bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Kinetic Energy Distribution in a Laser-Ablated Titanium Plume by Emission and Laser-Induced Fluorescence Spectroscopy
Authors: Chu S. S. , Grigoropoulos C. P.
Published: July 2002

Pulsed laser deposition (PLD) of thin films has become a viable technique for a wide range of applications over the last few decades. As kinetic energy of the ablated plume is an important parameter in determining the quality of the film; consequently there is great interest in nonintrusive evaluation of the plume kinetic energy. Spectroscopic techniques such as optical time-of-flight (TOF) utilizes emission spectroscopy or laser-induced-fluorescence (LIF) and is an excellent method for this purpose since they offer temporal and spatial resolution as well as the capability of distinguishing different species. In this paper, the effects of laser fluence and background gas pressure on the kinetic energies of the ablated species are found by the optical time-of flight technique and by emission imaging. Laser-induced-fluorescence is employed for spectrally resolved imaging. The axial velocity of neutral titanium is found to be as high as 2×104 m/s. The distribution of species within the plume is also determined. [S0022-1481(00)01704-7]
Turbulent Mixing, Viscosity, Diffusion, and Gravity in the Formation of Cosmological Structures: The Fluid Mechanics of Dark Matter
Authors: Gibson C. H.
Published: July 2002

Self-gravitational structure formation theory for astrophysics and cosmology is revised using nonlinear fluid mechanics. Gibson’s 1996–2000 theory balances fluid mechanical forces with gravitational forces and density diffusion with gravitational diffusion at critical viscous, turbulent, magnetic, and diffusion length scales termed Schwarz scales. Condensation and fragmentation occur for scales exceeding the largest Schwarz scale rather than LJ, the length scale introduced by Jeans in his 1902 inviscid-linear-acoustic theory. The largest Schwarz scale is often larger or smaller than LJ. From the new theory, the inner-halo 1021 m dark-matter of galaxies comprises ∼105fossil-LJ-scale clumps of 1012 Earth-mass fossil-LSV-scale planets called primordial fog particles (PFPs) condensed soon after the cooling transition from plasma to neutral gas, 300,000 years after the Big Bang, with PFPs tidally disrupted from their clumps forming the interstellar medium. PFPs explain Schild’s 1996 “rogue planets…likely to be the missing mass” of a quasar lens-galaxy, inferred from twinkling frequencies of the quasar mirages, giving 30 million planets per star. The non-baryonic dark matter is super-diffusive and fragments at large LSD scales to form massive outer-galaxy-halos. In the beginning of structure formation 30,000 years after the Big Bang, with photon viscosity values ν of 5×1026 m2 s−1, the viscous Schwarz scale matched the horizon scale LSV≈LH<LJ, giving 1046 kg proto-superclusters and finally 1042 kg proto-galaxies. Non-baryonic fluid diffusivities D∼1028 m2 s−1 from galaxy-outer-halo LSD scales 1022 m measured in a dense galaxy cluster by Tyson, J. A., and Fischer, P., 1995, “Measurement of the Mass profile of Abell 1689,” Ap. J., 446, pp. L55–L58, indicate non-baryonic dark matter particles must have small mass ∼10−35 kg to avoid detection. [S0098-2202(00)01504-2]
Determination of the Compressive Material Properties of the Supraspinatus Tendon
Authors: Zobitz Mark E. , Luo Zong-Ping , An Kai-Nan
Published: July 2002

A methodology was developed for determining the compressive properties of the supraspinatus tendon, based on finite element principles. Simplified three-dimensional models were created based on anatomical thickness measurements of unloaded supraspinatus tendons over 15 points. The tendon material was characterized as a composite structure of longitudinally arranged collagen fibers within an extrafibrillar matrix. The matrix was formulated as a hyperelastic material described by the Ogden form of the strain energy potential. The hyperelastic material parameters were parametrically manipulated until the analytical load-displacement results were similar to the results obtained from indentation testing. In the geometrically averaged tendon, the average ratio of experimental to theoretical maximum indentation displacement was 1.00 (SD: 0.01). The average normalization of residuals was 2.1g (SD: 0.9g). Therefore, the compressive material properties of the supraspinatus tendon extrafibrillar matrix were adequately derived with a first-order hyperelastic formulation. The initial compressive elastic modulus ranged from 0.024 to 0.090 MPa over the tendon surface and increased nonlinearly with additional compression. Using these material properties, the stresses induced during acromional impingement can be analyzed.
Thin-Walled Multicell Beam Analysis for Coupled Torsion, Distortion, and Warping Deformations
Authors: Kim J. H. , Kim Y. Y.
Published: July 2002

