bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration Modeling of Rotating Spindles Supported by Lubricated Bearings
Authors: Aini R. , Rahnejat H. , Gohar R.
Published: July 2002

This paper outlines a five degrees of freedom model of a rotating spindle supported by a pair of lubricated angular contact ball bearings. The ball to raceway contacts are simulated by non-linear contact springs, representing the elastic deformation of the mating rolling members and nonlinear spring/dampers, corresponding to the contact elastohydrodynamic oil film thickness. A regression formula is used to model the latter and includes the damping contributed by the squeeze film effect caused by the mutual convergence of bearing rings. Some results of simulation studies with the model are also presented, in both the time and frequency domains. They include the overall system response, when subjected to varying spindle mass or the number of balls in the support bearings. Furthermore, comparisons are made between the simulated response of the dry and lubricated models. The overall contribution to damping of the elastohydrodynamic oil films between the rolling elements and their raceways is shown to be slight.
Modified Hazen-Dupuit-Darcy Model for Forced Convection of a Fluid With Temperature-Dependent Viscosity
Authors: Narasimhan Arunn , Lage Jose´ L.
Published: July 2002

We investigate numerically the global pressure-drop of fluids with temperature dependent viscosity, flowing through a porous medium channel bounded by two parallel isoflux surfaces. By reviewing the development of the Hazen-Dupuit-Darcy (HDD) equation we bring to light the inappropriateness of the model in estimating the global pressure-drop of fluids with temperature dependent viscosity. Albeit this observation, we tested the accuracy of the HDD model in comparison with numerical results by using three alternatives, namely (1) fluid viscosity determined at the average bulk temperature, (2) fluid viscosity determined at the log-mean bulk temperature and (3) fluid viscosity replaced by a channel-length averaged fluid viscosity. The HDD model is inadequate because the temperature dependent fluid viscosity surprisingly affects both, viscous and form, global drag terms. We propose and validate a new global model, which accounts for the effects of temperature dependent viscosity in both drag terms of the original HDD model. Based on our new model, two regimes are discovered as the surface heat flux increases. In the first regime both drag terms are affected, while in the second regime only the form drag term is affected, prior to the model reaching an inviscid limit. Predictive empirical relations correcting the viscous and form drag terms, complementing the new model, are obtained as functions of the surface heat flux.
Some Aspects of the Aerodynamics of Gurney Flaps on a Double-Element Wing
Authors: Jeffrey David , Zhang Xin , Hurst David W.
Published: July 2002

Gurney flaps of different heights have been fitted to a generic double-element wing, and the effects at two typical flap angles have been observed using force and pressure measurements, and by performing flow surveys using Laser Doppler Anemometry. At a low flap setting angle of 20 deg the suction-surface flow remains attached to the trailing edge of the flap, and vortex flow features and perturbation velocities are all similar to those observed when Gurney flaps are fitted to single element wings. At a high flap deflection of 50 deg there is an extensive region of separated flow over the flap, yet the Gurney flap still alters the flow structure. The measurements suggest that the wake flow behind the Gurney flap consists of a von Karman vortex street of alternately shed vortices. The effects of the Gurney flap on the lift, zero-lift drag, and pressure distributions are reported, and the differences between the trends observed for single-element wings are discussed.
A Comparative Study of the Performance of Compact Model Topologies and Their Implementation in CFD for a Plastic Ball Grid Array Package
Authors: Shidore Sarang , Lee Tien Yu Tom
Published: July 2002

A detailed model of a die-up 256-pin Plastic Ball Grid Array (PBGA) package was created and validated against experimental data for natural convection and forced convection environments. Next, four compact models were derived; two two-resistor models (one created through a two-point computational cold plate test; the other using the DELPHI optimization approach), a multi-resistor Star network model and a shunt network model. The latter three models were derived using the methodology established by the DELPHI (Development of Libraries of Physical models for an Integrated design environment) project. The four compact models and the detailed model were each placed in natural convection and forced convection (velocities of 1,2, and 4 m/s) environments. Good agreement was obtained for the die-junction temperature rise for both the detailed and the shunt compact models. The star and two-resistor models were seen to be inferior in terms of accuracy. The two-resistor model created using the DELPHI methodology was found to be superior compared to the one created with the computational cold-plate test. The star model showed little gain in performance as compared to the DELPHI two-resistor model.
High Lift and Aft-Loaded Profiles for Low-Pressure Turbines
Authors: Howell R. J. , Ramesh O. N. , Hodson H. P. , Harvey N. W. , Schulte V.
Published: July 2002

