bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Study of Inhomogeneous Cyclic Plastic Deformation
Authors: Jiang Yanyao
Published: July 2002

A localized inhomogeneous cyclic plastic deformation phenomenon was experimentally investigated in a mild steel. Small strain gages were utilized to characterize the local deformation within the gage section and the gross deformation was measured with an extensometer. Both fully reversed symmetrical loading and asymmetrical loading with a mean stress were used in the cyclic experiments. Plastic deformation was initiated in local areas of the specimen and it propagated into the whole gage section in the specimen with increasing cyclic loading. The local inhomogeneous cyclic deformation was dependent on the loading magnitude and evolved with continued cyclic loading.
Blunt Injuries to the Patellofemoral Joint Resulting From Transarticular Loading Are Influenced by Impactor Energy and Mass
Authors: Atkinson Patrick J. , Ewers and Benjamin J. , Haut Roger C.
Published: July 2002

Various impact models have been used to study the injury mechanics of blunt trauma to diarthrodial joints. The current study was designed to study the relationship between impactor energy and mass on impact biomechanics and injury modalities for a specific test condition and protocol. A total of 48 isolated canine knees were impacted once with one of three free flight inertial masses (0.7, 1.5, or 4.8 kg) at one of three energy levels (2, 11, 22 J). Joint impact biomechanics (peak load, loading rate, contact area) generally increased with increasing energy. Injuries were typically more frequent and more severe with the larger mass at each energy level. Histological analyses of the patellae revealed cartilage injuries at low energy with deep injuries in underlying bone at higher energies.
Underplatform Dampers for Turbine Blades: Theoretical Modeling, Analysis, and Comparison With Experimental Data
Authors: Sanliturk K. Y. , Ewins D. J. , Stanbridge A. B.
Published: July 2002

This paper describes a theoretical model for analyzing the dynamic characteristics of wedge-shaped underplatform dampers for turbine blades, with the objective that this model can be used to minimize the need for conducting expensive experiments for optimizing such dampers. The theoretical model presented in the paper has several distinct features to achieve this objective including: (i) it makes use of experimentally measured contact characteristics (hysteresis loops) for description of the basic contact behavior of a given material combination with representative surface finish, (ii) the damper motion between the blade platform locations is determined according to the motion of the platforms, (iii) three-dimensional damper motion is included in the model, and (iv) normal load variation across the contact surfaces during vibration is included, thereby accommodating contact opening and closing during vibration. A dedicated nonlinear vibration analysis program has been developed for this study and predictions have been verified against experimental data obtained from two test rigs. Two cantilever beams were used to simulate turbine blades with real underplatform dampers in the first experiment. The second experiment comprised real turbine blades with real underplatform damper. Correlation of the predictions and the experimental results revealed that the analysis can predict (i) the optimum damping condition, (ii) the amount of response reduction, and (iii) the natural frequency shift caused by friction dampers, all with acceptable accuracy. It has also been shown that the most commonly used underplatform dampers in practice are prone to rolling motion, an effect which reduces the damping in certain modes of vibration usually described as the lower nodal diameter bladed-disk modes.
Superimposing Ultrasonic Waves on the Dies in Tube and Wire Drawing
Authors: Siegert Klaus , Ulmer Jochen
Published: July 2002

The forces during wire and tube drawing can be reduced by ultrasonically oscillating dies. It is a major problem of conventional wire and tube drawing to introduce high forces into the forming area. Compared to conventional wire and tube drawing, the forming process limits can be extended by superimposing ultrasonic waves due to decreasing drawing forces. Different techniques can be used to excite the die. One possibility is the variation of the vibration mode. In tube and wire drawing, the dies are usually excited longitudinally. If the vibration direction is parallel to the drawing direction, the main influence will be on the friction between workpiece and die. The Institute for Metal Forming Technology of the University of Stuttgart, Germany started a project to investigate the effect of ultrasonic waves on the tribology and on the formability of the workpiece. The objective of this investigation is to separate the ultrasonic effect on the surface from the volume effects. This paper shows that the reduction of the sliding friction between a longitudinal oscillating die and the workpiece can be explained by the so-called Sliding Friction Vector Effect (SFVE). A statistical evaluation of roughness-measurements makes it possible to show the effect of the ultrasonic vibration on the friction and gives an insight into the operation of the SFVE. The results are compared with wire and tube drawing experiments of copper and Ti-alloys. New tube- and wire-drawing experiments with longitudinally vibrating dies support the theoretical approach. The surface quality of the manufactured workpieces can be improved and the productivity increased.
Mechanical Properties and Microstructure of Intraluminal Thrombus From Abdominal Aortic Aneurysm
Authors: Wang David H. J. , Makaroun Michel , Webster Marshall W. , Vorp David A.
Published: July 2002

