bluuebunny/crossref_metadata_2025 huggingface dataset:
A Semi-Analytical Solution to the Dynamic Tracking of Non-contacting Gas Face Seals
Authors: Ruan Bo
Published: July 2002

The gas film stiffness and damping coefficients for a non-contacting gas face seal are obtained from the unsteady nonlinear Reynolds equation using the perturbation method. The seal assembly is converted to an equivalent spring-damper-mass system. The stator tracking motion is treated as a forced vibration caused by the rotor motion due to its runout and misalignment. The seal steady-state dynamic responses are solved semianalytically. Results for a typical spiral groove gas face seal agree well with that from a full numerical simulation. Stability of the seal axial pulsating and conical whirl are examined using the frequency dependent dynamic force and moment coefficients.
Influence of a Honeycomb Facing on the Heat Transfer in a Stepped Labyrinth Seal
Authors: Willenborg K. , Schramm V. , Kim S. , Wittig S.
Published: July 2002

The influence of a honeycomb facing on the heat transfer of a stepped labyrinth seal with geometry typical for modern jet engines was investigated. Heat transfer measurements were obtained for both a smooth stator and a stator lined with a honeycomb structure. In addition, an LDV system was used with the scaled up geometry to obtain a high local resolution of the velocity distribution in the seal. The experiments covered a wide range of pressure ratios and gap widths, typical for engine operating conditions. Local heat transfer coefficients were calculated from the measured wall and gas temperatures using a finite element code. By averaging the local values, mean heat transfer coefficients were determined and correlations for the global Nusselt numbers were derived for the stator and the rotor. The LDV results showed strong geometrical effects of the honeycomb structure on the development of the flow fields for the honeycomb seal. The distribution of the local heat transfer coefficients are compatible with the flow features identified by the LDV results and reveal a significantly reduced heat transfer with the honeycomb facing compared to the smooth facing.
Output-Only Subspace-Based Structural Identification: From Theory to Industrial Testing Practice1
Authors: Basseville Miche`le , Benveniste Albert , Goursat Maurice , Hermans Luc , Mevel Laurent , Van der Auweraer Herman
Published: July 2002

We address the problem of structural model identification during normal operating conditions and thus with uncontrolled, unmeasured, and nonstationary excitation. We advocate the use of output-only and covariance-driven subspace-based stochastic identification methods. We explain how to handle nonsimultaneously measured data from multiple sensor setups, and how robustness with respect to nonstationary excitation can be achieved. Experimental results obtained for three real application examples are shown.
The Application of Ultra High Lift Blading in the BR715 LP Turbine
Authors: Haselbach Frank , Schiffer Heinz-Peter , Horsman Manfred , Dressen Stefan , Harvey Neil , Read Simon
Published: July 2002

The original LP turbine of the BR715 engine featured “High Lift” blading, which achieved a 20-percent reduction in aerofoil numbers compared to blading with conventional levels of lift, reported in Cobley et al. (1997). This paper describes the design and test of a re-bladed LP turbine with new “Ultra High Lift” aerofoils, achieving a further reduction of approximately 11 percent in aerofoil count and significant reductions in turbine weight. The design is based on the successful cascade experiments of Howell et al. (2000) and Brunner et al. (2000). Unsteady wake-boundary layer interaction on these low-Reynolds-number aerofoils is of particular importance in their successful application. Test results show the LP turbine performance to be in line with expectation. Measured aerofoil pressure distributions are presented and compared with the design intent. Changes in the turbine characteristics relative to the original design are interpreted by making reference to the detailed differences in the two aerofoil design styles.
A Geometrical Approach to the Study of the Cartesian Stiffness Matrix
Authors: Zˇefran Milosˇ , Kumar Vijay
Published: July 2002

The stiffness of a rigid body subject to conservative forces and moments is described by a tensor, whose components are best described by a 6×6 Cartesian stiffness matrix. We derive an expression that is independent of the parameterization of the motion of the rigid body using methods of differential geometry. The components of the tensor with respect to a basis of twists are given by evaluating the tensor on a pair of basis twists. We show that this tensor depends on the choice of an affine connection on the Lie group, SE3. In addition, we show that the definition of the Cartesian stiffness matrix used in the literature [1,2] implicitly assumes an asymmetric connection and this results in an asymmetric stiffness matrix in a general loaded configuration. We prove that by choosing a symmetric connection we always obtain a symmetric Cartesian stiffness matrix. Finally, we derive stiffness matrices for different connections and illustrate the calculations using numerical examples.
Adherence of an Axisymmetric Flat Punch Onto a Clamped Circular Plate: Transition From a Rigid Plate to a Flexible Membrane
Authors: Wan K.-T.
Published: July 2002

A clamped circular film is adhered to a rigid cylindrical punch. An external force pulls the punch away causing delamination at the punch-plate interface. The deflections of the film are discussed for a range of film thickness and stiffness, detailing the continuous transition from a plate under bending to a membrane under stretching. An equilibrium theory of delamination mechanics is derived based on an energy balance. A complete separation at the punch-film interface, or the “pull-off” event, is predicted when the contact circle shrinks to approximately 0.18 of the film diameter. The values and trends, presented in dimensionless normalized form here, should have implications in biological and colloidal sciences in relation to thin-walled capsules and in electronics in relation to thin encapsulating films.
Solar Thermal Reduction of ZnO Using CH4:ZnO and C:ZnO Molar Ratios Less Than 1
Authors: Wieckert Christian , Steinfeld Aldo
Published: July 2002

