bluuebunny/crossref_metadata_2025 huggingface dataset:
Scaling of Performance for Varying Density Ratio Coolants on an Airfoil With Strong Curvature and Pressure Gradient Effects
Authors: Ethridge Marcia I. , Cutbirth J. Michael , Bogard David G.
Published: July 2002

An experimental study was conducted to investigate the film cooling performance on the suction side of a first-stage turbine vane. Tests were conducted on a nine times scale vane model at density ratios of DR=1.1 and 1.6 over a range of blowing conditions, 0.2⩽M⩽1.5 and 0.05⩽I⩽1.2. Two different mainstream turbulence intensity levels, Tu∞=0.5 and 20 percent, were also investigated. The row of coolant holes studied was located in a position of both strong curvature and strong favorable pressure gradient. In addition, its performance was isolated by blocking the leading edge showerhead coolant holes. Adiabatic effectiveness measurements were made using an infrared camera to map the surface temperature distribution. The results indicate that film cooling performance was greatly enhanced over holes with a similar 50 deg injection angle on a flat plate. Overall, adiabatic effectiveness scaled with mass flux ratio for low blowing conditions and with momentum flux ratio for high blowing conditions. However, for M<0.5, there was a higher rate of decay for the low density ratio data. High mainstream turbulence had little effect at low blowing ratios, but degraded performance at higher blowing ratios.
Performance of the Directly-Irradiated Annular Pressurized Receiver (DIAPR) Operating at 20 Bar and 1,200°C
Authors: Kribus A. , Doron P. , Rubin R. , Reuven R. , Taragan E. , Duchan S. , Karni J.
Published: July 2002

The Directly Irradiated Annular Pressurized Receiver (DIAPR) is a volumetric (directly-irradiated) windowed cavity receiver, designed for operation at a pressure of 10–30 bar, exit gas temperature of up to 1,300°C, and aperture radiation flux of up to 10 MW/m2. This paper presents test results obtained under various irradiation conditions and flow rates. Inlet aperture flux was up to 5 MW/m2; exit air temperatures of up to 1,200°C were obtained, while operating at pressures of 17–20 bar. Estimated receiver efficiency in these tests was in the range of 0.7–0.9. The absorber and window temperatures were 200-400°C below the permitted maximum, indicating that higher air exit temperatures are possible.
Analysis and Testing of Indentation Fracture Behavior of Piezoelectric Ceramics Under an Electric Field
Authors: Shindo Y. , Oka M. , Horiguchi K.
Published: July 2002

To estimate the electric fracture toughness, indentation fracture (IF) tests were made on piezoelectric materials under combined mechanical and electrical loads. Lead zirconate titanate (PZT) ceramics from a commercial source were used. A three-dimensional finite element analysis was also employed to calculate the energy release rate and stress intensity factor. Surface cracks produced by indentation with Vickers indented were modeled as two point-force loaded half-penny-shaped cracks.
Numerical Analysis of Impinging Air Flow and Heat Transfer in Plate-Fin Type Heat Sinks
Authors: Sasao Keiji , Honma Mitsuru , Nishihara Atsuo , Atarashi Takayuki
Published: July 2002

A numerical method for simulating impinging air flow and heat transfer in plate-fin type heat sinks has been developed. In this method, all the fins of an individual heat sink and the air between them are replaced with a single, uniform element having an appropriate flow resistance and thermal conductivity. With this element, fine calculation meshes adapted to the shape of the actual heat sink are not needed, so the size of the calculation mesh is much smaller than that of conventional methods.
Passive Control of Rotating Stall in a Parallel-Wall Vaned Diffuser by J-Grooves
Authors: Saha Sankar L. , Kurokawa Junichi , Matsui Jun , Imamura Hiroshi
Published: July 2002

In order to control and suppress instabilities caused by swirl flow, the authors have proposed a very simple passive method utilizing shallow grooves mounted on a casing wall or diffuser wall(s) parallel to the pressure gradient. The groove is termed a “J-groove.” The method is theoretically analyzed and experimentally proved capable of suppressing rotating stall in a vaneless diffuser. The performance curve instability is characterized by the positive slope of the head-capacity curve of a mixed flow pump for the entire flow range. In continuation, this work is aimed at realizing experimentally the effect of J-grooves on suppressing rotating stall in the vaned diffuser of a centrifugal turbomachine. Thirteen double curvature vanes with various radial positions, various setting angles, and J-grooves of different dimensions are tested in a parallel wall vaned diffuser with a semi-open radial impeller with and without J-grooves. The results show that J-grooves can also suppress rotating stall in the vaned diffuser for the entire flow range.
In Process Control of Strain in a Stretch Forming Process
Authors: Hardt D. E. , Norfleet W. A. , Valentin V. M. , Parris A.
Published: July 2002

The process of stretch forming is used extensively in the aerospace industry to form large sheet panels of mild curvature. This has traditionally been a low precision process requiring considerable hand-working at assembly. However, recent demands for faster, less wasteful production have placed new demands on the accuracy and consistency (quality) of this process. In this paper the various modes of control for this process are examined, from both an analytical and experimental point of view. It is shown clearly that the process is least sensitive to material and machine property variations if controlled to a target level of strain in specific areas of the sheet. This method is compared with the conventional methods of controlling either the force applied to the sheet during stretching or the displacement of the stretch jaws. A series of both lab scale and full production experiments concur with the analytical findings, demonstrating reduced process variation if strain feedback is used. Lab experiments and analysis indicate that far greater reductions are possible if a more precise form of strain control is used. In production trials forming wing leading edges, a manually implemented strain control showed a shape variation reduction of 50 percent over normal factory practice using force control.
Computational Analysis of Coupled Blood-Wall Arterial LDL Transport
Authors: Stangeby D. Kim , Ethier C. Ross
Published: July 2002