Accurate estimation of the wall stress distribution in an abdominal aortic aneurysm (AAA) may prove clinically useful by predicting when a particular aneurysm will rupture. Appropriate constitutive models for both the wall and the intraluminal thrombus (ILT) found in most AAA are necessary for this task. The purpose of this work was to determine the mechanical properties of ILT within AAA and to derive a more suitable constitutive model for this material. Uniaxial tensile testing was carried out on 50 specimens, including 14 longitudinally oriented and 14 circumferentially oriented specimens from the luminal region of the ILT, and 11 longitudinally oriented and 11 circumferentially oriented specimens from the medial region. A two-parameter, large-strain, hyperelastic constitutive model was developed and used to fit the uniaxial tensile testing data for determination of the material parameters. Maximum stiffness and strength were also determined from the data for each specimen. Scanning electron microscopy (SEM) was conducted to study the regional microstructural difference. Our results indicate that the microstructure of ILT differs between the luminal, medial, and abluminal regions, with the luminal region stronger and stiffer than the medial region. In all cases, the constitutive model fit the experimental data very well R2>0.98. No significant difference was found for either of the two material parameters between longitudinal and circumferential directions, but a significant difference in material parameters, stiffness, and strength between the luminal and medial regions was determined p<0.01. Therefore, our results suggest that ILT is an inhomogeneous and possibly isotropic material. The two-parameter, hyperelastic, isotropic, incompressible material model derived here for ILT can be easily incorporated into finite element models for simulation of wall stress distribution in AAA.
Modeling Passive Mechanical Interaction Between Aqueous Humor and Iris
Authors: Heys Jeffrey J. , Barocas Victor H. , Taravella Michael J.
Published: July 2002

Certain forms of glaucoma are associated with displacement of the iris from its normal contour. We present here a mathematical model of the coupled aqueous humor–iris system that accounts for the contribution of aqueous humor flow and passive iris deformability to the iris contour. The aqueous humor is modeled as a Newtonian fluid, and the iris is modeled as a linear elastic solid. The resulting coupled equation set is solved by the finite element method with mesh motion in response to iris displacement accomplished by tracking a pseudo-solid overlying the aqueous humor. The model is used to predict the iris contour in healthy and diseased eyes. The results compare favorably with clinical observations, supporting the hypothesis that passive iris deformation can produce the iris contours observed using ultrasound biomicroscopy.
Modeling Solid Particle Erosion in Elbows and Plugged Tees
Authors: Edwards Jeremy K. , McLaury Brenton S. , Shirazi Siamack A.
Published: July 2002

Predicted erosion patterns on the surface of a pipe fitting can now be obtained using a technique implemented into a computational fluid dynamics (CFD) code. This comprehensive erosion prediction procedure consists of 1) generation of a flow field simulation, 2) computation of a large number of particle trajectories inside the flow field, and 3) erosion model equations applied as particles impinge the walls of the geometry. Other quantities related to erosion, namely the particle deposition rate as well as local average impingement angle and velocity components, are also stored in the procedure. All predicted quantities (flow solution, particle trajectories, and erosion profiles) are analyzed using a three-dimensional visualization tool that was also developed. The current work focuses on two pipe fittings commonly used in the oil and gas production industry: elbows and plugged tees. First, the flow field and erosion predictions are evaluated through comparisons with experimental data. Erosion predictions yield trends and locations of maximum wear that are consistent with experimental observations. Next, two 90-deg pipe elbows with centerline curvature-to-diameter ratios of 1.5 and 5.0 are analyzed under prescribed erosive conditions. Predicted erosion results are presented in the form of surface contours. Finally, a simulated plugged tee geometry placed under erosive conditions is studied and erosion rates are compared to that of the two elbow test cases.
A Sequential-Quadratic-Programming Algorithm Using Orthogonal Decomposition With Gerschgorin Stabilization
Authors: Teng C.-P. , Angeles J.
Published: July 2002

This paper introduces a new approach to sequential quadratic programming. Upon application of the orthogonal-decomposition algorithm and the Gerschgorin Theorem for the stabilization of the Hessian matrix in the quadratic-programming solution, this novel approach offers an alternative to existing methods that, additionally, dispenses with a feasible initial guess.
Creeping Flow Through an Axisymmetric Sudden Contraction or Expansion
Authors: Sisavath Sourith , Jing Xudong , Pain Chris C. , Zimmerman Robert W.
Published: July 2002

Creeping flow through a sudden contraction/expansion in an axisymmetric pipe is studied. Sampson’s solution for flow through a circular orifice in an infinite wall is used to derive an approximation for the excess pressure drop due to a sudden contraction/expansion in a pipe with a finite expansion ratio. The accuracy of this approximation obtained is verified by comparing its results to finite-element simulations and other previous numerical studies. The result can also be extended to a thin annular obstacle in a circular pipe. The “equivalent length” corresponding to the excess pressure drop is found to be barely half the radius of the smaller tube.
The Stability of Fluid Production From a Flexible Riser
Authors: Montgomery Jonathan A. , Yeung Hoi C.
Published: July 2002

The prediction of slug formation and slug size has a direct impact on the design of topsides separation facilities and flow assurance to the process. The characteristics and stability of liquid production from an S-shaped riser have been studied over a range of pressures, focusing on the implications for flow management. Severe slugging in an S-shaped riser gives a period of no liquid production, followed by a period of steady production and finally a large production spike, many times larger than the steady production. In contrast with classical severe slugging in a vertical or catenary riser, the transient spike is broken into two parts as a direct consequence of the bend in the line. Little attention has been paid to transition-type flows (between stable and unstable flow) previously. Data collected to date has shown transition flows have production peaks that are larger than those of classical severe slugging.
Asymmetric Four-Point Crack Specimen
Authors: He M. Y. , Hutchinson J. W.
Published: July 2002

