bluuebunny/crossref_metadata_2025 huggingface dataset:
Alternative Derivation of Marguerre’s Displacement Solution in Plane Isotropic Elasticity
Authors: Gao X.-L.
Published: July 2002

An alternative derivation of Marguerre’s solution for displacements in plane isotropic elasticity is provided. It is shown that the present approach, which is based on Green’s theorem and parallel to the Airy stress function approach, is straightforward. Also, the current derivation establishes the completeness of the Marguerre solution. [S0021-8936(00)00302-0]
Initiation of SHS Flame Induced by Another SHS Flame—Evaluation of the Ignition Energy
Authors: Makino Atsushi
Published: July 2002

Relevant to the self-propagating high-temperature synthesis (SHS) process, an analytical study has been made to investigate dependence of its flame initiation on system parameters, such as operating and physicochemical parameters, in order to obtain ignition energy. Use has been made of the heterogeneous theory which can satisfactorily account for the premixed mode of the bulk flame propagation supported by the nonpremixed mode of particle consumption. It is found that the ignition energy strongly depends on not only heat loss, but also particle size of the higher melting-point metal, which has not been captured in the homogeneous theory.
Laser-Induced Fluorescence Measurements in Venturi-Cascaded Propane Gas Jet Flames
Authors: Qubbaj Ala R. , Gollahalli S. R.
Published: July 2002

Venturi-cascading is a technique to control pollutant emissions from diffusion flames by modifying air infusion and fuel-air mixing rates through changing the flow dynamics in the combustion zone with a set of venturis surrounding the flame. A propane jet diffusion flame at a burner-exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The venturi-cascading technique resulted in a decrease of 33 percent in NO emission index along with a 24-percent decrease in soot emission from the flame, compared to the baseline condition (same flame without venturis). In order to understand the mechanism behind these results, laser-induced fluorescence (LIF) spectroscopy was employed to study the concentration field of the radicals (OH, CH, and CN) in the baseline and venturi-cascaded flames. The LIF measurements, in the near-burner region of the venturi-cascaded flame, indicated an average decrease of 18, 24 and 12 percent in the concentrations of OH, CH, and CN radicals, respectively, from their baseline values. However, in the midflame region, a 40-percent average increase in OH from its baseline value was observed. In this region, CH or CN radicals were not detected. The OH radical concentration in the downstream locations was mostly affected by soot rather than by temperature.
A Mathematical Optimization Approach to a Subset of Location Tolerance Transfer Problems
Authors: Xi Min , Lehtihet E. Amine , Cavalier Tom M.
Published: July 2002

The tolerancing scheme attached to the print of a mechanical part is engineered to guarantee the functional aptitude of a part and its proper interaction with other parts in the assembly. At the manufacturing stage, the design datum reference system(s) (DRF) specified by the design tolerancing scheme may not constitute the most technologically or economically desirable or even feasible manufacturing datum reference frame(s). When substitute manufacturing datum reference frame(s) are selected, a tolerance transfer problem must be solved. This paper presents a mathematical optimization approach and solution to a subset of location tolerance transfer problems with DRF mobility of two, and three degrees of freedom.
Numerical Analysis of Two-Phase Pipe Flow of Liquid Helium Using Multi-Fluid Model
Authors: Ishimoto Jun , Oike Mamoru , Kamijo Kenjiro
Published: July 2002

The two-dimensional characteristics of the vapor-liquid two-phase flow of liquid helium in a pipe are numerically investigated to realize the further development and high performance of new cryogenic engineering applications. First, the governing equations of the two-phase flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model are presented and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the two-phase flow of liquid helium is shown in detail, and it is also found that the phase transition of the normal fluid to the superfluid and the generation of superfluid counterflow against normal fluid flow are conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. According to these theoretical results, the fundamental characteristics of the cryogenic two-phase flow are predicted. The numerical results obtained should contribute to the realization of advanced cryogenic industrial applications.
A Microplasticity Analysis of Micro-Cutting Force Variation in Ultra-Precision Diamond Turning
Authors: Lee W. B. , Cheung C. F. , To S.
Published: July 2002

This paper describes a microplasticity model for analyzing the variation of cutting force in ultra-precision diamond turning. The model takes into account the effect of material anisotropy due to the changing crystallographic orientation of workpieces being cut. A spectrum analysis technique is deployed to extract the features of the cutting force patterns. The model has been verified through a series of cutting experiments conducted on aluminum single crystals with different crystallographic cutting planes. The results indicate that the model can predict well the patterns of the cutting force variation. It is also found that there exists a fundamental cyclic frequency of variation of cutting force per revolution of the workpiece. Such a frequency is shown to be closely related to the crystallographic orientation of the materials being cut. The successful development of the microplasticity model provides a quantitative means for explaining periodic fluctuation of micro-cutting force in diamond turning of crystalline materials.
Impact of Low Temperatures on Solder Joint Failures
Authors: Mirman Boris
Published: July 2002

An experiment with solder joints of thin plastic packages, cycled between −10° and 110°C, has demonstrated that the majority of solder joint failures occurred at the low temperatures. In this experiment, the low temperatures caused high peeling stresses in the heel area of solder joints and, as usual, relatively low plastic shear strain (as compared with these strains at high temperatures). This fact suggests that the impact of solder peeling stresses on the solder failure is noticeably higher than is anticipated by applying the commonly used failure criteria.
Platinum Sulfide by XPS
Authors: Dembowski J. , Marosi L. , Essig M.
Published: July 2002