Due to the complicated deformations occurring in thin-walled multicell beams, no satisfactory one-dimensional beam theory useful for general quadrilateral multicells appears available. In this paper, we present a new systematic approach to analyze the coupled deformations of torsion, distortion, and the related warping. To develop a one-dimensional thin-walled multicell beam theory, the method to determine the section deformation functions associated with distortion and distortional warping is newly developed. In order to guarantee the singlevaluedness of the distortional warping function in multicells, distortional shear flows have been utilized. The superior result by the present one-dimensional theory is demonstrated with various examples.
Open Channel Boundary Layer Relaxation Behind a Forward Facing Step at Low Reynolds Numbers
Authors: Tachie Mark F. , Balachandar Ram , Bergstrom D. J.
Published: July 2002

This paper reports laser-Doppler anemometer measurements of mean velocity and turbulence statistics upstream and downstream of a 3-mm forward facing step in a shallow open channel flow. The Reynolds numbers based on the momentum thickness (θ) of the approaching upstream flow and step height (h) are in the range 1010⩽Reθ⩽2240 and 960⩽Reh⩽1890, respectively. Measurements are obtained at 50 step heights upstream of the leading edge of the step and 1⩽x/h⩽162 downstream of the step. The results show that the overlap region develops more slowly than the inner and outer regions. The mean field recovers at x/h=50. Distributions of the turbulence intensity tend to become self-similar for x/h>100 but the profiles do not necessarily collapse onto the upstream profiles.
Tooth Undercutting of Beveloid Gears
Authors: Liu Chia-Chang , Tsay Chung-Biau
Published: July 2002

A beveloid gear can be viewed as an involute gear of which the profile-shifted coefficient linearly decreases from the heel to the toe. Therefore, tooth undercutting occurs and singular points appear on the tooth surfaces near the toe. When undercutting occurs, the gear tooth is comparatively weak. In this study, the conditions of tooth undercutting of beveloid gears were derived and specific phenomena were also investigated by numerical illustrated examples. In addition, according to the characteristics of tooth undercutting on the beveloid gear tooth surface, two practicable methods were also proposed to avoid the tooth undercutting of beveloid gears.
An Alternative Decomposition of the Strain Gradient Tensor
Authors: Jiang H. , Huang Y. , Guo T. F. , Hwang K. C.
Published: July 2002

An alternative decomposition of the strain gradient tensor is proposed in this paper in order to ensure that the deviatoric strain gradient vanishes for an arbitrary volumetric strain field, which is consistent with the physical picture of plastic deformation. The theory of mechanism-based strain gradient (MSG) plasticity is then modified accordingly based on this new decomposition. The numerical study of the crack-tip field based on the new theory shows that the crack tip in MSG plasticity has the square-root singularity, and the stress level is much higher than the HRR field in classical plasticity.
Uncertainty Quantification for Multiscale Simulations1
Authors: DeVolder B. , Glimm J. , Grove J. W. , Kang Y. , Lee Y. , Pao K. , Sharp D. H. , Ye K.
Published: July 2002

A general discussion of the quantification of uncertainty in numerical simulations is presented. A principal conclusion is that the distribution of solution errors is the leading term in the assessment of the validity of a simulation and its associated uncertainty in the Bayesian framework. Key issues that arise in uncertainty quantification are discussed for two examples drawn from shock wave physics and modeling of petroleum reservoirs. Solution error models, confidence intervals and Gaussian error statistics based on simulation studies are presented.
Nonlinear Dynamics Analysis of a Laminated Printed Wiring Board
Authors: He Xiaoling , Fulton Robert E.
Published: July 2002

Nonlinear laminate theory is applied for the printed wiring board (PWB) dynamic response analysis. Equations of motion for the nonlinear elastic deformation of the isotropic laminates are derived for the dynamic response of a simply supported PWB. Numerical results are generated for the nonlinear response characterization of the PWB deformation. Comparisons are made between the response of linear and nonlinear systems. Results show that PWB is in large deflection under high acceleration or certain pressure load. Nonlinear theory gives more accurate results for the large deflection than the linear theory does. Besides, lamina stresses are analyzed and illustrated from finite difference computation. The analytical derivation in modal approach and the stress analysis provide the basis for PWB reliability studies, especially the defect and failure induced by the dynamic stress field.
B

2

and C2 Stress Indices for Large-Angle Bends
Authors: Kumar Rajnish , Saleem M. A.
Published: July 2002