Accurate results for the stress intensity factors for the asymmetric four-point bend specimen with an edge crack are presented. A basic solution for an infinitely long specimen loaded by a constant shear force and a linear moment distribution provides the reference on which the finite geometry solution is based. [S0021-8936(00)03601-1]
Numerical Simulation of Pulsatile Flow in a Compliant Curved Tube Model of a Coronary Artery
Authors: Qiu Yuchen , Tarbell John M.
Published: July 2002

The endothelial cells (ECs) lining a blood vessel wall are exposed to both the wall shear stress (WSS) of blood flow and the circumferential strain (CS) of pulsing artery wall motion. These two forces and their interaction are believed to play a role in determining remodeling of the vessel wall and development of arterial disease (atherosclerosis). This study focused on the WSS and CS dynamic behavior in a compliant model of a coronary artery taking into account the curvature of the bending artery and physiological radial wall motion. A three-dimensional finite element model with transient flow and moving boundaries was set up to simulate pulsatile flow with physiological pressure and flow wave forms characteristic of the coronary arteries. The characteristic coronary artery curvature and flow conditions applied to the simulation were: aspect ratio (λ)=10, diameter variation (DV)=6 percent, mean Reynolds number (Re)=150, and unsteadiness parameter (α)=3. The results show that mean WSS is about 50 percent lower on the inside wall than the outside wall while WSS oscillation is stronger on the inside wall. The stress phase angle (SPA) between CS and WSS, which characterizes the dynamics of the mechanical force pattern applied to the endothelial cell layer, shows that CS and WSS are more out of phase in the coronaries than in any other region of the circulation (−220 deg on the outside wall, −250 deg on the inside wall). This suggests that in addition to WSS, SPA may play a role in localization of coronary atherosclerosis. [S0148-0731(00)01201-2]
Influence of Inflow Disturbances on Stagnation-Region Heat Transfer
Authors: Bae S. , Lele S. K. , Sung H. J.
Published: July 2002

Numerical simulations of laminar stagnation-region heat transfer in the presence of freestream disturbances are performed. The sensitivity of heat transfer in stagnation-region to freestream vorticity is scrutinized by varying the length scale, amplitude, and Reynolds number. As an organized inflow disturbance, a spanwise sinusoidal variation is superimposed on the velocity component normal to the wall. An accurate numerical scheme is employed to integrate the compressible Navier-Stokes equations and energy equation. The main emphasis is placed on the length scale of laminar inflow disturbances, which maximizes the heat transfer enhancement. Computational results are presented to disclose the detailed behavior of streamwise vortices. Three regimes of the behavior are found depending on the length scale: these are the “damping,” “attached amplifying,” and “detached amplifying” regimes, respectively. The simulation data are analyzed with an experimental correlation. It is found that the present laminar results follow a general trend of the correlation. [S0022-1481(00)01102-6]
Finite Element Analysis of an Involute Spline
Authors: Kahn-Jetter and Zella L. , Wright Suzanne
Published: July 2002

Two finite element analyses of an involute spline are performed; one is axisymmetrically loaded and the other is nonaxisymmetrically loaded. An entire cross section of both an internal and external pair is analyzed for both models. It is shown that on the axisymmetrically loaded spline the highest stress experienced is the maximum compressive contact stress although the tensile stress in the shaft is also quite high. It is also shown that stress concentrations exist at the root and top of the tooth for both models. Furthermore, on the nonaxisymmetrically loaded spline at low torque, only a few teeth make initial contact, however, as torque is increased, more teeth come in contact. All the stresses remain relatively constant under increasing torque as more teeth are engaged. Once all teeth are in contact stress increases with higher torques. However, the maximum tensile stress (arising from stress concentrations) remains fairly constant, even at high torques, because the stress concentrations that occur at tooth roots appear to be relatively independent of the number of teeth in contact. [S1050-0472(00)00102-1]
Transient Non-Newtonian Thermohydrodynamic Mixed Lubrication of Dynamically Loaded Journal Bearings
Authors: Zhang Chao , Cheng H. S.
Published: July 2002

A transient non-Newtonian THD theory of dynamically loaded journal bearings in mixed lubrication is presented. A mass conserving cavitation is included and shear thinning and viscoelasticity are characterized by the power law and the upper convected Maxwell models, respectively. The 2-D energy equation is solved with ISOADI (isothermal shaft and adiabatic bushing inner surface) boundary conditions. The journal is treated as a quasi-steady and lumped thermal element. [S0742-4787(00)02001-4]
A Simplified Approach to Modeling Thermal Effects in Wet Clutch Engagement: Analytical and Experimental Comparison
Authors: Davis Coby L. , Sadeghi Farshid , Krousgrill Charles M.
Published: July 2002