This paper shows how it is possible to reduce the number of blades in LP turbines by approximately 15 percent relative to the first generation of high lift blading employed in the very latest engines. This is achieved through an understanding of the behavior of the boundary layers on high lift and ultra-high lift profiles subjected to incoming wakes. Initial development of the new profiles was carried out by attaching a flap to the trailing edge of one blade in a linear cascade. The test facility allows for the simulation of upstream wakes by using a moving bar system. Hot wire measurements were made to obtain boundary layer losses and surface-mounted hot films were used to observe the changes in boundary layer state. Measurements were taken at a Reynolds number between 100,000 and 210,000. The effect of increased lift above the datum profile was investigated first with steady and then with unsteady inflow (i.e., with wakes present). For the same profile, the losses generated with wakes present were below those generated by the profile with no wakes present. The boundary layer behavior on these very high lift pressure distributions suggested that aft loading the profiles would further reduce the profile loss. Finally, two very highly loaded and aft loaded LP turbine profiles were designed and then tested in cascade. The new profiles produced losses only slightly higher than those for the datum profile with unsteady inflow, but generated 15 percent greater lift.
An Aerodynamic Shroud for Automotive Cooling Fans
Authors: Morris Scott C. , Foss John F.
Published: July 2002

Results from an experimental investigation of an aerodynamic fan shroud are reported. The device was motivated by the relatively large (2.5 cm) tip clearance required in automotive cooling fans which are mounted to the engine. The shroud consists of a pressurized plenum and a Coanda attachment surface to deliver a jet of high momentum air into the tip clearance region. Both the performance and the efficiency for the initial system design were enhanced at higher flow rates, and degraded at lower flow rates. A small tuft was used to observe qualitative flow features in the near wake and tip clearance region of the fan. This information was used to create a modified design. The new geometry was tested and found to provide improved performance characteristics for a wider range of flow rate conditions.
A Mixing Based Model for Di-methyl Ether Combustion in Diesel Engines
Authors: Bek B. H. , Sorenson S. C.
Published: July 2002

A series of studies has been conducted investigating the behavior of di-methyl ether (DME) fuel jets injected into quiescent combustion chambers. These studies have shown that it is possible to make a good estimate of the penetration of the jet based on existing correlations for diesel fuel, by using appropriate fuel properties. The results of the spray studies have been incorporated into a first generation model for DME combustion. The model is entirely based on physical mixing, where chemical processes have been assumed to be very fast in relation to mixing. The assumption was made on the basis of the very high Cetane number for DME. A spray model similar to that proposed by Hiroyasu et al. [11] has been used, with the assumption that rapid combustion occurs when the local mixture attains a stoichiometric air fuel ratio. The spray structure is based on steady-state spray theory, where the shape of the spray has been modified to match the measured spray penetration rates. The spray theory and experimentally determined penetrations implicitly determine the rate of air entrainment into the spray. The results show that the combustion rates calculated during the mixing controlled portion of combustion agree well with experimental measurements from a previous study, without additional adjustment.
Challenges Involved in Piston Top Ring Designs for Modern SI Engines
Authors: Rabute´ R. , Tian T.
Published: July 2002

Driven by energy conservation and environment protection, modern SI engines are required to have higher and higher power density. Consequently, engines and engine components are becoming tighter and lighter, and engines are more often operated at elevated speed and component temperature. Piston and piston ring designs thus face constant challenge to provide proper control of blow-by, oil consumption, friction, wear, and oil consumption. This paper is intended to give an overview of the problems associated with top ring performance in modern SI engines, the mechanisms behind these problems, and possible solutions. The analysis is based on engine test data and computer models. Major topics covered in this paper include (1) top ring flutter and collapse, and their influence on blow-by; (2) top ring reverse flutter and its influence on oil consumption; (3) contact between top ring and its groove, and its potential influence on ring/groove wear and micro-welding; (4) top ring/liner lubrication and its influence on ring face friction, wear, and scuffing.
High-Pressure Steam-Driven Jet Pump—Part I: Mathematical Modeling
Authors: Beithou N. , Aybar H. S.
Published: July 2002

There are several proposed advanced reactor systems, which consider the utilization of a steam-driven jet pump (SDJP) as an emergency core cooling system. The steam-driven jet pump is a device without moving parts, in which steam is used as an energy source to pump cold water from a pressure much lower than the steam pressure to a pressure higher than the steam pressure. In this study, the mathematical modeling of the SDJP has been done. An experimental analysis of the high-pressure SDJP has been reported by Cattadori et al. The results of the mathematical modeling of the SDJP have been compared with Cattadori’s experimental results. The comparisons show that the experimental and calculated pressure distributions are in good qualitative agreement. A parametric analysis of the SDJP is ongoing.
H ∞ -Based Robust Torque Control of Harmonic Drive Systems
Authors: Taghirad H. D. , Be´langer P. R.
Published: July 2002

In this paper, the torque control of a harmonic drive system for constrained-motion and free-motion applications is examined in detail. A nominal model for the system is obtained in each case from experimental frequency responses of the system, and the deviation of the system from the model is encapsulated by a multiplicative uncertainty. Robust torque controllers are designed using this information in an H∞-framework, and implemented on two different setups. From time and frequency domain experiments, it is shown that the closed-loop system retains robust stability, while improving the tracking performance exceptionally well. To further improve the performance of the system for free-motion case, a feedforward friction-compensation algorithm is implemented in addition to the robust torque control. It is shown that friction-compensation will shrink the model uncertainty at low frequencies and hence, the performance of the closed-loop system will be improved at those frequencies.
Reduced NOx Diffusion Flame Combustors for Industrial Gas Turbines
Authors: Feitelberg A. S. , Tangirala V. E. , Elliott R. A. , Pavri R. E. , Schiefer R. B.
Published: July 2002

