bluuebunny/crossref_metadata_2025 huggingface dataset:
The Buckling Behavior of Pipes and Its Influence on the Axial Force Transfer in Directional Wells
Authors: Kuru Ergun , Martinez Alexander , Miska Stefan , Qiu Weiyong
Published: July 2002

An experimental setup was built at the University of Tulsa to study buckling and post-buckling behavior of pipes constrained in straight horizontal and curved wellbores. Experiments were conducted to investigate the axial force transfer with and without static internal pressure. Different stages of buckling phenomena and their relation to the axial force, the pipe diameter (1/4 and 3/8 in.) and the pipe end-support conditions have also been investigated. Experimental results have shown that the buckling load is a strong function of the pipe diameter and the pipe end-support conditions. Static internal pressure appears to have insignificant influence on the buckling behavior of pipes. A brief review of recently developed mathematical models to predict buckling behavior of pipes in inclined, curved, and horizontal sections of wellbore is also presented. Applications of the current theory are presented by using recently developed computer simulator. Results of the theoretical analysis have confirmed the versatility and effectiveness of computer simulator for better understanding and solving buckling related problems in the field. [S0195-0738(00)00903-1]
Surface Waves in Coated Anisotropic Medium Loaded With Viscous Liquid
Authors: Wu T.-T. , Wu T. Y.
Published: July 2002

The development of micro-acoustic wave sensor in biosensing created the need for further investigations of the surface wave propagation in a viscous liquid loaded layered medium. In this paper, we employed the sextic formalism of surface waves to study the viscous effect on the dispersion and attenuation characteristics of surface waves in a viscous liquid loaded layered medium. The dispersion relation for the viscous liquid loaded single-layered anisotropic half-space is given. Numerical examples of the Rayleigh wave and Love wave dispersion for the cases of a Cu/Fe layered half-space (isotropic) and of a SiO2/Si layered half-space (anisotropic) loaded with viscous liquid are calculated and discussed. [S0021-8936(00)01902-4]
Design of Structures and Compliant Mechanisms by Evolutionary Optimization of Morphological Representations of Topology
Authors: Tai K. , Chee T. H.
Published: July 2002

This paper demonstrates the automatic design synthesis of continuum structures by the process of topology/shape optimization. The problem is solved as a discrete optimization problem using the genetic algorithm (GA). Past efforts using this approach have not been very effective due to the lack of an appropriate structural geometric representation which is highly essential to the success of the evolutionary processes of the GA. Based on the morphology of living creatures, a representation scheme has been developed using arrangements of skeleton and ‘flesh’ to define structural geometry. This scheme facilitates the transmission of topological and shape characteristics across generations in the evolutionary process, and will not render any structurally invalid designs. Good results are illustrated using this scheme to design a compliant mechanism and a cantilever beam. [S1050-0472(00)02104-8]
Degradation in Gas Turbine Systems
Authors: Kurz R. , Brun K.
Published: July 2002

Any prime mover exhibits the effects of wear and tear over time. The problem of predicting the effects of wear and tear on the performance of any engine is still a matter of discussion. Because the function of a gas turbine is the result of the fine-tuned cooperation of many different components, the emphasis of this paper is on the gas turbine and its driven equipment (compressor or pump) as a system, rather than on isolated components. We will discuss the effect of degradation on the package as part of a complex system (e.g., a pipeline, a reinjection station, etc.). Treating the gas turbine package as a system reveals the effects of degradation on the match of the components as well as on the match with the driven equipment. This article will contribute insights into the problem of gas turbine system degradation. Based on some detailed studies on the mechanisms that cause engine degradation, namely, changes in blade surfaces due to erosion or fouling, and the effect on the blade aerodynamics; changes in seal geometries and clearances, and the effect on parasitic flows; and changes in the combustion system (e.g., which result in different pattern factors), the effects of degradation will be discussed. The study includes a methodology to simulate the effects of engine and driven equipment degradation. With a relatively simple set of equations that describe the engine behavior, and a number of linear deviation factors which can easily be obtained from engine maps or test data, the equipment behavior for various degrees of degradation will be studied. A second model, using a stage by stage model for the engine compressor, is used to model the compressor deterioration. The authors have avoided to present figures about the speed of degradation, because it is subject to a variety of operational and design factors that typically cannot be controlled entirely.
Predictive Model for the Full Biaxial Surface and Subsurface Residual Stress Profiles from Turning
Authors: Jacobus Kurt , DeVor R. E. , Kapoor S. G. , Peascoe R. A.
Published: July 2002

A model to predict the full biaxial surface and subsurface residual stresses from the turning process is presented. The model formulation includes thermomechanical coupling, plastic heating, frictional heating, convection, conduction, thermal softening and strain hardening. Calibration and validation of the model are undertaken. The predictive model stands as a tool both to optimize the turning process based on the resulting residual stresses and also to gain an in-depth understanding of the physics of residual stress development from the turning process. In addition, thorough analysis of the experimental results reveals insight into the effects of feed and depth of cut on the surface and subsurface machining-induced residual stresses.
Machine Tool Chatter Suppression by Multi-Level Random Spindle Speed Variation
Authors: Yilmaz Alpay , AL-Regib Emad , Ni Jun
Published: July 2002