The simplified isothermal model for wet clutch engagement previously developed by Berger, Sadeghi, and Krousgrill (Berger, E. J., Sadeghi, F., and Krousgrill, C. M., 1996, “Analytical and Numerical Modeling of Engagement of Rough, Permeable, Grooved Wet Clutches,” ASME J. Tribol., 119, p. 143) was extended to include fluid thermal effects. The modified Reynolds and thermal diffusion equations were simultaneously solved to obtain torque and temperature characteristics during wet clutch engagement. The modified Reynolds equation was integrated using the Adams-Gear scheme and the alternating direction implicit method (ADI) finite difference technique was used to solve the thermal diffusion equation. The model was used to study the effects of speed, temperature, and load on the torque transfer and lubricant temperature variation during wet clutch engagement. A comparison of thermal and isothermal results indicates that the thermal model generally predicts a longer engagement time and smaller peak torque than the isothermal model. Comparison of analytical and experimental results indicates that including fluid thermal effects in the model is critical for achieving good correlation between analytical and experimental results. [S0742-4787(00)01501-0]
Discussion: “An Asperity Microcontact Model Incorporating the Transition from Elastic Deformation to Fully Plastic Flow” [ASME J. Tribol., 122, No. 1, pp. 86–93 (2000)]1
Authors: Etsion Izhak
Published: July 2002

[S0742-4787(00)022002-5]
Mist Generation During Metal Machining
Authors: Thornburg Jonathan , Leith David
Published: July 2002

Use of metalworking fluids during machining results in a mist that is associated with adverse health effects. Experiments conducted on a small lathe quantified the amount of mist generated by evaporation/condensation, centrifugal force, and impaction. Evaporation/condensation was the most important mechanism, followed by centrifugal force, then impaction. For evaporation/condensation, rotational speed and cut depth determined the amount of heat generated during machining, whereas fluid flow determined the amount of heat transferred to the liquid. The flow-rotational speed interaction influenced mist generation by centrifugal force, whereas mist generation by impaction was determined only by fluid flow. [S0742-4787(00)01303-5]
A Detailed Analysis of Film-Cooling Physics: Part I—Streamwise Injection With Cylindrical Holes
Authors: Walters D. K. , Leylek J. H.
Published: July 2002

A previously documented systematic computational methodology is implemented and applied to a jet-in-crossflow problem in order to document all of the pertinent flow physics associated with a film-cooling flowfield. Numerical results are compared to experimental data for the case of a row of three-dimensional, inclined jets with length-to-diameter ratios similar to a realistic film-cooling application. A novel vorticity-based approach is included in the analysis of the flow physics. Particular attention has been paid to the downstream coolant structures and to the source and influence of counterrotating vortices in the crossflow region. It is shown that the vorticity in the boundary layers within the film hole is primarily responsible for this secondary motion. Important aspects of the study include: (1) a systematic treatment of the key numerical issues, including accurate computational modeling of the physical problem, exact geometry and high-quality grid generation techniques, higher-order numerical discretization, and accurate evaluation of turbulence model performance; (2) vorticity-based analysis and documentation of the physical mechanisms of jet–crossflow interaction and their influence on film-cooling performance; (3) a comparison of computational results to experimental data; and (4) comparison of results using a two-layer model near-wall treatment versus generalized wall functions. Solution of the steady, time-averaged Navier–Stokes equations were obtained for all cases using an unstructured/adaptive grid, fully explicit, time-marching code with multigrid, local time stepping, and residual smoothing acceleration techniques. For the case using the two-layer model, the solution was obtained with an implicit, pressure-correction solver with multigrid. The three-dimensional test case was examined for two different film-hole length-to-diameter ratios of 1.75 and 3.5, and three different blowing ratios, from 0.5 to 2.0. All of the simulations had a density ratio of 2.0, and an injection angle of 35 deg. An improved understanding of the flow physics has provided insight into future advances to film-cooling configuration design. In addition, the advantages and disadvantages of the two-layer turbulence model are highlighted for this class of problems. [S0889-504X(00)01201-0]
Unsteady Wake Effect on Film Temperature and Effectiveness Distributions for a Gas Turbine Blade
Authors: Teng Shuye , Sohn Dong Kee , Han Je-Chin
Published: July 2002

The film effectiveness and coolant jet temperature profile on the suction side of a gas turbine blade were measured using a transient liquid crystal and a cold-wire technique, respectively. The blade has only one row of film holes near the gill hole portion on the suction side of the blade. Tests were performed on a five-blade linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on cascade exit velocity was 5.3×105. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. Coolant blowing ratio was varied from 0.6 to 1.2. Wake Strouhal number was kept at 0 and 0.1. Results show that unsteady wake reduces film cooling effectiveness. Results also show that film injection enhances local heat transfer coefficient while the unsteady wake promotes earlier boundary-layer transition. The development of coolant jet temperature profiles could be used to explain the film cooling performance. [S0889-504X(00)00402-5]
Electro-Rheological Multi-layer Squeeze Film Damper and Its Application to Vibration Control of Rotor System
Authors: Guozhi Yao , Fah Yap Fook , Guang Chen , Guang Meng , Tong Fang , Yang Qiu
Published: July 2002

In this paper, a new electro-rheological multi-layer squeeze film damper (ERMSFD in short) is designed first and the constitutional Reynolds equation is established. Then the behavior of the rotor system is analyzed, the vibration around the first critical speed is suppressed and an on/off control is proposed to control the large amplitude around the first critical speed. A control method is used to suppress the sudden unbalance response. Finally, experiments are carried out to investigate the behavior of the rotor system to prove the effectiveness of the ER damper to suppress the vibration around the critical speed and the sudden unbalance response. [S0739-3717(00)00301-9]
TiO2 by XPS
Authors: Diebold Ulrike , Madey T. E.
Published: July 2002