B 2 and C2 stress indices are needed for evaluation of nuclear piping components. These indices are used in calculation of stress terms corresponding to moment loading. The formulas (B2=1.3/h2/3 and C2=1.95/h2/3) given in the ASME Boiler and Pressure Vessel Code for calculating these stress indices for elbows and bends are independent of bend angle. Author’s earlier work indicated that the values obtained by these formulas are conservative for bend angle ⩽90 deg. The objective of the present study was to investigate the values of B2 and C2 stress indices for elbows with bend angles larger than 90 deg and to evaluate the limit of the applicability of the ASME Code formulas in terms of the bend angle. For this purpose, elbows with bend angles ranging from 90 to 180 deg have been investigated in detail. Elbow sizes studied ranged from 2.5 to 20 NPS. Finite element models have been used for detailed analysis. To cover the worst case of stresses in the elbows, several hundred load cases were analyzed by varying the direction of the moment loading. It was found that the three independent loading cases corresponding to three orthogonal axes do not bound the worst-case stress in the elbows. The results of the analysis show that the calculated value of B2 stress index increases with bend angle; but its value, even for 180-deg bend angle, remains below the ASME Code value with a margin of at least 15%. Considering all analyzed elbows and bend angles from 90 to 180 deg, the calculated maximum value of C2 stress index is found to be within 2 percent of the ASME Code value. The maximum increase in the value of B2 stress index is 12.5 percent as the bend angle is increased from 90 to 180 deg. The corresponding increase in the C2 stress index is less than 8%. Based on these results and authors’ earlier work, a modification to ASME Code formulas is proposed for calculation of more realistic values of the stress indices for bends up to 180 deg.
Microstructure Characterization of Dislocation Wall Structure in Aluminum Using Transmission Electron Microscopy
Authors: Gan J. , Vetrano J. S. , Khaleel M. A.
Published: July 2002

The configuration of dislocation wall structures and the interactions between dislocations and dislocation walls play a significant role in the understanding of deformation processes in metals. Samples of single-crystal aluminum deformed by tensile-straining (15%) were analyzed using TEM. In tensile-deformed (15%) single crystal aluminum, a cell structure is well developed and dislocations in the cell boundaries consist of either one set of Burgers vector or two sets of Burgers vector. The three-dimensional image of cell wall structure, misorientation angle across the cell boundaries and the Burgers vectors of dislocations in the cell boundaries are characterized.
Failure Mechanisms of High Temperature Components in Power Plants
Authors: Viswanathan R. , Stringer J.
Published: July 2002

The principal mechanisms of failure of high temperature components include creep, fatigue, creep-fatigue, and thermal fatigue. In heavy section components, although cracks may initiate and grow by these mechanisms, ultimate failure may occur at low temperatures during startup-shutdown transients. Hence, fracture toughness is also a key consideration. Considerable advances have been made both with respect to crack initiation and crack growth by the above mechanisms. Applying laboratory data to predict component life has often been thwarted by inability to simulate actual stresses, strain cycles, section size effects, environmental effects, and long term degradation effects. This paper will provide a broad perspective on the failure mechanisms and life prediction methods and their significance in the context utility deregulation. [S0094-4289(00)00103-1]
An Effective Property, LHF-Type Model for Spray Combustion
Authors: Nazha Marouan A. A. , Rajakaruna Hobina , Crookes Roy J.
Published: July 2002

A mathematical model capable of describing the evaporation, mixing and burning characteristics of a confined reacting two-phase flow is presented. The flow field is described by solving the partial differential equations of continuity, momentum, and energy transport, together with the k-ε equations of turbulence. Evaporation is accounted for via a droplet evaporation sub-model which runs in parallel with the gas-phase solver exchanging data with it. Effective properties are calculated in each control volume and the property changes resulting from the evaporation are allowed to propagate according to the turbulent mixing model. Combustion follows the mixing process and is assumed to proceed to equilibrium. The model is validated against experimental results, and its applicability over a wide range of conditions is investigated. [S0742-4795(00)03002-7]
An Experimental Study of the Effect of Tube-to-Tube Ties on Fluidelastic Instability in an In-Line Tube Array
Authors: Weaver David S. , Feenstra Paul , Eisinger Frank L.
Published: July 2002

An experimental study was conducted on the effect of tube-to-tube ties on the fluidelastic instability of an in-line tube array with a streamwise pitch ratio of 1.33 and a transverse pitch ratio of 2.0. Various arrangements of tubes clamped in the streamwise direction were examined. The results showed that clipping two tubes together had a stabilizing effect, but also exhibited substantial hysteresis. On the other hand, longitudinal clipping of three, four, or six tubes together increased the fluidelastic stability threshold by a factor of more than three. [S0094-9930(00)01501-8]
Hexagonal Phase of Boron Nitride by AES
Authors: Simko Steven J. , Militello Maria C.
Published: July 2002