The transport of macromolecules, such as low density lipoproteins (LDLs), across the artery wall and their accumulation in the wall is a key step in atherogenesis. Our objective was to model fluid flow within both the lumen and wall of a constricted, axisymmetric tube simulating a stenosed artery, and to then use this flow pattern to study LDL mass transport from the blood to the artery wall. Coupled analysis of lumenal blood flow and transmural fluid flow was achieved through the solution of Brinkman’s model, which is an extension of the Navier-Stokes equations for porous media. This coupled approach offers advantages over traditional analyses of this problem, which have used possibly unrealistic boundary conditions at the blood-wall interface; instead, we prescribe a more natural pressure boundary condition at the adventitial vasa vasorum, and allow variations in wall permeability due to the occurrence of plaque. Numerical complications due to the convection dominated mass transport process (low LDL diffusivity) are handled by the streamline upwind/Petrov-Galerkin (SUPG) finite element method. This new fluid-plus-porous-wall method was implemented for conditions typical of LDL transport in a stenosed artery with a 75 percent area reduction (Peclet number=2×108). The results show an elevated LDL concentration at the downstream side of the stenosis. For the higher Darcian wall permeability thought to occur in regions containing atheromatous lesions, this leads to an increased transendothelial LDL flux downstream of the stenosis. Increased transmural filtration in such regions, when coupled with a concentration-dependent endothelial permeability to LDL, could be an important contributor to LDL infiltration into the arterial wall. Experimental work is needed to confirm these results.
Finite Element Modeling of Edge Trimming Fiber Reinforced Plastics
Authors: Arola D. , Sultan M. B. , Ramulu M.
Published: July 2002

A finite element model was developed to simulate chip formation in the edge trimming of unidirectional Fiber Reinforced Plastics (FRPs) with orthogonal cutting tools. Fiber orientations (θ) within the range of 0 deg⩽θ⩽90 deg were considered and the cutting tool was modeled as both a rigid and deformable body in independent simulations. The principal and thrust force history resulting from numerical simulations for orthogonal cutting were compared to those obtained from edge trimming of unidirectional Graphite/Epoxy (Gr/Ep) using polycrystalline diamond tools. It was found that principal cutting forces obtained from the finite element model with both rigid and deformable body tools compared well with experimental results. Although the cutting forces increased with increasing fiber orientation, the tool rake angle had limited influence on cutting forces for all orientations other than θ=0 deg and 90 deg. However, the tool geometry did affect the degree of subsurface damage resulting from interlaminar shear failure as well as the cutting tool stress distribution. The finite element model for chip formation provides a means for optimizing tool geometry over the total range in fiber orientations in terms of the cutting forces, degree of subsurface trimming damage, and the cutting tool stresses.
Solar-Hybrid Gas Turbine-based Power Tower Systems (REFOS)*
Authors: Buck Reiner , Bra¨uning Thomas , Denk Thorsten , Pfa¨nder Markus , Schwarzbo¨zl Peter , Tellez Felix
Published: July 2002

Solar hybrid power plants have a significant potential for cost reduction when the solar energy is introduced into a gas turbine system. The introduction into gas turbine systems could be realized with pressurized volumetric air receivers heating the compressed air of the gas turbine before it enters the combustor. A receiver module, consisting of a secondary concentrator and a volumetric receiver unit, was tested at the Plataforma Solar de Almerı´a, Spain. Air exit temperatures up to 815°C and power levels of 410 kW were achieved. Total solar test time summed up to 400 hours. Receiver efficiencies were in the range of 70%. A new secondary concentrator with improved efficiency was designed and built. Based on an inexpensive manufacturing technology, the secondary concentrator geometry was optimized to reduce the optical losses. Performance tests with this new secondary concentrator and a cold-water calorimeter proved the expected increase in efficiency of about 10%. Maximum operation power was 450 kW at the exit aperture. The dependency of performance on the incidence-angle showed good agreement with the predictions, as well as the results of a special photographic measurement campaign. Several configurations of solar-hybrid gas turbine cycles in the low to medium power range are examined for performance and costs. The results confirm the promising potential of this technology to reach competitiveness in certain power markets; a comparison between a 30 MW solar-hybrid combined cycle plant and an ISCCS power plant are presented. Future developments for system improvement and cost reduction are discussed.
Design of Robust Vibration Controller for a Smart Panel Using Finite
Element Model
Authors: Chang W. , Gopinathan Senthil V. , Varadan V. V. , Varadan V. K.
Published: July 2002