This paper presents a new method for varying the spindle speed to suppress chatter in machining. The spindle speed is varied in a pseudo-random fashion within the bandwidth of the spindle system. Both implementation issues and spindle system responses to such signals are investigated. A new method to analyze the stability of machining systems with varying spindle speed is also introduced. The effectiveness and advantages of the random spindle speed variation in chatter suppression is verified using numerical simulations and experiments.
A Unified Approach to Driver Assistance Systems Based on Artificial Potential Fields
Authors: Gerdes J. Christian , Rossetter Eric J.
Published: July 2002

This paper presents an approach to vehicle control based on the paradigm of artificial potential fields. Using this method, the dynamics of the vehicle are coupled with the environment in a manner that ensures that the system exhibits safe motion in the absence of driver inputs. The driver remains in control of the vehicle, however, with the control systems presenting a predictable and safe set of dynamics. With the control approach presented here, integration of various assistance systems is easily achieved through simple superposition of individual potential and damping functions. A simple example of a combined lanekeeping and stability system demonstrates how this can be accomplished. Preliminary simulation results suggest that both safety and driveability are achievable with such a system, prompting further investigation.
Traditional Engineering in the Biological Century: The Biotraditional Engineer
Authors: Friedman Morton H.
Published: July 2002

The increasing importance of life science in all engineering is prompting departments in the traditional engineering disciplines to offer life science as part of their curricula. Students who take advantage of this opportunity—“biotraditional engineers”—will be well positioned for careers in their discipline and in related areas of bioengineering. The founder engineering societies, such as the Bioengineering Division of ASME, are responding to this trend by broadening their scope and working increasingly across interdisciplinary borders.
Ballistic-Diffusive Equations for Transient Heat Conduction From Nano to Macroscales
Authors: Chen Gang
Published: July 2002

In this paper, we present the derivation of a new type of heat conduction equations, named as the ballistic-diffusive equations, that are suitable for describing transient heat conduction from nano to macroscale. The equations are derived from the Boltzmann equation under the relaxation time approximation. The distribution function is divided into two parts. One represents the ballistic transport originating from the boundaries and the other is the transport of the scattered and excited carriers. The latter is further approximated as a diffusive process. The obtained ballistic-diffusive equations are applied to the problem of transient heat conduction across a thin film and the results are compared to the solutions for the same problem based on the Boltzmann equation, the Fourier law, and the Cattaneo equation. The comparison suggests that the ballistic-diffusive equations can be a useful tool in dealing with transient heat conduction problems from nano to macroscales. Boundary conditions for the derived equations are also discussed. Special emphasis is placed on the consistency of temperature used in the boundary conditions and in the equations.
The History of the B2 Stress Index
Authors: Matzen Vernon C. , Tan Ying
Published: July 2002

The history of the primary stress design equations for Class 1 and 2 elbows in the ASME Boiler and Pressure Vessel Code (Section III, Division 1, Subsections NB and NC) is reviewed. The review includes the early analytical solutions for elbow bending, Markl’s stress-intensification factor, the development of Code equation (9), the relationship between SIFs and the C2 and B2 stress indices, development of B2 equations that are functions of internal pressure and bend angle, and a suggested definition of the B2 index which is based on nonlinear finite element analysis.
An Experimental and Numerical Investigation into the Thermal Behavior of the Pressure Die Casting Process
Authors: Bounds S. , Davey K. , Hinduja S.
Published: July 2002

The modeling of the pressure die casting process generally requires the specification of heat transfer coefficients at the surfaces of the die. The coefficients at the cavity-casting interface and at the cooling channel surfaces are of particular importance. In order to provide estimates for these heat transfer coefficients, the behavior of a specifically designed zinc alloy casting is investigated using a three dimensional thermal model whose predictions are supported by experimentally obtained results. The numerical model uses the boundary element method for the dies, as surface temperatures are of particular importance, and the finite element method for the casting, where the nonlinear material behavior makes this technique suitable. The experimental data comprises of thermocouple measurements of both die, casting, and coolant temperatures for three sets of operating conditions. These measurements are complemented by qualitative data of casting defects caused by incomplete solidification and thermal imaging temperature measurements. An experimental technique for obtaining average heat transfer coefficients for the casting–die interface is presented. Although the technique circumvents the need to place thermocouples in the casting and provides average heat transfer coefficients of sufficient accuracy for modeling purposes, it is not sufficiently responsive to provide accurate transient information. The presence of coolant boiling is detected by its effect on the rates of heat extraction. Heat transfer coefficients are determined for the cooling channels using a boiling model. Comparison between predicted and experimental rates of heat transfer to the coolant support the need for a boiling model. Good agreement is obtained between experimental and numerical predictions. [S1087-1357(00)00601-8]
Silver Gallium Sulfide by XPS
Authors: Kuhn W. Kevin
Published: July 2002

High quality single crystal AgGaS2 has been analyzed by x-ray photoelectron spectroscopy. This material is one of a group of I–III–VI2 compounds that crystallize in a tetragonal chalcopyrite structure and have been shown to have very promising nonlinear optical properties. The spectra presented here include survey and high resolution scans of the photoemission peaks and valence band spectra.
Modeling a microfluidic system using Knudsen’s empirical equation for flow in the transition regime
Authors: Robertson J. K. , Wise Kensall D.
Published: July 2002