Auger electron spectra of the hexagonal phase of boron nitride are presented. The line shapes of the boron and nitrogen KLL transitions are characteristic for this phase of boron nitride. Therefore, hexagonal-boron nitride can be distinguished from other phases of boron nitride based on Auger line shapes. The powder specimen was prepared by burnishing onto an indium substrate.
E-35 Pitch-based Carbon Fiber by Core Level and Valence Band XPS
Authors: Xie Yaoming , Sherwood Peter M. A.
Published: July 2002

Both XPS core level and valence band spectra were obtained from Du Pont E-35 pitch-based carbon fiber surface. The XPS data showed that the E-35 fiber had more oxygen on the surface than the higher modulus pitch-based carbon fibers (e.g., Du Pont E-120 and E-75, and Amoco P55X carbon fibers), but less than the PAN-based carbon fibers (Hercules AU4 and AS4). [See Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992).] The E-35 fiber also had a fairly good graphitic structure in both the surface and the bulk as evidenced by both XPS and XRD. No nitrogen was found on this E-35 fiber and other pitch-based carbon fiber surfaces, but it was found on PAN-based fibers. Our previously reported work [Y. Xie and P. M. A. Sherwood, Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992)], showed that XPS valence band spectra were more sensitive to chemical environment on the carbon fiber surface than core level spectra, and could be well interpreted by X–α calculations with model compounds. In this work, the valence band spectrum showed that there were at least two different types of oxygen species on the E-35 fiber surface. The two well separated O 2s features in the E-35 fiber valence band spectrum were both more significant than those in the E-75 fiber valence band spectrum.
Amorphous Boron Carbide by AES
Authors: Epp June M.
Published: July 2002

The Auger electron spectra for amorphous boron carbide (B4C) are presented. The first derivative C KLL Auger electron spectrum of a crystalline carbide exhibits a peak shape different from that of adventitious hydrocarbon. The peak shape of the C KLL spectrum for a carbide such as TaC contains three components present at the approximate kinetic energies of 250, 260, and 270 eV, with the peak at 270 eV having a greater intensity in the positive direction than the C KLL spectrum for adventitious hydrocarbon. The features exhibited in the differentiated C KLL Auger spectrum for amorphous B4C are similar, but not identical to other metal carbides and are characteristically different from adventitious hydrocarbon, graphite, SiC, and other metal carbides.
Microbial Cells by XPS: Analysis of Brewing Yeast Saccharomyces cerevisiae
Authors: Dengis Pascale B. , Genet Michel J. , Rouxhet Paul G.
Published: July 2002

The surface chemical composition of top fermenting brewing yeast Saccharomyces cerevisiae MUCL 38475 was determined by XPS. The sample was prepared by washing the harvested cells in distilled water, freezing the suspension in liquid nitrogen, freeze drying, filling a trough with the powder and pressing gently. The yeast surface is mainly composed of carbon, oxygen, and nitrogen. Phosphorus and potassium were found as minor elements. The C 1s, O 1s, and N 1s peaks were broken down into components which were assigned to chemical functions on the basis of analysis of sugar derivatives and homopeptides. The XPS analysis of brewing yeasts relates the surface chemical composition to physicochemical properties (electrical properties, hydrophobicity) and cell behavior (flocculation, flotation).
Biolite®, a Thin Amorphous Carbon Film Employed in Biomechanical Applications, by XPS
Authors: Thoma Randall J. , Chinn Joseph A. , Hofmann Gregory J. , Cole David A.
Published: July 2002

Biolite®, a vapor deposited, thin, amorphous carbon film, has been used successfully as a component of implantable medical devices during the last 25 years. Biolite® has not been previously characterized using XPS. We have used XPS to explore the chemical composition of Biolite® samples that are typical of those deposited onto implantable medical devices; we report the findings here. This data is an important part of any effort regarding understanding why Biolite® is a good biocompatible material. The data were collected using a Perkin–Elmer 5000-LS ESCA spectrometer with monochromated Al Kα excitation, at a resolution of 1.7895 eV.
Pyrolite® Characterized by XPS
Authors: Thoma Randall J. , Chinn Joseph A. , Cole David A.
Published: July 2002

Pyrolite® has been used in many implantable medical devices over the last 25 years. This test specimen is typical of Pyrolite® as manufactured for implantable products. Minor statistical variation from the reported values can be expected due to variation in the manufacturing process as a result of different component geometries. The data is critical as new pyrolytic carbons that approximate Pyrolite® are developed. The data were collected using a Perkin–Elmer 5000-LS ESCA spectrometer, with monochromated Al Kα excitation at a resolution of 1.7895 eV.
Potassium Dichromate by XPS
Authors: Epling William S. , Hoflund Gar B. , Minahan David M.
Published: July 2002

