bluuebunny/crossref_metadata_2025 huggingface dataset:
A crossed molecular beams study of the O(3P)+H2 reaction: Comparison of excitation function with accurate quantum reactive scattering calculations
Authors: Garton Donna J. , Minton Timothy K. , Maiti Biswajit , Troya Diego , Schatz George C.
Published: January 2003

We present the first measurements of the relative excitation function for the O(3P)+H2 reaction, performed with the use of a crossed molecular beams apparatus in conjunction with a high-energy (laser detonation) source of O atoms. The results are in excellent agreement with accurate quantum wave packet calculations.
Energy dissipation rate and energy spectrum in high resolution direct numerical simulations of turbulence in a periodic box
Authors: Kaneda Yukio , Ishihara Takashi , Yokokawa Mitsuo , Itakura Ken’ichi , Uno Atsuya
Published: January 2003

High-resolution direct numerical simulations (DNSs) of incompressible homogeneous turbulence in a periodic box with up to 40963 grid points were performed on the Earth Simulator computing system. DNS databases, including the present results, suggest that the normalized mean energy dissipation rate per unit mass tends to a constant, independent of the fluid kinematic viscosity ν as ν→0. The DNS results also suggest that the energy spectrum in the inertial subrange almost follows the Kolmogorov k−5/3 scaling law, where k is the wavenumber, but the exponent is steeper than −5/3 by about 0.1.
The effects of the human MDR1 genotype on the expression of duodenal P‐glycoprotein and disposition of the probe drug talinolol
Authors: Siegmund Werner , Ludwig Karen , Giessmann Thomas , Dazert Peter , Schroeder Eike , Sperker Bernhard , Warzok Rolf , Kroemer Heyo K. , Cascorbi Ingolf
Published: January 2003

Background and objectives

A single‐nucleotide polymorphism (SNP) of the human multidrug‐resistance gene in wobble position of exon 26 reportedly predicts expression and function of P‐glycoprotein in human enterocytes and lymphocytes. Several other allelic variants of MDR1 have been identified, some of which lead to amino acid exchange with as yet unknown functional relevance.

Methods

In healthy white volunteers, we investigated the influence of the hereditary variants C3435T in exon 26 and G2677T/A (Ala893Ser/Thr) in exon 21 and the influence of 7 frequent or putative functional SNPs on duodenal MDR1 messenger ribonucleic acid (n = 32) and immunoreactive P‐glycoprotein (n = 37) expression. Moreover, the disposition of the probe drug talinolol was evaluated in 55 subjects after oral administration (100 mg) and in 23 subjects after intravenous administration(30 mg).

Results

Duodenal MDR1 messenger ribonucleic acid and P‐glycoprotein, as assessed by real‐time polymerase chain reaction (TaqMan) and immunostaining, were not influenced by any MDR1 polymorphism studied. Talinolol disposition was not affected by the exon 26 mutation C3435T. In carriers of the TT/TA variants of G2677T/A, the area under the serum concentration‐time curve values of oral talinolol were slightly but significantly elevated compared with those in carriers of at least 1 wild‐type allele (P < .05, Kruskal‐Wallis test; P = .014, Mann‐Whitney U test). However, multiple comparisons with combinations of putative functional SNPs did not confirm a significant influence of the MDR1 genotype on talinolol disposition.

Conclusions

We did not identify any influence of MDR1 genotypes on duodenal expression of P‐glycoprotein and disposition of talinolol in humans.

Clinical Pharmacology & Therapeutics (2002) 72, 572–583; doi: 10.1067/mcp.2002.127739
Cytochrome P450 3A4 and P‐glycoprotein mediate the interaction between an oral erythromycin breath test and rifampin
Authors: Paine Mary F. , Wagner David A. , Hoffmaster Keith A. , Watkins Paul B.
Published: January 2003

Background

The intravenous 14C‐erythromycin breath test (ERMBTIV) does not measure aggregate liver and intestinal cytochrome P450 (CYP) 3A4 activity. Accordingly, we evaluated an oral stable‐labeled (13C) formulation of the test (ERMBToral) as an alternative CYP3A4 phenotyping probe.

Methods

After an overnight fast, 14 young healthy volunteers (5 women and 9 men) received the ERMBTIV (0.07 μmol, 3 μCi), followed by the ERMBToral (500 mg). The next morning, the CYP3A4 inhibitor troleandomycin (500 mg) was given, and both ERMBTs were repeated. After at least 24 hours, the CYP3A4 and P‐glycoprotein inducer rifampin (600 mg; INN, rifampicin) was given daily for 7 days, and both ERMBTs were repeated 24 hours after the last dose of rifampin. Plasma samples were collected for 10 hours with each administration of the ERMBToral, and erythromycin levels were measured by liquid chromatography‐mass spectrometry. Finally, the effect of troleandomycin on erythromycin transport was examined in Caco‐2 cell monolayers.