Knudsen’s model for gas flow in the transition regime is successfully applied to a micromachined flow path of varying cross-sectional area where the type of flow changes from the viscous to the molecular regime as the gas flows through the device. The gas flow model was originally developed to aid in the design of an integrated microflow controller [J. K. Robertson, Ph.D. thesis, University of Michigan, 1996, and J. K. Robertson and K. D. Wise, Proc. IEEE Micro Electro Mechanical Systems 7 (1994)] and to diagnose problems encountered with the microvalves during testing of the device. The main flow channel was rectangular in shape ∼12.8 μm high, 400 μm wide and 2694 μm long. The model was fit to the data by adjusting a single parameter. The model successfully predicted the conductance of the channel for differential pressures greater than 500 Torr—where the gas entered the flow path in the viscous regime and exited in the molecular regime—and less than 11 Torr—where the gas entered the flow path in the transition regime and exited in the molecular regime. The model is computationally simple, can be easily set up on a spreadsheet, and should be useful for the rapid modeling of other micromachined flow paths.
Extension velocities for level set based surface profile evolution
Authors: Richards David F. , Bloomfield Max O. , Sen Suchira , Cale Timothy S.
Published: July 2002

Topography simulations are widely used in the microelectronics industry to study the evolution of surface profiles during such processes as deposition or etching. Comparisons between simulations and experiments are used to test proposed transport and chemistry models. The method used to move the surface (the moving algorithm) should not interfere with this testing process; i.e., it should not introduce artifacts. The reference method, shown to be accurate by several groups in many studies, is conservation law based “front tracking.” Level set approaches are being increasingly used, largely for their robustness to topological changes. They have not been tested against front tracking to determine their accuracy. In this article, we present guidelines on the use of level set methods for two-dimensional surface evolutions as commonly used. Specifically, we deal with two major issues with level set algorithms: the need for “extension velocities” and the rounding of sharp corners due to contouring. We also deal with a specific approach to velocity extension that is called “fast marching.” Although all methods discussed can provide the same results within the limit of small enough time steps, we demonstrate that our proposed “Riemann based” extension velocities can improve overall simulation efficiency by approximately a factor of 2, depending upon the complexity of the process being simulated. We also show that as the grid size used in the level set method decreases, extracted surface profiles can approach those calculated by front tracking, and hence to experiments.
Multiple Collision Method of Measuring Sticking Coefficients and Studying Reflections on Oxide Surfaces
Authors: Benck Ralph F. , Ward John W. , Bloore Ernest W.
Published: July 2002

A new method of measuring sticking coefficients using multiple surface collisions of vapor is presented. Metal vapors pass from a cup into a long, hollow, right cylindrical tube where they come to rest after one or more strikes on the inner surface of the tube. Analysis of the data are made by Monte Carlo statistical calculations of the behavior of atoms in a similar (though hypothetical) tube and using various assumptions regarding sticking coefficients and types of reflections. The sticking coefficient for silver on Pyrex in a residual vacuum of approximately 10−5 Torr and 20 °C is 0.68±0.02. Reflections from Pyrex surfaces are shown, within experimental uncertainty, to be satisfactorily diffuse.
Apparatus for the Study of the Electron Impact Desorption of Ions and Neutrals from Solid Surfaces
Authors: Nishijima Mitsuaki , Propst Franklin M.
Published: July 2002

A cylindrical magnetic spectrometer for the study of the electron impact desorption of ions and neutrals from solid surfaces is described. The instrument has an energy resolution of approximately 4% and sufficient sensitivity to allow the measurement of the ion energy distributions for systems in which the ion yield is 10−9 ions per electron or greater. In addition, the apparatus allows the determination of the mass-to-charge ratio of the emitted ions. The design of the apparatus and experimental procedures are discussed. Examples of typical measurements are reported.
Influence of the impact angle on the depth resolution and the sensitivity in SIMS depth profiling using a cesium ion beam
Authors: Wittmaack K.
Published: July 2002

We have measured the falloff of the SIMS signal of surface impurities (C, O, and F) on Si and GaAs to determine the angular dependence of the depth resolution in sputter profiling under 8-keV Cs+ bombardment. The decay lengths characterizing the exponential tails decreased with increasing impact angle. The relative gain in depth resolution is largest in cases where the resolution is poor at normal beam incidence. The sputtering yield was found to increase approximately as 1/cos2θ, whereas the secondary ion yields of Si− and As− decreased by several orders of magnitude as θ was increased from 0 to 60°. This effect is attributed to a strong angular dependence of the stationary cesium coverage of the ion-bombarded samples. Some information concerning the efficiency for ion-induced desorption is also derived from the experiments.
Metastable amorphous and crystalline (α,σ) phase in physical vapor deposited Fe–(Cr)–Ni–(C) deposits
Authors: Malavasi S. , Oueldennaoua A. , Foos M. , Frantz C.
Published: July 2002