This paper presents a model reduction method and uncertainty modeling for the design of a low-order H∞ robust controller for suppression of smart panel vibration. A smart panel with collocated piezoceramic actuators and sensors is modeled using solid, transition, and shell finite elements, and then the size of the model is reduced in the state space domain. A robust controller is designed not only to minimize the panel vibration excited by applied uniform acoustic pressure, but also to be reliable in real world applications. This paper introduces the idea of Modal Hankel Singular values (MHSV) to reduce the finite element model to a low-order state space model with minimum model reduction error. MHSV measures balanced controllability and observability of each resonance mode to deselect insignificant resonance modes. State space modeling of realistic control conditions are formulated in terms of uncertainty variables. These uncertainty variables include uncertainty in actuators and sensors performances, uncertainty in the knowledge of resonance frequencies of the structure, damping ratio, static stiffness, unmodeled high resonance vibration modes, etc. The simplified model and the uncertainty model are combined as an integrated state space model, and then implemented in the H∞ control theory for controller parameterization. The low-order robust controller is easy to implement in an analog circuit to provide a low cost solution in a variety of applications where cost may be a limiting factor.
Kinematic and Kinetostatic Synthesis of Planar Coupled Serial Chain Mechanisms
Authors: Krovi Venkat , Ananthasuresh G. K. , Kumar Vijay
Published: July 2002

Single Degree-of-freedom Coupled Serial Chain (SDCSC) mechanisms form a novel class of modular and compact mechanisms with a single degree-of-freedom, suitable for a number of manipulation tasks. Such SDCSC mechanisms take advantage of the hardware constraints between the articulations of a serial-chain linkage, created using gear-trains or belt/pulley drives, to guide the end-effector motions and forces. In this paper, we examine the dimensional synthesis of such SDCSC mechanisms to perform desired planar manipulation tasks, taking into account task specifications on both end-effector motions and forces. Our solution approach combines precision point synthesis with optimization to realize optimal mechanisms, which satisfy the design specifications exactly at the selected precision points and approximate them in the least-squares sense elsewhere along a specified trajectory. The designed mechanisms can guide a rigid body through several positions while supporting arbitrarily specified external loads. Furthermore, torsional springs are added at the joints to reduce the overall actuation requirements and to enhance the task performance. Examples from the kinematic and the kinetostatic synthesis of planar SDCSC mechanisms are presented to highlight the benefits.
Enhancing the Performance Evaluation and Process Design of a Commercial-Grade Solid Oxide Fuel Cell via Exergy Concepts
Authors: Haynes Comas , Wepfer William J.
Published: July 2002

Fuel cell technology is a promising means of energy conversion. As the technology matures, process design and analysis are gaining importance. The conventional measures of fuel cell performance (i.e., gross real and voltage efficiencies) are limited indices-of- merit. Contemporary second law concepts (availability/exergy, irreversibility, exergetic efficiency) have been used to enhance fuel cell evaluation. A previously modeled solid oxide fuel cell has been analyzed using both conventional measures and the contemporary thermodynamic measures. Various cell irreversibilities were quantified, and their impact on cell inefficiency was better understood. Exergetic efficiency is more comprehensive than the conventional indices-of- performance. This parameter includes thermal irreversibilities, considers the value of effluent exergy, and has a consistent formulation. Usage of exergetic efficiency led to process design discoveries different from the trends observed in conjunction with the conventional efficiency measures. The decision variables analyzed were operating pressure, air stoichiometric number (inverse equivalence ratio), operating voltage and fuel utilization.
A Reconciliation of Local and Global Models for Bone Remodeling Through Optimization Theory
Authors: Subbarayan G. , Bartel D. L.
Published: July 2002

Remodeling rules with either a global or a local mathematical form have been proposed for load-bearing bones in the literature. In the local models, the bone architecture (shape, density) is related to the strains/energies sensed at any point in the bone, while in the global models, a criterion believed to be applicable to the whole bone is used. In the present paper, a local remodeling rule with a strain “error” form is derived as the necessary condition for the optimum of a global remodeling criterion, suggesting that many of the local error-driven remodeling rules may have corresponding global optimization-based criteria. The global criterion proposed in the present study is a trade-off between the cost of metabolic growth and use, mathematically represented by the mass, and the cost of failure, mathematically represented by the total strain energy. The proposed global criterion is shown to be related to the optimality criteria methods of structural optimization by the equivalence of the model solution and the fully stressed solution for statically determinate structures. In related work, the global criterion is applied to simulate the strength recovery in bones with screw holes left behind after removal of fracture fixation plates. The results predicted by the model are shown to be in good agreement with experimental results, leading to the conclusion that load-bearing bones are structures with optimal shape and property for their function. [S0148-0731(00)00601-4]
Emission Control Through Cu-Exchanged X-Zeolite Catalysts: Experimental Studies and Theoretical Modeling
Authors: Bhattacharyya S. , Das R. K.
Published: July 2002

Catalysts based on X-zeolite have been developed by exchanging its Na+ ion with Copper ions and its effectiveness in reducing NOx in an actual SI engine exhaust has been tested. Unlike noble metals, the doped X-zeolite catalysts, studied here, exhibit significant NOx reduction for a wide λ range and exhibit a slow rate of decrease with increase in λ ratio. Back pressure developed across the catalyst bed was found to be well-affordable and power loss due to back pressure is only minimal. During 30 hours of testing of the catalyst, no significant deactivation was observed. Additionally a mathematical model has been developed to predict the performance of the catalyst and to validate that against experimental results. Results predicted by the mathematical model agree well with the experimental results and absolute average deviation of experimental conversion efficiency is found to be less than 5 percent of the predicted value. [S0742-4795(00)01601-X]
Fuel Gas Cleanup Parameters in Air-Blown IGCC
Authors: Newby Richard A. , Yang Wen-Ching , Bannister Ronald L.
Published: July 2002