The surfaces of titanium oxide belong to the most-studied oxide systems in the surface science literature. This is in part because TiO2 surfaces and interfaces play a major role in several technological applications, e.g., as promoters in catalysis, as photocatalysts, and as gas sensors. TiO2 is a reducible oxide, i.e., several phases with different stoichiometries exist. Because Ti is highly reactive towards oxygen, titanium oxides are formed readily when Ti is exposed to an atmosphere containing water or oxygen. The oxidation behavior of the metal is of interest for the properties of protective coatings. Although accurate knowledge of the XPS binding energies of different oxidation states is necessary for XPS investigations of titanium oxides, a recent review of the 16 literature data of the binding energy of Ti 2p3/2 from Ti4+ showed wide scatter of the reported values with a mean of 458.7 eV and a standard deviation of 1.3 eV [J. Mayer, E. Garfunkel, T. E. Madey, and U. Diebold, J. Electron Spectrosc. Relat. Phenom. 73, 1 (1995)]. TiO2 is easy to handle experimentally. Although it has a bulk band gap of 3 eV, no charging problems occur during surface spectroscopies after single-crystalline samples are reduced by heating in UHV (1000 K, 45 min). This treatment causes loss of bulk oxygen and results in n-type doping. A stochiometric TiO2 surface can reproducibly be prepared through sputtering and annealing in oxygen (2 × 10−4 Pa, 900 K). Our XPS core level spectra are measured from a bulk-reduced titanium dioxide (rutile) (110) surface using a VSW hemispherical analyzer. The binding energy of Ti 2p3/2 is determined as 459.3 eV, and the binding energy of O 1s as 530.4 eV.
Nickel layers on indium arsenide
Authors: Hill C. J. , Beach R. A. , McGill T. C.
Published: July 2002

We report here on the preparation and characterization of InAs substrates for in situ deposition of ferromagnetic contacts, a necessary precursor for semiconductor devices based on spin injection. InAs has been grown on InAs(111)A and (100) substrates by molecular-beam epitaxy and then metalized in situ in order to better understand the mechanisms that inhibit spin injection into a semiconductor. Initial x-ray characterization of the samples indicate the presence of nickel arsenides and indium–nickel compounds forming during deposition at temperatures above room temperature. Several temperature ranges have been investigated in order to determine the effect on nickel-arsenide formation. The presence of such compounds at the interface could greatly reduce the spin-injection efficiency and help elucidate previous unsuccessful attempts at measuring spin injection into InAs.
Monte Carlo Simulation of the Nucleation of Thin Films
Authors: Feber R. C. , Allen L. D. F. , Grimmer D.
Published: July 2002

Nucleation of thin films was simulated by a Monte Carlo computer technique, assuming nucleation commences with the formation of a critical nucleus consisting of one atom. The population densities of adatoms, paired atoms, and larger clusters, as functions of surface coverage, were determined for this model at several incident fluxes and with and without reevaporation of adatoms. The results are compared to current atomistic nucleation theory.
Sorption Pumping of Hydrogen by Carbon Dioxide Cryodeposits
Authors: Tempelmeyer K. E. , Dawbarn Ronald , Young R. L.
Published: July 2002

A systematic experimental investigation of the cryosorption of H2 by cold cryodeposited-CO2 frost is reported. It is shown that the sorption capacity of the frost depends upon the conditions at which the frost was formed and its temperature history. Frosts formed in a manner to make them porous or disordered are shown to possess greater sorption capacities. It appears that surface diffusion of absorbed molecules into a disordered frost structure is the basic pumping mechanism. Isotherms for H2 sorbed by CO2 frosts formed over a wide range of conditions are presented. Also, the reuse sorption capacity of the frost is well documented. As a result of the present tests, it is now possible to put the process of frost-cryosorption pumping into better perspective.
The Flow of Highly Rarefied Gases through Tubes of Arbitrary Length
Authors: Clausing P.
Published: July 2002

Editor's Note: Translated from the German [Ann. Physik (5) 12, 961 (1932)]. Since this classic paper is referred to so frequently by workers in vacuum technology, it has been decided to publish an English translation. The translation was made available through the courtesy of Veeco Instruments, Inc., who also supported its publication.
Thin-film adhesion
Authors: Chapman B. N.
Published: July 2002

Adhesion is of vital interest in thin-film science because the fragile film relies on the underlying substrate, and the adhesion between the two for durability. In addition, the formation and structure of the film depend on the adhesive interaction between the depositing material and the substrate. Despite its general relevance, adhesion is one of the aspects of thin-film science about which little is known. A considerable problem arises with the measurement of adhesion, or more precisely with its lack of susceptibility to measurement. The approaches that have been used are reviewed. A further problem is concerned with the meaning and relevance of “adhesion”, and this point will be discussed from both the practical and theoretical points of view. Based as much on empiricism as on understanding, some means of modifying adhesion have been found and these also are reviewed.
Nanofabrication using structure controlled hydrogenated Si clusters deposited on Si surfaces
Authors: Kanayama Toshihiko , Watanabe Miyoko O. , Bolotov Leonid , Uchida Noriyuki
Published: July 2002