This paper describes reduced NOx diffusion flame combustors that have been developed for both simple cycle and regenerative cycle MS3002 and MS5002 gas turbines. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NOx emissions from the new combustors are about 40 percent lower than NOx emissions from the standard combustors. CO emissions are virtually unchanged at base load, but increase at part load conditions. Commercial demonstration tests have confirmed the laboratory results. The standard combustors on both the MS3002 and MS5002 gas turbine are cylindrical cans, approximately 10.5 inches (27 cm) in diameter. A single fuel nozzle is centered at the inlet to each can and produces a swirl stabilized diffusion flame. The walls of the cans are louvered for cooling, and contain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature. The MS3002 turbine is equipped with six combustor cans, while the MS5002 turbine is equipped with twelve combustors. The new, reduced NOx emissions combustors (referred to as a “lean head end,” or LHE, combustors) retain all of the key features of the conventional combustors; the only major difference is the arrangement of the mixing and dilution holes in the cylindrical combustor cans. By optimizing the number, diameter, and location of these holes, NOx emissions can be reduced considerably. Minor changes are also sometimes made to the combustor cap. The materials of construction, pressure drop, and fuel nozzle are all unchanged. The differences in NOx emissions between the standard and LHE combustors, as well as the variations in NOx emissions with firing temperature, are well correlated using turbulent flame length arguments. Details of this correlation are presented.
Output Feedback Second-Order Sliding Mode Control for a Class of Nonlinear Systems With Non-Matched Uncertainties
Authors: Ferrara Antonella , Giac¸omini Luisa
Published: July 2002

The problem of the design of an output feedback second-order sliding mode control for a class of nonlinear systems affine in the control law with non-matched uncertainties is considered in this paper. An observer-based backstepping design procedure is followed to construct a suitable sliding manifold that guarantees the attainment of a tracking control objective. The construction of the sliding manifold is performed so that the problem of steering the sliding quantity to zero in finite time turns out to be solvable locally through a second-order sliding mode control approach, as in the conventional matched uncertainty case, and the associated zero dynamics is minimum phase. On the other hand, the observer operates in first-order sliding mode, also fed by the control signal generated by the backstepping-second-order sliding mode algorithm. This signal presents the advantage of being continuous by virtue of the second-order sliding mode nature of the controller, enabling the fast convergence to zero of the observation error.
Prediction of Radiative Heat Transfer in Industrial Equipment Using the Radiation Element Method
Authors: Guo Zhixiong , Maruyama Shigenao
Published: July 2002

The radiation element method by ray emission method, REM2, has been formulated to predict radiative heat transfer in three-dimensional arbitrary participating media with nongray and anisotropically scattering properties surrounded by opaque surfaces. To validate the method, benchmark comparisons were conducted against the existing several radiation methods in a rectangular three-dimensional media composed of a gas mixture of carbon dioxide and nitrogen and suspended carbon particles. Good agreements between the present method and the Monte Carlo method were found with several particle density variations, in which participating media of optical thin, medium, and thick were included. As a numerical example, the present method is applied to predict radiative heat transfer in a boiler model with nonisothermal combustion gas and carbon particles and diffuse surface wall. Elsasser narrow-band model as well as exponential wide-band model is adopted to consider the spectral character of CO2 and H2O gases. The distributions of heat flux and heat flux divergence in the boiler furnace are obtained. The difference of results between narrow-band and wide-band models is discussed. The effects of gas model, particle density, and anisotropic scattering are scrutinized.
The Asymmetry of Transient Response in Compression Versus Release for Cartilage in Unconfined Compression
Authors: Li L. P. , Buschmann M. D. , Shirazi-Adl A.
Published: July 2002

Observations in compression tests of articular cartilage have revealed unequal load increments for compression and release of the same amplitude applied to a disk with an identical previously imposed compression (in equilibrium). The mechanism of this asymmetric transient response is investigated here using a nonlinear fibril-reinforced model. It is found that the asymmetry is predominantly produced by the fibril stiffening with its tensile strain. In addition, allowing the hydraulic permeability to decrease significantly with compressive dilatation of cartilage increases the transient fibril strain, resulting in a stronger asymmetry. Large deformation also enhances the asymmetry as a consequence of stronger fibril stiffening.
A Three-Dimensional Model for the Surface Texture in Surface Grinding, Part 1: Surface Generation Model
Authors: Salisbury Erik J. , Domala K. Vinod , Moon Kee S. , Miller Michele H. , Sutherland John W.
Published: July 2002

A geometric-kinematic model for the generation of surface topography in a single-pass surface grinding process is presented. The model incorporates the effects of process parameters such as table speed and wheel speed and also takes into account the wheel topography and original workpiece surface texture. Comparisons between model-simulated output and experimental results show a good match, supporting the validity of the model.
Thermal Contact Conductance of Non-Flat, Rough, Metallic Coated Metals
Authors: Lambert M. A. , Fletcher L. S.
Published: July 2002