It is known from crystallographic investigations that there are two distinct Pt–S modifications, PtS and PtS2 [see R. Collins, R. Kaner, P. Russo, A. Wold, and D. Avignant, Inorg. Chem. 18, 727 (1979); A. Finley, D. Schleich, J. Ackerman, S. Soled, and A. Wold, Mater. Res. Bull. 9, 1655 (1974); S. Soled, A. Wold, and O. Gorochov, ibid. 11, 927 (1976); L. Thomasson, Z. Phys. Chem. Bd. 2, 349; and L. Thomasson, ibid. 4, 277]. They are not commercially available in high grade purity. In the present study the production of pure PtS reference materials and its characterization by x-ray photoelectron spectroscopy is presented. The PtS2 investigation is shown in a second submission. The PtS samples were produced by annealing stoichiometric mixtures of elemental platinum (DEGUSSA, grade 99.9%) and sulfur (Riedle de Haen, grade 99.5%). Both powders were blended homogeneously and pressed into pellets. The pellets were annealed for 3 weeks in an evacuated quartz tube (800 °C, 10-4 Pa) and cooled in defined steps to room temperature over 8 days. The materials were investigated by x-ray diffraction. The diffraction spectrum of PtS agrees with JCPDS 18-972. This demonstrates the crystalline purity of the reference material. The samples were also characterized by transmission electron microscopy (TEM). The PtS sample consists of isometric particles with sizes between 1 and 3 μm. Selected area diffraction (SAD) and energy dispersive x-ray spectroscopy (EDXS) give no indication of impurities in the samples.
Characterization of Slightly Hydrated Ni(OH)2 by XPS
Authors: Mansour A. N. , Melendres C. A.
Published: July 2002

We report x-ray photoemission spectra (XPS) of slightly hydrated Ni(OH)2. XPS spectra were measured with the Physical Electronics Model 5400 x-ray photoelectron spectrometer using unmonochromatized Mg Kα x rays at two pass energy settings corresponding to analyzer energy resolutions of 1.34 and 0.54 eV. We present the survey spectrum (binding energy range of 0–1100 eV) measured at an analyzer energy resolution of 1.34 eV. Multiplexes of the C, O, and Ni photoemission lines, valence band region, as well as Ni LVV Auger lines were measured at an analzyer energy resolution of 0.54 eV. The slightly hydrated Ni(OH)2 sample was prepared by reacting stoichiometric Ni(NO3)2 with KOH in CO2 free H2O at 35 °C.
Interfacial silicon oxide formation during oxygen annealing of Ta2O5 thin films on Si: Oxygen isotope labeling
Authors: Park H. J. , Mao A. , Kwong D.-L. , White J. M.
Published: July 2002

Ta 2 O 5−x films prepared on Si(100) by chemical vapor deposition and annealed in oxygen gas, both natural abundance and isotope labeled [16O2(77%)+18O2(23%)], were analyzed by in situ x-ray photoelectron spectroscopy and ex situ time-of-flight secondary ion mass spectroscopy (TOFSIMS). Before annealing at 800 °C, the film was oxygen deficient, i.e., Ta2O5−x, and there was a very small amount of interfacial SiOy. During annealing in O2, additional Si was oxidized and the Ta2O5−x approached stoichiometric composition. Based on TOFSIMS depth profiles of O18-labeled ions, Si at the interface is oxidized during O2 annealing mainly by transfer of O from Ta to Si, not by migration of gas phase O2 through Ta2O5−x to the unoxidized Si. The atomic oxygen from the dissociative reaction of gas phase O2 is transported through Ta2O5−x by a vacancy mechanism and replenishes the loss of O from Ta2O5−x to Si.
Interaction of Hydrogen with the Surface of Type 304 Stainless Steel
Authors: Beavis L. C.
Published: July 2002

Experiments were performed to determine if oxygen is available on Type 304 stainless steel in a state which could cause oxidation of active metals during hydrogen exposure. A bakeable ultrahigh vacuum system was used in making measurements of hydrogen interaction with stainless steel. Mass spectra were taken throughout the experiments. The experiments indicated that stainless steel reacts in a hydrogen atmosphere to form water. This effect is greater at high than at low temperature. The stainless steel can be passivated by treating the surface with oxygen during heating to high temperature.
LEED/Auger Spectroscopy Study of the Adsorption of Alkali Metals on Mo(110)
Authors: Thomas S. , Haas T. W.
Published: July 2002

LEED and Auger electron spectroscopy have been used to study the adsorption of Na, K, Rb, and Cs on a Mo(110) surface. Alkali ions were deposited (at room temperature; pressure <1×10−10 Torr) from zeolite ion sources which enabled the absolute coverage to be measured. Peak-peak heights of Cs-47, K-251, Rb-56 and 75 eV Auger peaks and of Mo Auger lines were monitored as a function of coverage. Quantitative estimates of Na adsorption could not be made using AES owing to the low Auger yield of Na. LEED patterns showed a hexagonal close packed arrangment of the alkalis on Mo(110).
Depolarization Field and Stability Considerations in Thin Ferroelectric Films
Authors: Batra I. P. , Wurfel P. , Silverman B. D.
Published: July 2002