Several microstructural features revealed by transmission electron microscopy in dc sputter deposits of various Fe–(Cr)–Ni–(C) alloys are discussed. The deposits are sputtered on metallic substrates with different Ar/CH4 gas mixtures at temperatures lower than 130 °C. The target’s source material are made of 304, 316, and 310 stainless steel or of Fe–Ni and 55Fe–45(Cr,Ni) alloys with various Cr/Ni ratios. The mean grain size d̄ of the crystalline deposits decreases as the carbon content x increases (x=0, d̄=15 nm) and, for a critical value xc, their structure is wholly amorphous (xc=3 wt. % C in a Fe–25Cr–20Ni–C deposit). All the crystalline deposits exhibit some bcc metastable ferrite coexisting with the fcc equilibrium γ austenite and a 〈111〉γ or 〈200〉γ texture essentially depending on the composition. Those that contain carbon lead to a very fine precipitation of M23C6 carbides upon heating above 500 °C. Mössbauer spectroscopy achieved on several two-phase Fe–Ni deposits has clearly shown that ferrite and austenite do not have the same composition. Moreover, it is surprising to identify sometimes, locally, the Frank–Kasper σ phase which reveals small twin domains rotated by 30° about the same c axis. In the amorphous deposits (with x<7.5 wt. % C), small austenitic grains first crystallize near 400–450 °C and, above 500 °C, M7C3 carbides nucleate and grow, embedding the primary austenitic grains.
Multipurpose plasma generator suitable for diamondlike carbon film formation
Authors: Varga I. K.
Published: July 2002

A plasma generator with a large open secondary plasma has been developed and used to fragment and ionize hydrocarbon gas for diamondlike carbon (DLC) film formation. It is also useful for other materials and as a research tool. The open secondary plasma is created and maintained using electrons from an adjacent plain cylindrical magnetron. The importance of argon partial pressure on the hydrocarbon plasma stability is discussed and the optical emission spectra of various plasmas is presented. The use of a thermal fragmenter is also discussed and the effect it has on the ion energy needed for film formation is highlighted. The conditions necessary for the formation of high-quality, thick, stress-free DLC films are given.
Ultrahigh vacuum precise positioning device utilizing rapid deformations of piezoelectric elements
Authors: Yamagata Y. , Higuchi T. , Saeki H. , Ishimaru H.
Published: July 2002

Recently precise positioning devices with low outgassing rates have been required for production systems of very large scale integrated circuits, surface analysis systems, and scanning tunneling microscopes in ultrahigh vacuum. A bakable XYθ three-axis positioning table using a unique positioning mechanism utilizing friction and inertial forces caused by rapid deformations of piezoelectric elements was developed. The table has a hexagonal shape of 120 mm in diameter and is mainly made of aluminum alloys with an EX-process. The table has three feet with an Si3N4 ball on each bottom side and set on a plate made of Pyrex glass. The table was able to operate in an ultrahigh vacuum environment of the order of 10−12 Torr.
Effect of the microscopic electronic states of the tip on the scanning tunneling microscopy image
Authors: Ohnishi S. , Tsukada M.
Published: July 2002

Based on the first-principles electronic state theory of the sample/tip system, the tunneling conductances for Si(100) and Si(111) surfaces with the W tip are calculated numerically with a cluster model approach. The tunnel current derived from the tunnel Hamiltonian formalism is expressed by the linear combination of atomic orbital scheme with the norm-conserving pseudopotentials, which makes numerical simulation for STM image feasible from the data of electronic states of the separated tip and sample system. The W8 cluster is studied as a model of the (111) protrusion of the W tip. Four active orbitals in an energy range of 1.3 eV which predominantly contribute to the tunneling conductance are found. All of them mainly comprise the dzz and pz orbitals of the tip having a large amplitude at the apex atom with the lobe directed towards the surface.
Influence of the filament potential wave form on the sensitivity of glass-envelope Bayard–Alpert gages
Authors: Abbott Patrick J. , Looney J. Patrick
Published: July 2002

Nonlinearities of ∼10%–15% in the sensitivity of glass envelope Bayard–Alpert gages (BA gages) have been observed in the pressure range 10−7–10−2 Pa. These nonlinearities were studied in modified BA gage tubes with platinum coatings on their inner glass surfaces by measuring the equilibrium potential of the platinum coating as a function of pressure. The sensitivities of the gage systems (gage tube plus controller) were found to depend on the inner surface potential, and this potential was found to depend on pressure and on the details of the filament potential waveform provided by the gage controller. It was found that the nonlinearities could be minimized by holding the inner surface to a fixed direct-current (dc) potential, by modifying the alternating-current filament potential wave form, or by using a controller that provides a noise-free dc filament-heating current.
Surface characterization of titanium implants
Authors: Raikar G. N. , Gregory J. C. , Ong J. L. , Lucas L. C. , Lemons J. E. , Kawahara D. , Nakamura M.
Published: July 2002

