are under investigation and any new systems of gas storage should be secure, light, efficient and not expensive. Three technologies involving hydrogen gas energy have already been proposed: gas liquefaction at low temperature, gas compression at high pressure and the formation of metallic hydrides. Another technology corresponding to a variant of gas compression concerns gas adsorption under pressure.

Considerable activity has been devoted to the experimental and numerical studies of nanoscale‐dimension material adsorptive properties in order to store hydrogen gas by adsorption. Thus, within the framework of studying hydrogen storage for future clean vehicles, we performed hydrogen adsorption on both current active carbons and promising new adsorbents. We carried out analysis of the gas/solid interface reactivity by numerical simulations. More specifically, we studied the potential of hydrogen adsorption by new graphitic materials, for which recent works have demonstrated that these adsorbents may have high adsorptive capacities owing to their surface reactivity in relation to their nanometric dimensions. These adsorbents present structures that are favourable to the adsorption phenomenon because of the attractive interaction range between gas molecules and adsorbent atoms. In this work, we studied the gas/solid interface reactivity in order to discuss the potential influence of carbon nanofibre dimensions on hydrogen adsorption. We performed Monte‐Carlo numerical simulations of gas adsorption on materials that could represent these adsorbents in reality. We computed these simulations in order to analyse interface reactivity and to obtain interface information and predictions of gas adsorption, with the aim of optimizing adsorbent structures for hydrogen adsorption. Moreover, we realized experimental studies of gas adsorption in microporous material in order to validate our numerical predictions and to obtain other information on the reactivity of the gas/solid interface. Copyright © 2002 John Wiley & Sons, Ltd.
Structure and composition of electrochemically prepared oxide layers on Co in alkaline solutions studied by XPS
Authors: Foelske Annette , Strehblow Hans‐Henning
Published: October 2002

Passive layers on cobalt were prepared in 0.1 N NaOH (pH 13) under potentiostatic control with systematic variation of the relevant parameters, such as time and potential, and examined by x‐ray photoelectron spectroscopy (XPS). The electrochemical preparation of the sputter‐cleaned samples and their transfer to the ultrahigh vacuum was performed in a closed system under protection of purified argon. Evaluation of the XPS signals occurs on the basis of well‐characterized standards. The results are compared with those obtained in borate buffer (pH 9.3), which have been published previously in this journal.

Depending on the potential, cobalt forms two different passive layers. In 0.1 N NaOH (pH 13) the potential range of primary passivity goes from −0.4 to 0.3 VSHE. The passive layer consists of a pure Co(OH)2 film that grows from 10 nm after 5 min of passivation up to 37 nm within 90 min. The layer forms most probably according to a dissolution precipitation mechanism. For E > 0.0 VSHE a thinner layer of only 4 nm (E = 0.2 VSHE for 5 min) is formed. In the range of secondary passivity at E = 0.3–0.8 VSHE Co(III) dominates the layer composition with contributions of Co3O4, CoOOH and Co2O3. After 5 min of passivation the layer thickness in this potential range increases slightly with increasing potential from 4 up to 7 nm. After 90 min the thickness reaches 9 nm, independent of the potential. Copyright © 2002 John Wiley & Sons, Ltd.
Adsorption of released ions from dental amalgams on titanium
Authors: Asami K. , Takada Y. , Okuno O.
Published: October 2002

Effects of titanium plate in contact with amalgams of ‘Hi Atomic M’ (HA) and ‘Lumi Alloy’ (LM) on the release of metal ions from those amalgams into 0.9% NaCl solution were investigated using inductively coupled plasma atomic emission spectroscopy, electron probe microanalysis and XPS. Except for Hg, the release of ions increased about ten times on Ti contact, whereas that of Hg was diminished several‐fold. No measurable amounts of Ti ions were found in solution. Where the Ti is in contact with the amalgam, every element was deposited almost proportionally to the solution composition. Tin oxide containing several percent of In2O3 covered the top surface of Ti connected to the conventional HA amalgam. However, the dominant species on Ti connected to the high‐copper LM amalgam were Cu and Sn oxides. On the Ti connected to the amalgams, the concentrations of other elements were very low. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative AES depth profiling of iron and chromium oxides in solid solution, (Cr1−xFex)2O3
Authors: Asteman H. , Norling R. , Svensson J.‐E. , Nylund A. , Nyborg L.
Published: October 2002