It is shown that the polarization in a thin ferroelectric film is always incompletely compensated. The associated depolarization field significantly modifies the phase stability of a ferroelectric film of sufficiently small thickness. For a slightly conducting ferroeletric film sandwiched between metallic electrodes, the polarization and transition temperature are depressed below the bulk values but the order of the phase transition remains unchanged. With semiconducting electrodes, even the order of the phase transition is modified for a thin ferroelectric film. A critical point exponent is calculated in each case within the framework of the Landau Theory. The results are compared and contrasted with the findings for other cooperative phenomena.
Lithographically defined nano and micro sensors using “float coating” of resist and electron beam lithography
Authors: Zhou H. , Chong B. K. , Stopford P. , Mills G. , Midha A. , Donaldson L. , Weaver J. M. R.
Published: July 2002

The combination of direct-write electron beam lithography and bulk silicon micromachining is shown to give great flexibility in the definition of nanosensors. The technique is based on a novel method for coating the specimen with electron beam resist allowing high resolution features to be defined on the top of micromachined asperities or in 200 μm deep etched holes. Examples of sensors fabricated using this method include advanced magnetic nanosensors such as Hall probe sensors, electromagnetic coils or combined coils and Hall probes. Near-field optical atomic force microscope probes are demonstrated with reproducible aperture size down to 20×35 nm. Near-field optical probes using a shaped aperture to allow the passage of linearly polarized light are shown to offer optical throughputs up to 2% with modest collection optics. The use of a near-field optical probe having a crossed slit form is demonstrated to give high throughput and resolution in two dimensions for the imaging of fluorescent objects. Near-field optical probes with multiple apertures of closely matched size are demonstrated.
Hydrogen outgasing from titanium-modified layers with various surface treatments
Authors: Mizuno Y. , Tanaka A. , Takahiro K. , Takano T. , Yamauchi Y. , Okada T. , Yamaguchi S. , Homma T.
Published: July 2002

In an extremely high-vacuum (XHV) system, hydrogen outgassing is the most important factor to obtain vacuum pressure below 1.0×10−10 Pa. Titanium is an interesting material for applications in XHV construction. This work will demonstrate a clear correlation between hydrogen outgassing and surface structures of pure titanium in vacuum technology. The titanium surfaces were prepared following treatments such as chemical, electrical, buffing, and mechanochemical polishing. Characterization of oxide layers has been carried out using Auger electron spectroscopy and angle-resolved x-ray photoelectron spectroscopy, and a cross section of the modified layer has been observed by using an optical microscope. The hydrogen distribution in a surface region was measured by elastic recoil detection analysis. The oxide thicknesses were from 20 to 50 nm, although the finished titanium surfaces were covered with TiO2 for chemical polish, electrical polish, buffing polish (BP), and mechanochemical polish (MCP); also, TiO was formed under the top layer for MCP. The thick modified layers (about 1 μm) on the surfaces were made in BP and MCP processing, and the modified layers had extremely high-density distributions of hydrogen (H/Ti of about 1 to 2). Thermal desorption spectroscopy measurements indicated that the desorption behavior of hydrogen was not strongly dependent on the thickness of the oxide layer, and the hydrogen outgassing rates from the surfaces of samples were less than 4.0×10−7 Pa m s−1 at room temperature. We report the results of the relation between the quantities of desorbed hydrogen gas and the structure of modified layers on titanium polished surfaces.
Galvanic corrosion behavior of GaAs in acid solutions
Authors: Weng G. S. , Luo J. L. , Ivey D. G.
Published: July 2002

The galvanic corrosion behavior of both n-GaAs and p-GaAs coupled to Au, at room temperature, have been examined using the zero resistance ammeter technique (direct measurement), as well as the method of superposition of polarization curves (indirect measurement). Galvanic current densities, which can be converted to corrosion rates, were measured as a function of the cathode-to-anode (C /A) area ratio. In addition, corrosion rates were predicted from superposition of cathodic polarization curves for Au and anodic polarization curves for GaAs. With some exceptions, the current densities increased with increasing C/A ratio, and the agreement between the indirect and direct measurements was quite good. This indicates that the former can be used to determine semiconductor corrosion rates. Sample surfaces, examined using transmission electron microscopy, showed an As-rich surface layer, with a thickness dependent on dopant type and polarization potential.
Low-Pressure Sputtered Germanium Films
Authors: Wolsky S. P. , Piwkowski T. R. , Wallis G.
Published: July 2002

Germanium films were sputtered onto fused quartz and self-substrates in a low-pressure thermionically supported discharge. Reflection electron diffraction and x-ray examination showed that over comparable temperature ranges the orientation of sputtered germanium films on fused quartz differed from that of evaporated films. Epitaxy was obesrved on self-substrates at 150 °C. Electrical characteristics of evaporated and sputtered films were strikingly similar despite wide variation in substrate material and temperature and in deposition rates.
UPS, ESCA, and Auger spectroscopy study of vacuum deposited silver halide films
Authors: Von Bacho P. S. , Ceasar G. P. , Saltsburg H. M. , Baetzold R. C.
Published: July 2002