The solar thermal reduction of ZnO, using solar process heat and CH4 or C as reducing agent, is investigated for CH4:ZnO or C:ZnO molar ratios ranging from 0 (thermal decomposition at above about 2000°C) to 1 (stoichiometric reduction at above about 1000°C). At 1400°C, in thermodynamic equilibrium ZnO can be completely reduced using a CH4:ZnO molar ratio of 0.3 and produces one fuel (Zn-metal) rather than two for the stoichiometric case (Zn and syngas). The maximal reactor thermal efficiency without heat recovery from the offgas, defined as the ratio of the heating-value of the zinc produced to the total thermal energy input, is 55%. CO2-emissions are reduced by a factor of 10–15 compared to fossil-fuel-based zinc-production technologies. For a closed materials cycle, in which power is extracted from the solar zinc using a fuel cell and the ZnO formed is recycled to the solar reactor, the total exergy efficiency, defined as the work output of the fuel cell to the thermal energy input, varies between 30 to 40% when based on the absorbed solar power in the reactor. These efficiency values are very encouraging, especially since the solar ZnO/Zn cycle allows—in contrast to other regenerative power plants—to store and transport solar energy.
In Situ Matrix Shear Response Using Torsional Test
Data of Fiber Reinforced Unidirectional Polymer Composites
Authors: Yerramalli Chandra S. , Waas Anthony M.
Published: July 2002

The in situ shear response of the matrix in polymer matrix composites (PMC) has been studied. Torsion tests were performed on solid cylinders of unidirectional glass fiber reinforced/vinylester and unidirectional carbon fiber reinforced/vinylester composites. The composite specimens were subjected to a uniform rate of twist. From the composite stress-strain curve, a plot of tangent shear modulus vs shear strain was derived. Then, using the Halpin-Tsai equations, the in situ matrix shear modulus was determined. The in situ matrix properties obtained from glass/vinylester and carbon/vinylester composites were found to be different. In addition, the properties of the in situ matrix were found to be a function of fiber volume fraction and the elastic properties of the reinforcing fiber. The behavior of the in situ matrix as a function of the fiber volume fraction was explained by using a three cylinder interphase model. The validity of the interphase model in predicting the composite shear modulus was studied by comparison of results against a conventional 2 cylinder model.
Continuous Model for the Transverse Vibration of Cracked Timoshenko
Beams
Authors: Carneiro Sergio H. S. , Inman Daniel J.
Published: July 2002

A continuous model for the transverse vibrations of cracked beams including the effect of shear deformation is derived. Partial differential equations of motion and associated boundary conditions are obtained via the Hu-Washizu-Barr variational principle, which allows simultaneous and independent assumptions on the displacement, stress and strain fields. The stress and strain concentration caused by the presence of a crack are represented by so-called crack disturbance functions, which modify the kinematic assumptions used in the variational procedure. For the shear stress/strain fields, a quadratic distribution over the beam depth is assumed, which is a refinement of the typical constant shear stress distribution implicit in the Timoshenko model for uncracked beams. The resulting equations of motion are solved by a Galerkin method using local B-splines as test functions. As a numerical verification, natural frequencies of the linear, open-crack model are computed and the results are compared to analytical results from similar models based on Euler-Bernoulli assumptions and experimental results found in the literature. For short beams, results from a 2-D finite element model are used to confirm the advantages of the proposed model when compared with previous formulations.
Numerical Simulation of Pulsed Laser Bending
Authors: Zhang X. R. , Chen G. , Xu X.
Published: July 2002

The aim of this work is to develop an efficient method for computing pulsed laser bending. During pulsed laser bending, thousands of laser pulses are irradiated onto the target. Simulations of the thermomechanical effect and bending resulted from all the laser pulses would exceed the current computational capability. The method developed in this work requires only several laser pulses to be calculated. Therefore, the computation time is greatly reduced. Using the new method, it is also possible to increase the domain size of calculation and to choose dense meshes to obtain more accurate results. The new method is used to calculate pulsed laser bending of a thin stainless-steel plate. Results calculated for a domain with a reduced size are in good agreement with those obtained by computing all the laser pulses. In addition, experiments of pulsed laser bending are performed. It is found that experimental data and computational results are consistent.
Fluid Flow and Heat Transfer in a Rotating Two-Pass Square Duct With In-Line 90-deg Ribs
Authors: Liou Tong-Miin , Chen Meng-Yu , Tsai Meng-Hsiun
Published: July 2002

Laser-doppler velocimetry and transient thermochromic liquid crystal measurements are presented to understand local fluid flow and surface heat transfer distributions in a rotating ribbed duct with a 180 deg sharp turn. The in-line 90-deg ribs were arranged on the leading and trailing walls with rib height-to-hydraulic diameter ratio and pitch-to-height ratio of 0.136 and 10, respectively. The Reynolds number, based on duct hydraulic diameter and bulk mean velocity, was fixed at 1.0×104 whereas the rotational number varied from 0 to 0.2. Results are compared with those of the rotating smooth duct flow in terms of maximum streamwise mean velocities Umax/Ub and turbulence intensities u′max/Ub, skewness of mean velocity profiles, secondary flow pattern, turn-induced separation bubble, and turbulence anisotropy. Nusselt number ratio mappings are also provided on the leading and trailing walls. The relationships between the fluid flow and local heat transfer enhancement are also documented. It is found that the rotating ribbed duct flow provides higher Umax/Ub,u′max/Ub, and stronger total averaged secondary flow and, hence heat transfer is enhanced. Comparisons with heat transfer data published by other research groups are also made. Furthermore, simple linear correlations between regional averaged Nusselt number ratio and rotation number are developed.
A Quantitative Similarity Metric for Design-by-Analogy
Authors: McAdams Daniel A. , Wood Kristin L.
Published: July 2002