Fuel gas cleanup processing significantly influences overall performance and cost of IGCC power generation. The raw fuel gas properties (heating value, sulfur content, alkali content, ammonia content, “tar” content, particulate content) and the fuel gas cleanup requirements (environmental and turbine protection) are key process parameters. Several IGCC power plant configurations and fuel gas cleanup technologies are being demonstrated or are under development. In this evaluation, air-blown, fluidized-bed gasification combined-cycle power plant thermal performance is estimated as a function of fuel type (coal and biomass fuels), extent of sulfur removal required, and the sulfur removal technique. Desulfurization in the fluid bed gasifier is combined with external hot fuel gas desulfurization, or, alternatively with conventional cold fuel gas desulfurization. The power plant simulations are built around the Siemens Westinghouse 501F combustion turbine in this evaluation. [S0742-4795(00)00502-0]
Experimental Measurements of Actively Controlled Bearing Damping With an Electrorheological Fluid
Authors: Vance John M. , Ying Daniel
Published: July 2002

Selection criteria and design evaluations of several types of bearing dampers with active control for application to aircraft engines were described in a companion paper. A disk type electrorheological (ER) damper was chosen for further study and testing. The results of the tests and the final conclusions of the study are described in this paper. Experimental results including stiffness and damping coefficients are presented for the ER bearing damper with two types of ER fluid, 350 CS and 10 CS (centistokes) viscosity. The vibration attenuation performance of the ER damper was measured on a rotordynamic test rig in the form of free vibration decay, rotor orbits, and runup unbalance responses. The results show that the ER fluid with lower viscosity has the better characteristics for rotordynamic applications. It was found that ER fluids produce both Coulomb and viscous damping. If only the damping is considered, the Coulomb type is less desirable, but with active control it can also achieve control of rotor stiffness. A feedback control system was developed and applied to the ER damper with the objective of improving the overall rotordynamic performance of the rotor bearing system, considering both vibration amplitudes and dynamic bearing forces. A “bang–bang” (on and off) simple control logic was found to work better in practice than more sophisticated schemes. The measured runup response of the rotor-bearing system with this control approximated the desired vibration response curves fairly well. The tests highlighted some of the practical considerations that would be important for aircraft engine applications, such as the ER fluid limitations, the electrical power supply requirements, the electrical insulation requirements, the nonlinear relationship between the voltage and the damping, and the relative benefits of active control. It is concluded that active control of bearing damping is probably not a practical improvement over the passive squeeze film dampers currently used in most aircraft gas turbine engines. [S0742-4795(00)01202-3]
Flying Height Response to Mechanical Shock During Operation of a Magnetic Hard Disk Drive
Authors: Harrison Joshua C. , Mundt Michael D.
Published: July 2002

A complementary experimental and numerical study of fly height response to applied mechanical shock during disk drive operation is reported in this paper. Numerical predictions of dynamic fly height response at the slider close point, due to measured drive component response to externally applied mechanical shocks, are plotted versus time and versus input shock, and are compared with the disk glide avalanche height. HDI contact pressure, as predicted using the Greenwood-Williamson contact model, is also plotted versus amplitude and sense of the externally applied mechanical shocks. The effects of measured disk motion on fly height response to operational shock are described, and are shown to be significant. It is concluded that design changes that modify disk response can be a efficacious path for the disk drive designer to improve fly height response to operational shock. [S0742-4787(00)03301-4]
X-ray Photoelectron Study of TiN
Authors: Chourasia A. R. , Chopra D. R.
Published: July 2002

Thin films of TiN were deposited from TiCl4, NH3, and H2 in a lamp heated single wafer “warm wall” low pressure chemical vapor deposition reactor. The deposition was carried out on a TiSi2/Si sample. The thickness of the films is estimated to be 100 nm. The films were analyzed by x-ray diffraction, Rutherford backscattering spectroscopy, and x-ray photoelectron spectroscopy. The XPS data in Ti 2p, N 1s, Ti L3M23V, and Ti L3M23M23 regions are presented.
CdTe(110) by XPS
Authors: Poirier D. M. , Weaver J. H.
Published: July 2002

XPS spectra were recorded for a CdTe single crystal cleaved in situ to expose the (110) surface (Accession #00103). For comparison, spectra were also recorded for a surface cleaved in air and exposed to air for 70 min (Accession #00104). The electronic record includes the 3d and 4d regions for Cd and Te. The MNN Auger region and valence bands are also included.
Analysis of a Poly(propylene)(PP) Homopolymer by XPS
Authors: Lannon John M. , Meng Qingru
Published: July 2002

We report x-ray photoemission spectra for a poly(propylene)(PP) homopolymer. 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 photoelectron peak.
Effects of oxygen gettering and target mode change in the formation process of reactively sputtered Pt oxide thin films
Authors: Abe Y. , Kawamura M. , Sasaki K.
Published: July 2002