Results

Compared with baseline values, the median ERMBTIV and ERMBToral results and erythromycin apparent oral clearance (CL/F) all significantly decreased, by at least 70%, with troleandomycin treatment (P = .001 for each comparison). With rifampin treatment, the median ERMBTIV result and CL/F increased 2‐fold (P ≤ .01), but the median ERMBToral result was unchanged (P = .30). There were no rank‐order correlations between the ERMBTIV and ERMBToral results or between either ERMBT result and CL/F within each treatment group (P ≥ .07). In addition, troleandomycin had no effect on erythromycin transport in Caco‐2 cells (P ≥ .20).

Conclusions

The ERMBToral was influenced by processes in addition to intestinal and hepatic CYP3A4 activity and therefore did not provide a straightforward measure of aggregate CYP3A4 phenotype. The erythromycin‐rifampin interaction cannot be attributed to CYP3A4 induction alone and probably also reflected intestinal P‐glycoprotein induction.

Clinical Pharmacology & Therapeutics (2002) 72, 524–535; doi: 10.1067/mcp.2002.128387
Improving peer review: A guide for reviewers of biomedical research
Authors: Reidenberg June W.
Published: January 2003

Clinical Pharmacology & Therapeutics (2002) 72, 469–473; doi: 10.1067/mcp.2002.128870
Single‐dose and steady‐state pharmacokinetics of celecoxib in children
Authors: Stempak Diana , Gammon Janet , Klein Julia , Koren Gideon , Baruchel Sylvain
Published: January 2003

Background and Objective

Celecoxib is a member of a novel group of agents that selectively inhibit cyclooxygenase 2 (COX‐2). COX‐2 inhibitors have emerged as an important class of drugs because of the lower incidence of side effects when compared with traditional nonsteroidal anti‐inflammatory drugs, which inhibit both cyclooxygenase 1 and COX‐2. Because children often differ from adults with respect to drug disposition, the objective of this study was to determine the single‐dose and steady‐state pharmacokinetics of celecoxib in pediatric patients.

Methods

Celecoxib plasma concentrations were determined at intervals over 12 hours after a 250‐mg/m2 dose and again 1 week later after twice‐daily dosing (steady state).

Results

Peak plasma concentrations (1234 ± 528 μg/L) were achieved 3 hours after drug administration. The area under the celecoxib plasma concentration‐time curve was 7709 ± 3176 μg/L · h, the elimination half‐life (t½) was 3.7 ± 1.1 hours, the apparent volume of distribution was 7.9 ± 7.8 L/kg, and the lower oral clearance of the drug was 1.4 ± 1.0 L · h−1 · kg−1. Statistical analysis revealed a significantly higher apparent oral clearance and longer t½ (P < .05) at steady state compared with pharmacokinetics after a single dose. In addition, when the results were compared in children and adults, the drug was cleared approximately twice as fast in children and had a t½ that was approximately half as long.

Conclusions

This is the first report of celecoxib pharmacokinetics in children, and the results indicate that there are significant differences between children and adults with respect to celecoxib disposition; hence these data may have implications when dosing schedules are planned for this population.

Clinical Pharmacology & Therapeutics (2002) 72, 490–497; doi: 10.1067/mcp.2002.129322
European perspectives on welfare reform: A tale of two vicious circles?
Authors: Gray Anne
Published: January 2003

This paper discusses the effects of ‘welfare to work’ and ‘making work pay’ policies such as tax credits on job quality in the wider labour market. It examines the consequences of two policy approaches to the problem of work incentives for the unemployed. One approach is greater conditionality of benefits systems, of which the extreme case is workfare; the other is transfers to supplement low wages. It is argued that both approaches, individually or in combination, threaten to set up vicious circles, creating yet more of the problems they attempt to solve. Through qualitative interview material from Britain, France, Germany and Belgium, from a recent international project supported by the EU,1 the paper illustrates how the responses of the unemployed to the four countries' benefits systems and insertion programmes structure the effects of these policies on the labour market.
Women and pensions in Northern Ireland: Observations from recent research
Authors: Evason Eileen , Spence Lynda
Published: January 2003

The paper reviews the implications for women and pensions policy in the United Kingdom in the light of recent and ongoing research in Northern Ireland.
Measurement systems for large aerospace components
Authors: Saadat M. , Cretin L.
Published: January 2003

This paper results from research carried out to survey the various large commercial aerospace engineering component measurement systems. The commercial aircraft manufacturing industry is special due to the size of the components involved. Accuracy constraints remain very close, despite the size, and therefore accurate methods of measurement are necessary to control the quality of the final product. A survey of various current methods of measurement for such components is presented. These methods are based around three main principles: theodolites, photogrammetry, and laser technology. Each method has its own advantages and disadvantages in terms of accuracy, repeatability, range and cost. It is also often necessary to consider what each technique provides in terms of data storage and analysis. Most techniques use computer‐based systems to store results and perform various calculations. These systems also have their own requirements in terms of the environment in which they are used. It is important to consider whether a particular system can be installed in an area suitable to measure the required component, as well as ensuring that the stability requirements are met. In this paper the principles and characteristics of conventional optical tooling, electronic triangulation, electronic trilateration, photogrammetry, laser trackers, and laser scanners are reviewed.
Flow conditioners design and their effects in reducing flow metering errors
Authors: Ouazzane A.K. , Benhadj R.
Published: January 2003