The initial biocompatability of titanium (Ti) implants is associated with surface and not bulk properties; hence surface characterization of these implants is critical for their clinical success. A goal of this study was to characterize the Ti (ASTM F67) samples after conducting three different surface treatments. In this article, the results of x-ray photoelectron spectroscopy, Auger electron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy performed on surface-modified Ti samples, and also samples immersed in alpha-modification of Eagle’s medium and in phosphate buffered saline solution after different surface treatments, are presented. Surface analysis prior to immersion revealed an amorphous oxide layer on all the samples similar in composition to TiO2. No significant difference in oxide thicknesses was observed. After exposure to the two media an amorphous or finely crystalline Ca–P layer was exhibited on all Ti surfaces, having a chemistry similar to brushite.
Large grain size CdTe films grown on glass substrates at low temperature
Authors: Zapata-Torres M. , Castro-Rodríguez R. , Zapata-Navarro A. , Wallace John L. , Pomes Ramón , Peña J. L. , Farías M. H.
Published: July 2002

Polycrystalline films of CdTe were prepared by the hot wall-close-spaced vapor transport technique on Corning glass substrates at substrate temperatures below 450 °C. The thickness of the films was constant at 25 μm for all samples grown at different substrate temperatures and different gas pressures. The film thickness was found to be a function of deposition time only (5 μm per min), and virtually independent of substrate temperature and control gas pressure. The grain size was a monotonic function of film thickness, reaching 40 μm for a film thickness of 50 μm.
Ion beam assisted deposition of Al films on Si
Authors: Terrasi A. , Ravesi S. , Marcellino C. , Spinella C. , Pannitteri S.
Published: July 2002

Ion beam assisted deposition (IBAD) was used to grow thin Al films (∼100 nm thick) onto Si substrates at room temperature. Al was deposited by electron gun evaporation, while an Ar+ ion beam bombarded the film during the growth. Ion beam energies of 300, 500, and 650 eV were used, with current densities ranging between 4 and 20 μA/cm2. Polycrystalline Al films have been obtained, whose structural properties were strictly related to the IBAD parameters (ion current and energy). Samples were analyzed by transmission electron microscopy and Rutherford backscattering spectrometry, pointing out the following effects: (1) IBAD produces smaller polycrystalline Al grains with respect to a film evaporated in standard high vacuum conditions; (2) the Al grain size decreases by increasing the ion current or decreasing the ion energy; (3) sputtering yields during IBAD are higher with respect to a postdeposition bombardment process, and show an inverse trend with the ion beam energy. Results have been explained in terms of modification of kinetics of growth induced by IBAD. A simple model is also proposed to take into account the unexpected result about the sputtering yield. Finally, the IBAD capability to modify the microstructure of the Al films was used to improve the coverage of artificially stepped substrates.
Fabrication of special inertial confinement fusion targets using a depolymerizable mandrel technique
Authors: Letts Stephan A. , Fearon Evelyn M. , Allison Leslie M. , Cook Robert
Published: July 2002

A technique was developed for fabricating spherical shell targets for implosion physics experiments with diameters up to several millimeters and with unique structural features such as thin metal layers or texture on the inside surface. We start with a spherical bead or thin shell of poly(alpha-methylstyrene) (PAMS) of the desired size, which can be textured by laser photoablation or overcoated with a thin layer of diagnostic material. The mandrel is next overcoated with plasma polymer (CH) 2–50 μm thick. Upon heating, the PAMS depolymerizes to a gaseous monomer which diffuses through the thermally stable plasma polymer coating leaving a hollow shell. Shells produced by this technique are uniform in wall thickness, and highly spherical. If the PAMS mandrel is textured, the mandrel topology is transferred to the inner wall of the plasma polymer shell. Likewise, thermally stable coatings on the mandrel are transferred to the inner shell wall.
Proposal for an etching mechanism of InP in CH4-H2 mixtures based on plasma diagnostics and surface analysis
Authors: Feurprier Y. , Cardinaud Ch. , Grolleau B. , Turban G.
Published: July 2002

The influence of CH4-H2 mixture composition and rf power input on the etching mechanism of InP is discussed. Argument is based on etch rate measurements, plasma diagnostics (optical emission spectroscopy and mass spectrometry) and quasi in situ x-ray photoelectron spectroscopy (XPS) surface analysis. Results show that the key mechanistic parameters are the CH3 flux density and the ion energy flux density on the InP surface. The In removal mechanism is the most important feature as it is the one which limits the effective etching and controls the surface stoichiometry. This mechanism depends mostly upon the CH3 flux but needs ion assistance. On another hand, the P removal mechanism appears to be strictly controlled by the ion energy flux. Based on these observations an analytical model is proposed to describe the etching. The mechanism can be described as an ion-assisted chemical etching mechanism. Its originality is that In and P removal mechanisms are considered separately although they are strongly interdependent as indicated by XPS. A quantitative determination of the CH3 flux and the ion energy flux density on the InP surface by means of mass spectrometry allow to show that the model is applicable in a wide range of gas mixture composition and rf power. Moreover, it gives an estimation of the number of In atom etched per incident CH3 in agreement with the generally admitted assumption that trimethylindium is the major etch product of In, and allows an estimation of the surface coverage in methyl radicals.
Effects of plasma conditions on the shapes of features etched in Cl2 and HBr plasmas. I. Bulk crystalline silicon etching
Authors: Vyvoda M. A. , Lee H. , Malyshev M. V. , Klemens F. P. , Cerullo M. , Donnelly V. M. , Graves D. B. , Kornblit A. , Lee J. T. C.
Published: July 2002