This paper presents AES concentration‐dependent sensitivity factors and a method to determine the atomic concentrations of O, Fe and Cr in (Cr1−xFex)2O3 solid solutions. In addition, a solution to the problem of the overlap between the O KVV and Cr LMV peaks is presented. The new approach to evaluate solid solutions of (Cr1−xFex)2O3 then has been used to evaluate the oxide formed on 304L stainless steel oxidized at 600°C in 0.9 bar O2 + 0.1 bar H2O for 168 h. The result shows great improvement in comparison to the conventional quantitative analysis of Auger results. Copyright © 2002 John Wiley & Sons, Ltd.
Auger Si LVV lineshape analysis of porous p‐type silicon electroplated with Fe–Co alloys
Authors: Hamadache F. , Bertrand P.
Published: October 2002

Different electrochemically produced porous p‐type silicon layers filled with Fe–Co alloys are investigated through AES depth profiling. In this study, we analysed the lineshape changes of the Auger Si LVV transition with the sputter depth and alloy composition. Application of factor analysis to this line, together with Fe and Co LVV transitions, enabled us to identify the dominant chemical state of Si atoms at the pore walls. The structure of the Si LVV lineshape of the metallized porous p‐type silicon compared with that of oxidized porous p‐type silicon suggests that Si atoms are slightly bonded to oxygen. Room‐temperature formation of interfacial Si–Fe–Co compounds is likely to occur upon pore filling with the alloy. This is supported by the change of this lineshape with Fe–Co composition and by the appearance of plasmon loss peaks in the Fe and Co LVV lineshapes. Copyright © 2002 John Wiley & Sons, Ltd.
Factor analysis applied to the study of valence band resonant photoemission spectra in transition‐metal compounds
Authors: Sánchez‐Agudo M. , Soriano L. , Trigo J. F. , Quirós C. , Fuentes G. G. , Morant C. , Elizalde E. , Sanz J. M.
Published: October 2002

We have applied factor analysis to the study of the valence band resonant photoemission spectra of a TiO2 thin film. Classical analysis of the photoemission spectra as a function of the photon energy through the Ti 2p → 3d absorption edge does not give a clear understanding of the resonant process, because the resonance phenomenon is present along the valence band and the only differences on the resonance are related to the distribution of cationic d‐states. However, factor analysis of the spectra allows a more quantitative analysis of the resonance phenomena. Using theoretical partial Ti 3d and O 2p density of states as starting bases in principal component analysis, it is shown that only the hybridized Ti 3d states at the valence band resonate. The Ti 3d constant initial state (CIS) curve maps the Ti 2p x‐ray absorption spectrum. Experimental relative photoemission cross‐sections of the Ti 3d states at the absorption edge (455–470 eV) have been obtained. It is shown that resonant photoemission gives a sixfold enhancement of the Ti 3d cross‐section at 463 eV with respect to the values at energies off‐resonance. Copyright © 2002 John Wiley & Sons, Ltd.
Instrumental effects in the principal component structure of a set of spectra
Authors: Balcerowska G. , Cyrankiewicz M. , Siuda R. , Engelhard H. , Buergener M. , Goldmann A.
Published: October 2002

Principal components analysis (PCA) is a mathematical technique widely used for the diagnosis of structure in a set of spectra, followed by factor analysis for decomposition of the spectra into physically meaningful constituents. Among the effects that can influence the principal component structure for a set of spectra, one can distinguish effects that come from the imperfect operation of particular devices that constitute the spectrometer. When one wants to apply PCA to detect subtle effects (e.g. very small shifts between spectral lines), then instrumental imperfections disturbing the data cannot be neglected, even if they are not very distinct. This paper reviews, classifies and presents the influence of instrumental effects on the principal component structure of recorded spectra. Copyright © 2002 John Wiley & Sons, Ltd.
XPS and SIMS depth profiling of chlorine in high‐temperature oxynitrides
Authors: Vanzetti L. , Bersani M. , Sbetti M. , Iacob E. , Giubertoni D. , Barozzi M. , Zonca R. , Crivelli B. , Carpanese C. , Zanderigo F.
Published: October 2002