The sensitivity of differential‐pressure flow meters to the quality of the approaching flow continues to be a cause for concern to flow meter manufacturers and users. Distortions to the approaching velocity profiles generated by pipe fittings and installations located upstream of a flow meter, can lead to considerable errors in flow metering. This cannot be ignored because of the likely cost and process efficiency implications. This paper describes the effects of various entrance flow velocity profiles on the performance of an orifice flow meter with and without flow conditioning. Asymmetric swirling velocity profiles were generated by a ball valve. These caused significant shifts to the meter’s calibration. The use of a vaned‐plate flow conditioner, consisting of six vanes attached to a 70 per cent porosity plate, greatly improved the performance of the meter. Thus, the device can be used as part of a flow metering package that will have considerably reduced installation lengths. The less‐sophisticated NEL plate proved to be a good flow straightener, i.e. a good swirl remover, but was not an efficient flow conditioner.
Interlibrary services in the UK
Authors: Line Maurice B.
Published: January 2003

The Editorial Board decided it would be a good idea to select a few of the earlier articles published in ILDS and its predecessors, and to reprint them together with commissioned papers reviewing what has happened since. How much has the situation changed, and in what ways? Have forecasts made in the earlier papers been fulfilled?
Application of water‐borne binders to anticorrosive coatings
Authors: Kalenda P.
Published: January 2003

The paper deals with comparison of aqueous polymer dispersions from the point of view of the application thereof to anticorrosive primers. The corrosion tests performed with the coatings formulated on various water‐borne binders indicate considerable differences in the protective coating function. The differences in binders are given by the chemical composition and also by the sizes of polymeric particles forming the binder.
Synthesis and dyeing properties of a new class of condensed carbocyclic arylazopyrazolo[1,5‐a] pyrimidines
Authors: Elgemeie Galal H. , Helal Maher H. , Ahmed Kawther A.
Published: January 2003

Several new condensed carbocyclic arylazopyrazolo[1,5‐a]pyrimidine derivatives were obtained from 4‐arylazo‐3,5‐diaminopyrazoles as starting components. The application and dye characteristics for the synthesized dyes are demonstrated.
Thinking about relationship marketing: where are we now?
Authors: Rao Sally , Perry Chad
Published: January 2003

Relationship marketing (RM) has emerged as a new marketing idea for many firms in Western countries. The aim of this paper is to review the evolution of RM ideas. Definitional difficulties are sorted out, a typology of many of the relationships is developed, structural and social bonds are identified and whether RM is a paradigm shift for marketing theorists and practitioners is debated. This paper argues that RM is not a paradigm shift, but rather an appropriate marketing approach when management considers product/service, customer, and organization factors. The paper’s contribution is its comprehensiveness and up‐to‐date review of the evolution of core RM ideas.
A Collaborative Feature Modeling System
Authors: Bidarra Rafael , van den Berg Eelco , Bronsvoort Willem F.
Published: January 2003

Collaborative systems are distributed multiple-user systems that are both concurrent and synchronized. An interesting research challenge is to develop a collaborative modeling system that offers all facilities of advanced modeling systems to its users, while at the same time providing them with the necessary coordination mechanisms that guarantee effective collaboration. To achieve this, a web-based collaborative feature modeling system, webSpiff, has been developed. It has a client-server architecture, with an advanced feature modeling system as a basis for the server, providing feature validation, multiple views and sophisticated visualization facilities. A careful distribution of the functionality between the server and the clients has resulted in a well-balanced system. On the one hand, the server offers all the functionality of the original feature modeling system. On the other hand, all desirable interactive modeling functionality is offered by the clients, ranging from display of feature model images to interactive model specification facilities. The architecture of webSpiff, the distribution of model data, the functionality of the server and the clients, and the communication mechanisms are described. It is shown that a good compromise between interactivity and network load has been achieved, and that indeed advanced feature modeling with a collaborative system is feasible.
Acoustic Modeling and Control of Conical Enclosures
Authors: Farinholt Kevin M. , Leo Donald J.
Published: January 2003

Acoustic modeling and control of conical enclosures with an actuator boundary condition is presented. Acoustic impedances are coupled with electrical and mechanical actuator dynamics to generate a coupled state-space model of the system. Analysis of the acoustic impedance illustrates that pole-zero cancellation occurs when the length of the conic section becomes large compared to the distance from the apex to the actuator boundary condition. Used as a platform for control design, positive position feedback is applied for acoustic attenuation. The model predicts the first four resonance frequencies to within 1.75 percent of experimentally measured values. Standing waveforms are presented and related to the effects of the actuator boundary condition. A feedback controller is implemented on an experimental testbed with global reductions of 38.4 percent or 4.2 dB observed over a 50-400 Hz frequency range. Experimental results demonstrate that global sound attenuation is possible with a single feedback channel.
Steady-State Responses in Systems of Nearly-Identical Torsional Vibration Absorbers
Authors: Alsuwaiyan A. S. , Shaw Steven W.
Published: January 2003