We studied structure formation by deposition of hydrogen-saturated Si clusters Si6H13+ and Si8H19+ on Si (111)-(7×7) surfaces using the deposition system of cluster ions equipped with a scanning tunneling microscope (STM) for surface observation. The system uses a quadrupole ion trap as a mass-selective source of cluster ion beams and delivers to the substrate a beam of Si6H13+ focused to 2 mm diameter with a current of ∼100 pA for the cluster kinetic energy on impact with the surface >5 eV. It was observed that when these clusters are deposited with suitable kinetic energy, i.e., ∼2 eV/Si atom, the impact energy makes the clusters mobile on the surface, leading to self-formation of cluster-agglomerated structures at step edges and along domain boundaries of (7×7) phases. Intentional manipulation of the deposited clusters is also possible using the STM tip; the clusters can be accumulated to the tip position by applying bias voltage larger than 3 V.
Epitaxial CrN(001) Grown and Analyzed In situ by XPS and UPS. I. Analysis of As-deposited Layers
Authors: Haasch R. T. , Lee T. -Y. , Gall D. , Greene J. E. , Petrov I.
Published: July 2002

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to characterize as-deposited epitaxial CrN(001) layers grown in situ. The films were deposited on MgO(001) at 650 °C in pure N2 discharges maintained at a pressure of 5 mTorr (0.67 Pa). Mg Kα and monochromatic Al Kα sources were used to obtain the XPS spectra, while the UPS data was generated by He I and He II UV radiation. Analysis of the results show that the CrN(001) surfaces are free of O and C. A distinct splitting of the Cr 2p3/2 line is also observed. The films were found to be stoichiometric with Rutherford backscattering spectroscopy (RBS) results, yielding a N/Cr ratio of 1.04 ± 0.02. However, composition determined by XPS (N/Cr=0.73) show an excess of chromium.
Observation of surface reaction layers formed in highly selective SiO2 etching
Authors: Matsui Miyako , Tatsumi Tetsuya , Sekine Makoto
Published: July 2002

We characterized the surface reaction layers formed by a fluorocarbon plasma for SiO2 selective etching over Si and Si3N4, in order to understand the etch mechanism and develop a process and tool for future ultralarge-scale integrated circuit processing. Specimens were etched using C4F8/Ar/O2 plasma in a dual-frequency (27/0.8 MHz) parallel-plate reactive ion etching system. The relationship between ion energy (assumed to be equal to the peak-to-peak voltage Vpp of the rf bias) and the thickness of the surface reaction layers was quantitatively analyzed using x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The fluorocarbon polymer layer and the SiFxOy layer on the substrates were observed. We found that the etch rate was strongly affected by the ion energy and the thickness of the fluorocarbon film on etched materials. In a highly selective etch process, the thickness of the fluorocarbon layer on the SiO2 surface was below 1 nm, while that on the Si3N4 and Si substrates were about 5–6 nm. It is considered that the difference in the fluorocarbon layer thickness on each material is the cause of the selectivity. Both TEM and XPS observations revealed that reaction layers (1–5 nm) were formed at the interface between the fluorocarbon layer and Si, Si3N4. The XPS analysis showed the composition of the reaction layer was SiFxOy. These SiFxOy layers were thicker when the ion energy was high and the fluorocarbon film was thin, i.e., a high etch rate condition for Si and Si3N4. SiFxOy is thought to be an intermediary product when the Si3N4 and Si are etched. In a highly selective etch process, the fluorocarbon film on SiO2 was so thin that ion energy was not reduced when ions passed through the film. However, at the surface of Si3N4 and Si, thicker fluorocarbon films were formed and reduced the etch rate, resulting in thin SiFxOy layers being formed.
Resonant infrared pulsed-laser deposition of polymer films using a free-electron laser
Authors: Bubb Daniel M. , Horwitz J. S. , Callahan J. H. , McGill R. A. , Houser E. J. , Chrisey D. B. , Papantonakis M. R. , Haglund R. F. , Galicia M. C. , Vertes A.
Published: July 2002

Thin films of polyethylene glycol (MW 1500) have been prepared by pulsed-laser deposition (PLD) using both a tunable infrared (λ=2.9 μm, 3.4 μm) and an ultraviolet laser (λ=193 nm). A comparison of the physicochemical properties of the films by means of Fourier transform infrared spectroscopy, electrospray ionization mass spectrometry, and matrix-assisted laser desorption and ionization shows that when the IR laser is tuned to a resonant absorption in the polymer, the IR PLD thin films are identical to the starting material, whereas the UV PLD show significant structural modification. These results are important for several biomedical applications of organic and polymeric thin films.
Characterization of Cu surface cleaning by hydrogen plasma
Authors: Baklanov M. R. , Shamiryan D. G. , Tökei Zs. , Beyer G. P. , Conard T. , Vanhaelemeersch S. , Maex K.
Published: July 2002

When a Cu surface is exposed to a clean room ambient, a surface layer containing Cu2O, CuO, Cu(OH)2, and CuCO3 is formed. Thermal treatment in a vacuum combined with hydrogen plasma can remove this layer. Water and carbon dioxide desorb during the thermal treatment and the hydrogen plasma reduces the remaining Cu oxide. Ellipsometric, x-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectroscopy analyses indicate that the mechanism of interaction of the H2 plasma with this layer depends on temperature. When the temperature is below 150 °C, H2 plasma cannot completely reduce Cu oxide. Hydrogen diffuses through the oxide and hydrogenation of the Cu layer is observed. The hydrogenated Cu surface has a higher resistance than a nontreated Cu layer. The hydrogen plasma efficiently cleans the Cu surface when the substrate temperature is higher than 150 °C. In this case, hydrogen atoms have enough activation energy to reduce Cu oxide and adsorbed water forms as a byproduct of Cu oxide reduction. When the wafer temperature is higher than 350 °C, the interaction of the Cu film with hydrogen and residual oxygen is observed.
Calculational study on membrane mask distortion and correction
Authors: Murooka Ken-ichi , Lim Michael H. , Smith Henry I.
Published: July 2002