Thermal contact conductance is an important consideration in such applications as nuclear reactor cooling, electronics packaging, spacecraft thermal control, and gas turbine and internal combustion engine cooling. In many instances, the highest possible thermal contact conductance is desired. For this reason, soft, high conductivity, metallic coatings are sometimes applied to contacting surfaces (often metallic) to increase thermal contact conductance. O’Callaghan et al. (1981) as well as Antonetti and Yovanovich (1985, 1988) developed theoretical models for thermal contact conductance of metallic coated metals, both of which have proven accurate for flat, rough surfaces. However, these theories often substantially overpredict the conductance of non-flat, rough, metallic coated metals. In the present investigation, a semi-empirical model for flat and non-flat, rough, uncoated metals, previously developed by Lambert and Fletcher (1996), is employed in predicting the conductance of flat and non-flat, rough, metallic coated metals. The models of Antonetti and Yovanovich (1985, 1988) and Lambert and Fletcher (1996) are compared to experimental data from a number of investigations in the literature. This entailed analyzing the results for a number of metallic coating/substrate combinations on surfaces with widely varying flatness and roughness. Both models agree well with experimental results for flat, rough, metallic coated metals. However, the semi-empirical model by Lambert and Fletcher (1996) is more conservative than the theoretical model by Antonetti and Yovanovich (1985, 1988) when compared to the majority of experimental results for non-flat, rough, metallic coated metals.
A Survey of Computer-Aided Modeling Tools for Aesthetic Design
Authors: Catalano Chiara Eva , Falcidieno Bianca , Giannini Franca , Monti Marina
Published: July 2002

The goal of this paper is to discuss the key issues in the computer-aided surface modeling tools used in the industrial aesthetic design workflow and to highlight the problems that still make styling activities difficult. Based on the experience gained while working on two different European projects, with the collaboration of industrial designers of different fields, a general industrial design workflow is illustrated, pointing out the main differences between the automotive and non-automotive sectors. Among the emerged critical issues, particular emphasis is given to the high request of tools more suitable for the mentality of creative users; short research surveys aimed to meet this request are included, and finally authors indicate a branch of research in which they are investigating and they consider particularly worth exploring further.
Passivity and Noncollocation in the Control of Flexible Multibody Systems
Authors: Damaren Christopher J.
Published: July 2002

Collocation of actuation and sensing in flexible structures leads to the desirable input-output property of passivity which greatly simplifies the stabilization problem. However, many control problems of interest such as robotic manipulation are noncollocated in nature. This paper examines the possibility of combining collocated and noncollocated outputs so as to achieve passivity. An appropriate combination is shown to depend on the interplay between collocated and noncollocated mass properties. Tracking problems are also studied and a controller with adaptive feedforward elements is introduced. An experimental study using a simple flexible apparatus with one rigid degree of freedom and two vibration modes is used to validate the analysis. [S0022-0434(00)01701-9]
Control of a Class of Mechanical Systems With Uncertainties Via a Constructive Adaptive/Second Order VSC Approach
Authors: Ferrara A. , Giacomini L.
Published: July 2002

A wide class of mechanical systems with uncertainties can be modeled through a state equation in parametric-pure-feedback form. Thus, in principle, the well-known backstepping design procedure can be applied to solve a regulation or a tracking problem. Yet, this is no more possible if a clear parametric dependence on the control signal (torque or force) cannot be established. Systems to which this happens can be efficaciously controlled via the proposed approach which inherits n−1 steps of the classical backstepping procedure. This latter procedure is used to attain a partial system state transformation, completed with the construction of a suitable sliding manifold upon which a second order sliding mode is enforced. [S0022-0434(00)01901-8]
Nonlinear Continuous Dynamic System Identification by Automatic Localized Modeling
Authors: Li and C. James , Huang Tung-Yung
Published: July 2002

This paper describes an automated localized modeling method to identify continuous nonlinear dynamic systems from their operating data. Using a method similar to finite element method’s automatic mesh generation, the input space is partitioned into overlapped regions that are small enough that a local model, such as a simple neural network, can approximate the data well in each region. Subsequently, adjacent regions are inspected to see if they can be represented well by a single local model to minimize the number of regions and local models needed to approximate a system. A nonlinear oscillator is used to test the proposed method, and the method was able to generate models that can simulate the system well. [S0022-0434(00)01902-X]
Modeling of Flexible Robot-Payload Systems Through Component Synthesis
Authors: Zhou, T. , Zu, and J. W. , Goldenberg A. A.
Published: July 2002

In this paper, a new modeling method is developed for analyzing the dynamic behavior of a system consisting of a rigid robotic manipulator and a flexible sheet metal payload. The component mode synthesis method is applied to reduce the degrees of freedom of the payload and to model the interfaces between the robot gripper and the payload. Using nonlinear compatibility functions, the method is modified to synthesize the dynamics of the entire robot-payload system. Exact models are developed capable of describing both large and small rigid-body motions. A modular form is derived and the coupling dynamics is formulated in a computationally efficient manner. Numerical examples are presented to demonstrate the effectiveness of the modeling method. [S0022-0434(00)01102-3]
An Interdisciplinary Framework for the Design and Life Prediction of Engineering Systems
Authors: Raj Rishi
Published: July 2002