In this paper we consider the steady-state response of a rotor fitted with a system of nearly identical torsional vibration absorbers. The absorbers are of the centrifugal pendulum type, which provide an effective mean of attenuating torsional vibrations of the rotor at a given order. The model considered employs absorbers that are tuned close to the order of the excitation, with an intentional mistuning that is selected by design, and imperfections among the absorbers which arise from manufacturing, wear, and other effects. It is shown that these systems can experience localized responses in which the response amplitude of one or more absorbers can become relatively large as compared to the response of the corresponding system with identical absorbers. The results are based on an exact steady-state analysis of the mathematical model, and they show that the strength of the localization depends on the average level of absorber mistuning (a design parameter), the magnitude of the relative imperfections among the absorbers, and the absorber damping. It is found that the most desirable situation is one in which the relative imperfections are kept as small as possible, and that this becomes more crucial when the levels of mistuning and damping are very small. The results of the analysis are confirmed by simulations of the fully nonlinear equations of motion of the rotor/absorber system. It is concluded that the presence of localization should be accounted for in absorber designs, since its presence makes the absorbers less effective in terms of vibration reduction and, perhaps more significantly, it can drastically reduce their operating range, since such absorbers typically have limited rattle space.
Noncontacting Excitation and Measurement of Light Structures
Authors: Amraoui Yacine M. , Lieven Nick A. J.
Published: January 2003

This paper demonstrates a new method of conducting a noncontacting vibration measurement on light structures. Although laser vibrometry provides a routine method of acquiring response data, the method of achieving noncontacting point excitation of structures remains problematic. This is the primary concern of the paper. There is understandable motivation to develop a viable noncontacting excitation method as exciting methods involve contact thereby altering the structure’s in-situ properties. The method demonstrated in the paper explores the use of focused acoustic excitation. An ellipsoid cavity has been constructed which is designed to emit focused plane wave excitation over an area of 1 in. diameter, thus approximating to point excitation. The paper outlines the design and construction of the ellipsoid shell and discusses the design parameters in relation to the frequency response and footprint of the excitation. The results presented compare measurements acquired via this new method and the corresponding Frequency Response Functions obtained by the electrodynamic excitation. Significant differences are observable, largely arising from the mass loading effects associated with the standard modal testing procedures.
Analysis of Triaxial Vibration Data for Health Monitoring of Helicopter Gearboxes
Authors: Tumer Irem Y. , Huff Edward M.
Published: January 2003

Research on the nature of the vibration data collected from helicopter transmissions during flight experiments has led to several crucial observations believed to be responsible for the high rates of false alarms and missed detections in aircraft vibration monitoring systems. This work focuses on one such finding, namely, the need to consider additional sources of information about system vibrations. In this light, helicopter transmission vibration data, collected using triaxial accelerometers, are explored in three different directions, analyzed for content, and then combined using Principal Components Analysis (PCA) to analyze changes in directionality. The frequency content of the three different directions is compared and analyzed using time-synchronously averaged vibration data. To provide a method for analysis and monitoring purposes, the triaxial data are decorrelated using a mathematical transformation, and compared to the original axes to determine their differences. The benefits of using triaxial data for vibration monitoring and diagnostics are explored by analyzing the changes in the direction of the principal axis of vibration formed using all three axes of vibration. The statistical variation introduced due to the experimental variables is further analyzed using an Analysis of Variance approach to determine the effect of each variable on the overall signature. The results indicate that triaxial accelerometers can provide additional information about the frequency content of helicopter gearbox vibrations, and provide researchers and industry with a novel method of capturing and monitoring triaxial changes in the baseline vibration signatures.
Twice-Running-Speed Response Due to Elliptical Bearing Clearances
Authors: Childs Dara W.
Published: January 2003

Yamamoto [1] examined a vertical Jeffcott rotor model with bearing clearances and showed that a small bearing “dead-band” clearance could have a dramatic influence on synchronous rotor response. Recent test results for a turbopump in a liquid-rocket-engine development program showed a twice-running-speed response (2E) on the order of 8 gs over a wide speed range, while synchronous response levels were only at an 0.5 g level. Childs [2] predicted a sharp 2E response for the Advanced Technology Development, High-Pressure Fuel Turbopump (ATD-HPFTP) of the Space Shuttle Main Engine due to bearing clearances, when the running speed was nearly one half of a housing-mode natural frequency, i.e., when the 2E frequency was close to the housing mode natural frequency. However, his model did not predict significant 2E response over a broad running-speed range. Ellipticity of the bearing dead-band clearances was suggested as a possible cause for the observed 2E phenomenon. An extension of Yamamoto’s analysis [1] is presented including bearing ellipticity to examine that proposed explanation. The analysis results show that clearance ellipticity will produce 2E response over a considerable running-speed range during which the bearing clearance is engaged; however, the predicted 2E-response amplitude corresponding to an ellipticity of 0.1 were about 10% of the synchronous levels, and the projected 2E acceleration levels were about 40% of synchronous. The predicted 2E response includes a resonance peak (that can be sharp) at speeds slightly above 25% of the rotor critical speed. The perturbation-analysis results provide an explanation for persistent, lower 2E-response levels observed in many turbopumps, but do not explain the high levels observed with this turbopump.
Nesting Arbitrary Shapes Using Geometric Mating
Authors: Yu Chan , Manoochehri Souran
Published: January 2003