Thin silver halide films were vacuum deposited on various metallic substrates to avoid the sample charging effects previously observed with these same films on mica supports. The UPS spectra of a given silver halide on different substrates were not identical to one another even though all of the samples had been prepared simultaneously in the same apparatus. Using ESCA and Auger techniques, it was found that cations of the substrate were present throughout the films. This results from reaction of the silver halide or free halogen (from decomposed halide) with the substrate. Rapid diffusion then results in a distribution of these impurity cations throughout the deposited layer extending to the free surface. When the impurity cation does not reach the free surface, its presence in the layer near the surface perturbs the electronic structure and thus the UPS spectra is altered; both the ESCA and Auger spectra however appear to originate from uncontaminated silver halides.
Elementary theory of heterojunctions
Authors: Harrison Walter A.
Published: July 2002

An LCAO theory of heterojunction band-edge discontinuities is formulated and tested for approximate self-consistency. It leads to a table of valence-band maxima for all tetrahedral semiconductors; discontinuities can be obtained from the table directly by subtraction. The discrepancies with the current scattered data do not appear significantly larger than the uncertainty in those data, a few tenths of electron volts. A pseudopotential theory of such discontinuities is also formulated, based upon self-consistent atomic pseudopotentials. This leads to valence-band maxima reasonably consistent with the LCAO theory, except for junctions between materials of significantly different bond length. It also suggests that the Frensley–Kroemer scheme does produce self-consistency for systems of matching lattice constant, but produces incorrect trends with mismatch in lattice constant. The goal in any case is taken to be a table of valence-band maxima. LCAO values seem a better standard than photoelectric thresholds, though a comparison of the two indicates them to be roughly consistent for treating junctions if both sides are homopolar or if both sides are polar.
Quantitative analysis of AlxGa1−xAs by Auger electron spectroscopy
Authors: Arthur J. R. , LePore J. J.
Published: July 2002

Thirty-five epitaxial films of AlxGa1−xAs grown by LPE on GaAs substrates with 0.0<x<0.95 were examined by Auger electron spectroscopy. By averaging results obtained using the ratios of peak-to-peak heights for all three components obtained at both high and low energies and for several measurements, compositions reproducible to ±3% or better were obtained. While preferential sputtering of one component could affect the absolute accuracy, our results suggest that errors from this source were less than 2% at worst. The film compositions obtained in this manner were in excellent agreement with thermodynamic calculations based on growth conditions.
Flow rate effects in plasma etching
Authors: Chapman B. N. , Minkiewicz V. J.
Published: July 2002

Experimental data concerning the dependence of plasma etching rates on the flow rate of the etching gas have been analyzed in terms of the consumption of the gas, and a simple model is proposed to explain the observed dependence. The decrease in etch rates at low flow rates is shown to be due to an inadequate supply of the etching gas; at high flow rates, etching is retarded because active species are pumped away.
Surface blistering of molybdenum irradiated with 75–350-keV helium ions
Authors: Fahlstrom C. R. , Sinha M. K.
Published: July 2002

Polycrystalline molybedenum samples have been irradiated at room temperature with helium ions of energy from 75 to 350 keV in high vacuum. Irradiation parameters such as ion energy, total dose, and dose rate were varied and surfaces were examined in a scanning electron microscope. The average blister diameter increases with increasing ion energy and the blister number density increases with increasing total dose of helium. The critical dose for blister formation is independent of the beam flux in the range of 6.7×1013 to 2×1015 ions cm−2 s−1. However, the average blister diameter changes with the change of flux. When the molybdenum surface is successively bombarded with varying ion energies, both the diameter and the number density of the blisters is significantly reduced as compared to monoenergetic helium bombardment.
Chemical reaction and charge redistribution at metal–semiconductor interfaces
Authors: Brillson L. J.
Published: July 2002

Interface compound formation and metal-induced surface states are observed at representative metal–semiconductor interfaces. These phenomena are associated with microscopic dipoles at the intimate contacts which account for the macroscopic Schottky barrier heights. The barrier heights exhibit a correlation with chemical reactivity and display a pronounced transition between reactive and unreactive interfaces. Thus, local charge redistribution rather than any intrinsic surface states of the semiconductor determine Schottky barrier formation at the metal–semiconductor interfaces.
Apparatus for simultaneous measurement of mass change, optical transmittance, and reflectance of thin films
Authors: Prince E. T. , Helbig H. F. , Czanderna A. W.
Published: July 2002

An apparatus consisting of a vacuum ultramicrobalance and optical equipment for measuring transmittance and front surface reflectance of thin films from 400 to 800 nm is described. Thin films formed on substrates by thermal or reactive evaporation can be heated in reactive gases of different compositions and pressures. As the chemical composition of the film changes, the optical changes in the film can be monitored simultaneously using computerized data collection, control, and analysis.
Radio-frequency-sputtered tetragonal barium titanate films on silicon
Authors: Panitz Janda K. G. , Hu Cheng-Cheng
Published: July 2002

Polycrystalline films of BaTiO3 displaying electron diffraction patterns identical to that of bulk tetragonal BaTiO3 and ferroelectric properties are regularly observed for BaTiO3 films thicker than 1000 Å rf-sputtered deposited at 5 Å/min onto silicon substrates at temperatures above 500°C. A severe interaction problem between the silicon substrate and the BaTiO3 contaminates the film, but can be avoided by growing a passivation barrier of SiO2 on the silicon substrate before depositing BaTiO3. Despite a coefficient of thermal expansion mismatch between BaTiO3 and silicon, thin films with good electrical insulation properties can be obtained by reducing the substrate temperature during the deposition by 7.0°C/min to a final substrate temperature of 200°C.
Sputter etching in an argon–oxygen plasma and its implications to device fabrication
Authors: Krongelb S. , Romankiw L. T.
Published: July 2002