During the design and development of new products, design engineers use many techniques to generate and define new and “good” concepts. Inherent in this search for solutions is the conscious and unconscious reliance on prior experience and knowledge, or design-by-analogy. In this paper, a quantitative metric for design-by-analogy is developed. This metric is based on the functional similarity of products. By using this product-similarity metric, designers are able to formalize and quantify design-by-analogy techniques during concept and layout design. The methods, as developed in this paper, allow a designer with limited experience to develop sophisticated solutions that enhance the overall design of a new product. Also, a designer’s current design-by-analogy vocabulary can be extended beyond his or her immediate experience, providing access and contributions to new domains by discovering different products with common functions. The similarity metric and its application are clarified and validated through a case study. The case study is the original design of a pickup winder.
Modeling of Interphases in Fiber-Reinforced Composites Under Transverse Loading Using the Boundary Element Method
Authors: Liu Y. J. , Xu N. , Luo J. F.
Published: July 2002

In this paper, interphases in unidirectional fiber-reinforced composites under transverse loading are modeled by an advanced boundary element method based on the elasticity theory. The interphases are regarded as elastic layers between the fiber and matrix, as opposed to the spring-like models in the boundary element method literature. Both cylinder and square unit cell models of the fiber-interphase-matrix systems are considered. The effects of varying the modulus and thickness (including nonuniform thickness) of the interphases with different fiber volume fractions are investigated. Numerical results demonstrate that the developed boundary element method is very accurate and efficient in determining interface stresses and effective elastic moduli of fiber-reinforced composites with the presence of interphases of arbitrarily small thickness. Results also show that the interphase properties have significant effect on the micromechanical behaviors of the fiber-reinforced composites when the fiber volume fractions are large. [S0021-8936(00)02501-0]
Integrated Flow Analysis During Filling and Post-Filling Stage of Semiconductor Encapsulation
Authors: Han Sejin , Wang K. K.
Published: July 2002

In this paper, flow during the filling and post-filling stages in semiconductor chip encapsulation has been analyzed. A finite-element method based on the Hele-Shaw approximation is used for the flow analysis in the chip cavity. The compressibility of the epoxy-molding compound has been considered to analyze the post-filling stage. The model has been verified by comparing resulting predictions with experimental results. Specifically, pressure has been measured in a rectangular cavity and compared with simulation results. The calculated and experimental results show good agreement. [S1043-7398(00)00101-8]
Span Limits for Elevated Temperature Piping
Authors: Becht Charles , Chen Yaofeng
Published: July 2002

Pipe deflection due to self-weight quite often governs in the determination of the spacing between supports. Methods are readily available for calculation of elastic deflection of the pipe. However, such methods are not available for calculation of long-term deflection due to creep, which can be many times the initial elastic deflection for pipe operating in the creep regime of the material. Closed-form solutions for simple span conditions are presented which can be used by the analyst to develop charts for specific applications. These solutions provide insights into the problem of establishing span limits for elevated temperature pipe. [S0094-9930(00)01101-X]
The Effects of Converging and Diverging Axial Taper on the Rotordynamic Coefficients of Liquid Annular Pressure Seals: Theory Versus Experiment
Authors: Lindsey W. Todd , Childs Dara W.
Published: July 2002

Experimental results are compared to predictions for turbulent flow, short (D=76.2mm,L/D=.17), smooth annular seals with converging and diverging axial taper. Results are presented for four geometries with the same minimum clearances: two convergent, two divergent, and a constant-clearance. Measurements were taken at seal pressure differentials and shaft rotation rates ranging from 1.34 to 3.54 MPa and 10,200 to 24,600 rpm, respectively. Measurements parameters include leakage, direct stiffness, cross-coupled stiffness, and direct damping coefficients. Results show that direct stiffness generally increases with converging axial taper and decreases with diverging axial taper; however, direct stiffness decreases in the first increase in the taper angle, contrary to predictions. Direct damping and cross-coupled stiffness were shown to decrease with increasing convergent or divergent taper. Measured damping values increase with increased running speed and decreasing average clearance. Theoretical predictions for rotordynamic coefficients are in reasonable qualitative agreement with measured results. The theory consistently underpredicts leakage by ranges of 10∼30 percent. The accuracy of predictions for leakage and rotordynamic coefficients was not influenced by running speed. [S0739-3717(00)70102-4]
Spin Cast Polycarbonate Film on Glass Substrate by XPS
Authors: Ackeret Michael , Ratner Buddy D.
Published: July 2002