We have developed an analytical technique that predicts both in-plane and out-of-plane distortion arising from an arbitrary stress distribution on a membrane surface. Our technique can also solve the inverse problem; i.e., we can predict the stress distribution which, when applied to any existing distortion, eliminates it. These techniques, based on the variational method, require one to formulate the total energy that results from the membrane distortion, which is a straightforward task even for complicated stress distributions. One then iteratively searches for the distortion map that minimizes this total energy, which, according to minimum energy principle, should be the true membrane distortion for a given stress distribution. The inverse problem is solved analytically by performing a functional minimization on the total energy and solving for the stress distribution. This calculational technique should enable us to correct for arbitrary distortions by, for example, applying another film or differential heating.
Optical properties of InGaAs/AlAsSb type I single quantum wells lattice matched to InP
Authors: Georgiev Nikolai , Mozume Teruo
Published: July 2002

InGaAs/AlAsSb quantum well structures have been grown by molecular beam epitaxy nominally lattice matched to InP substrates and characterized by photoluminescence. The exciton transitions from the n=1 electron to heavy-hole subbands were investigated and the band-edge discontinuity of an InGaAs/AlAsSb heterostructure was evaluated using an envelope function method. The type I band lineup with a band-edge discontinuity was estimated to be about 1.6 eV for As terminated samples, which exhibit the lowest compositional fluctuations across heterointerfaces. The dominant photoluminescence line-broadening mechanisms were found to be monolayer fluctuations in the well width and a random alloy compositional variation in sublayers, as well as exciton-optical phonon scattering. Using an optimized growth condition, short intersubband transitions in the 1.3–1.5 μm wavelength range were measured in the coupled double quantum well structures.
Characterization and modeling of volumetric and mechanical properties for step and flash imprint lithography photopolymers
Authors: Colburn Matthew , Suez Itai , Choi Byung Jin , Meissl Mario , Bailey Todd , Sreenivasan S. V. , Ekerdt John G. , Willson C. Grant
Published: July 2002

Step and flash imprint lithography (SFIL) is an alternative approach to high-resolution patterning based on a bilayer imprint scheme. SFIL utilizes the in situ photopolymerization of an oxygen etch resistant monomer solution in the topography of a template to replicate the template pattern on a substrate. The SFIL replication process can be affected significantly by the densification associated with polymerization and by the mechanical properties of the cured film. The densities of cured photopolymers were determined as a function of pendant group volume. The elastic moduli of several photopolymer samples were calculated based on a Hertzian fit to force–distance data generated by atomic force microscopy. The current SFIL photopolymer formulation undergoes a 9.3% (v/v) densification. The elastic modulus of the SFIL photopolymer is 4 MPa. The densification and the elastic modulus of the photopolymer layer can be tailored from 4% to 16%, and from 2 to 30 MPa, respectively, by changing the structure of the photopolymer precursors and their formulation. The complex interaction among densification, mechanical properties (elastic modulus and Poisson’s ratio) and aspect ratio (height:width) was studied by finite element modeling. The effect of these parameters on linewidth, sidewall angle, and image placement was modeled. The results indicate that the majority of densification occurs by shrinkage in the direction normal to the substrate surface and that Poisson’s ratio plays a critical role in defining the shape of the replicated features. Over the range of material properties that were determined experimentally, volumetric contraction of the photopolymer is not predicted to adversely affect either pattern placement or sidewall angle.
Single cell detection with micromechanical oscillators
Authors: Ilic B. , Czaplewski D. , Zalalutdinov M. , Craighead H. G. , Neuzil P. , Campagnolo C. , Batt C.
Published: July 2002

The ability to detect small amounts of materials, especially pathogenic bacteria, is important for medical diagnostics and for monitoring the food supply. Engineered micro- and nanomechanical systems can serve as multifunctional, highly sensitive, immunospecific biological detectors. We present a resonant frequency-based mass sensor, comprised of low-stress silicon nitride cantilever beams for the detection of Escherichia coli (E. coli)-cell-antibody binding events with detection sensitivity down to a single cell. The binding events involved the interaction between anti-E. coli O157:H7 antibodies immobilized on a cantilever beam and the O157 antigen present on the surface of pathogenic E. coli O157:H7. Additional mass loading from the specific binding of the E. coli cells was detected by measuring a resonant frequency shift of the micromechanical oscillator. In air, where considerable damping occurs, our device mass sensitivities for a 15 μm and 25 μm long beam were 1.1 Hz/fg and 7.1 Hz/fg, respectively. In both cases, utilizing thermal and ambient noise as a driving mechanism, the sensor was highly effective in detecting immobilized anti-E. coli antibody monolayer assemblies, as well as single E. coli cells. Our results suggest that tailoring of oscillator dimensions is a feasible approach for sensitivity enhancement of resonant mass sensors.
Effect of chamber wall conditions on Cl and Cl2 concentrations in an inductively coupled plasma reactor
Authors: Ullal Saurabh J. , Godfrey Anna R. , Edelberg Erik , Braly Linda , Vahedi Vahid , Aydil Eray S.
Published: July 2002