The presence of oxygen in a sputter etching (SPE) plasma can have both beneficial and detrimental effects. An argon–oxygen plasma can create conditions which are particularly favorable for the fabrication of magnetic bubble devices. The effects of oxygen in a conventional diode rf SPE system on etch rates and on the magnetic properties of unmasked permalloy (NiFe) films are discussed. In particular, it is shown that the etch rate of NiFe relative to Au is suppressed and that the increase in coercivity of the NiFe caused by SPE is minimized when oxygen is introduced in the plasma. Application of these findings is made to bubble domain device fabrication. Conversely, the presence of unwanted oxygen can have a detrimental effect on pattern profiles when an organic resist mask is used and can generally lead to irreproducible etch rates. Ways to minimize these undesired effects are discussed.
Sputter etching studies of Fe–Ni and Fe–Pd films
Authors: Lee Wen-Yaung
Published: July 2002

Sputtering studies of Fe1−x–Nix (x=0.05 to 0.95) films were made and compared with those of Fe1−x–Pdx (x=0.06 to 0.7) films. Plots of steady-state AES and ESCA signal intensity ratios versus bulk composition ratios for the Fe–Pd system gave two straight lines intersecting near x=0.38, where a bcc to fcc phase transition occurs. Similar plots for the Fe–Ni system showed a single straight line across the whole composition range although a similar phase transition occurs at x∠0.4. Values of slopes obtained from normalized AES and ESCA data were similar for the Fe–Ni but differed by a factor of 3 for the Fe–Pd system. Since ESCA has a larger sampling depth than AES for both alloy systems, these differences are attributed to the presence of a significant altered layer on the sputtered Fe–Pd surface, which is absent on sputtered surfaces of Fe–Ni films. This result is compared to the different diffusion rates of these two systems: (1) Depth profiles for air-exposed and deliberately oxidized (160°–250 °C) films indicated that diffusion is much faster in the Fe–Ni than the Fe–Pd systems, and (2) direct measurement of interdiffusion in Fe–Ni and Fe–Pd couples demonstrated much faster interdiffusion in the Fe–Ni system.
Ejection of molecular clusters from ion-bombarded surfaces
Authors: Garrison Barbara J. , Winograd Nicholas , Harrison Don E.
Published: July 2002

We have modeled, using classical dynamics, the dissipation of momentum of a 600-eV Ar+ ion as it bombards a metal single crystal. The model correctly predicts relative sputtering yields, secondary particle energy distributions, and angular distributions. In addition, it also gives considerable insight into the mechanism of molecular cluster formation. For the three low index faces of copper, for example, the observed dimers, trimers, and higher multimers form over the surface but within interaction range of the solid. The clusters show rearrangement of their constituent atoms from their original surface positions, but do arise from a localized region of radius ∠5 Å. We have also examined oxygen atoms and CO molecules adsorbed on copper and nickel, respectively. For the chemisorbed O atoms, the clusters Cu2, CuO, O2, Cu3, Cu2O, CuO2, and O3 have all been observed to form over the surface, analogous to the clean metal case. For CO, however, most of the ejection occurs molecularly due to the strong carbon–oxygen bond (∠11 eV). The formation of NiCO and Ni2CO clusters occurs over the surface.
Effect of H2 on an argon discharge for planar magnetron sputtering
Authors: Maniv S. , Westwood W. D.
Published: July 2002

A planar magnetron has been operated in Ar/H2 mixtures to determine whether H2 has a significant effect on the sputtering characteristics as it does in diode systems. An Al target was sputtered in dc and rf discharges at powers up to 2.3 kW and H2/Ar ratios from 0 to 1.1. At a fixed argon flow, the total pressure increased from 0.6 to 1.3 Pa as the H2 flow rate increased to 4.4 cc/min. For the same rf power, the target self-bias voltage was independent of the H2 partial pressure but the dc impedance did increase with H2 flow; to maintain a current of 3A, the dc voltage had to be increased from 370 to 450 V as the H2 flow rate increased to 5.0 cc/min. The deposition rate of Al was measured by a quartz microbalance as a function of power and no significant decrease in rate was evident up to the highest H2/Ar ratio. In diode sputtering, a ratio of 0.01 causes a 10% decrease in rate. A set of reactions for the formation and removal of Ar+, H+, and ArH+ have been used to model the relative ion concentrations. A correlation between the model and experimental results suggests that the H+ concentration is significant in the diode case and causes a decrease in sputtering rate but it is negligibly small in the magnetron discharge due to the much higher electron density and the electron trapping.
Ion beam deposition of ferroelectric thin films sputtered from multicomponent targets
Authors: Castellano R. N.
Published: July 2002

Ion beam sputtering is evaluated as a technique for the deposition of thin films of mixed oxide ferroelectrics. With this technique, the plasma is contained in the ion gun so that the target and substrate are maintained in a plasma-free environment at ground potential. Several parameters that affect thin film properties such as substrate and target angle and position, substrate temperature, etc., could therefore be varied. Dielectric constant, film thickness, and elemental ratios were found to vary with the position and angle of the substrate. Films deposited at substrate temperatures below 325°C had the pyrochlore structure. Above 325°C, the ferroelectric perovskite structure was obtained. Deposition at elevated temperatures resulted in PbO volatilization, with a resultant decrease in the dielectric constant and remanent polarization, and an increase in the coercive field. These PbO losses were compensated by fabricating a target with excess PbO so that correct film stoichiometry was maintained. The limiting factor in obtaining thin films with properties comparable to those of the bulk has been determined to be the small (600 Å) grain size of the films.
Crossed fields nitriding in air atmosphere
Authors: Brokman A.
Published: July 2002