Thin oxides deposited by low‐pressure chemical vapour deposition (LPCVD) at high temperature are being widely investigated in VLSI technology to be used as possible substitutes for the usual thermal oxides. High‐temperature oxide deposition involves reactions between N2O and dichlorosilane or silane. Considering possible active dielectric applications, the effect of further nitridation and annealing of deposited films has to be considered. Evaluation of the nitrogen content and the distribution profile of these dielectrics then becomes a relevant analytical issue. Moreover, it is also crucial to monitor the amount of possible contaminant species, such as chlorine, introduced by the precursor gases during the deposition. In this work we present the development of an analytical methodology for quantitative depth profiling of chlorine in thin oxides using SIMS and XPS. In addition, the evolution of chlorine distribution in an appropriate set of high‐temperature oxide films submitted to nitridation and further thermal processes will be shown. Copyright © 2002 John Wiley & Sons, Ltd.
The fractured, polished and Ar+‐sputtered surfaces of natural enargite: an XPS study
Authors: Velásquez P. , Ramos‐Barrado J. R. , Leinen D.
Published: October 2002

The natural mineral enargite (Cu3AsS4) has been studied by XPS combined with 4 keV Ar+ depth profiling. The fracture surface, the mechanically polished surface and the 4 keV Ar+‐bombarded enargite surface has been studied by XPS. The fracture surface reveals a stoichiometry in accordance with Cu3AsS4, whereas the polished and the ion‐bombarded surface show strong deviations. In the polished surface a loss of As and Cu leads to polysulphide formation at the sample surface. Enargite subjected to 4 keV Ar+ bombardment reveals a preferential loss of As and, to a lesser extent, sulphur atoms from the sample surface, yielding a steady‐state composition near to chalcocite (Cu2S). The compositional change in the ion‐bombardment‐altered layer is discussed in terms of the thermal spike model, taking into account the volatility of the constituent atoms or possible compounds in the altered layer. Copyright © 2002 John Wiley & Sons, Ltd.
Composition and temperature dependence of Y–Ba–Cu–O high‐temperature superconductor electronic structure
Authors: Shabanova I. N. , Naimushina Ye. A. , Terebova N. S.
Published: October 2002

The electronic structure of YBa2Cu3O7−· was studied by x‐ray electron spectroscopy with variation of the oxygen content and temperature. The use of an x‐ray electron magnetic spectrometer in this research allowed spectra to be obtained in the temperature range from room temperature to the temperature of liquid nitrogen; mechanical cleaning of sample surfaces was performed while taking the XPS spectra. The XPS spectra are compared with the results of the band structure calculations carried out by the full‐potential method of linear muffin‐tin orbitals (FP‐LMTO).

It is shown that with an increase in the oxygen content the intensity of the Cu2+ component spectrum increases, which correlates with an increase in the temperature Tc. The increase in intensity of the additional maxima appearing in the O 1s, Ba 3d, Ba 4d spectra is observed in the superconductive state. Copyright © 2002 John Wiley & Sons, Ltd.
X‐ray photoelectron spectroscopy of alkali germanate glasses
Authors: Di Martino D. , Santos L. F. , Almeida R. M. , Montemor M. F.
Published: October 2002

Several alkali germanate glasses of molar composition (100 − x)GeO2·xM2O (M = Na, with 0 ⩽ x ⩽ 35, or M = Cs, with 0 ⩽ x ⩽ 30) were prepared by melting, and their XPS spectra were recorded and analysed as a function of the alkali content. The simultaneous presence of bridging oxygen (BO) and non‐bridging oxygen (NBO) atoms was evaluated in both glass systems. In order to clarify the role of the alkali ions on the formation of NBO species, a series of different alkali germanate glasses were analysed (M = Na, K, Rb, Cs) for a particular glass composition 70GeO2·30M2O. This comparison revealed that the percentage of NBO atoms increased upon insertion of the heavier alkali ions. Some explanations are proposed to account for the ways in which the different alkali ions modify the structure of these germanate glasses, in connection with the so‐called germanate anomaly. Copyright © 2002 John Wiley & Sons, Ltd.
Surface and electrical studies of Fe–Si–B powders for soft magnetic applications
Authors: Godec M. , Mandrino Dj. , Šuštaršič B. , Jenko M.
Published: October 2002