A genetic algorithm-based optimization method is proposed for solving the problem of nesting arbitrary shapes. Depending on the number of objects and the size of the search space, realizing an optimal solution within a reasonable time may not be possible. In this paper, a mating concept is introduced to reduce the solution time. Mating between two objects is defined as the positioning of one object relative to the other by merging common features that are assigned by the mating condition between them. A constrained move set is derived from a mating condition that allows the transformation of the object in each mating pair to be fully constrained with respect to the other. Properly mated objects can be placed together, thus reducing the overall computation time. Several examples are presented to demonstrate the efficiency of utilizing the mating concept to solve a nesting optimization problem.
Modeling Information Needs in Engineering Databases Using Tacit Knowledge
Authors: Song Shuang , Dong Andy , Agogino Alice
Published: January 2003

Online resources of engineering design information are a critical resource for practicing engineers. These online resources often contain references and content associated with technical memos, journal articles and “white papers” of prior engineering projects. However, filtering this stream of information to find the right information appropriate to an engineering issue and the engineer is a time-consuming task. The focus of this research lies in ascertaining tacit knowledge to model the information needs of the users of an engineering information system. It is proposed that the combination of reading time and the semantics of documents accessed by users reflect their tacit knowledge. By combining the computational text analysis tool of Latent Semantic Analysis with analyses of on-line user transaction logs, we introduce the technique of Latent Interest Analysis (LIA) to model information needs based on tacit knowledge. Information needs are modeled by a vector equation consisting of a linear combination of the user’s queries and prior documents downloaded, scaled by the reading time of each document to measure the degree of relevance. A validation study of the LIA model revealed a higher correlation between predicted and actual information needs for our model in comparison to models lacking scaling by reading time and a representation of the semantics of prior accessed documents. The technique was incorporated into a digital library to recommend engineering education materials to users.
Interactive Visualization of Line Congruences for Spatial Mechanism Design
Authors: Larochelle Pierre M. , Vance Judy M. , Kihonge John N.
Published: January 2003

This paper presents a framework for generating, representing, and interacting with the line congruences associated with four general finite poses. These line congruences are the solution space of spatial 4C mechanisms which will guide a moving body through the four prescribed poses. Hence, the contributions of this paper are applicable to developing interactive tools for designing spatial 4C mechanisms for four pose motion generation. Moreover, the strategies employed to address this difficult interactive visualization challenge are presented. The goal here being to facilitate future works which address other interactive visualization challenges. First, a methodology for generating a parameterized representation of the line congruences is reviewed. This is followed by strategies for visually representing the line congruences which are appropriate for both workstation and immersive virtual reality computer graphics. Next, strategies and supporting algorithms for interacting with the line congruences to obtain solution mechanisms with fixed links or coupler links in desired regions of the workspace are presented. The result is an intuitive interactive visual design methodology for generating and interacting with the line congruences associated with four general finite spatial poses for spatial 4C mechanism design. It is our desire that this effort, albeit focused upon the challenge of creating computer-aided design environments for spatial 4C mechanisms, will facilitate as well as motivate other efforts to address the inherent visualization and interaction challenges in designing three dimensional mechanical systems.
An Evolutionary Modeling Approach for Automotive Bumper System Design and Analysis
Authors: Ge Ping (Christine) , Wang Nancy , Lu Stephen C-Y.
Published: January 2003

Surrogate models play an important role in improving design productivity and discovering knowledge at early design stage. In this paper, a preliminary version of an E_volutionary M_odeling A_pproach (EMA) is presented to generate surrogate models for highly nonlinear system with a large design space and limited resources. Through an evolutionary process, less accurate surrogate models gradually evolve into more accurate ones as the quality of the sampling data set is improved. Its use is demonstrated through an application at the early stage of automotive bumper system design and analysis. The results are verified by both FEA and physical test data.
Monte Carlo simulation method for etching of deep trenches in Si by a SF6/O2 plasma mixture
Authors: Marcos G. , Rhallabi A. , Ranson P.
Published: January 2003

A Monte Carlo method which determines the evolution of a Si etched surface under an SF6/O2 plasma mixture in a high-density low-pressure reactor is presented. The approach consists of a two-dimensional discretization of the initial target (mask and substrate) in a series of same size cells, to determine the substrate time–space evolution according to plasma-surface interactions. One ion transport model through the sheath is introduced to determine the angular and energetic distribution function of ions near the substrate surface. Spontaneous chemical etching by SiF4 desorption and preferential sputtering are studied. Etch profile simulations were performed to interpret the role of certain parameters such as mask geometry and F sticking probability. The simulation results show that the neutral reemission in the trench is implicated in the undercut formation. Moreover, the predicted etch profiles let a bowing appear at the sidewalls. The model reveals that these zones are sputtered by an incident ion flux reflected from the mask sides.
Growth of highly c-axis textured AlN films on Mo electrodes for film bulk acoustic wave resonators
Authors: Lee Si-Hyung , Lee Jeon-Kook , Yoon Ki Hyun
Published: January 2003