When a magnetic field is applied to an ion-nitriding tube, the low pressure that can be obtained eliminates oxidation problems. Therefore, nitriding in air atmosphere is possible.
Effects of oxygen on properties of rf sputtered NiFe films
Authors: Hammer W. N. , Ahn K. Y.
Published: July 2002

Oxygen contamination during rf sputter deposition of NiFe films is shown to cause adverse electrical and magnetic properties. This contamination is most pronounced in films deposited at low bias voltages. Although the bias voltage is not a direct cause of these changes, it is a factor which determines the amount of available oxygen in the sputtering gas which is incorporated into the interior of the films. In addition, a thin oxide layer is frequently found on both top and bottom surfaces of the films. It contains as much as 2 at. % oxygen, a concentration which is shown to mark the onset of deteriorating electrical and magnetic properties when occurring uniformly throughout NiFe in films.
Submicron optical lithography using an inorganic resist/polymer bilevel scheme
Authors: Tai K. L. , Vadimsky R. G. , Kemmerer C. T. , Wagner J. S. , Lamberti V. E. , Timko A. G.
Published: July 2002

The Ag2Se/GeSe inorganic photoresist system has been used to produce submicron features by optical lithography. A practical process incorporating this material is the inorganic resist/polymer bilevel scheme. The successful printing of 0.5 μm lines and spaces is explained by the existence of an ’’edge sharpening’’ effect which accompanies the photo-doping process. Conventionally accepted limitations of photolithography are circumvented by the Ag2Se/GeSe resist, whose properties also include high contrast, resistance to O2 plasma, and high absorbance of UV light.
Angle-resolved and -integrated photoemission from a ZnSe (110) surface
Authors: Ebina A. , Unno T. , Suda Y. , Koinuma H. , Takahashi T.
Published: July 2002

Angle-resolved and -integrated photoemission spectra from the ZnSe(110) surface were measured with He I (21.2 eV) light. Angle-resolved spectra were taken for the ? -?′, ? -?, and ? -? symmetry lines. From oxygen-contamination tests and by comparing the experimental result with a calculated surface electronic structure, we expect both surface and bulk states to contribute to the emission spectrum. The dispersion of the surface states at ∠−1.0 eV (energy zero is taken at the valence-band maximum) near the ?′ point and at ∠−1.5 eV near the ? point are reproduced by the calculation, while the presence of the surface state at −4 eV near the ? point is not predicted by the calculation. The Se-s-like surface state is detected at ∠0.5–1.0 eV above the upper edge of the lower valence band. The emission features due to valence-band states are interpreted by a model which disregards conservation of the wave vector perpendicular to the surface. The energies of the valence-band states at the X, W, and L critical points are determined: X5 = −2.5, X3 = −5.25, W2 = −3.4, W1 = −5.1, and L1 = −5.7 eV.
Plasma-developed ion-implanted resists with submicron resolution
Authors: Venkatesan T. , Taylor G. N. , Wagner A. , Wilkens B. , Barr D.
Published: July 2002

Resist materials and processes are described for use with low energy ion beam lithographic tools. Ion implanted regions on polymer and (SiO2) resists serve as in situ etch masks during reactive ion etch development of unexposed regions. Presumably, nonvolatile inorganic compounds formed from the implanted ions act as the in situ masks. Two classes of resist have been employed (1) an inorganic SiO2 layer exposed by In+ ions and developed in a fluorocarbon plasma and (2) a thick organic polymer exposed by In+ and developed in an oxygen plasma. For the latter, Rutherford backscattering spectroscopy was used to analyze the amount and depth distribution of the implanted ions before and after the reactive ion etching process (RIE). Between 5% and 15% of the implanted species are lost during the RIE development. Ionic organic resists exhibited deeper In+ distributions after a 3 keV implant and subsequent reactive ion etching than insulating organic materials. Conducting resists are required for finely focussed ion beam writing because of charging which occurs on insulating materials and causes beam broadening. Using a finely focussed In+ ion beam at 20 keV, and RIE, it was possible to fabricate 2500 Å wide lines, about O.8 μm high at an exposure dose of 2×1016 ions/cm2 in a 2:1 mixture of the semiconducting poly (vinyl carbazole) -trinitrofluorenone complex. Regions of the stepped beam as small as 500 Å were also reproduced.
Modulated semiconductor structures: An overview of some basic considerations for growth and desired electronic structure
Authors: Madhukar A.
Published: July 2002

An overview of the underlying considerations of importance for fabrication of lattice-matched modulated semiconductor structures and their electronic structure is presented. Particular consideration is given to a comparative discussion of group III–V/III–V and group IV/III–V heterointerfaces and the expected role of substrate crystallographic orientation in governing their growth and properties. Rather than presenting an exhaustive glossary of systems fabricated, the article focuses on basic concepts. Note is made of areas requiring greater and systematic investigation. A few variations on the basic technique of molecular beam epitaxy (MBE) are noted and suggested to exploit the kinetic aspects of MBE for creation of a variety of metastable phases.
Intense-pulsed plasma x-ray sources for lithography: Mask damage effects
Authors: Hyman H. A. , Ballantyne A. , Friedman H. W. , Reilly D. A. , Southworth R.C. , Dym C. L.
Published: July 2002