XPS data were collected from a pressed potassium dichromate powder. A small amount of contamination is present in hydrocarbon and carbide states. A small amount of subsurface dissolved O is also apparent. The spectra obtained from the as-received powder indicate that single states of K and Cr are present and therefore these data can be considered to be characteristic of K2Cr2O7.
Epitaxial MgO(100) Film Grown on a NiO(100) Single Crystal Surface, Studied by XPS and UPS
Authors: Imaduddin Syed , Lad R. J.
Published: July 2002

MgO and NiO have the rocksalt structure with a less than 1% lattice mismatch. Therefore, they are excellent materials for studies of epitaxial oxide film growth. This article reports comparison XPS and UPS spectra from both a clean stoichiometric NiO(100) single crystal substrate and a 5 nm thick MgO(100) epitaxially grown film, measured using a double-pass CMA. The NiO(100) surface was prepared by cleaving a NiO single crystal along the (100) plane in air, inserting it in UHV, and treating the surface with an Ar+ bombardment and oxidation treatment. The MgO film was grown by thermally evaporating Mg on the NiO(100) substrate at 523 K at an O2 partial pressure of 7 × 10−5 Pa. Epitaxial (100) structure of the MgO film was confirmed by LEED and in situ RHEED. Steady state sample charging was evident in UPS and XPS spectra from both the NiO surface and the MgO film. The charging was minimized by acquiring spectra at 523 K, rather than 298 K, due to the increased bulk conductivity of NiO. To correct for charging, all XPS spectra reported here are charge referenced to the measured Ni 2p3/2 of NiO, which is assigned a binding energy of 854.2 eV. The UPS spectra are referenced to the top of the valence band.
Glycine Adsorption on Pt(111) in the Monolayer and Multilayer Regime
Authors: Krozer A. , Aronsson B.-O. , Löfgren P. , Lausmaa J. , Kasemo B.
Published: July 2002

Glycine (GL) overlayers of varying thickness were deposited in situ on the clean Pt(111) surface by evaporating commercially available glycine powder. The temperature-stabilized evaporation source, made of Cu, was kept at 420 K during evaporation. The distance between Pt and the evaporation source was about 240 mm. The deposition rate and the total amount of glycine deposited were monitored by a quartz crystal microbalance that could be moved to intersect the GL beam approximately 40 mm downstream compared to the Pt position. The total amount of glycine in the reproduced spectra was 34 (~0.5 ML) and 340 ng/cm2 (~ 5 ML), respectively. We discuss the spectra with reference to both the neutral and zwitterionic states. There are two glycine-related C 1s peaks at both low and high GL coverages and a shoulder at ~ 285 eV most probably due to partial decomposition of glycine inside the evaporation source, at least for a thicker GL layer. The C 1s peak at lower binding energy is usually attributed to the C 1s carbon, while the peak at higher BE is supposed to stem from the carboxyl group. The energy of the peaks shifts with coverage, mainly due to the differences in charge transfer between Pt-GL (low coverage) compared to the GL-GL (high coverage). Slight charging of the sample (3.7 meV/ML) takes place, but results in a virtually uniform shift of all the GL levels involved. In the N 1s spectral region there appear two different N 1s components. The intensity of the peak at lower BE levels off with increased coverage from ~25% of the total N 1s intensity at low coverage to ~8% at higher coverages. The energy position of this lower BE peak is characteristic of NH2-like bonding. The position of the second N 1s peak suggests NH3+-like bonds. At high GL coverages the N 1s peak at low BE, and a C 1s shoulder at 285 eV, stem mainly from a slight decomposition of GL inside the evaporation source (below 8%). At low glycine coverages (<1 ML) there exist two different GL states on the surface: a majority of the amino acid molecules form zwitterions, while the remaining part is either neutral or decomposes into fragments some of which contain the NH2 group.
CoO(100) and CoO(100)/Co3O4 Fuchs-Kliewer Phonon Spectra
Authors: Carson G. A. , Nassir M. H. , Langell M. A.
Published: July 2002

The CoO(100) HREELS spectrum has been reported with features that, atypically, cannot be attributed to known phonon losses. This article presents both HREELS Fuchs-Kliewer phonon spectra and XPS spectra of both stoichiometric CoO(100) and of this substrate exposed to oxygen gas. CoO(100) O 1s and Co 2p binding energies, and Co 2p satellite structure, were comparable to literature values. As expected, the stoichiometric CoO(100) surface yielded one fundamental phonon loss (∼69.4 meV) with additional losses only at integral multiples of this value. Exposure of the CoO surface to oxygen results in additional losses attributed to the oxidation of the near-surface region, with the single loss phonon varying in energy with oxygen partial pressure. Higher oxide phase results, including XPS spectra, have similarities to those reported for Co3O4. Regardless of the nature of the higher oxide overlayer, the present results demonstrate that with respect to fundamental phonon mode and n-multiple losses, the CoO(100) surface HREELS spectrum is comparable to other rock-salt transition metal monoxides, with additional HREELS spectrum features indicating a deviation in the CoO(100) surface stoichiometry.
Surface Phonon Spectra of Mineral TiO2 Anatase (001) and (100)
Authors: Poelman H. , Fiermans L.
Published: July 2002