Pt, and Pt oxide thin films were prepared by reactive sputtering of Pt in Ar and O2 gas mixtures, and the influence of O2 flow ratio on their formation process was studied. O2 gettering by Pt atoms was confirmed from plasma emission spectra and pressure change in a sputtering chamber before and after striking the discharge. At O2 flow ratios below 20%, almost all of the introduced O2 molecules were gettered and Pt films were deposited. At O2 flow ratios above 20%, the number of supplied O2 molecules overcame the gettering effect and the O2 partial pressure began to increase, and Pt oxide films were deposited. The deposition rate of Pt oxide films decreased at O2 flow ratios above 30%, because the target surface state changed from a metallic target mode to an oxide target mode.
Epitaxial ferromagnetic metal/GaAs(100) heterostructures
Authors: Chen L. C. , Dong J. W. , Schultz B. D. , Palmstro/m C. J. , Berezovsky J. , Isakovic A. , Crowell P. A. , Tabat N.
Published: July 2002

Ferromagnetic bcc-FexCo1−x(100) films have been successfully grown on GaAs(100) and ScyEr1−yAs(100) by molecular beam epitaxy. X-ray diffraction combined with reflection high energy electron diffraction and low energy electron diffraction patterns revealed the epitaxial orientation of bcc-FexCo1−x(100)〈010〉‖GaAs(100)〈010〉 and bcc-FexCo1−x(100) 〈010〉‖ScyEr1−yAs(100)〈010〉. Rutherford backscattering channeling minimum yields, χmin∼3%, suggest epitaxial films of high crystalline quality. Vibrating sample magnetometry measurements show in-plane uniaxial anisotropy and fourfold in-plane anisotropy for FexCo1−x grown on GaAs(100) and ScyEr1−yAs(100), respectively. The difference in magnetic anisotropy is interpreted as arising from the ScyEr1−yAs interlayer altering the surface symmetry from twofold symmetry for GaAs(100) to fourfold symmetry. Misoriented substrates were also used to increase the step density in the [011] direction, which induced an additional uniaxial anisotropy with a [011] easy axis and a [011̄] hard axis. This step structure symmetry-induced magnetic anisotropy generated a split field ∼50 Oe in the hard axis for bcc-FexCo1−x(100) grown on ScyEr1−yAs(100) surfaces.
Kinetics and crystal orientation dependence in high aspect ratio silicon dry etching
Authors: Blauw M. A. , Zijlstra T. , Bakker R. A. , van der Drift E.
Published: July 2002

A quantitative study of dry etch behavior in deep silicon trenches in high density plasmas (electron cyclotron resonance, inductively coupled plasma) at low temperatures (160–210 K) is presented. The quantitative approach implies etch behavior being studied in relation to the relevant particle fluxes (atomic F and O and ions) as measured by in situ diagnostics. Two etch modes are observed. In one mode faceting shows up as due to crystallographic orientation preference, i.e., Si〈111〉 being etched slower than Si〈100〉. In the other mode the normal anisotropic ion-induced behavior is observed. Controlled switch from one mode to the other is studied under influence of process parameters like pressure, ion energy, and substrate temperature. The second part of this study deals with aspect ratio dependent etching (ARDE). Both vertical and horizontal trenches have been taken into account as to distinguish between radical and ion-induced effects. The flux of radical species into the deep trench is governed by Knudsen transport, with a reaction probability of atomic fluorine of about 0.5. As a consequence depletion of the fluorine content at the bottom is the main reason for ARDE. With the bottleneck identified, the plasma process has been readily tuned to the aspect ratio independent etch regime. This regime coincides with the crystallographic preference mode where surface reaction kinetics form the rate limiting step. Detailed surface analysis studies by x-ray photoelectron spectroscopy, in situ ellipsometry, and transmission electron microscopy have been used to characterize the surface reaction process.
Plasma Anodization of Metals and Semiconductors
Authors: O’Hanlon John F.
Published: July 2002

This paper presents a review and analysis of the literature on plasma anodization in the negative glow of the dc discharge. New data by the author on anodic film contamination by reactive cathode sputtering are presented. It is shown that certain anomalous data in the literature may be explained as being caused by cathode sputtering and sputter etching of the anodic film. Some applications of anodization are discussed.
Structure of Evaporated PtSi on Si
Authors: Walker G. A. , Wnuk R. C. , Woods J. E.
Published: July 2002

Due to the many conflicting reports on the structure of evaporated Pt on Si substrates, a study of the system was made with special emphasis on possible experimental errors. It is shown that for annealing temperatures up to 700 °C the only phases present are Pt and PtSi for evaporated and sputtered Pt.
Electronic Structure of Adsorbed Atoms and Molecules
Authors: Grimley T. B.
Published: July 2002

The coupling of an atom (or molecule) to a metal converts originally discrete levels which fall in the energy bands of the metal to virtual levels (resonances) with fractional occupancies determined by their positions with respect to the Fermi level. The calculation of these resonances and occupancies is a major problem in the theory of adsorption: It is discussed here in terms of a model Hamiltonian of Anderson's type. The concept of a surface molecule, i.e., a local molecular structure whose molecular orbitals correspond to the resonances, arises with transition metal adsorbents. This concept is used for Na and S on Ni(100) in the pyramidal Ni4X local geometry. The experimental binding energy is used to predict the electronic structure and resonances for Na, and the experimental resonance to predict the structure and binding energy of S.
Surface Passivation of Semiconductors
Authors: Nicollian E. H.
Published: July 2002