This paper is constructed on the assumption that innovation in systems of the future would depend on how the synergies among various disciplines can be exploited and implemented in design strategies. A framework that can serve this purpose is presented; it is based on the concept that an “end-user” system can be partitioned into subsystems and linking variables. The subsystems generally lie along traditional disciplines, e.g., materials science, mechanical engineering, manufacturing etc. The linking variables serve as the vehicle for multidimensional coupling among the subsystems. System level design and life prediction is carried out in the linking variable space (LVS). The potential for this framework is illustrated by applying it to the design and life prediction of the light bulb. This example serves to illustrate how the design regime is created in LVS by overlaying the results from engineering design and materials science subsystems. The linking variables also define the pathway for assessing the influence of the critical parameters residing within each subsystem, on the overall variability in the life of the light bulb. In this way it becomes possible to understand how much the uncertainties from each of the subfields contribute to the overall uncertainty of the system. [S0094-4289(00)01803-X]
Aerothermal Considerations for the Design of Two-Phase High Speed Impact Cleansers
Authors: Lear W. E. , Sherif S. A.
Published: July 2002

An alternative method employed in industrial cleansing applications involves injecting liquid water in a flow of gaseous nitrogen and discharging the mixture through a converging-diverging nozzle onto the surface. This paper is an extension of a previous analysis, which was geared towards understanding the gas/liquid mixture dynamics through the nozzle. The analysis presented here takes into account the effect of the nozzle area ratio and is thus geared towards the nozzle designer and provides additional fundamental insight into the required geometry. [S0098-2202(00)01901-5]
Discussion: “Thermal Contact Resistance of Silicone Rubber to AISI 304 Contacts” [ASME J. Heat Transfer, 121, pp. 700–702 (1999)]1
Authors: Madhusudana C. V.
Published: July 2002

[S0022-1481(00)02802-4]
InP(110) by XPS
Authors: Poirier D. M. , Weaver J. H.
Published: July 2002

XPS spectra were recorded for the (110) cleavage surface of an InP single crystal. For comparison, air-exposed (Accession #00117) and cleaved in situ (Accession #00116) surfaces were examined. The electronic record includes the P 2p, In 4d, In 3d, In MNN, and valence band regions.
Poly(Amino Acids) by XPS: Analysis of Poly-L-Leucine
Authors: Lhoest Jean-Benoît , Bartiaux Stéphane , Gerin Patrick A. , Genet Michel J. , Bertrand Patrick , Rouxhet Paul G.
Published: July 2002

Poly(L-leucine) was analyzed as a model compound representative of poly(amino acids) with alkyl pendant groups. Two specimens of different origins and molecular masses were examined. One (A) was pressed on an indium foil to allow recording time of flight secondary ion mass spectrometry (TOF SIMS) spectra in parallel and, therefore, insure good electrical charge dissipation. The other one (B) was placed in a stainless steel trough and then pressed. The C 1s peak was recorded first and recorded again at the end; no difference was found between the two records, indicating that poly(L-leucine) did not suffer beam damage. The C 1s peak of specimen A was split into three components: one fixed at 284.8 eV and due to C_—(C,H), the other two found at 286.1 and 287.8 eV and due to C_—N and O=C_—N, respectively. The O 1s peak centered at 531.2 eV and due to O_=C—N showed a tail which indicated the presence of a small component at 533.0 eV, possibly due to water or C—O_H of contaminating compounds. The N 1s peak was symmetric and centered at 399.7 eV. The position of the peak components of specimen B were coincident with specimen A within 0.1 eV. The ratio of the molar concentration, with respect to N, of [O_=C—N], [O=C_—N], and [C_—N], on the one hand, and of [C_—(C,H)], on the other hand, fitted the expected values of 1 and 4 within 5%, except for one component of one specimen which showed a deviation of 15%. The choice of the background shape (S shape or linear) has no significant influence on the results. These spectra may be used as references for the characterization of polypeptides and proteins.
Aqueous-based photoresist drying using supercritical carbon dioxide to prevent pattern collapse
Authors: Goldfarb Darı́o L. , de Pablo Juan J. , Nealey Paul F. , Simons John P. , Moreau Wayne M. , Angelopoulos Marie
Published: July 2002