We have studied the effects of source and bias powers, pressure, and feed gas composition on the shapes of SiO2-masked crystalline silicon features etched in a transformer-coupled high density plasma system. Higher etching rates were obtained at higher source and bias powers, and higher pressure. The etching rates of isolated and nested trenches, isolated lines, and holes were nearly the same, indicating a negligible pattern density dependence. We did, however, observe a very weak decrease in etch rates with increasing aspect ratio at 2 mTorr in a pure Cl2 plasma. At 10 mTorr, no aspect ratio dependence was observed, except at the highest source and bias powers. Microtrenching was observed under certain plasma conditions and could be reduced by using higher bias powers. At 10 mTorr in a pure chlorine plasma, we observed a slight taper at the bottoms of the etched features and the formation of narrow microtrenches near feature corners. At 2 mTorr, the microtrenches were broader and overlapped near the center of narrow trenches to form pyramid-shaped trench bottoms. When a HBr plasma was used instead of Cl2, the etching rate decreased by 50% but the etching profiles were more vertical and the trench bottoms were flat. Isolated lines etched in the HBr plasma, however, revealed broad but shallow microtrenches near the edges of the line, suggesting that the flat trench bottoms were a result of broad microtrenches that overlapped. Trenches of 3 μm depth and aspect ratios of 7 have been obtained using either HBr or Cl2, exhibiting similar microfeatures as observed when etching shallower trenches.
Characterization of the Ti-doped diamond-like carbon coatings on a type 304 stainless steel
Authors: Hsieh W. P. , Wang D. Y. , Shieu F. S.
Published: July 2002

The microstructure and chemistry of a functionally gradient Ti-doped diamond-like carbon (DLC) coating prepared by a closed field unbalanced magnetron sputtering system (CFUBMS) on a type 304 stainless steel was analyzed by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and scanning electron microscopy (SEM). Three distinct regions including the steel substrate, Ti interlayer, and the functionally gradient coating are observed from the cross-section TEM micrograph. Further analysis of the graded coating using selected area diffraction reveals that the early deposited film is mainly composed of TiN located next to the Ti interlayer; subsequently it changes to a mixture of TiC0.7N0.3 and TiC, and finally a very complicated mixture containing Ti, TiC, graphite, possibly diamond and amorphous carbon near the coating surface is observed. The graded Ti-doped DLC coating exhibits columnar structure and preferred orientation illustrated by the arced electron diffraction patterns. Chemical analysis carried out by EELS of the surface coating layer using the plan-view TEM specimen indicates that the bonding state of carbon in the Ti-doped DLC coating depends on the content of Ti. For a Ti-rich region, the carbon K edge favors the formation of a Ti–C bond, whereas graphitic and/or amorphous carbon dominates in the Ti-deficient regions. In addition, the coated specimens were immersed in a 60% H3PO4 (85+%) and 40% H2SO4 (95+%) solution to investigate their corrosion resistance and then examined by SEM and energy-dispersive x-ray spectroscopy (EDS). It is found that the surface coating layer, in which microcracks were observed in the plan-view TEM micrograph, has lower packing density than the subsurface coating. By analysis of the secondary and backscattered electron images, and x-ray mapping, it is believed that the submicron-sized particles that survived the corrosion test in the Ti-doped DLC coating are diamond microcrystallites.
Role of surface chemistry on the nature of passive oxide film growth on Fe–Cr (low and high) steels at high temperatures
Authors: Seal S. , Nardelli R. , Kale A. , Desai V. , Armacanqui E.
Published: July 2002

High temperature materials degradation or protection of Fe–Cr alloys are often related to the nature of their oxide scale formation. Breakdown of passive oxide films leads to localized corrosion. Various alloying elements are often incorporated in these alloys to prevent high temperature oxidation. The addition of selected alloying elements is cumbersome and not always cost effective. In this article, we investigate the role of rare earth oxide coatings on high temperature corrosion prevention of both low and high Cr steel. An in situ high temperature oxidation setup has been built to study the oxidation kinetics of both coated and uncoated low and high Cr steels under ambient pressure and dry air. Reduction in scale growth kinetics is observed in the presence of coating. While scanning electron microscopy and x-ray diffraction are employed to study the structure and morphology of the oxide films, x-ray photoelectron spectroscopy and Auger electron spectroscopy are used to study the surface chemistry of the oxide layer. This article relates some of these data to explain the nature of scale growth kinetics (linear or logarithmic or parabolic) observed in both low and high Cr steels.
Improvement in downflow etching rate using Au as a catalyst
Authors: Kataoka Yoshinori , Shinmura Tadashi , Kanoh Masaaki
Published: July 2002