A review is given of the work on the passivation of silicon surfaces with thermally grown silicon dioxide films. This work has led to the high performance and stability of bipolar transistors and insulated gate field-effect transistors used in integrated circuits. The main emphasis is on the processing methods and measurements which have led to the optimization of the passivating properties of silicon dioxide films by controlling fixed charge, interface states, and drift.
Sorption of Nitrogen at Low Pressures by Titanium
Authors: Nagasaka Michio , Yamashina Toshiro
Published: July 2002

The sorption kinetics of nitrogen at pressures of 1×10−5 to 1×10−3 Torr on titanium foil was studied ill the range 600 °–800 °C, by using an ultrahigh vacuum microbalance. In the similar way to oxygen, the rate law of nitrogen sorption was separable into two types, i.e., the linear rate law in the initial period and the parabolic rate law in the latter period. The linear rate law was obeyed for shorter times as the nitrogen pressure and the reaction temperature increased. In the initial linear part, the sorption rate was proportional to the nitrogen pressure at each temperature, which showed the linear sorption to be controlled by the rate of arrival. The sticking probability and pumping speed per unit area (cm2) for nitrogen were constant with change of nitrogen pressure, e.g., at 800 °C, 0.0045 for sticking probability and 0.098 (liter sec−1) for pumping speed. The transtion in the sorption rate laws and critical pressure of nitrogen for the transition are discussed on the basis of a diffusion theory.
The EPR Observation of O2− Chemisorbed on a Metallic Silver Surface
Authors: Clarkson R. B. , Cirillo A. C.
Published: July 2002

The adsorption of oxygen on metallic silver surfaces has been studied using an EPR technique. The interaction of O2 with these surfaces at room temperature results in the rapid formation of a radical species having gxx = 2.0042, gyy = 2.0115, and gzz = 2.034. The stability of the radical to prolonged outgassing and thermal desorption is studied, and reactivity with moderate pressures of CO (∼20 Torr) at room temperature has been observed. Ageing of the silver surface under cyclic outgassing, adsorption, outgassing, and reduction with H2 at 110°C has been noted. On the basis of g values and molecular parameters λ/δ and λ/Δ calculated from theory, we postulate the radical to be the superoxide, O2−, in an adsorption site with a component of electric field perpendicular to the internuclear axis of the molecular ion.
Amorphous Memories and Bistable Switches
Authors: Adler David , Moss Simon C.
Published: July 2002

The two types of switching phenomena that characterize thin films of covalent amorphous solids are described in detail. Several mechanisms that can account for these phenomena are presented and analyzed in view of recent experimental data. Two applications of bistable switching to computer memories are discussed—the electronically alterable Read-Mostly Memory (RMM) and the mass optical memory (MOM).
Theory of Chemisorption
Authors: Schrieffer J. R.
Published: July 2002

The basic concepts in the theory of chemisorption of atoms on metals will be reviewed. The sharp atomic levels of the free atom are broadened into virtual levels by electron tunneling between the atom and the solid. For rapid tunneling, correlation effects on the adatom are weak and a self-consistent field molecular orbital approach is appropriate. The adatom density of states can vary from a Lorentzian level to states split above and below the valence band of the solid, corresponding to the bonding and antibonding orbitals of a surface complex formed between the adatom and its surroundings. The Anderson model treats only Coulomb interactions on the adatom, while the CNDO method of quantum chemistry has been recently employed to include Coulomb interactions in the solid. For strong intra-atomic Coulomb interaction on the adatom, correlation effects are important and the localized magnetic moment on the adatom as predicted by the unrestricted Hartree–Fock approximation is quenched. Correlations have been treated by extended valence bond methods, multiple scattering theory, and configuration mixing techniques. Semiquantitative agreement with experiment is obtained in a number of systems.
Simultaneous SIMS, ElD, and Flash-Filament Investigations of the Interaction of Gases with a Tungsten Surface
Authors: Benninghoven A. , Loebach E. , Treitz N.
Published: July 2002

A UHV system, containing a heatable (up to >2600 °K) W ribbon target, a Finkelstein ion source (Ar+, 2 keV) with magnetic mass separator, an electron source (300 eV), a quadrupole secondary ion mass filter with a counting channel electron multiplier and a quadrupole gas analyzer, is used for the study of the adsorption and desorption of H2, O2, and CO on W by simultaneous, i.e., fast interchanging “static” SIMS [secondary (ion induced) ion mass spectroscopy] and EID [electron induced (ion) desorption] and by flash-filament measurements. Different binding states can be distinguished. The emission cross sections of the adsorbate-specific ions by ion bombardment depend far less upon the gas exposure (and therefore upon the coverage) than those corresponding to electron bombardment.
Adsorption and Flash Decomposition of Ethylene on Tungsten Single-Crystal Faces
Authors: Barford B. D. , Rye R. R.
Published: July 2002