Highly c-axis textured AlN films on Mo could be obtained using the structural modification of Mo thin films by the reactive rf magnetron sputtering at a low temperature. The correlation of structural properties of Mo and the degree of c-axis texturing in AlN films was studied as a function of sputtering pressure during the dc sputter deposition of Mo. The microstructure and residual stress of Mo films were found to be very dependent on the sputtering pressure. As the pressure decreases and the stress changes from tension to compression, the surface morphology and roughness of Mo films became gradually denser and smoother. It is found that the controlled smooth surface of Mo electrodes plays a key role in the growth of highly c-axis textured AlN films deposited onto them. A full width at half maximum of the x-ray rocking curve of the best AlN film on the surface-controlled Mo electrode was 2.30°. Film bulk acoustic wave resonators with an effective coupling coefficient of 5.6% could be achieved using the improved AlN films.
Characterization of damage in reactive ion etched ZnTe
Authors: Guo Qixin , Matsumoto Yuichi , Tanaka Tooru , Nishio Mitsuhiro , Ogawa Hiroshi
Published: January 2003

Reactive ion etching of ZnTe has been carried out at various applied rf powers and CH4/H2 concentrations. The damage induced during dry etching is characterized by low-temperature photominescence (PL) measurements. It is observed that the PL intensity of the free excitons decreases with increasing applied rf power, which is ascribed to the increase of the surface damage by ion bombardment. The amount of the surface damage can be reduced by adding more CH4 in the gas mixture due to the effect of chemical etching.
Deposition, microstructure, and properties of nanocrystalline Ti(C,O,N) coatings
Authors: Ruppi S. , Larsson A.
Published: January 2003

Chemical vapor deposition of Ti(C,N) coatings from the TiCl4–CH3CN–N2–H2 system on cemented carbide substrates was studied. The morphology and grain size of the coatings were modified using carbon monoxide (CO). Transmission electron microscopy confirmed that grain refinement of the Ti(C,N) coatings could be obtained by means of CO doping and nanocrystalline coatings were obtained at CO levels exceeding 6%. CO doping resulted in the incorporation of oxygen in the structure, but no segregation of oxygen to grain boundaries was observed. The coatings appeared to be of homogeneous composition even at the highest CO levels. Both improved coating hardness and surface quality were obtained with decreasing grain size. However, the coatings exhibited clearly lower crater wear resistance in the nanograined region. This was explained by an increased tendency for grain-boundary sliding in the nanocrystalline coatings leading to more pronounced plastic deformation.
Interaction of hydrogen-terminated Si(100), (110), and (111) surfaces with hydrogen plasma investigated byin situreal-time infrared absorption spectroscopy
Authors: Shinohara Masanori , Kuwano Takayuki , Akama Yosuke , Kimura Yasuo , Niwano Michio , Ishida Hiroyasu , Hatakeyama Rikizo
Published: January 2003

We have used infrared absorption spectroscopy (IRAS) in the multiple internal reflection (MIR) geometry to investigate the interaction of hydrogen-terminated Si(100), (110), and (111) surfaces with hydrogen plasma at room temperature. We have measured infrared absorption spectra in the Si–H stretching vibration region of the hydrogen-terminated surfaces during H-plasma treatment. IRAS data show that at initial stages of H-plasma treatment, surface hydride species (SiHx,x=1–3) are removed from the surface. A long-term H-plasma treatment of Si(100) and (110) surfaces reproduces monohydride species and creates hydrogen-terminated Si vacancies (VHx) at subsurface regions, i.e., near the surface. On Si(111), no hydride species are reproduced even after a long-term H-plasma treatment. We suggest that monohydride is rather stable against attack of hydrogen radicals as compared to higher hydride species, SiH2 and SiH3. We find that formation of VHx depends on the crystallographic orientation of the Si surface: VHx formation is more favored on Si(110) than on Si(100), and no VHx form on Si(111).
Particle-size dependence of alloy phase formation in isolated particles in the In–Sn system
Authors: Lee J. G. , Mori H.
Published: January 2003

Particle-size dependence of alloy phase formation in isolated particles has been studied by transmission electron microscopy at room temperature, using alloy particles in the In–Sn binary system. In approximately 16-nm-sized particles, essentially the same alloy phases as those in bulk materials formed. Namely, at compositions near the eutectic composition, a mixture of two crystalline phases formed. However, when the size of particles was decreased down to approximately 10 nm in diameter, a liquid phase, which is not an equilibrium phase in bulk materials at room temperature, formed. The formation of a liquid phase is ascribed to the large suppression of the eutectic temperature associated with size reduction.
Structure and properties of anatase TiO2 thin films made by reactive electron beam evaporation
Authors: van de Krol Roel , Goossens Albert
Published: January 2003

Thin, smooth anatase TiO2 films with a thickness of about 100 nm have been made by reactive electron beam evaporation of reduced TiO2. The influence of the oxygen partial pressure is investigated in the range from 2×10−5 to 2×10−3 mbar, and the influence of the substrate temperature is studied in the range from 150 to 300 °C. The structure and properties of the films are investigated with x-ray diffraction, transmission electron microscopy, Raman spectroscopy, impedance spectroscopy, and capacitance–voltage profiling. Depending on the type of substrate, two different morphologies are obtained. On titanium-coated fused silica, grains with a preferred (004) orientation and sizes ranging from 40 to 60 nm in directions parallel to the surface, and from 20 to 125 nm perpendicular to the surface are found. On fused silica, a monolayer of randomly oriented single crystal disks with lateral sizes between 0.2 and 2 μm is found. These films may provide a convenient alternative to single crystals in fundamental studies on the properties of anatase TiO2.
Epitaxial Ti1-xWxN alloys grown on MgO(001) by ultrahigh vacuum reactive magnetron sputtering: Electronic properties and long-range cation ordering
Authors: Tian F. , D’Arcy-Gall J. , Lee T.-Y. , Sardela M. , Gall D. , Petrov I. , Greene J. E.
Published: January 2003