The surface properties of TiO2 anatase are of great importance in chemical technology because this material is frequently used as a support for oxide catalysts. In the framework of an extensive study of the system V2O5/TiO2 anatase, the vibrational properties of single crystal anatase (001) and (100) have been examined by means of HREELS. Both of these surfaces are believed to provide a good lattice match with V2O5(001). Single crystal anatase samples were obtained by orienting and sawing natural minerals. The resulting samples were yellowish transparent and gave rise to a LEED image after adequate UHV cleaning. Despite the insulating character of TiO2 anatase, HREELS could be performed without charging problems, due to the natural contamination. Energy loss spectra were recorded in the range −140 to 40 meV, with an instrument resolution of about 3 meV, and displayed surface vibrational modes.
The Pd M4,5N1N2,3 Transition of Palladium Oxide
Authors: Voogt E. M. , Mens A. J. M. , Gijzeman O. L. J. , Geus J. W.
Published: July 2002

The palladium M4,5N1N2,3 transition, which is almost absent in palladium metal, becomes quite intense in palladium oxide. The intensity of the transition is linearly proportional to the amount of palladium oxide. We present AES spectra of palladium metal particles and palladium oxide particles. The particles are supported on SiO2/Si(100).
Core Level XPS Spectra of Elemental Silicon Using Zirconium Radiation
Authors: Chourasia A. R.
Published: July 2002

Core levels of elemental silicon have been studied by x-ray photoelectron spectroscopy. Zirconium L radiation (2042.4 eV) was employed for this purpose. The XPS data in the 1s, 2s, 2p, and Auger KLL regions are presented. The data set will serve as a source of valuable information for evaluating the Auger parameter.
Analysis of a 40% Glass-filled Poly(propylene) Polymer by XPS
Authors: Lannon John M. , Meng Qingru
Published: July 2002

We report x-ray photoemission spectra for a 40% glass-filled poly(propylene) (PP) polymer. 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 and O 1s photoelectron peaks.
Low cost, mechanically refrigerated diffusion pump baffle for ultrahigh vacuum chambers
Authors: Chambreau Steven , Neuburger Monica L. , Ho Tom , Funk Brian , Pullman David
Published: July 2002

In the course of constructing an ultrahigh vacuum apparatus employed in molecular beam scattering from crystal surfaces, we have designed, tested, and now continuously employ a simple diffusion pump cryobaffle that is mechanically refrigerated to approximately −50 °C. Modifications were made to a commercial water baffle for this purpose. After baking the chamber at 140–150 °C for three or four days, we routinely achieve a base pressure of 1–2×10−10 Torr. Relative to a conventional liquid nitrogen trap, the cost and maintenance of the cryobaffle are minimal. The surprising feature of the baffle is its usefulness in helping generate such a high vacuum, despite the relatively high temperature of −50 °C. As might be expected, the baffle operates by eliminating backstreaming of the diffusion and mechanical pump fluids. However, water vapor is not cryopumped; rather, it passes through the baffle and is removed by the diffusion pump.
Growth and characterization of GaTlAs
Authors: Antonell M. J. , Gila B. , Powers K. , Abernathy C. R.
Published: July 2002

The growth of GaTlAs has been attempted by gas source molecular beam epitaxy using a variety of growth conditions. At substrate temperatures ⩾275 °C a two-phase mixture of metallic Tl droplets in a matrix of GaAs was produced, similar to that often observed in the InTlAs material system. However, at low temperatures (∼200 °C), a specular morphology was obtained with incorporation of 5 at. % Tl as measured by electron microprobe analysis (EMPA). Increasing the Tl flux for films grown at a substrate temperature of 200 °C produced layers containing as high as 15 at. % Tl, although with slightly rougher surface morphologies. Backscattered electron imaging showed no phase contrast, indicating there was no spatial variation in the distribution of Tl throughout the film, nor was there any evidence of metallic Tl droplets from powder x-ray diffraction scans. EMPA also indicated a much higher As/group III ratio, with values up to 3/2 obtained. Films grown at 200 °C showed no evidence of oxidation as is normally associated with the Tl containing materials. Cross-sectional transmission electron microscopy revealed the material to be amorphous. A large shift in the absorption edge was observed, but is believed to be due to the incorporation of large amounts of As rather than the Tl.
Dynamical behavior of hydrogen molecule on GaAs(001) surface
Authors: Ohashi Masafumi , Ozeki Masashi , Cui Jie
Published: July 2002