X-ray photoelectron spectroscopy was used to analyze polycarbonate, a pure spin cast polymer. This polymer was centrifugally spun cast onto a glass substrate and stored in an UV/ozone cleaned, O-ring sealed aluminum container. The polymer was examined at three different electron takeoff angles to verify homogeneity. Data were collected and atomic compositions calculated with a Hewlett-Packard 5950B ESCA. Measured atomic composition percentages closly matched the expected stochiometry of the polymer.
Effect of Crystallinity on the XPS Spectrum of Poly(Ethylene Terephthalate)
Authors: Beamson G. , Clark D. T. , Hayes N. W. , Law D. S-L.
Published: July 2002

High resolution x-ray photoelectron spectra (XPS) are reported for poly(ethylene terephthalate) (PET) in the form of biaxially oriented crystalline film and amorphous polymer melt (i.e., molten inside the spectrometer during analysis). A small(∼0.14 eV) but unambiguous shift of the C 1s glycol component, relative to the aromatic and carboxyl components, is observed on going from crystalline film to amorphous polymer melt. It is known from x-ray diffraction data and infrared spectroscopy that the crystalline to amorphous transition is accompanied by a change from trans to gauche conformation of the glycol unit of the polymer repeat unit, and we ascribe the observed C 1s glycol shift to the same effect. Small differences between crystalline and amorphous PET are also observed in the valence band. Under the conditions of the XPS analysis the polymer melt appears to be electrically conducting.
Sulfided Platinum Black by XPS
Authors: Muhler M. , Paál Zoltan
Published: July 2002

X-ray photoelectron spectra are reported for a Pt black reduced from an aqueous solution of H2PtCl6 by hydrazine and sulfided ex situ by 10% H2S+90% H2 at 633 K. The Pt 4f line showed predominantly metallic Pt, together with a low intensity shoulder corresponding to PtS and/or adsorbed sulfur. PtS2 was not present. Two S 2p peaks indicated the simultaneous presence of sulfide and sulfate. O 1s and C 1s impurities were also present with peak shapes similar to unsulfided Pt black.
Reference Spectra for Environmentally Important Secondary Minerals: Ettringite (Ca6Al2(SO4)3(OH)12⋅26H2O) by XPS
Authors: Comans Rob N. J. , Eighmy T. Taylor , Shaw Elisabeth L.
Published: July 2002

Ettringite, found in metamorphosed limestone and also as an important secondary mineral in concrete and certain combustion waste environments, plays an important role in concretion strength development, and in the control of pH and immobilization of trace elements in alkaline hazardous wastes. Consequently, the ability to identify ettringite via surface-sensitive spectroscopies is important for understanding cementitious mechanisms and the environmental behavior of wastes. We have used x-ray photoelectron spectroscopy (XPS) to study the binding energy of principal photoelectrons from an air-exposed external crystal surface of a well-formed needle-shaped ettringite sample from a bituminous limestone deposit in Asad, Israel. General survey and high resolution spectra were collected under standard operating conditions using a Perkin Elmer Physical Electronics 5200C spectrometer. Adventitious carbon was used as the energy referencing method. Charge-corrected binding energies were identified for the Ca 2p3/2, Ca 2p1/2, Al 2p, S 2p3/2, S 2p1/2, and O 1s photoelectrons. The mineral contains three oxygen species. Probable loss of waters of hydration resulted in the determination of binding energies for only the hydroxyl and sulfate oxygens. Nominal binding energies for all three species are also provided. These spectra are useful in using XPS to identify ettringite in leaching environments of combustion residues where the secondary mineral precipitated at ash particle surfaces.
Analysis of a Filled Poly(vinyl chloride) Polymer by XPS
Authors: Lannon John M. , Meng Qingru
Published: July 2002

We report x-ray photoemission spectra for a CaCO3 filled poly(vinyl chloride) (PVC) polymer with dioctyl pthalate plasticizer. XPS spectra were acquired with a SSI model SSX-100 instrument using monochromated Al Kα x-rays. We present the survey spectrum (binding energy 0–1000 eV) and a narrow spectrum of the C 1s, O 1s, and Cl 2p photoelectron peaks.
Hinsdalite (PbAl3PO4SO4(OH)6) Characterized by XPS: An Environmentally Important Secondary Mineral
Authors: Eighmy T. Taylor , Kinner Amy E. , Shaw Elisabeth L. , Eusden J. Dykstra , Francis Carl A.
Published: July 2002

Hindsdalite (PbAl3PO4SO4(OH)6) is an environmentally important secondary phosphate mineral. It is of significance geochemically in oxidized zones around sulfidic ore bodies, and in soil, sedimentary, and waste systems. We have used XPS to study the binding energy of primary photoelectrons from an air-exposed, well-formed, small, hexagonal barrel crystal sample (a pseudomorph after pyromorphite). The sample is from Zeehan, Tasmania and was supplied by the Excalibur-Cureton Mineral Company. General survey and high-resolution spectra were collected using a Perkin Elmer Physical Electronics 5200C spectrometer. Adventitious carbon was used for energy referencing. Charge corrected binding energies for the Pb 4f7/2, Pb 4f5/2, P 2p3/2, P 2p1/2, P 2s, O 1s, S 2p3/2, S 2p1/2, and Al 2p photoelectrons are reported. Two species of Pb and S were observed; likely representing a mixture of both hinsdalite and galena (PbS). These spectra are useful in identifying environmentally important lead phosphate minerals such as hinsdalite in ore bodies, soils, sediments, and phosphate-stabilized waste systems.
Effects of composition and N2 plasma treatment on the barrier effectiveness of chemically vapor deposited WSix films
Authors: Wang M. T. , Chuang M. H. , Chen L. J. , Chen M. C.
Published: July 2002