A supercritical drying process was developed to eliminate the capillary forces naturally present during normal drying of photoresist materials. Supercritical carbon dioxide (scCO2), organic solvents and surfactants were used to prevent the collapse of high-aspect-ratio structures fabricated from aqueous-based photoresist. Nondistorted resist lines were patterned with this process with aspect ratios of at least 6.8. Water rinsed resist structures cannot be dried directly with scCO2 due to the low solubility of water in the supercritical phase. In our process we introduced the replacement of the aqueous rinse by n-hexane mediated by a compatible surfactant. The surfactant allowed to incorporate the aqueous phase into micellar microdomains in the organic phase while keeping the interfacial tension at values close to zero. Noncollapsed supercritically dried structures were rewet in n-hexane or water and dried using nitrogen at atmospheric pressure. Under these conditions, the patterns were collapsed as a result of capillary forces acting on the resist walls. The effect of capillary forces on pattern stability were qualitatively compared to the relative surface tension values between n-hexane and water. The advantage of using supercritical CO2 in the drying stage of resists compared to normal drying highlights the importance of eliminating the surface (or interfacial) tension forces created by the rinse fluid, if a reduction of linewidth and spacing between resist lines is pursued, while keeping the aspect ratio constant.
Effects of chemical etching with nitric acid on glass surfaces
Authors: Jang H. K. , Chung Y. D. , Whangbo S. W. , Kim T. G. , Whang C. N. , Lee S. J. , Lee S.
Published: July 2002

Glass slides were chemically etched with nitric acid using five different methods. We investigated the effects of chemical etching treatments on such properties as chemical composition, surface roughness, transmittance, and thermal stability of the glass. Sodium, calcium, and aluminum atoms in the surface of the glass are effectively reduced by chemical etching with nitric acid. Especially, boiling the glass in a 70% nitric acid solution for 30 min is more effective in the reduction of sodium, calcium, and aluminum atoms at the surface of the glass than other etching methods with nitric acid. The surface morphologies of the glasses were very similar regardless of the chemical etching treatments with nitric acid etchant. Root-mean-square surface roughness of the bare glass was 0.58 nm but that of the glass etched with nitric acid was ranged from 5.4 to 6.8 nm. Sodium concentration at the glass surface was largely reduced from 2.44% to 0.25%. In order to investigate the thermal stability of the glass, the bare glass and the glass samples boiled for 30 min in a 70% HNO3 solution were annealed in air at 300, 400, 500, and 600 °C for 1 h. Sodium, aluminum, and calcium at the surface of the glass increased with an annealing temperature regardless of chemical etching with nitric acid, but the Na, Al, and Ca content at the surface of the glass boiled in 70% HNO3 for 30 min was greatly reduced relative to that of the surface of the bare glass at an annealing temperature of 500 °C.
X-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and x-ray diffraction characterization of CuO–TiO2–CeO2 catalyst system
Authors: Francisco M. S. P. , Nascente P. A. P. , Mastelaro V. R. , Florentino A. O.
Published: July 2002

X-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and x-ray absorption spectroscopy (XAS) techniques have been applied to characterize the surface composition and structure of a series of CuO–TiO2–CeO2 catalysts. For a small loading of cerium, ceria was mainly dispersed on the titania surface and a minor amount of CeO2 crystallite appeared. At higher loading of cerium, the CeO2 phase increased and the atomic Ce/Ti ratio values were smaller than the nominal composition, as a consequence of cerium agglomeration. This result suggests that only a fraction of cerium can be spread on the titania surface. For titanium-based mixed oxide, we observed that cerium is found as Ce3+ uniquely on the surface. The atomic Cu/(Ce+Ti) ratio values showed no influence from cerium concentration on the dispersion of copper, although the copper on the surface was shown to be dependent on the cerium species. For samples with a high amount of cerium, XPS analysis indicated the raise of second titanium species due cerium with spin-orbit components at higher binding energies than those presented by Ti4+ in a tetragonal structure. The structural results obtained by XAS are consistent with those obtained by XRD and XPS.
Etching of high-k dielectric Zr1−xAlxOy films in chlorine-containing plasmas
Authors: Pelhos K. , Donnelly V. M. , Kornblit A. , Green M. L. , Van Dover R. B. , Manchanda L. , Hu Y. , Morris M. , Bower E.
Published: July 2002

As new, advanced high-k dielectrics are being developed to replace SiO2 in future generations of microelectronics devices, understanding their etch characteristics becomes vital for integration into the manufacturing process. We report on the etch rates and possible mechanisms for one such dielectric, Zr1−xAlxOy (x≈0.2), in plasmas containing a mixture of Cl2 and BCl3, as a function of gas composition and ion impact energy. Higher concentrations of BCl3 enhance the etch rate as well as selectivity of Zr1−xAlxOy etching as compared to the etching of α-Si, whereas increasing ion energy increases the etching rates but decreases selectivity. In a high density helical resonator plasma, etching rates on the order of 700 Å/min and 1:1 selectivity are typical. Angle-resolved x-ray photoelectron spectroscopy was used to study the composition of the upper ∼30 Å of the film, before and at the end of the etching process. We found that the etching rate of Zr1−xAlxOy does not change with time for the range of Cl2/BCl3 ratios and ion energies investigated, whereas the α-Si etching rate in pure BCl3 plasma and at zero substrate bias decreases with time, due to the formation of a B–Si film on the surface.
Static friction and surface roughness studies of surface micromachined electrostatic micromotors using an atomic force/friction force microscope
Authors: Sundararajan Sriram , Bhushan Bharat
Published: July 2002