We have been studying in dynamical behaviors of hydrogen on the GaAs(001) surface using a supersonic molecular beam apparatus. We measured the angular and time of flight distributions of reflected beams, when hydrogen molecules were injected at [110] and [1̄10] directions onto the GaAs(001) 2×4 surface. A comparison of measurement and classical trajectory simulation showed that angular distribution consisted of inelastic direct scattering and complicated multiple scattering on the GaAs(001) 2×4 surface with large surface corrugation. The depth of the potential well of hydrogen molecules on the GaAs(001) 2×4 surface was estimated to be 0.4 kcal/mol, indicating the importance of information on energy exchange from translational to rotational modes.
Red SrTiO3:Pr,Al phosphor as potential field emission display material
Authors: Yokoyama Meiso , Yang Su-Hua
Published: July 2002

This article describes the low-voltage red SrTiO3:Pr,Al phosphors prepared by solid-state sintering for field emission displays. The characteristics of these phosphors will be discussed. For phosphors fired at 1000 °C for 10 h, it was found that the value of full width at half maximum of x-ray diffraction spectra increased little even after being doped with Pr or Al. The photoluminescence (PL) intensities varied with the concentrations of PrCl3 and Al(OH)3 with the maximum red emission at PrCl3=0.5 mol %. The PL spectra show that Al acts as an enhancer for red emission. This phenomenon is also observed from cathodoluminescent measurements. For an electron-gun voltage of 2 kV and an anode current of 2 μA, a luminance of 12.2 cd/m2 is obtained. The Commission International de l’Echairage chromaticity coordinates of SrTiO3:Pr,Al of x=0.6 and y=0.33, is red emission.
BN and ZrN AES Spectra Obtained by Depth Profiling of ZrN/BN Multilayers
Authors: Sanz J. M. , Prieto P. , Quirós C. , Elizalde E.
Published: July 2002

AES depth profiling has been used to measure a (BN20 nm/ZrN40 nm)3/Si multilayer. The spectra shown in this work correspond to the Bn and ZrN material of the first bilayer. They have been obtained after several minutes of 2 keV Ar+ bombardment.
Characterization studies of diamond-like carbon films grown using a saddle-field fast-atom-beam source
Authors: Sarangi D. , Panwar O. S. , Kumar S. , Bhattacharyya R.
Published: July 2002

In this article, we report results of an extensive characterization study involving scanning electron microscopy, spectroscopic ellipsometry (SE), photothermal deflection spectroscopy (PDS), x-ray photoelectron spectroscopy, x-ray Auger electron spectroscopy (XAES), current–voltage (I–V) measurements, hydrogen content evaluated from Fourier transform infrared spectroscopy and elastic recoil detection analysis, and also measurement of stress and hardness of diamond-like carbon (DLC) films. These films were grown using methane (CH4), acetylene (C2H2) gases, and benzene (C6H6) vapors into a saddle-field fast-atom-beam (FAB) source. DLC films formed by the saddle-field FAB source technique exhibit extremely low residual stress (0.12–0.26 GPa) and high Knoop hardness (9–22 GPa) measured at 50 g load. The values of optical constants (n, k, ε1, ε2) evaluated from SE, characteristic energy of band tail (Urbach energy, E0) evaluated from PDS studies, sp2 percentage evaluated from XAES data, the density of states [N(EF)] derived from space-charge-limited conduction, and the hydrogen content are found to decrease, and the sp3/sp2 ratio evaluated are found to increase with the increase of carbon-to-hydrogen ratio in the hydrocarbon gases/vapors used for growing DLC films by this technique. The values of E0, N(EF), hydrogen content, and sp3/sp2 ratio of these DLC films are found to be in the range of 180–280 meV, 1–6×1017 eV−1 cm−3, 3–8 at. % and 5.2–12.3, respectively, which are lower than the values of E0 (300–500 meV), N(EF) (∼1018 eV−1 cm−3), and hydrogen content (15–40 at. %) and higher than sp3/sp2 ratio (1.3–2.5) of DLC films grown by the more conventional rf self-bias technique reported in the literature.
Relative Atomic and Molecular Secondary Ion Yields for SIMS O2+ Analysis of Column 13 Ion Implants in Silicon
Authors: Granger C. N. , Stevie F. A.
Published: July 2002