This work investigates the thermal stability of chemically vapor deposited amorphous WSix layers used as a diffusion barrier between Cu and Si substrate, in which the WSix layers were deposited to a thickness of about 50 nm using the SiH4 reduction of WF6 at various SiH4/WF6 flow ratios. For 30 min annealing in nitrogen ambient, the effectiveness of the WSix layers as barriers between a copper overlayer and a p+–n junction diode decreases as the Si/W atomic ratio, x, increasing from 1 to 1.3. This composition change is obtained by raising the SiH4/WF6 flow ratio from 3 to 50. As deposited, all films are x-ray amorphous. Their resistivity increases roughly linearly with x. The barrier capability of WSix layers can be significantly improved by an in situ N2 plasma treatment. The N2 plasma treatment produces a very thin layer of WSiN (about 5 nm) on the surfaces of WSix layers. In particular, the Cu/WSiN/WSix/p+–n junction diodes with the WSix layers deposited with a SiH4/WF6 flow ratio of 3 were able to remain intact up to at least 600 °C.
New polymer materials for nanoimprinting
Authors: Schulz H. , Scheer H.-C. , Hoffmann T. , Sotomayor Torres C. M. , Pfeiffer K. , Bleidiessel G. , Grützner G. , Cardinaud Ch. , Gaboriau F. , Peignon M.-C. , Ahopelto J. , Heidari B.
Published: July 2002

We have investigated new aromatic polymers for nanoimprint and subsequent dry etching, namely thermoset and thermoplastic compounds. They were tested in a SiO2 patterning process under low pressure and high plasma density conditions and feature a selectivity about twice as high as poly(methylmethacrylate) (PMMA). The imprint behavior is comparable to PMMA and, in particular, the thermoplastic polymers show excellent imprint quality. This was demonstrated by replication of large arrays of lines down to 50 nm width. The thermoset polymers showed excellent dry etch stability and Teflon-like antisticking layers helped to imprint them without sticking.
Low-Pressure Oxidation of Cb–1Zr Alloy
Authors: Lyon T. F.
Published: July 2002

Resistively heated strip specimens of Cb-1Zr alloy were exposed at 927 °C in a vacuum chamber at various levels of total pressure in the 10−6-Torr range and oxygen partial pressures in the 10−7-Torr range. Pressure levels were maintained by controlled in-leakage of air. Oxygen reacts rapidly with Cb–1Zr alloy under these conditions and final oxygen content of the specimens was between 4000 and 9000 ppm for exposure times between 200 and 500 h. Oxygen reaction rates (sticking probabilities) were calculated both from the total oxygen pickup and from the vacuum chamber gas analyses. Good agreement was obtained between the two methods. Oxygen sticking probabilities were found to depend on whether or not the specimens were annealed immediately before the test exposure. These results indicate that a normally undetectable oxide film exists on the Cb–1Zr surface as a result of oxidation by ambient air, and causes the sticking probability to be lower than on the clean metal surface. Sticking probabilities ranged from 0.65 on the clean surface to 0.16 on the surface with the oxide film. Mechanical tests of the contaminated material showed that Cb–1Zr alloy is considerably strengthened by addition of oxygen to an oxygen level of about 6000 ppm, while still maintaining reasonably good room temperature ductility. At higher oxygen levels, the ductility decreases markedly with little additional increase in strength. Welded and annealed Cb–1Zr is considerably more sensitive to oxygen contamination. The weld metal is brittle after addition of 4300 ppm oxygen.
Accommodation Pumping—A New Principle for Low Pressures
Authors: Hobson J. P.
Published: July 2002

A new principle of vacuum pumping, termed accommodation pumping, has been tested experimentally. Two volumes at room temperature are joined by a passage, the walls of which are alternately atomically rough and atomically smooth. When alternate smooth-rough junctions are held at a temperature other than room temperature, a pumping action develops and gas is transferred from one volume to the other. Experimental parameters studied are: time, location of temperature transition, pressure, number of pumping stages, nature of gas, nature of surfaces, effect of preadsorbed layers, and temperatures. A simple theory is given which yields first order agreement with pumping performance.
Introduction of Water Vapor into Vacuum Systems and the Adsorption by the Walls
Authors: Deitz Victor R. , Turner Noel H.
Published: July 2002

A technique is described whereby precise amounts of water vapor can be introduced into evacuated glass–Kovar stainless-steel systems. The adsorption of water vapor by the walls of a typical vacuum system maintained at 26.8°C is reported in the range 0.03–0.20 relative pressure. A continuous dynamic behavior was observed over time intervals up to 4000 min, where time zero corresponds to the initial contact of the walls with the water vapor. At a constant contact time, the pressure dependence of each isochrone followed a conventional Type II physical adsorption isotherm and a linear B.E.T. plot was observed in the range 0.04 and 0.18 relative pressures. It is quite feasible to follow the adsorption of water vapor volumetrically on a variety of solids at all pressures above an absolute pressure of 0.1 Torr due to the good reproducibility of the wall adsorption, provided the isochronal nature of the adsorption process is recognized.
An Investigation of Heat Flow in Unidirectional Solidification of Vacuum-Cast Airfoils
Authors: Monteith B. G. , Piwonka T. S.
Published: July 2002