Epitaxial Ti1−xWxN alloys with 0⩽x⩽0.6 were grown on MgO(001) substrates at 500 °C by ultrahigh vacuum reactive magnetron sputtering from Ti and W targets in pure N2. X-ray diffraction, transmission electron microscopy (TEM), and cross-sectional TEM show that the 0.3-μm-thick Ti1−xWxN(001) alloys are single crystals with the B1-NaCl structure. Rutherford backscattering spectroscopy investigations indicate that alloys with x⩾0.05 are slightly overstoichiometric with N/(Ti+W)=1.06±0.05. The alloy lattice parameter a⊥ along the film growth direction is 4.251 Å, irrespective of the WN concentration, for x⩽0.41 and decreases slightly at higher concentrations. TEM analyses show that Ti0.5W0.5N(001) alloys have long-range CuPt-type atomic ordering on the cation sublattice. The room-temperature resistivity increases linearly from 13 μΩ cm for TiN to 287 μΩ cm for Ti0.42W0.58N due primarily to alloy scattering while the temperature coefficient of resistivity is positive in Ti1-xWxN alloys with x⩽0.21 and negative for x>0.21 due to weak charge carrier localization. The superconducting critical temperature Tc of Ti1-xWxN alloys initially increases with x, due to a larger density of states at the Fermi level, consistent with valence band x-ray photoelectron spectroscopy measurements. Tc reaches a maximum of 6.67 K at x=0.21 and decreases for larger x values.
Experimental and theoretical study of ion distributions near 300 μm tall steps on rf-biased wafers in high density plasmas
Authors: Woodworth J. R. , Miller P. A. , Shul R. J. , Abraham I. C. , Aragon B. P. , Hamilton T. W. , Willison C. G. , Kim D. , Economou D. J.
Published: January 2003

We present an experimental and theoretical study of ion fluxes, energy distributions, and angular distributions close to 300 μm tall “steps” on rf-biased wafers in high-density argon plasmas. This feature size is important in the etching of microelectromechanical systems. The theory and data show good agreement in most of the trends in the ion distributions as our sampling point approaches the foot of the step: (1) the ion flux decreases, (2) the ions move away from vertical, turning towards the step, and (3) the widths of the double-peaked ion energy distributions become narrower. The theory predicts that the hot neutral flux near the foot of the step is comparable to the ion flux. These hot neutrals may have important effects on the etching process.
Effect of neutral transport on the etch product lifecycle during plasma etching of silicon in chlorine gas
Authors: Kiehlbauch Mark W. , Graves David B.
Published: January 2003

In this article, we report a computer simulation of silicon etching in chlorine gas. We focus on the lifecycle of silicon containing etch products and how this lifecycle is affected by neutral transport. The lifecycle of silicon in an etch reactor consists of etching, fragmentation by gas phase chemistry, deposition on the walls and wafer, and removal from the reactor. All of these processes are affected by neutral transport. Flow rate and reactor geometry are varied, and the characteristics of the resulting flow fields are analyzed. With the reactor inlet located at the center of the top dielectric, there is significant convective flow at the wafer surface at a chlorine feed rate of 500 sccm. The convective flow helps remove etch products from the reactor. This reduces etch product fragmentation to depositing species in the plasma; thereby reducing wall and wafer deposition. With a showerhead inlet, or with an inlet located at the outer rim of the top dielectric, there is little convective flow at the wafer for any of the simulated flow rates. This results in diffusion dominated transport of etch products. The diffusion is driven by species gradients induced by gas phase and surface reactions. As flow rate decreases, the primary redeposition precursor shifts from SiCl (at 500 sccm) to Si (at 45 sccm), changing the profile of redeposition on the wafer.
Relative sputter rate measured in Cu/Co multilayer using Ar+ ion bombardment at grazing angle of incidence
Authors: Barna A. , Menyhard M. , Zsolt G. , Khanh N. Q. , Zalar A. , Panjan P.
Published: January 2003

The relative sputter rate of copper with respect to cobalt was determined by means of Auger electron spectroscopy depth profiling a Co/Cu multilayer structure as a function of the angle of incidence in the range of 47°–86° at 1 keV Ar+ ion bombardment. It was found that the relative Cu/Co sputter rate, YCu/YCo, decreases from 47° to 82°, exhibiting a minimum at 82°. Above 82° it sharply increases. In the literature we did not find sputtering yield data for such sputtering conditions. TRIM simulation and the Yamamura et al. (Y. Yamamura, Y. Itayekawa, and N. Itoh, Nagoya University of Plasma Physics Report JPPJ-AM-26) equation were compared with the experimental data. Though both predict the increase of YCu/YCo at high angles of incidence, the agreement between the theories and experiment is poor. Reasonably good agreement between the measurements and TRIM simulation was found if the surface binding energy of Cu was chosen to be an unphysical low value.
Antimony and bismuth passivations of InP and characterizations of InP metal-insulator-semiconductor structures fabricated by plasma oxidation of Sb- and Bi-passivated InP
Authors: Morikita Shinya , Ikoma Hideaki
Published: January 2003