A technique to measure the static friction forces (stiction) encountered in surface micromachined micromotors using a commercial atomic force microscope (AFM)/friction force microscope has been developed and is described. An AFM tip is pushed against a rotor arm of the micromotor so as to generate lateral deflection (torsion) of the tip, which is measured by the AFM. The maximum value of the lateral deflection obtained prior to rotor movement (rotation) is a measure of the static friction force of the micromotors. This technique was employed to study the effect of humidity and rest time on the static friction force of polysilicon motors, both unlubricated and lubricated using perfluoropolyether lubricants. Surface roughness parameters (rms, peak-to-valley distance, skewness, and kurtosis) and microscale friction properties of the various surfaces of the motor were measured. Dramatic differences between the roughness of the underside and top surfaces of the rotor and between the surface beneath the rotor and adjacent areas were observed. The mechanisms responsible for stiction in such devices are discussed. Lubrication methods to minimize friction problems are also presented.
Scanning Hall probe microscopy on an atomic force microscope tip
Authors: Chong B. K. , Zhou H. , Mills G. , Donaldson L. , Weaver J. M. R.
Published: July 2002

We present a Hall magnetometer combined with a conventional atomic force microscope (AFM) tip. The Hall nanosensor AFM probe is fabricated in bismuth using direct-wire electron-beam nanolithography and silicon micromachining. The magnetometer is integrated into a conventional force microscope silicon cantilever which permits reliable control of the sensor-sample distance. The magnetic sensor is situated at the end of a sharp AFM allowing good access to the specimen and providing high resolution simultaneous topographic images. Since the sensors are defined lithograpically, the size and shape of sensors are well controlled and reproducible. We present the results of magnetic field imaging using this probe demonstrating quantitative magnetic field measurement and good spatial resolution.
Stability of the inelastic mean free paths determined by elastic peak electron spectroscopy in nickel and silicon
Authors: Jiricek P. , Zemek J. , Lejček P. , Lesiak B. , Jablonski A. , Čerňanský M.
Published: July 2002

Compilation of the inelastic mean free path (IMFP) values obtained from elastic peak electron spectroscopy (EPES) indicates a large scatter of these parameters. Furthermore, the measured IMFPs deviate from the values resulting from the predictive formulas, i.e., the equation TPP-2M and the equation G1. The differences in the measured IMFPs originate from the statistical error of the measurement and the systematic error of the EPES method. The contributions to the systematic error arise due to instrumental factors, reliability of the Monte Carlo model, and accuracy of the input parameters for the Monte Carlo algorithm. In this work, the authors investigate the possible effects of the sample surface roughness, the texture, the grain size, and the standard selected on the IMFPs determined by the EPES method for four Ni and two Si specimens. The Cu and Ag standards are used in the EPES method. The scatter between the measured IMFPs obtained in the present work and predictive formulas IMFP values is determined. The sources of errors are extensively discussed.
Ionized-cluster beam deposition
Authors: Takagi T. , Yamada I. , Sasaki A.
Published: July 2002

We describe a form of deposition in which material is vaporized in a crucible and the vapor then ejected through a fine nozzle at the focus of an electron beam in a high vacuum. The vapor, on emerging from the nozzle, is partially condensed into clusters that are ionized by electron bombardment and then accelerated onto the substrate. The deposited films show good adhesion and large crystallite size. Examples include the deposition of Cu onto glass, Si onto Si, and ZnS onto NaCl.
Mean free path of negative ions in diode sputtering
Authors: Harper J. M. E. , Cuomo J. J. , Gambino R. J. , Kaufman H. R. , Robinson R. S.
Published: July 2002

Negative ions produced in the sputtering of certain compounds (e.g., SmAu, EuAu, CsAu, and LaF3) are capable of dominating the film-growth process in a thin-film depostion system. Under some conditions sputter etching of substrates is observed due to a high flux of negative ions accelerated from the target surface. The energy and collimation of these negative ions are examined by evaluating the cross sections for electron detachment and directed momentum loss. Under typical sputtering conditions the negative ions are found to retain their charge long enough to accelerate to the full dark space voltage. The mean free path at this energy is estimated from the Ar–Ar interaction potential and found to be many times longer than the thermal mean free path. These results explain the sharply outlined region of substrate etching by the negative ion flux and lead to a picture of a highly collimated, energetic particle beam directed away from the target surface. negative ion flux and lead to a picture of a highly collimated,
Surface and interface properties of Zn3P2 solar cells
Authors: Kazmerski L. L. , Ireland P. J. , Catalano A.
Published: July 2002

The compositional properties of Zn3P2 thin films are investigated using surface analysis techniques. Relative sensitivity factors of S(ZnLMM) = 0.29 and S(PLMM) = 0.34 are determined for this semiconductor using AES standard spectra. The interfacial properties of the Mg/Zn3P2 thin-film solar cell are studied using AES depth-compositional profiling in conjunction with complementary SIMS and XPS data. Evidence is presented for the formation of Mg3P2 at the metal–semiconductor interface. This compound has a bandgap near that of Zn3P2, and the possible formation of a heterojunction as a result of the interfacial reaction is discussed.
Preferential sputtering of TiC and TiB2 coatings under D+ and 4He+ bombardment: Partial yields
Authors: Kaminsky M. , Nielsen R. , Zschack P.
Published: July 2002