In order to better understand the thermal events occurring during the unidirectional solidification of Mar M-200 (proprietary alloy of Martin-Marietta, Inc.) alloy turbine blades, an analytical thermal model was developed which permitted simulation of the solidification process. A representative turbine blade was divided into isothermal nodes, and an electrical analog thermal model was constructed and solved using a digital computer. The technique was verified by comparing calculated and measured external mold surface temperatures during solidification. The analytical thermal model showed that thermal gradients in the liquid–solid growth zone are high near the chill, and decrease as the distance from the chill increases. Temperature profiles were converted into solidification profiles from experimental data which showed the percent solid as a function of temperature in the solidification zone. The curves permit a qualitative explanation of the occasional occurrence of segregation and hot cracking in this alloy, and indicate that precautions must be taken in the solidification process to avoid these phenomena.
Improved Method of the Resolution for Quadrupole Mass Spectrometers
Authors: Sakai T. , Ino Y. , Sakimura M.
Published: July 2002

Resolution mode of quadrupole mass filter is well represented by mass scan line on stability diagram. All mass peaks just disappear on the cutoff scan line which passes through the origin and to the apex of the stability diagram. When a scan line is shifted downward by a small amount parallel to the cutoff scan line, it can be expected theoretically that all mass peaks give a constant peak width independent of mass. Adjustment of resolution is carried out based on this theory. As the peak height is proportional to the peak width, a mass spectrum obtained experimentally with this mode of operation gives a constant pattern coefficient in adjusting the resolution.
Computer Control of Van de Graaff Accelerator Vacuum Systems
Authors: Woods R. , Jennings H. K. , Collins M. W. , Harder D. G. , McMillan D. E.
Published: July 2002

The seven main diffusion-pump vacuum systems on our Tandem Van de Graaff accelerator are controlled by a Honeywell H610 digital control computer. Each system has a local control panel with a hardwire protection shutdown system but no recovery capability. Control is normally left to the computer, which, through analog and digital inputs, senses trouble and secures the system according to the difficulty. The computer then recovers the systems completely or to the level of the difficulty. The computer operators’ console includes control buttons to enable/disable the securing function or the recovery function for a system. An alarm typewriter informs the operator of any action that the computer has taken, including which inputs are out of limit. An Adage AGT-10 display system shows each vacuum system and the status of each input. This takes the place of the usual remote indication panel.
Electrode and Substrate Considerations in Discontinuous Thin Film Resistance
Authors: Dryer J. , Gore D. , Speiser R.
Published: July 2002

In discontinuous films the difference between the electrostatic energy of a charge at rest on an island and a charge which has just been placed on an island by tunneling must be accounted for in a phenomonological explanation of the conduction mechanism. This energy difference can exceed the static electrostatic energy which is normally assumed to give rise to the thermally activated resistance experimentally observed in such films. It is also shown that the initial charge creation in discontinuous films may be more likely to arise from carrier injection at the electrodes than from island ionization in the middle of the film because of a lowered energy barrier height and an enhanced electric field in the vicinity of the electrodes. Under suitable conditions electrode injection will show a barrier energy lowering proportional to the square root of the applied field as is experimentally observed. Experimental results which may be indicative of electrode injection are presented.
Extreme ultraviolet carrier-frequency shearing interferometry of a lithographic four-mirror optical system
Authors: Naulleau Patrick P. , Goldberg Kenneth A. , Bokor Jeffrey
Published: July 2002

The phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to address the problem of at-wavelength metrology of extreme ultraviolet (EUV) optical systems. Although extremely accurate, the fact that the PS/PDI is limited to use with coherent EUV sources, such as undulator radiation, is a drawback for its widespread use. An alternative to the PS/PDI, with relaxed coherence requirements, is lateral shearing interferometry (LSI). Here we describe various LSI implementations and demonstrate the use of a cross-grating, carrier-frequency configuration to characterize a large-field 4×-reduction EUV lithography optic. The results obtained are directly compared with PS/PDI measurements.
Method for calculation of gas flow in the whole pressure regime through ducts of any length
Authors: Livesey R. G.
Published: July 2002

Useful approaches to the calculation of gas flows in the molecular–continuum transition region have been presented by a number of authors. However they are restricted in application to particular conditions, such as long ducts or orifices with a large pressure difference, or have some theoretical limitation. A particular problem derives from the assumption of isentropic flow through an orifice. While a close approximation for high speed flows, the assumption leads to significant errors in nonchoked viscous flow. These errors then occur in transitional flow models which combine free molecular and viscous flows, particularly when these are applied to short ducts. In this article a simple model which overcomes some of the limitations of current models and enables calculation for all conditions of long or short ducts and large or small pressure differences through the whole pressure regime is presented. The results are found to agree well with published experimental data and with theoretically derived data for long tubes.
Influence of substrate bias on the microstructure and internal stress in Cu films deposited by filtered cathodic vacuum arc
Authors: Cheng Y. H. , Tay B. K. , Lau S. P. , Shi X. , Tan H. S.
Published: July 2002