The interaction of ethylene with the (100), (110), (111), and (211) faces of tungsten was studied by means of thermal desorption spectroscopy. Ethylene decomposition yields a single broad hydrogen peak at ∼300 K on W(111), two poorly resolved hydrogen peaks at ∼300 and ∼400 K on W(211), hydrogen peaks at ∼300 and ∼450 K with an area ratio of 1:2 on W(110), and a single decomposition peak at ∼275 K on W(100). Assuming di-σ-bonded ethylene, these results are consistently interpreted in terms of the limitations on ethylene adsorption imposed by the structure of the surface; and the stability of adsorbed ethylene is interpreted from consideration of the structure of the resulting ethylene-surface complex. The absence of two equal peaks on all except the (211) face eliminates the possibility of a two-step decomposition suggested by previous work.
Interaction of Atomic and Molecular Hydrogen Beams with Surfaces at Very Low Temperatures
Authors: Marenco G. , Schutte A. , Scoles G. , Tommasini F.
Published: July 2002

The transfer of energy from beams of atomic and molecular hydrogen to various surfaces (H2O, Ne, Ar) at liquid helium temperatures and UHV conditions has been investigated by means of a microcalorimetric technique. Evidence is given of the recombination of atomic hydrogen on H2O and Ar surfaces. Seeding the surfaces with up to one monolayer of H2 is found to increase the energy transfer by an order of magnitude.
Orbital Energy Spectra of CO and Hg Adsorbed on Ni(100)
Authors: Becker G. E. , Hagstrum H. D.
Published: July 2002

Orbital energy spectra of CO and Hg adsorbed individually and co-adsorbed on Ni (100) have been determined by ion-neutralization spectroscopy (INS) and ultraviolet photoelectron spectroscopy (UPS) at 45 ° incidence. In the case of CO, two orbitals derived from the 5σ and 1π orbitals of free CO are observed 7.8 and 11.1 eV below the Fermi level, respectively, by UPS, with INS revealing only the 7.8-eV orbital since 11.1 eV is outside its accessible range. In the case of Hg, UPS and INS both reveal orbital peaks 7.8 and 9.7 eV below EF, identified, respectively, with the 5d5/2 and 5d3/2 states of Hg. The Hg(6s) orbital is not in evidence in the energy spectra obtained by either method. We have determined energy shifts of the observed orbitals with respect to their positions in the free molecule or atom and have discussed these shifts in terms of the effects of bonding and electric charge shifts in the metal-adsorbate complexes. This work permits a fairly detailed intercomparison of INS and UPS. It also bears on the problem of peak shifts due to interference between bulk and surface photoemission and possible perturbation by the probing ion in the case of ion neutralization.
Substrate Effects in the Theory of Negative Differential Resistance
Authors: Hayes T. M. , Thornburg D. D.
Published: July 2002

Current-controlled negative differential resistance under the constraint of uniform current flow is shown to result from the incorporation of realistic boundary conditions in solving for the steady-state electrical and thermal behavior of a Joule heated semiconducting thin film mounted on a substrate. The thermal conductance of the substrate, which is a necessary feature of the experimental situation, is shown to influence significantly the measured properties of the film-substrate combination. An analytic expression is induced for the voltage at the onset of negative differential resistance (the turnover voltage), and is demonstrated to be an approximate solution of the model for all values of substrate thermal conductance. The predictions of this model are shown to be consistent with experimental measurements of the threshold voltage as a function of film thickness and of ambient temperature.
Glow Discharge Optical Spectroscopy for Monitoring Sputter Deposited Film Thickness
Authors: Greene J. E. , Sequeda-Osorio F.
Published: July 2002

Glow discharge optical spectroscopy was used as a technique for monitoring the rate of sputtering and the rate of film deposition. It was determined that within the pressure and voltage range of these experiments the product of the electroluminescent emission intensity of a given sputtered target species in the discharge and the time of sputtering is linearly proportional to both the change in mass of the target and the final thickness of the deposited film. In the case of compound targets, the emission intensity from either constituent can be monitored. The emission signal was shown to be generated primarily in a narrow region directly in front of the target.
Development of the large field extreme ultraviolet lithography camera
Authors: Watanabe T. , Kinoshita H. , Nii H. , Li Y. , Hamamoto K. , Oshino T. , Sugisaki K. , Murakami K. , Irie S. , Shirayone S. , Gomei Y. , Okazaki S.
Published: July 2002

We have developed a three-aspherical mirror system which is capable of replicating in a large exposure area (30 mm×28 mm). This system consists of the synchronized scanning mechanism of a mask and a wafer, the alignment optics between a mask and a wafer, the focus detector of a wafer position, and the load-lock chamber for exchanging wafers. The aspherical mirrors have a figure error of 0.58 nm and a surface roughness of 0.3 nm. To obtain a high efficiency mirror, a couple of mirrors were coated with a graded d spacing Mo/Si multilayer. The peak reflectivity is 65% at the wavelength of 13.5 nm. The wavelength matching of each mirror spans 0.45 nm. The mirrors were aligned with a Fizeau-type phase shift interferometer, and a final wave front error of less than 3 nm was achieved. Exposure experiments carried out at NewSUBARU synchrotron facility and a diffraction limited resolution of 56 nm was obtained in an exposure-field size of 10 mm×2 mm in static exposure. Furthermore, fine patterns in an area of 10 mm×5.2 mm were obtained using the mask and wafer synchronized scanning stages. These results revealed that this system can be applied to fabricate large scale integrated devices.
In situ real-time studies of nickel silicide phase formation
Authors: Tinani M. , Mueller A. , Gao Y. , Irene E. A. , Hu Y. Z. , Tay S. P.
Published: July 2002