Soft magnetic composite (SMC) materials for soft magnetic applications were developed. The most important property of SMC materials, especially those used in a high‐frequency range, is that the soft magnetic powder particles are well insulated from each other. Alloy Fe–Si–B powders were prepared by water atomization. The surface of microcrystalline powders was heat treated in dry or wet hydrogen, chemically treated and investigated by AES and XPS. The electrical breakdown voltages of the powders and SMCs were measured. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of NiAl thin layers by AES and EXAFS
Authors: Mozetič M. , Zalar A. , Jagielski J. , Arčon I. , Panjan P.
Published: October 2002

The composition and structure of NiAl thin films prepared from Ni/Al were studied. Ni/Al Multilayers of Ni/Al were prepared by sputter deposition on well‐polished Si(111) substrates. The average composition was 50 at.% Ni and 50 at.% Al. In order to facilitate migration of particles between layers, two techniques were applied: thermal treatment in hydrogen plasma and ion beam mixing. The composition of the samples was determined by AES, and the structure by extended x‐ray absorption fine structure (EXAFS). In the case of thermal treatment, the periodicity of multilayers vanished at ∼800 K, but the structure remained similar to that of the untreated sample. In the case of ion beam mixing, however, the NiAl phase started growing at a temperature of ∼500 K. The concentration of NiAl phase reached ∼85% at ∼580 K and remained constant with further increase of the temperature during ion beam mixing. Copyright © 2002 John Wiley & Sons, Ltd.
Sensors from electrodeposited metal nanowires
Authors: Walter E. C. , Penner R. M. , Liu H. , Ng K. H. , Zach M. P. , Favier F.
Published: October 2002

Based on their electronic conductivity behaviour, metallic nanowires may have analytical applications ranging from interconnects to sensors. We present in this paper an electrochemical method for synthesizing Mo and Pd metal nanowires ranging in diameter from a few tens of nanometres up to one micrometre, with millimetre lengths. Nanowires are prepared by the electrodeposition of metal at step edges present on a graphite surface. These nanowires can be used to connect metal nanoparticles (Ni, Au, etc.). Once transferred in a polymer cast, they can operate as sensors. We describe how these nanowires may be manipulated to make devices for analytical chemistry and, as an example of such nanodevice, a detailed overview of the characteristics of the first nanowire‐based sensor of hydrogen gas (H2) is given. Copyright © 2002 John Wiley & Sons, Ltd.
Study of ultrathin silicon oxide films by FTIR‐ATR and ARXPS after wet chemical cleaning processes
Authors: Rouchon D. , Rochat N. , Gustavo F. , Chabli A. , Renault O. , Besson P.
Published: October 2002

The narrowest feature on current integrated circuits is the gate oxide—the thin dielectric layer that forms the basis of field effect device structures. Silicon dioxide is the dielectric of choice and, if the present miniaturization trend continues, the projected oxide thickness will be <1 nm in 2005. Therefore, ultrathin silicon oxide layers using various preparation conditions have been studied by angle‐resolved x‐ray photoemission spectroscopy (ARXPS) and Fourier transform infrared attenuated total reflection (FTIR‐ATR).

The silicon oxides obtained by wet chemical treatments such as RCA (SC1 + SC2), SC1 (standard clean), RHO3 (RCA + HF + O3) and DDC (diluted dynamic clean) are characterized in terms of chemical oxide quality before and after thermal annealing. The presence of suboxides (SiOx), as revealed by XPS results, is correlated with Ox–Si–H bonds observed by FTIR‐ATR. The FTIR‐ATR spectra, deconvoluted into four peaks in the asymmetrical stretching SiO bond region (1000–1200 cm−1), show differences between all these chemical oxides. The AS1 (in phase) and AS2 (out of phase) vibrations are compared in terms of position and intensity. The influence of thermal annealing on the chemical oxide quality is also presented. Copyright © 2002 John Wiley & Sons, Ltd.
SIMS depth profiling of ultrashallow P, Ge and As implants in Si using MCs2+ ions
Authors: Holliger P. , Laugier F. , Dupuy J. C.
Published: October 2002