We studied the improvement in the polycrystalline silicon (poly-Si) etching rate in the downflow etching process using microwave-excited CF4/O2 plasma by enhancing the dissociation reaction of the etching gas and the etching reaction on the poly-Si film surface through the use of a catalyst. A piece of platinum (Pt), gold (Au) or silver (Ag) was placed in a quartz tube as a potential catalyst for the downflow etching of poly-Si films. The results revealed that the etching rate using Au was up to 3.6 times higher than that without any catalyst. The mechanism for the improvement in the etching rate using a Au catalyst was analyzed by evaluating the plasma and etching species in transportation paths using optical emission spectral analysis and mass spectrometry, and by examining the poly-Si film with thermal desorption spectrometry, scanning electron microscopy and x-ray photoelectron spectroscopy. The Au placed between the plasma and the sample is oxidized by the active gas dissociated from CF4/O2 gas, and Au oxides and their compounds including F and CFx are transported and deposited onto the surface of the poly-Si film. Although, the precise mechanism of these reactions is not clear, it was presumed that the gold oxides and their reaction compounds acted as catalysts in the etching reaction of the poly-Si film and significantly accelerated the etching rate.
Scanning probe microscopy tip–sample interactions in primary alcohols of varying chain length
Authors: Ralich R. M. , Wu Y. , Ramsier R. D. , Henriksen P. N.
Published: July 2002

Interactions between chemically functionalized tips and substrates in scanning probe microscopy are usually investigated by utilizing an intervening liquid medium, however the results may be influenced in various ways by the medium itself. In this study the chain length of a series of primary alcohols is shown to affect adhesion measurements. The measurements are performed between a layer of phosphonic acid adsorbed on an aluminum substrate and an aluminum-coated silicon nitride tip. The phosphonic acid/oxidized aluminum system has been characterized previously by vibrational spectroscopy and forms a stable, well-defined system for studying the effects of the medium on adhesion. Adhesion forces between the tip and sample are observed to decrease as the alcohol chain length is increased, and to increase as the dielectric constant of the medium increases. The experimental results of this study cannot be explained by the use of a single model for the role of solvents in force-curve measurements, indicating that a combination of mechanisms may be responsible for adhesion in this system.
Reflection high-energy electron diffraction and scanning tunneling microscopy study of InP(001) surface reconstructions
Authors: LaBella V. P. , Ding Z. , Bullock D. W. , Emery C. , Thibado P. M.
Published: July 2002

The reconstructions of the InP(001) surface prepared by molecular beam epitaxy have been studied with in situ reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). The growth chamber contains a highly accurate temperature measurement system and uses a solid-source, cracked phosphorus, valved effusion cell. Five InP(001) reconstructions are observed with RHEED by analyzing patterns in three principal directions. Under a fixed P2 flux, decreasing the substrate temperature gives the following reconstructions: c(2×8), (2×4), (2×1), (2×2), and c(4×4). In situ STM images reveal that only two of these reconstructions yields long-range periodicity in real space. InP(001) does not form the metal rich (4×2) reconstruction, which is surprising because the (4×2) reconstruction has been coined the universal surface reconstruction since all III–V(001) surfaces were thought to favor its formation.
Two-dimensional Haar thinning for data base compaction in Fourier proximity correction for electron beam lithography
Authors: Haslam M. E. , McDonald J. F. , King D. C. , Bourgeois M. , Chow D. G. L. , Steckl A. J.
Published: July 2002

Fourier transforms have been successfully employed to produce fast, accurate calculations for dose precompensation in proximity effect correction for electron beam lithography. The principle advantage of this method is that it lends itself to implementation on special purpose computing hardware which is optimized for the generation of one- and two-dimensional Fourier transforms. However, the extremely accurate data base produced by the direct employment of the method is excessively large and, therefore, not practical. A controlled method for approximating this accurate solution is required which gives rise to the least mean-square error in the net exposure. This process of approximation can reduce the data base by ‘‘thinning’’ or selectively removing larger and larger features. In this paper we explore the use of two-dimensional Haar transforms for thinning the data base. An additional benefit of using Haar transforms is that they may also be computed with the same hardware accelerators which speed up the calculation of Fourier transforms.
InSb–CdTe interfaces: A combined study by soft x-ray photoemission, low-energy electron diffraction, and Raman spectroscopy
Authors: Mackey K. J. , Zahn D. R. T. , Allen P. M. G. , Williams R. H. , Richter W. , Williams R. S.
Published: July 2002

CdTe layers have been deposited on c(2×8) (100) InSb and cleaved (110) InSb substrates under molecular-beam epitaxy conditions at room and elevated temperatures. The low-energy electron diffraction and soft x-ray photoemission spectroscopy (XPS) results show that the interfaces formed at room temperature are reasonably abrupt, though disordered. Deposition on substrates at elevated temperatures, however, leads to a nonabrupt interface and new chemical phases. The thickness of the intermediate layer formed increases with substrate temperature and is shown to be semiconducting by the soft XPS measurements. It is suggested that the layer predominantly consists of In2Te3. In order to investigate this further, Raman spectroscopy studies have been carried for CdTe layers on InSb prepared at both room and elevated temperatures and also on In2Te3 crystals. The spectra obtained clearly indicate the existence of excess Te at the room temperature interface, whereas In2Te3 and segregated Sb were observed at elevated temperature interfaces. The thickness of the intermediate layer has been estimated using the half-widths of the Raman signal. The results have been compared with thermodynamical considerations and points of interest are discussed.
Thin-layer p–n junction fabrication using Ga and In focused ion beam implantation
Authors: Lin C-M. , Steckl A. J. , Chow T. P.
Published: July 2002