The effect of chamber wall conditions on the Cl and Cl2 concentrations in a Cl2 discharge was studied in an inductively coupled plasma reactor. Cl and Cl2 mole fractions were determined using optical emission spectroscopy in conjunction with actinometry, while the state of the reactor walls was monitored using a surface probe that enables detection of films and adsorbates that deposit on these walls. Prolonged exposure of the chamber walls to a Cl2 plasma increases the Cl concentration in the discharge. This increase is due to the decreasing recombination probability of Cl atoms on the walls which with time are covered with a thin SiO2 film. The source of the SiO2 is the quartz dielectric window which is sputtered by ion bombardment. A SF6/O2 plasma etches the SiO2 film from the chamber walls and restores the chamber walls to a “clean” state. The Cl concentration in the reactor with these two different states of the wall conditions, under otherwise identical plasma operating conditions, was dramatically different and implied that the wall recombination probability of Cl atoms on the SiO2 covered walls is considerably lower than that on the clean anodized Al. Changing the state of the walls also changes the rate controlling step for Cl recombination from diffusion limited for the reactor with the clean walls to surface reaction limited for the SiO2 covered walls. This change in the rate controlling step changes the dependence of the plasma composition on the power, pressure, and gas flow rate.
Impact of probe penetration on the electrical characterization of sub-50 nm profiles
Authors: Clarysse T. , Vanhaeren D. , Vandervorst W.
Published: July 2002

The spreading resistance probe (SRP) and four point probe (FPP) use, respectively, two or four metal probes with loads in the range of 5–100 g to obtain indispensable information on the electrical characteristics (sheet resistance, junction depth, activation degree, profile shape) of impurity depth profiles in silicon. Recently, however, it has been reported that FPP sheet values are becoming irreproducible and that SRP depth profiles can be significantly shallower than the corresponding secondary ion mass spectrometry dopant profiles for ultrashallow structures. In this work we analyze the impact of probe penetration on the accuracy of SRP and FPP measurements for a series of sub-50 nm profiles with different steepness and substrate level. The probe penetration has been measured by atomic force microscopy and ranged from 5 to 130 nm. The FPP sheet resistance errors of up to 300%, as found for the higher loads, can be correlated with the penetration of the probes through the electrical junction taking into account material removal effects. Experimental data and simulations indicate that SRP raw data are relatively insensitive to probe penetration for source/drain implantation and diffusion profiles. Dependent on the structure involved, however, the SRP depth scale must be corrected for an offset due to probe penetration.
Comparison of secondary ion mass spectroscopy analysis of ultrashallow phosphorus using Cs+, O2+, and CsC6− primary ion beams
Authors: Loesing R. , Guryanov G. M. , Phillips M. S. , Griffis D. P.
Published: July 2002

It is well known that reducing the work function of the sample surface using Cs+ ions increases the negative ion yield of phosphorus. It is also well known that a shallow primary beam implantation depth (RP) is required for achieving high depth resolution during the analysis of ultrashallow implant profiles. The combination of the opposite polarities of the positive Cs+ primary ion beam and the negatively biased sample (the combination most often used for P analysis using magnetic sector secondary ion mass spectroscopy) unfortunately accelerates the Cs+ ions towards the sample thus limiting the degree to which the primary ion impact energy can be reduced [R. Loesing, G. M. Guryanov, J. L. Hunter, and D. P. Griffis, J. Vac. Sci. Technol. B 18, 509 (2000)]. A low primary ion beam impact energy and high impact angle, both of which result in lower RP, can be obtained using a negatively charged cluster ion such as CsC6− (Peabody negative ion source) impacting on a negatively biased sample [G. Gillen, L. King, B. Freibaum, R. Lareau, and J. Bennett, in Secondary Ion Mass Spectrometry, SIMS XII, edited by A. Benninghoven et al. (Elsevier, Amsterdam, 2000), p. 279; R. Loesing, G. M. Guryanov, and D. P. Griffis, in Proceedings of the 13th Annual SIMS Workshop, Lake Tahoe, 2000, p. 36]. If, however, Cs is not required to improve secondary ion yield, a low energy O2+ primary beam impacting on a positively biased sample can be used [I. M. Abdelrehim, T. H. Büyüklimanli, S. P. Smith, and C. W. Magee, in Secondary Ion Mass Spectrometry SIMS XII, edited by A. Benninghoven (Elsevier, Amsterdam, 2000), p. 279; S. P. Smith, C. J. Hitzman, and C. W. Magee, in Secondary Ion Mass Spectrometry, SIMS XI, edited by G. Gillen (Wiley, Chichester, 1998), p. 277]. In this case, the reduction in sensitivity for P due to the loss of the negative ion yield enhancing Cs can be partly compensated by flooding the sample surface with oxygen. In this study Cs+, CsC6−, and O2+ primary ions are compared for depth profiling of ultrashallow phosphorus in Si in terms of decay length, sensitivity, and crater bottom roughness.