The coating of first wall components in fusion devices with materials of low to medium atomic number Z such as TiB2 and TiC, can help improve plasma impurity control and reduce surface erosion. One of the important tests of coatings for fusion applications deals with measurements of plasma impurity release by sputtering. In the sputtering of two component systems such as TiC, the preferential emission of one of the components, e.g., C, may occur. This paper reports experimentally determined partial sputtering yields for B, C, and Ti for D+ and 4He+ irradiations of TiB2 and TiC coatings with energies ranging from 3 to 60 keV. The coatings were irradiated at ambient temperature and at normal incidence. Chemical vapor deposited TiB2 and TiC coatings on Poco graphite substrates have been studied for surfaces which were mechanically polished or left in their as-deposited state. The equivalent B, C, and Ti thicknesses of the sputter deposits were determined by the Rutherford backscattering technique. The partial yields for both polished and unpolished coating surfaces are observed to decrease with increasing ion energy. This trend is in agreement with theoretical predictions. The partial yields for B and C are found to be larger than for Ti. This can lead to improved plasma impurity control since a larger concentration of impurities with low Z can be tolerated than with high Z.
New developments in the calculation of the molecular flow conductance of a straight cylinder
Authors: Carette J.-D. , Pandolfo L. , Dubé D.
Published: July 2002

Recent calculations of the conductance of a cylindrical pipe in the molecular flow state are presented. They have been performed using the Monte Carlo method which is recognized nowadays to be based on the most significant physical foundations. Previous results obtained with the help of this method did cover a very limited range of the cylinder length to radius ratios (0≤L/R≤5). Our calculations have permitted us to extend this range to a value 20 times larger (0≤L/R≤100). A striking feature of the results obtained, is a discrepancy between our data and these obtained from Clausing’s analytico-statistical analysis of this problem. It is increasing as a function of L/R, the difference reaching asymptotically 50% for L/R→100; Clausing’s results being about two times smaller than ours around L/R=100. Moreover, it is found that the previously available data obtained by the Monte Carlo method deviate from ours up to about 25% for L/R=5. We demonstrate that this is a consequence of an incorrect method of determining the angle of the emission cosine law for the particles at the entrance of the duct. Finally, we propose a parametrical relation, obtained by the least squares method, that permit the calculation of the value of the conductance of a cylindrical pipe within the range 0≤L/R≤100 and very likely well above this range.
Medium energy ion scattering studies of clean and CO covered Ni(110)
Authors: Törnqvist E. , Adams E. D. , Copel M. , Gustafsson T. , Graham W. R.
Published: July 2002

The technique of medium energy ion scattering, using channeling and blocking, has been used to study the geometric structure of clean and adsorbate covered Ni(110). The experimental setup includes a specially constructed 180 keV ion accelerator and a UHV scattering chamber, equipped with a three axis goniometer and a solid state detector for energy analysis of the scattered beam. The results for clean Ni(110) show that the spacing between the two outermost layers is contracted by 4±1%, in excellent agreement with earlier high resolution studies. When CO is adsorbed in a configuration [a (2×1)p1g1 LEED pattern] with one CO atom for each Ni surface atom, the surface returns to the normal bulk configuration.
Electrical transport properties of AlN/Al cermets produced by voltage controlled, reactive, dc, planar magnetron sputtering
Authors: Affinito J. , Fortier N. , Parsons R. R.
Published: July 2002

Voltage controlled, reactive, dc, planar magnetron sputtering is shown to be ideally suited for the deposition of AlN/Al cermets from a single metallic (Al) target. X-ray diffraction, transmission electron microscope (TEM), Hall, and resistivity versus temperature measurements have been made as a function of the volume fraction of Al (Xv) and correlated with the deposition glow discharge characteristics. A percolation threshold is observed in the conductivity at a critical volume fraction for Al of Xvc =0.72±0.02. This appears to be the highest value for Xvc reported to date. The conductivity exhibits critical behavior both above and below Xvc. Above Xvc, σ∼(Xv−Xvc)t, with t=1.75±0.1 in excellent agreement with the theoretical prediction of 1.7. [See Ref. 1: Phys. Rep. 54, 1 (1979).] Below Xvc conduction is via tunneling and σ∼(Xvc−Xv)−s with s=4.3±0.1. To date, theories for critical behavior below Xvc have dealt only with mixtures of two ‘‘normal’’ conductors and have not discussed the critical behavior of tunneling conduction. The observed power law behavior for tunneling below Xvc warrants further theoretical and experimental investigation. Further, the temperature behavior of the conductivity for Xv just below Xvc [where σ∼(Xvc−Xv)−s] is consistent with the view that the tunneling is from defect to defect within the insulating grains as opposed to direct tunneling between metal islands. In addition, evidence for electron localization effects for Xvc≲Xv≲0.8 is observed in the temperature dependence of ρ.