A characteristic of pulsed plasma sources is that each intense x-ray pulse is of very short time duration, typically ∼1–100 ns. Thermal energy is thus deposited almost instantaneously into the x-ray mask elements, and since the heat cannot be dissipated in such a short time, the potential exists for damaging the mask. A theoretical analysis has been carried out to examine such mask damage effects and their role in constraining key system parameters (e.g., throughput, resolution). It is shown that the timescale for interpulse cooling by heat conduction in a helium environment is adequate for source repetition rates up to a few hundred pulses per second. Thermal stress-induced mask failure mechanisms are discussed. Finally, it is concluded that plasma x-ray sources capable of being repetitively pulsed at rates >1 Hz appear to be promising candidates for high-resolution, high-throughput lithography.
Growth of epitaxial Fe on GaAs by metalorganic CVD
Authors: Kaplan R.
Published: July 2002

Epitaxial Fe films with excellent properties have been grown on GaAs(100), by the thermal decomposition of  Fe(CO)5 at heated substrates. Characterization of the films by LEED and AES at different intervals during deposition, has contributed to an understanding of the growth process. The approach used, since it provides in situ determination of film crystallinity and chemical composition, should be particularly useful in the investigation of the deposition of materials not previously grown epitaxially by MOCVD.
Analysis of hydrogen and deuterium by secondary ion mass spectrometry as applied to fusion technology
Authors: Magee Charles W.
Published: July 2002

This paper will focus on hydrogen detection using secondary ion mass spectrometry (SIMS), an established technique that has been used relatively infrequently for hydrogen analysis in fusion research. Fusion technology-related examples will be shown of hydrogen detection using SIMS. These include flux and energy measurements of H and D in the edge plasma, H and D isotope saturation and exchange studies; and species-mix determination for H and D in neutral beams from high power injectors.
Diffusion of gold and mercury self-diffusion in N-type Bridgman-grown Hg1−x CdxTe (x≂0.2)
Authors: Brown Margaret , Willoughby Arthur F. W.
Published: July 2002

The diffusion behavior of mercury in Hg0.8 Cd0.2Te was investigated using radiotracer techniques. Complex concentration versus distance profiles resulted from both the gold and mercury diffusion anneals. At 225 °C, complementary error function curve fits to the surface and tail components of the mercury diffusion profile yielded diffusion coefficients of ≂8×10−14 and ≂2.5×10−11 cm2s−1 for the surface and tail regions, respectively. Mercury diffusion coefficients were similar for as-grown and mercury preannealed samples. Surface concentrations were unknown for the gold diffusion profiles and accurate diffusion coefficient calculations were not made, but the migration rate of gold appeared faster than mercury in Hg0.8 Cd0.2Te. A mechanism was proposed for depletion of gold in the near-surface region of the HgCdTe for long diffusion times in a mercury ambient, which involved the formation of Au/Hg compounds at the slice surface.
Initial ordering kinetics of a randomly stepped GaAs(110) surface
Authors: Clearfield H. M. , Lagally M. G.
Published: July 2002

The flattening of a randomly stepped GaAs(110) surface is studied as a function of time for a range of annealing temperatures from 410 to 540 °C using LEED angular profile analysis. The average terrace width grows initially as the square root of the annealing time, with an activation enthalpy of 1.17 eV/atom. The angular profiles are fitted with a geometric distribution function, and the results are discussed in terms of random growth of ordered regions in a system in which ordered and disordered phases coexist, but in which the disordered phase is initially supersaturated.
Effects of ion implantation doping on the formation of TiSi2
Authors: Park H. K. , Sachitano J. , McPherson M. , Yamaguchi T. , Lehman G.
Published: July 2002

Si samples implanted at various energies and with various doses of 75As+, 31P+, and 11B+ were evaluated for the formation of TiSi2 from Ti films (400 Å) deposited after a postimplant annealing. Experimental results suggested that implantation conditions strongly affect the formation of TiSi2 at temperatures of 570–700 °C and result in a wide range of sheet resistance values, especially in the case of 75As+ and 31P+ implantations. This is believed to be due to the differences in the extent of the TiSi2 formation reaction, which depends on dopant concentration and distribution. We found that, in order to form appreciable silicide and obtain low sheet resistances, the concentrations of As and P should be kept lower than the critical concentrations at the Ti/Si interface.
Surface instability of platinum modified aluminide coatings during 1100 °C cyclic testing
Authors: Deb P. , Boone D. H. , Manley T. F.
Published: July 2002