The formation of NiSi films on Si was studied using Rutherford backscattering spectrometry, atomic force microscopy, and ellipsometry. NiSi is an attractive candidate for use as a gate contact material due to its low metal-like resistivity and large processing window (350–750 °C). Three phases, Ni2Si, NiSi, and NiSi2, were identified in this temperature range, and their optical databases in the 2–4 eV photon range were established, and used to model real-time ellipsometry data. It is shown that real-time ellipsometry can be used to monitor and follow the formation of the various Ni–Si phases. We have also observed the onset of agglomeration of the silicide for longer time anneals at temperatures of 500–700 °C, which is much lower than 1000 °C where agglomeration has been reported to occur.
Charging of dust particles on surfaces
Authors: Sternovsky Zoltán , Horányi Mihály , Robertson Scott
Published: July 2002

Experimental investigations have been made of the charge on dust particles resting upon a metal surface in vacuum. The surface is agitated so that the particles drop through a small hole and a Faraday cup beneath measures the charge on each particle. The surfaces are metals (Hf, Zr, V, W, Co, Ni, Pt, and stainless steel) and the dust grains are both metallic conductors (Zn, V, and stainless steel) and insulators (silica and alumina) in the size range of 50–200 μm. The contact charge is consistent with a model based upon the grain capacitance and the effective contact potential between the grain and surface. An electric field above the surface induces an additional charge on metallic grains consistent with Gauss’s law. The induced charge on insulating grains increases with repeated contact. UV irradiation may increase or decrease the charge depending upon the relative importance of photoemission and photoconductivity.
Deep reactive ion etching of silicon carbide
Authors: Tanaka S. , Rajanna K. , Abe T. , Esashi M.
Published: July 2002

In this article, we describe more than 100-μm-deep reactive ion etching (RIE) of silicon carbide (SiC) in oxygen-added sulfur hexafluoride (SF6) plasma. We used a homemade magnetically enhanced, inductively coupled plasma reactive ion etcher (ME-ICP-RIE) and electroplated nickel masks. First, 5 h etching experiments using etching gases with 0%, 5%, 10% and 20% oxygen were performed by supplying rf power of 150 and 130 W to an ICP antenna and a sample stage, respectively. They demonstrated a maximum etch rate of 0.45 μm/min and residue-free etching in the case of 5% oxygen addition. Observation of the cross sections of etched samples using a scanning electron microscope confirmed a microloading effect, which is reduction of the etched depth with a decrease in the mask opening width. Next, a 7 h etching experiment using an etching gas with 5% oxygen was performed by increasing the rf power to the sample stage to 150 W. This yielded an etched depth of 216 μm.
Encapsulation materials for SrRuO3 to avoid H2 anneal-induced decomposition
Authors: Lin Jun , Tsunoda Kohji , Eguchi Kazuhiro , Heida Katsuhiko , Matsunaga Daisuke
Published: July 2002

Perovskite SrRuO3 (SRO) films are promising for use as electrodes for (Ba,Sr)TiO3 and Pb(Zr,Ti)O3 film capacitors. However, SrRuO3 decomposes during the forming gas (3% H2+balanced N2) anneal at temperatures as low as 200 °C. An adequate encapsulation layer for SrRuO3 is necessary in order to avoid the H2 anneal-induced decomposition of SrRuO3. Al2O3,SiO2,Si3N4, and Si3N4/SiO2 are studied as encapsulation layers for SRO, and it is confirmed that Al2O3 and Si3N4/SiO2 coatings on SRO can effectively prevent its decomposition.
Ballistic electron emission microscopy of “on-surface” self-assembled InAs dots and wetting layers
Authors: Rakoczy D. , Strasser G. , Smoliner J.
Published: July 2002

In this work ballistic electron emission microscopy and spectroscopy (BEEM/BEES) are employed to investigate electronic properties of self-assembled InAs quantum dots on a GaAs substrate. BEEM spectra are presented for positions on the dots on the one hand and for “off-dot” regions, i.e., on the wetting layer, on the other hand. The local barrier height variations on the dots and on the InAs wetting layer are studied systematically and compared with data from the literature obtained on homogeneous InAs layers of various thickness. In addition, the temperature dependence of the InAs–GaAs barrier height is investigated. At low temperatures, evidence of higher conduction bands both in the GaAs and in the InAs dots is found.
Electrical characteristics of ultrathin ZrO2 prepared by wet oxidation of an ultrathin Zr-metal layer
Authors: Jeon Sanghun , Hwang Hyunsang
Published: July 2002

The electrical and reliability characteristics of ultrathin ZrO2 prepared by thermal oxidation of a sputter deposited Zr-metal layer in a H2O and a D2O ambient were investigated. For the case of lightly oxidized zirconium oxide, an anomalous high capacitance and dispersion characteristics were observed, which can be explained by space charge polarizations of metallic zirconium in zirconium oxide. Based on x-ray photoelectron spectroscopy analysis, the lightly oxidized ZrO2 samples show metallic Zr peaks. By optimizing the wet oxidation conditions, excellent characteristics of ZrO2, such as a capacitance equivalent oxide thickness of 11 Å, negligible dispersion characteristics and leakage current density less than 10 mA/cm2 at 1 V below the flatband voltage were obtained. Compared with the H2O oxidation of Zr, D2O wet oxidation improves the reliability characteristics of ZrO2.