The fabrication of shallow p–n junction impurity profiles using Ga and In focused ion beam (FIB) implantation in conjunction with rapid thermal annealing is reported. A 75-keV focused ion beam with 80 mA/cm2 current density and 0.5-μm beam diameter was used to implant Ga+ and In+ into (100) Si substrates at doses ranging from 1×1013 to 5×1015/cm2. The annealing temperature was varied from 600 to 1000 °C for various times, 10–30 s. Secondary ion mass spectrometry and spreading resistance profiling were used to measure the implanted species atomic and carrier concentration depth profiles. As compared to the conventional broad beam implantation, the FIB implanted Ga concentration depth profiles exhibit higher activation percentage in the end-of-range and tail region. This results in thicker layers and deeper p+–n junctions, but with lower sheet resistance and leakage current. A similar phenomenon is also observed in In FIB-implanted samples. The damage generated by the high dose rate implantation is possibly responsible for this phenomenon. p+–n diodes fabricated using Ga FIB doping exhibit very good diode electrical characteristics: ideality factor as low as 1.01, leakage current density below 1 nA/cm2 at −1 V reverse bias, and breakdown voltage of ∼35 V. Diodes fabrication with In generally exhibit shallower junctions, but higher leakage current. Bipolar transistors have been fabricated using FIB-implanted Ga and In thin base layers. Common emitter current gain of 70 and 10 were obtained for Ga and In FIB-implanted bipolar transistors, respectively.
Mechanism of SiNxHy deposition from N2–SiH4 plasma
Authors: Smith Donald L. , Alimonda Andrew S. , von Preissig Frederick J.
Published: July 2002

The N2 –SiH4 rf glow-discharge plasma has been analyzed by line-of-sight mass spectrometry of species impinging on the deposition electrode (including N atoms), and properties of SiNx Hy films deposited from this plasma have been examined. At high rf power and low SiH4/N2 gas ratio, most of the SiH4 is consumed by reaction of SiHm radicals with N atoms at the film surface and becomes incorporated into the film. No Si–N precursor species are seen in the plasma. This is in contrast to the NH3–SiH4 plasma, where the Si(NH2)3 radical is the key gas-phase precursor. If power is insufficient or SiH4 flow is excessive, disilane is formed in the plasma. Under disilane-free plasma conditions, films slightly N rich with no Si–H bonding and only 11 at. % H (as N–H) can be deposited at high rate (21 nm/min). The film tensile stress characteristic of the NH3 process is absent in the N2 process due to the absence of precursor chemical condensation beneath the growing surface. However, step coverage is much worse in the N2 process due to the much higher sticking coefficients of the reactant radicals. The N2 plasma chemistry is the same using 400 kHz or 13 MHz rf power, but compressive stress and H content are both higher at the lower frequency due to H+ implantation.
Evidence of pronounced positional order at the graphite–liquid crystal interface of a bulk nematic material
Authors: Brandow Susan L. , DiLella Daniel P. , Colton Richard J. , Shashidhar Ranganathan
Published: July 2002

We present scanning tunneling microscopy images of a bulk nematic liquid crystal, viz., 4′-n-hexyl-4-cyanobiphenyl, on the surface of graphite. These images clearly show the existence of pronounced positional order at the solid–liquid crystal interface for a material with no positional order in the bulk. A feature of the molecular arrangement is the pronounced interdigitation of the aromatic cores. The unit cell consists of two opposing molecules, the aromatic core of one of them lying flat on the graphite surface, while the core of the adjacent molecule lies on its side. The packing arrangement also features large open spaces of uncovered substrate between the alkyl tails. The molecular arrangement is compared with that of the smectic alkylcyanobiphenyls.
High-density plasma mode of an inductively coupled radio frequency discharge
Authors: Amorim J. , Maciel H. S. , Sudano J. P.
Published: July 2002

Experimental observations concerning the formation of a high-density plasma in an inductively coupled radio frequency (11.4 MHz) discharge in argon are described. These observations are complemented by probe measurements that provide a quantitative description of plasma properties over an useful range of vapor pressure, 0.02–0.2 Torr, and rf power, 50–400 W. It is shown that a dense plasma of the order of 1012 cm−3 can be easily formed, having the configuration of a luminous plasmoid embedded in a low-density, 1010 cm−3, diffuse plasma.
Factory of the future: The ‘‘whole factory’’ view
Authors: Harrell Sam
Published: July 2002

The primary task of a semiconductor factory is to produce integrated circuits of outstanding performance at a steeply declining cost per electronic function delivered. The semiconductor industry over the next decade will need to continue to drive costs down in order to maximize manufacturing productivity in the climate of rising product complexity, equipment cost, and risk. Historically we have concentrated on aggressive yield improvement and declining wafer fab cost per cm2 as the dominant factors for increasing productivity. To continue to be competitive, SEMATECH is extending its focus beyond cost per cm2 to the more total view of cost per function. We are working toward a combination of solutions to meet our manufacturing challenges recognizing that no single solution will provide enough benefit to achieve the productivity gains end users expect. The ‘‘whole factory’’ view is a useful strategic planning tool for defining the future of manufacturing in the semiconductor industry.