Copper films were deposited by a novel off-plane double bend filtered cathodic vacuum arc technique at ambient temperatures. X-ray diffraction (XRD) and atomic force microscopy (AFM) are used to characterize the film’s structure and surface morphology. The substrate bending method was used to study the internal stress. The influence of substrate bias on the surface morphology, grain size, crystalline structure, and internal stress was systematically studied. XRD results indicate that all the deposited Cu films exhibit face-centered cubic-type (fcc) crystallite structure with (111) preferred orientation growth. The increase of substrate bias results in the improvement of (111) preferred orientation. At the substrate bias of 0 V, the deposited films are composed of nano-sized columnar grains, which contribute to the tensile stress in the deposited films. The grain size and surface roughness increase gradually with increasing substrate bias up to −200 V. Further increase of substrate bias results in the drastic decrease of grain size and surface roughness due to self-sputtering. The internal stress in the deposited films is also strongly dependent on the substrate bias. The increase of substrate bias results in the decrease of tensile stress in the deposited films, and the transition of tensile to compressive stress at the substrate bias of −300 V. Further increase of substrate bias results in the linear increase of compressive stress in the deposited films. At the substrate bias of −300 V, dense and stress-free Cu films can be obtained.
Critical dimension guarantee for the next generation photomasks with critical dimension scanning electron microscope
Authors: Iwamatsu Takayuki , Hiruta Koji , Morimoto Hiroaki , Ataka Masashi , Nitta Jun
Published: July 2002

Advanced critical dimension (CD)-scanning electron microscope was evaluated as a photomask CD guarantee tool. Measurement repeatability was 2.3 nm (3σ) for each measurement, and reproducibility (range of average value in five days) was 3 nm. The contamination effect was evaluated by measuring isolated Cr line and isolated space patterns. The contamination effect on measured CD value was estimated as 0.02 nm/scan (reticle scale) from the result of 500 scans at the same position. This result was quite different from the results of the aerial image of approximately 0.3 nm/scan (reticle scale) evaluated by MSM100 (λ=248 nm) and exposure results (λ=193 nm). The difference between these two evaluation results was probably due to the transmittance reduction of the electron beam scanning area of quartz substrate. This consideration was supported by atomic force microscopy and simulation results. There was no degradation on measurement repeatability and no image shift caused from the charging effect for the most severe condition (0.4 μm Cr isolated dot, global coverage of 20%, and local coverage of 0.05% under the magnification of 88 000×).
Chemistry and electrical properties of surfaces of GaN and GaN/AlGaN heterostructures
Authors: Hashizume Tamotsu , Ootomo Shinya , Oyama Susumu , Konishi Masanobu , Hasegawa Hideki
Published: July 2002

Chemical and electrical properties of the surfaces of GaN and GaN/AlGaN heterostructures were systematically investigated by x-ray photoelectron spectroscopy (XPS), capacitance–voltage, and current–voltage measurements. From in situ XPS study, relatively smaller band bending of 0.6 eV was seen at the GaN (2×2) surface grown by radio frequency-assisted molecular beam epitaxy on the metalorganic vapor phase epitaxy GaN template. After exposing the sample surface to air, strong band bending took place at the surface. The surface treatment in NH4OH solution and N2 plasma was found to reduce the surface Fermi level pinning. Surface passivation process of GaN utilizing SiNx film by electron-cyclotron-resonance assisted plasma chemical vapor deposition (ECR–CVD) achieved low interface state density, 2×1011cm−2 eV−1. No pronounced stress remained at the SiNx/GaN interface, which was confirmed by Raman spectroscopy. The present NH4OH/ECR–N2 plasma treatment was also found to be effective in realizing well-ordered and nearly oxide-free surface of a GaN/AlGaN heterostructure. The subsequent passivation process using the ECR–CVD SiNx film enhanced the drain current in the gateless GaN/AlGaN high electron mobility transistor. A surface passivation process utilizing an ultrathin Al-oxide layer reduced leakage current and improved gate controllability of two-dimensional electron gas in the Schottky gate contact fabricated on the GaN/AlGaN heterostructures.
Microscopic structure of spontaneously formed islands on the GaAs(001)-(2×4) reconstructed surface
Authors: LaBella V. P. , Ding Z. , Bullock D. W. , Emery C. , Thibado P. M.
Published: July 2002

Islands are found to spontaneously form on the GaAs(001)-(2×4) reconstructed surface. The geometry and size of these islands are examined as a function of substrate temperature and island coverage. Both the islands’ coverage and size increase with increasing temperature. The islands are elongated rectangles and the aspect ratio is independent of temperature. A relationship between the islands’ aspect ratio and the step formation energies is presented. These results are also related to recent theoretical work on equilibrium island geometry.
Growth of germanium quantum dots on different dielectric substrates by chemical-vapor deposition
Authors: Kim Dong-Won , Kim Young-Hee , Chen Xiangdong , Lee Choong-Ho , Song Seoung-Chel , Prins Freek E. , Kwong Dim-Lee , Banerjee Sanjay
Published: July 2002