Quantitative determination of dose and junction depth in the source/drain region of future CMOS devices (typically 50 nm for the contact and 25 nm for the extension) requires SIMS instruments capable of measuring dopant profiles with high depth resolution and low detection limits. In this work we investigate the analytical usefulness of monitoring MCs2+ ions for semiconductor profiling of n‐type dopants such as P, Ge or As with a primary (Cs+ beam) impact energy of 1 keV on a SIMS Cameca IMS‐5f instrument. The results obtained on ultrashallow implants in Si and SiO2 indicate an improvement in the characterization by using the MCs2+ technique; this technique has the advantage over the MCs+ technique of providing higher useful yields for electronegative elements by up to 102 and can therefore be applied to perform more precise junction measurements in terms of concentration, dose, decay length and detection limit. Copyright © 2002 John Wiley & Sons, Ltd.
Composition and growth of anodic and thermal oxides on InP and GaAs
Authors: Pakes A. , Skeldon P. , Thompson G. E. , Hussey R. J. , Moisa S. , Sproule G. I. , Landheer D. , Graham M. J.
Published: October 2002

Research using surface analytical techniques (Auger, XPS and 16O/18O SIMS) to characterize anodic films (formed in aqueous electrolytes at ambient temperature) and thermal oxides (formed at ∼500°C) on both InP and GaAs is summarized. Anodic and thermal oxides on InP comprise an outer indium‐rich layer and an inner layer containing In2O3, phosphorus oxide and P–O compounds with indium. For anodic films, sequential 16O/18O SIMS experiments indicate oxygen ion ingress with inner layer growth at the film/substrate interface and outer layer growth of In2O3 at the film/electrolyte interface. Electrical measurements performed on metal–insulator–semiconductor (MIS) structures indicate the oxides on InP to be ‘leaky’. Thermal oxides formed on GaAs in oxygen consist primarily of Ga2O3 with a small amount of arsenic (a few per cent) at the outer oxide surface as both As2O3 and As2O5 and a significant accumulation of elemental arsenic at the oxide/substrate interface. This probably leads to a high density of electronic traps and poor electrical properties. Anodic oxides (∼40 nm thick) formed in phosphate solution, however, have better electrical properties exhibiting low current densities (up to 6 V), making these films potentially useful for device applications. Copyright © 2002 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
Nano‐oxidation of titanium films with large atomically flat surfaces by means of voltage‐modulated scanning probe microscopy
Authors: Unal Kerem , Aronsson Björn‐Owe , Mugnier Yannick , Descouts Pierre
Published: October 2002

Titanium films with large atomically flat surfaces were produced by adapting the template stripping method. The morphology of these surfaces was characterized by contact mode atomic force microscopy and a root‐mean‐square roughness of 0.23 nm at a 1 µm2 area was obtained. Sample bias voltage modulation was used for nanometer‐scale anodic oxidation of the Ti film. The oxide structures produced showed high reproducibility, with aspect ratios of 0.18 and 0.07 for voltage modulation and static pulse oxidation, respectively. The maximum height of oxide structures was found at ∼20 Hz voltage modulation frequency. Using a negative voltage on the sample in a combination with a Pt/Ir‐coated tip enhanced further the aspect ratio and increased the oxide structure height. The influence of control parameters on the aspect ratio of the oxide structures was studied. Copyright © 2002 John Wiley & Sons, Ltd.
Interaction of ultrathin nickel oxide films with single‐crystal zirconia and alumina surfaces
Authors: Sygellou L. , Zafeiratos S. , Tsud N. , Matolin V. , Kennou S. , Ladas S.
Published: October 2002

The behaviour upon thermal annealing of ultrathin nickel oxide films formed on yttria‐stabilized ZrO2(100) (YSZ) and α‐Al2O3(0001) (sapphire) by in situ oxidizing vapour‐deposited Ni films of 0.2–5 ML thickness, was investigated by XPS/x‐ray‐induced Auger electron spectroscopy (XAES). The sapphire substrate was also used following room‐temperature argon ion sputtering to create a defective surface. Heating the nickel oxide films in ultrahigh vacuum (UHV) leads to decomposition in a temperature range strongly dependent on the substrate. On YSZ, the oxide decomposes towards metallic Ni at ∼200 K lower temperature compared with sapphire, where the decomposition temperature is close to the estimated thermodynamic stability limit for nickel oxide in the UHV chamber (∼900 K). This result supports the previously conjectured substrate‐mediated nickel oxide decomposition on YSZ. Furthermore, upon oxide decomposition on sapphire, a chemical interaction with the substrate is evidenced, especially by XAES. This interaction, which appears to exist already at 580 K on the sputtered sapphire substrate, is attributed to the formation of an NiAl2O4 spinel‐like interfacial compound. Copyright © 2002 John Wiley & Sons, Ltd.
Interaction of NH3 with oxygen‐pretreated Ni at 600 K
Authors: Lescop B. , Fanjoux G. , Galtayries A. , Le Nadan A.
Published: October 2002