Platinum additions to aluminide coatings have been reported to be beneficial in both hot corrosion and oxidation environments. The data, however, are somewhat limited and strongly dependent upon structure and test conditions. Therefore, a study of the effects of surface structure under 1100 °C cyclic oxidation conditions of the platinum modified and the unmodified aluminide coatings on the IN-738 substrate was initiated. During the early stages of this evaluation surface upheavals on the order of 50 μm, often called ‘‘rumpling,’’ were observed for both systems. The degree of rumpling was greater in the platinum modified coatings but was observed to a significant extent with the unmodified coatings as well. The amount of rumpling observed during cyclic testing can be attributed to a number of possible effects including (i) coefficient of thermal expansion mismatch, (ii) thermal gradient across the coated specimen, and (iii) coating mechanical properties. An effect of coating thickness is also observed although it must be noted that for diffusion-type coatings such as the Pt–Al system, coatings with different thicknesses have different compositions. Therefore, the resulting performance of the coating is a complex interplay of the above-mentioned variables. Excellent Al2O3 adherence is seen for all the platinum modified aluminides tested, even on the highly convoluted surfaces. The role of rumpling in the high temperature protectively is not known but should be given more consideration as a potential high-temperature degradation mechanism of these coatings.
Effect of translational and vibrational energy on adsorption: The dynamics of molecular and dissociative chemisorption
Authors: Ceyer S. T. , Beckerle J. D. , Lee M. B. , Tang S. L. , Yang Q. Y. , Hines M. A.
Published: July 2002

The dominant features of the molecule–surface potential energy surface which governs the dynamics of molecular and dissociative chemisorption are probed by molecular beam techniques coupled to electron spectroscopy. The collision energy and the vibrational energy of the incident adsorbate are the convenient probes of the interaction potential and high-resolution electron energy-loss spectroscopy is the sensitive and chemically specific detector of the result of the dissociative chemisorption event. The dissociative and molecular chemisorption of CH4 and CO on Ni (111) have been studied with these techniques. The results of these studies are summarized to illustrate the power of these techniques to provide information on the mechanism and dynamics of chemisorption.
Monte Carlo simulations of magnetron sputtering particle transport
Authors: Myers A. M. , Doyle J. R. , Abelson J. R. , Ruzic D. N.
Published: July 2002

Monte Carlo simulations of the particle transport process during dc magnetron sputter deposition were performed to determine the energy and angular distributions of the energetic deposition species. The model itself is quite general, and here we present the specific example of hydrogenated amorphous silicon film growth. This process involves the sputtering of a silicon target in an argon-plus-hydrogen plasma. The three-dimensional model incorporates fractal trim data for the distribution of Si energies and emission angles sputtered from the target surface. Modified ‘‘universal’’ interatomic potentials are used to determine the scattering processes during gas phase transport. Energy and angular distributions of the deposition flux reaching the substrate are calculated as a function of pressure from 0.01 to 5.5 mTorr. As the pressure increases we find that the average energy per deposited atom remains essentially constant, but the energy and angular distributions of the arrival flux change dramatically.
Temperature programming for isothermal desorption rate measurements
Authors: DeAngelis Michael A. , Anton A. Brad
Published: July 2002

We describe a digital feedforward/feedback controller for the implementation of rapid changes in the temperature of a small, resistively heated metal adsorbent in ultrahigh vacuum. The feedforward loop is based on a second-order model of the system’s thermal response, modified by inclusion of a time delay to account for the characteristic time for heat conduction in the adsorbent, and the feedback loop includes proportional and derivative actions. These features allow the temperature of a nickel single crystal, 10 mm diameter and 1 mm thick, to be increased 80 K within approximately 4 s without overshoot, after which desorption rates can be measured at constant surface temperature with a mass spectrometer. The performance of the temperature controller and the advantages of isothermal data collection and analysis are demonstrated with CO desorption from Ni(110), for which the functional dependence of the rate on surface coverage at constant temperature identifies clearly the participation of a mobile precursor state in the desorption process.
Thermal decomposition of very thin oxide layers on Si(111)
Authors: Kobayashi Y. , Sugii K.
Published: July 2002

We investigate the thermal decomposition and desorption of very thin oxide layers prepared on Si(111) by oxygen adsorption as well as by chemical treatments. The oxides are examined by Auger electron spectroscopy, thermal desorption spectroscopy, and atomic force microscopy. The decomposition mechanism changes drastically at an oxide thickness of ∼6 Å; the decomposition temperature depends on the formation method for oxides thicker than 6 Å, but the dependence disappears for oxides thinner than 6 Å. The former result can be qualitatively interpreted by the difference in SiO diffusivity between the oxides. The latter suggests that the decomposition rate is governed by reactions at the oxide/Si interface because the oxide layer is so thin that diffusion is not the dominant factor. The possibility of thermally removing the thin oxide layer in a dry oxygen/Si system for layer-by-layer etching or ‘‘monolayer peeling’’ is also discussed.
Very high atomic oxygen coverages on Ru(001)
Authors: Malik Igor J. , Hrbek Jan
Published: July 2002

Very high oxygen coverages−up to θO ≊ 40 (forty)−were obtained by dissociative adsorption of NO2 on Ru(001) at elevated temperatures. O2 desorption data show three desorption peaks at ≊1100, ≊1000, and ≊900 K, and suggest strong oxygen–oxygen repulsions in the overlayer. An Arrhenius plot of the leading edge desorption rates of the 900 K peak yields EA = 53 kcal/mol, implying zero-order desorption kinetics. O2 is the only desorption product for θO< 3; additional RuO+x (x=0–3) species were detected at higher coverages. However, neither the O 1s and Ru 3d core levels, nor the valence band spectra showed any evidence for chemical changes, i.e., an oxide formation. The process of an underlayer formation as a distinct stage in the oxidation of the Ru metal will be discussed in terms of a model for subsurface penetration of O on transition metals.