The growth of Ge quantum dots on various nitrided oxides has been achieved by ultra-high-vacuum chemical-vapor deposition with GeH4 gas at temperatures between 550 and 650 °C. The characteristics of the Ge dots were investigated using atomic-force microscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy in order to find the mechanism of the Ge dot formation. On N2O-annealed nitrided oxide films, we obtained Ge dots with height and diameters of 3.2 and 11 nm, respectively. No Ge dots were formed on surfaces of other dielectric substrates at 550 °C. From our experimental results, we suggest that the surface of N2O-annealed nitrided oxide contains a large amount of defects such as dangling bonds, which act as Ge nucleation sites. This is further confirmed by studying the growth kinetics and the influence of in situ annealing of the samples.
In situ monitoring of molecular-beam-epitaxy grown Hg1−xCdxTe by Fourier transform infrared spectroscopy
Authors: Badano G. , Daraselia M. , Sivananthan S.
Published: July 2002

One of the major drawbacks associated with in situ pyrometry is the fact that the sample emissivity is unknown. Real-time in situ measurements of HgCdTe growth temperature are made even more difficult by the change in emissivity that takes place during deposition. In this article, a Fourier transform infrared spectrometer was utilized to measure simultaneously the sample emission and its emissivity, thereby making it possible to determine the sample temperature at any growth stage. Two different methods of temperature determination from the spectral radiance were compared, and applied to the in situ monitoring of the growth of a HgCdTe/CdTe(211)B/Si(211) heterostructure. A computer simulation of the measuring procedure showed that the technique is very sensitive to signal reduction resulting from beam misalignment and/or imperfect calibration of the detector spectral response.
Potential distribution and field intensity for a hyperboloidal probe in a uniform field
Authors: Passian A. , Wig A. , Meriaudeau F. , Ferrell T. L.
Published: July 2002

The scalar potential and electric field distributions in the gap region of a probe-substrate system are calculated. The probe, modeled as a dielectric medium with the geometry of a one sheeted hyperboloid of revolution, is located above a charged substrate surface which is modeled as a dielectric half space interfaced with a uniform surface charge density. The potential and field distributions are then calculated as functions of the dielectric constant of the medium filling the space between the tip and the surface, and as functions of the hyperboloidal shape parameter. Comparisons are made with the case of a dielectric spheroidal body. The analytical results attained can be used to study other related quantities such as energy density or Coulomb interaction in the neighborhood of the nanometer sized apex region without resorting to numerical methods. This investigation allows for tip shape related field variation in various dielectric media to be studied. Application of this approach to modeling probe tip-sample (probe tip-substrate) interaction in scanning probe microscopy, or to modeling dielectric breakdown processes, are examples of the potential use of the method.
Deep level centers in silicon introduced by high-energy He irradiation and subsequent annealing
Authors: Nakano Yoshitaka , Ishiko Masayasu , Tadano Hiroshi
Published: July 2002

Deep level transient spectroscopy measurements have been performed to investigate deep levels in epitaxially grown n-type Si layers introduced by high-energy He2+ irradiation and subsequent annealing at various temperatures. Three deep levels (D1: 0.46–0.49 eV; D2: 0.52 eV; D3: 0.64 eV) are found to be generated near the mid-gap level after post-annealing at temperatures of 300–450 °C. The generation behavior of these deep levels is in reasonable agreement with the annihilation of divacancies. Therefore these energy levels are associated with high-order vacancy clusters which are formed by combination of some vacancies during the anneal-out of divacancies, and are probably attributed to various dangling-bonds like electronic states presenting on the internal surfaces of the clusters.
Microfabrication of silicon tip structures for multiple-probe scanning tunneling microscopy
Authors: Bale M. , Palmer R. E.
Published: July 2002

We report the fabrication of arrays of silicon tips suitable for multiple-tip scanning tunneling microscopy applications (STM). We have produced silicon tips by reactive ion etching using only photoresist masks, removing the need for the extra processing required to produce oxide masks. These tips have been oxide-sharpened to reduce their radius of curvature to less than 10 nm. Metallic coating of the tips makes them suitable for STM measurements, by the addition of an appropriate metallic layer. The use of thick resist layers makes it possible to protect the tips during further processing such that they have been integrated on 20 μm mesa structures. Further patterning of thick resists over these structures enables individual contact to be made to the tips via lift-off. We have also produced single silicon tips suitable for STM by selecting individual tips from arrays. Images of grating structures shows these tips have well defined tip shape compared with STM tips produced by conventional methods, while atomic resolution STM measurements have also been obtained.
Ion-graphy implanter with stencil mask
Authors: Nishihashi T. , Kashimoto K. , Fujiyama J. , Sakurada Y. , Shibata T. , Suguro K. , Sugihara K. , Okumura K. , Gotou T. , Saji S. , Tsunoda M.
Published: July 2002

Recently, the demand for semiconductor devices has been greatest in the consumer market for such products as video games, cellular phones, and DVD players. In order to satisfy these demands, semiconductor manufacturers are now designing new production lines, such as mini fabs, to decrease the processing time for various types of semiconductor devices. Over the past few decades, the availability and throughput of ion implanters have improved dramatically. However, the implantation process itself has, except for a slight change, remained basically the same. A recent article (Ref. 1) describes the basic concept of an ion-implantation process that does not require use of a photoresist mask. This article reports the experimental data and the basic functions of a type of ion implanter currently being developed. This implanter implants ions in one chip at a time through a stencil mask without the use of a photoresist mask. This ion-implantation technology, called stencil mask ion implantation technology, and the ion implanter, called a stencil mask lithographic ion implanter, will be exceptionally suitable for future semiconductor manufacturing processes.