The aim of the present study was to investigate the reaction between ammonia and pre‐adsorbed oxygen on Ni at 600 K using metastable impact electron spectroscopy (MIES) and UPS techniques. For a given oxygen‐pretreated nickel surface, the changes in the MIES spectra along with ammonia adsorption can be decomposed into three different steps: a first domain without significant changes, a second domain corresponding to drastic changes in the intensity of a signal at 15.8 eV; and a third domain where no more change is detected. The first domain may correspond to the ammonia chemisorption on the surface, whereas the changes in the second domain would be attributed to surface dehydroxylation. The existence of NHx groups on the surface has been detected by UPS; they result from ammonia chemisorption. The changes in the MIES spectra have also been studied versus the initial oxygen uptake on Ni. It emerged that the first domain is larger with increasing initial oxygen exposure: this may be explained by the poorer surface reactivity of NiO, contrary to the oxygen‐adsorbed phase. Copyright © 2002 John Wiley & Sons, Ltd.
Surface chemical and electrokinetic characterizations of membranes containing different carriers by x‐ray photoelectron spectroscopy and streaming potential measurements: study of the effect of pH
Authors: Ariza M. J. , Rodríguez‐Castellón E. , Muñoz M. , Benavente J.
Published: October 2002

Two activated membranes containing 200 mM of di‐(2‐ethylhexyl) phosphoric acid (DEHPA‐2) and di‐(2‐ethylhexyl)dithiophosphoric acid (DTPA‐2) as carriers have been studied. The electrokinetic characterization of the membrane/solution interface was carried out by means of tangential streaming potential measurements, with the membranes in contact with an NaCl solution (5 × 10−4 M) at different pH (3.5 ≤ pH ≤ 8.5). These measurements allow the determination of the zeta potential, the electrokinetic surface charge density and the isoelectric point of the membranes. Other membrane characteristic parameters such as the acidic dissociation constant or the number of acidic sites per membrane area (density of acidic sites) can be determined if a site dissociation model is used. On the other hand, chemical changes in the membrane surfaces due to contact with solutions at different pH were determined by comparing XPS spectra of the used samples with the original ones. In order to see the influence of each type of carrier on electrokinetic parameters, a comparison with the polymeric base membrane (B0) has also been made. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of hydrogen gas diffusion electrodes for reduction of metal from industrial process liquids
Authors: Schulze M. , Lorenz M. , Wagner N.
Published: October 2002

Gas diffusion electrodes can be operated in a lot of electrochemical processes and devices, such as fuel cells, electrolysis and cleaning of waste water from electrochemical treatments of metals (electrochemical machining, electrochemical drilling and galvanic processes). Carbon black‐supported platinum is mixed with polytetrafluoroethylene (PTFE) in a knife mill and rolled onto a metal web to form an electrode. The electrodes were characterized before and after electrochemical operation with x‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Induced by the rolling process of the PTFE–carbon black powder, the PTFE forms thin fibres that are spun to a web in the electrode.

The surface composition of the electrodes for electrochemical metal treatment and cleaning of galvanic waste water changes during the operation time. Owing to the presence of metal ions in the liquid electrolyte in these applications, metal is deposited onto the electrode surface during the operation time. Depth profiling of the electrodes shows that metal is not only deposited on the surface but also in the electrodes. Copyright © 2002 John Wiley & Sons, Ltd.
Optical characterization of thin films non‐uniform in thickness by a multiple‐wavelength reflectance method
Authors: Ohlídal M. , Ohlídal I. , Franta D. , Králík T. , Jákl M. , Eliáš M.
Published: October 2002

An original method enabling us to characterize the non‐uniformity of thin‐film thickness is described. This method employs the interpretation of data obtained by multiple‐wavelength reflectometry (MWR). Within this MWR method the values of the reflectance are measured for several wavelengths in many points lying along the area of the film. The spectral dependence of the refractive index of the material forming the film is determined using variable‐angle spectroscopic ellipsometry (VASE). The MWR method is then used to evaluate the values of the thickness along the area of the non‐uniform film under investigation. Within the experimental set‐up employed for applying the MWR method, a multi‐wavelength laser is used as a light source. A CCD camera equipped with a zoom objective is utilized as a detector. A suitable beamsplitter allows to measure the values of the relative reflectance of the film against a reference sample with known reflectance. By using the set‐up employed it is possible to characterize the thin‐film spreading over large areas of substrates. Copyright © 2002 John Wiley & Sons, Ltd.
Study of Zr1−xSnxTiO4 thin films prepared by a polymeric precursor route
Authors: Gusmano G. , Bianco A. , Viticoli M. , Kaciulis S. , Mattogno G. , Pandolfi L.
Published: October 2002