The passivation effects of Sb and Bi on InP were investigated. Sb and Bi were vacuum-evaporated on the InP (100) substrates with their thicknesses being changed from 0 nm (not deposited) to about 10 nm and the Schottky current–density–voltage (J–V) characteristics were measured for evaluation of the extent of passivation. The J–V characteristics were substantially improved when the Sb and Bi layers with appropriate thicknesses (about 6 nm for Sb and 4 nm for Bi). The reverse leakage current density largely decreased (from about 10−2 A/cm2 for the native InP sample) to 4×10−5 and 10−7 A/cm2 for, respectively, the Sb(6 nm)/InP and Bi(4 nm)/InP samples. The Schottky barrier heights were as high as 0.59 and 0.75 eV for, respectively, the optimum Sb- and Bi-layer thicknesses, as compared with that (0.45 eV) for the native InP one, which suggested the partial removal of the strong Fermi level pinning at (EC-0.2) eV (EC: conduction band bottom). The J–V characteristics showed the ohmic behavior as the thicknesses of Sb and Bi were large (>8–10 nm). The secondary ion mass spectroscopic (SIMS) data suggested that the Au–Bi-alloy/Bi-terminated-InP structure was fabricated with the optimum Bi thickness, while the Au–Bi-alloy/metallic–Bi/InP structure was produced for the thicker Bi layers, leading to the ohmic behavior (or small Schottky barrier height) because of low work function of Bi. The case of Sb can similarly be considered. It was also shown by the x-ray photoelectron spectroscopic (XPS) data that Sb and Bi removed the native oxides of InP by their reductive natures. Finally, the Sb/InP and Al/Bi/InP structures were exposed to helicon-wave excited O2–Ar plasma to fabricate the Sb2O3/InP and Al2O3–Bi2O3/InP metal-insulator-semiconductor (MIS) structures, which showed relatively well capacitance-voltage (C-V) characteristics.
Modeling gas-phase nucleation in inductively coupled silane-oxygen plasmas
Authors: Suh S.-M. , Girshick S. L. , Kortshagen U. R. , Zachariah M. R.
Published: January 2003

A detailed chemical kinetics mechanism was developed to model silicon oxide clustering during high density plasma chemical vapor deposition of SiO2 films from silane-oxygen–argon mixtures. An inductively coupled plasma reactor was modeled in a one-dimensional multicomponent two-temperature framework. Spatial distributions of species concentrations were calculated. The effects of discharge parameters and the main processes contributing to cluster formation were examined. A sensitivity analysis was conducted to determine the dominant reactions that affect the model results.
Optimization of wear-resistant coating architectures using finite element analysis
Authors: Gorishnyy T. Z. , Olson L. G. , Oden M. , Aouadi S. M. , Rohde S. L.
Published: January 2003

The goal of this work was to develop an approach for the design of multilayer coatings with enhanced toughness to fracture and improved adhesion for wear-resistant applications. Finite element analysis (FEA) was utilized to investigate the distribution of stress in single layer, bilayer and multilayer films under combined normal and tangential loads. Two-dimensional models were created for single layer CrN and Cr2N films and for a number of multilayer combinations of Cr, CrN and Cr2N layers. The FEA results were validated for uncoated solids through comparison with analytical solutions for Hertzian contacts, with and without frictional effects. A good fit was observed in all cases. Then the influence of film architecture and substrate material on the mechanical stress within the films was studied. It was determined that metallic layers had significantly lower σxx stress than ceramic layers, while both σyy and τxy stress within the layers was largely independent of the layer material. Simulation data was then compared to actual data obtained from several chromium nitride based thin films with architectures corresponding to those of the FEA models. Coatings were deposited by unbalanced reactive magnetron sputtering on A2 steel and 2024 aluminum substrates. Residual stress in the films was determined from sin2 Ψ x-ray measurements. When used in multilayer architectures CrN films had high compressive stress on both steel and aluminum substrates, while Cr films had lower compressive stress on steel substrates and tensile stress on aluminum substrates. The residual stress in Cr2N layers could not be determined due to overlap of the x-ray peak. Coating adhesion was measured by a scratch test and wear rates were measured using a pin-on-disk testing apparatus under normal loads of 4 and 10 N for the aluminum and A2 steel substrates, respectively. The strongest correlations were found between the σxx stress at the film–substrate interface and coating adhesion and wear resistance. The stress at the interface between ceramic layers and metallic substrates was very high, resulting in an overall reduction in performance of single layer Cr2N and multilayer CrN/Cr2N films. The highest adhesion and the lowest wear rates were observed in the films that consisted of alternating CrN layers separated by thin Cr layers. Increasing the thickness of the Cr layers degrades the performance of the films due to a decrease in the overall stiffness of the coating.