Zirconium–stannate titanate Zr1−xSnxTiO4 (ZTS) thin films, undoped and doped with Sb, Ta and Nb, were prepared by a polymeric precursor technique. The ZTS films were deposited on the multilayered substrates (Pt/Ti/SiO2/Si) by means of multiple spin‐coating. After this deposition, the samples were heated at different temperatures (300–700°C). The chemical composition of these films and bulk ZTS samples was investigated by using x‐ray photoelectron spectroscopy and selected‐area XPS depth profiling. A partial surface segregation of SnIV and the presence of Sn0, TiII and TiIII species in the films were revealed from XPS depth profiles. An optimized ZTS deposition process, where an oxidizing agent (H2O2) is added to the gel, is proposed. Copyright © 2002 John Wiley & Sons, Ltd.
V2O5 thin films deposited by means of d.c. magnetron sputtering from ceramic V2O3 targets
Authors: Poelman H. , Tomaszewski H. , Poelman D. , Fiermans L. , De Gryse R. , Reyniers M.‐F. , Marin G. B.
Published: October 2002

The deposition of stoichiometric V2O5 films for abrasion‐resistant V2O5/TiO2 anatase catalysts was investigated. Direct current magnetron sputtering from ceramic oxide targets in an argon/oxygen atmosphere was chosen as the deposition technique. Layers were prepared with different oxygen mole fractions in the plasma and the influence upon electronic and optical properties was investigated. Surface XPS measurements showed that stoichiometric layers are obtained for low oxygen flows, whereas for higher oxygen contributions reduced vanadium species are increasingly present. This departure from stoichiometry is ascribed to active re‐sputtering of the deposited layer by O− ions, due to the higher sputter yield of oxygen compared with vanadium. Polycrystalline V2O5 layers were obtained at elevated substrate temperatures. Optical absorption coefficients in the visible region were found to correlate well with the layer stoichiometry, as deduced from the XPS lineshape analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Work of adhesion and fretting: influence of material surface properties and medium
Authors: Lambert Mathieu , Duluc Sébastien , Paris Jean‐Yves , Baziard Yves , Denape Jean
Published: October 2002

This work attempts to link tribological and adhesion phenomena in fretting conditions. Fretting experiments were carried out in three environmental conditions (air atmosphere, demineralized water and kerosene) and with various couples of industrial materials. Contacting materials and liquids were chosen mainly for their surface properties, in order to have a wide range of surface free energies. The fretting device included a pin‐on‐plane configuration. The pin (or slider) was fixed and the plane was the moving substrate. The total distance (dT) covered by the moving substrate was chosen as the tribological parameter representative of the history of an experiment. The distance dT was then compared to surface parameters such as Dupré's work of adhesion between the two substrates in contact (W12) and with three bodies (W132), the index 3 being the liquid medium. In these conditions, dT = f(W12) and dT = f(W132) variations were found to be linear, thus showing a clear link between friction and adhesion. Copyright © 2002 John Wiley & Sons, Ltd.
Clinical research and trials in developing countries
Authors: Yusuf Salim
Published: October 2002

Over 80 per cent of the global disease burden occurs in developing countries. Yet the proportion of research conducted in these countries is less than 10 per cent of the global research activity. This article emphasizes the need to conduct research in developing countries on locally relevant questions, provides general principles that may assist in establishing such studies, and describes some experiences in the cardiovascular area. Copyright © 2002 John Wiley & Sons, Ltd.
The extended campus—safety abroad
Authors: Scharman Janet S.
Published: October 2002

Study abroad has evolved from small, isolated programs for students to a more integral part of many students’ undergraduate experience. Institutions are beginning to consider the safety aspects beyond the academic program itself. This chapter covers procedures and processes for administrators to consider.
Cytotoxic effects of triphenylbismuth on rat thymocytes: Comparisons with bismuth chloride and triphenyltin chloride
Authors: Arata Tomohiro , Oyama Yasuo , Tabaru Ken , Satoh Masaya , Hayashi Hiromi , Ishida Shiro , Okano Yoshiro
Published: October 2002

The biomedical and industrial uses of organobismuth compounds have become widespread, although there is limited information concerning their cytotoxicity. Therefore, the actions of triphenylbismuth on rat thymocytes were examined using a flow cytometer with ethidium bromide, annexin V‐FITC, fluo‐3‐AM, and 5‐chloromethylfluorescein (5CMF) diacetate. Triphenylbismuth at 3–30 μM increased the population of cells stained with ethidium, indicating a decrease in cell viability. Organobismuth at 30 μM increased the population of cells positive to annexin V, suggesting an increase in the population of apoptotic cells. Triphenylbismuth at 3 μM or more decreased cellular glutathione content (5CMF fluorescence intensity) and increased intracellular Ca2+ concentration ([Ca2+]i, fluo‐3 fluorescence intensity) in a dose‐dependent manner. Because an increase in [Ca2+]i is linked to cell death or cell injury and a decrease in cellular glutathione content increases cell vulnerability to oxidative stress, the triphenylbismuth‐induced changes in cellular parameters may be responsible for triphenylbismuth‐induced cytotoxicity. Bismuth chloride at 10–30 μM did not significantly affect cell viability. These results suggest that triphenylbismuth at micromolar concentrations exerts cytotoxic action on rat thymocytes, possibly related to a health hazard. Although the cytotoxicity of triphenylbismuth was less than that of triphenyltin, one of the environmental pollutants, it is necessary to direct our attention to the use and disposal of organobismuth compounds. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 472–477, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10081
Recording a line profile across ion‐implanted conductor paths in Si wafers by a synchrotron beam microprobe
Authors: Klockenkämper R. , von Bohlen A. , Radke M. , Knöchel A. , Palmetshofer L.
Published: October 2002

Synchrotron radiation was applied to recording a line profile across buried conductive paths in a silicon 〈100〉 wafer. For that purpose, Co ions were first implanted in a depth of 60 nm below the silicon surface with a dose of 1017 cm−2 and an energy of 100 keV. By means of a photoresist mask, small strips of ca 150 and 40 µm width were produced. The analytical characterization was performed at DESY/HASYLAB by concentrating the synchrotron beam with a cylindrical and a tapered capillary with an effective diameter of 10 and 4 µm, respectively. The implanted wafer was shifted in steps of 1 µm on a straight line along a capillary in order to record a line profile of the implanted element cobalt across the buried strips. An internal standard was used in order to compensate for the large long‐term drift and the strong fluctuations of the synchrotron beam. A 0.1 µm thin Ti foil turned out to be a very simple standard easily placed in front of the implanted wafer. This aid facilitates an examination of buried layers with a flank down to only micrometer steepness and with a uniform plateau down to only 1% deviations. Copyright © 2002 John Wiley & Sons, Ltd.
Functional, comparative and cell biological analysis of Saccharomyces cerevisiae Kre5p
Authors: Levinson Joshua N. , Shahinian Serge , Sdicu Anne‐Marie , Tessier Daniel C. , Bussey Howard
Published: October 2002

Saccharomyces cerevisiae kre5Δ mutants lack β‐1,6‐glucan, a polymer required for proper cell wall assembly and architecture. A functional and cell biological analysis of Kre5p was conducted to further elucidate the role of this diverged protein glucosyltransferase‐like protein in β‐1,6‐glucan synthesis. Kre5p was found to be a primarily soluble N‐glycoprotein of ∼200 kDa, that localizes to the endoplasmic reticulum. The terminal phenotype of Kre5p‐deficient cells was observed, and revealed a severe cell wall morphological defect. KRE6, encoding a glucanase‐like protein, was identified as a multicopy suppressor of a temperature‐sensitive kre5 allele, suggesting that these proteins may participate in a common β‐1,6‐biosynthetic pathway. An analysis of truncated versions of Kre5p indicated that all major regions of the protein are required for viability. Finally, Candida albicans KRE5 was shown to partially restore growth to S. cerevisiae kre5Δ cells, suggesting that these proteins are functionally related. Copyright © 2002 John Wiley & Sons, Ltd.