SIMS depth profiles for ion implants of column 13 elements in Si have been obtained using O2+ primary beam and detection of positive secondary atomic and molecular ions using high mass resolution. The species monitored were M2+, M+, MO+, M2+, MSi+, and MSiO+, where M is the element of interest.
Thin Film GaAs Photocathodes Deposited on Single Crystal Sapphire by a Modified rf Sputtering Technique
Authors: Hyder S. B.
Published: July 2002

Thin films of GaAs were grown epitaxially on single crystal sapphire substrates by a modified sputtering technique. The (0001), (0112¯) and (0221¯) substrate orientations were used at various temperatures from 150 ° to 500 °C, and the carrier concentration of about 1018/cm3 was achieved in GaAs films by the diffusion of zinc. The spectral response of the photoelectrons was measured in the incidence and transmission mode after activation by cesium and oxygen. The photoelectric yield at 2.8-eV photon energy was within an order of magnitude to that from a bulk crystal for a 0.88-μ-thick reflection photocathode. An electron diffusion length of 0.32 μ and an escape probability of 0.005 was measured for photon energies near the band edge. The photoelectric yield from transmission photocathodes was within an order of magnitude to that from the reflection photocathodes only at wavelengths longer than 0.8 μ.
An Ionization Gauge Using a Channel Electron Multiplier for Pressures Below 10−12 Torr
Authors: Blechschmidt D.
Published: July 2002

A new ionization gauge of an estimated low pressure limit below 10−15 Torr and of a sensitivity of 2×109  Torr−1 is presented. The ions, which are produced in an ionizer of conventional design, are extracted through a shield aperture and collected by the funnel-type cathode of a channel electron multiplier. Since the high gain of this multiplier allows the gauge to be operated with an emission current of only several nanoamperes, practically no heat is produced in the gauge. The gauge is mounted on a 412-in. flange and has approximately the size of a normal Bayard-Alpert gauge. A general expression for the low pressure limit of hot filament ionization gauges is given. The results as obtained from this expression for gauges of similar geometry are discussed together with the low pressure limit as found for the new gauge.
Cylindrical Diode Continuous Vacuum Sputtering Equipment for Laboratory and High Volume Production
Authors: George Carroll H.
Published: July 2002

To meet anticipated extremely large volume demands for integrated capacitor-resistor tantalum thin film circuits, which require six to eight times the sputtering time of resistor circuits only, Western Electric has capitalized on the several hundred percent vacuum deposition efficiency advantage that the cylindrical geometry holds over the in-line geometry with its development of a cylindrical diode continuous sputtering machine. An experimental vacuum head fitted to a 56-cm commercially available bell jar vacuum system and equipped with an air-locked separately pumped magazine was used to prove feasibility of the concept, to solve nonuniformity problems inherent in the cylindrical geometry, to develop a system for uniformly diffusing the reactive gas over the large (1000 cm2) substrate area, to prove the concept of substrate bakeout and preheat outside the vacuum, and to characterize film properties produced. The influence of ten optimizing design features incorporated in the machine are discussed and both models are briefly described. Film properties deviating from the normal which are discussed include TCR controllable around zero having improved stability and much faster initial aging effect (first 24 h) believed to be attributal to less interstitial oxygen in the film.
Mass Spectrometer Calibration under Pulsed Molecular Flow Conditions: Sample Inlet Influences
Authors: Winterbottom W. L.
Published: July 2002

A model has been developed to describe the influence of a slit-type sampling system on the pressure response of a mass spectrometer. Under molecular flow conditions, a distorted pressure waveform response is predicted for a time dependent pressure variation. A quantitative comparison between experiment and model prediction is presented to demonstrate both the effect and a method for spectrometer calibration.
Tungsten silicide for the alternate gate metal in metal-oxide-semiconductor devices
Authors: Roh K. , Youn S. , Yang S. , Roh Y.
Published: July 2002

We proposed Si-rich tungsten silicide (WSix) films for the alternate gate electrode of deep-submicron metal–oxide–semiconductor (MOS) field effect transistors. The investigation of WSix films deposited directly on SiO2 indicated that the annealing of as-deposited films using a rapid thermal processor (RTP) results in low resistivity, as well as negligible fluorine (F) diffusion. Specifically, the resistivity of RTP-annealed samples at 800 °C for 3 min in vacuum was ∼150 μΩ cm, and the irregular growth of an extra SiO2 layer due to F diffusion during annealing has not been observed. In addition, the analysis of the WSix–SiO2–Si (MOS) capacitors exhibits excellent electrical characteristics.
Epitaxial ScN(001) Grown and Analyzed In situ by AES After (1) Deposition and (2) Ar+ Sputter Etching
Authors: Finnegan N. , Lee T.-Y. , Haasch R. T. , Greene J. E. , Petrov I.
Published: July 2002

In situ Auger electron spectroscopy (AES) spectra were obtained on single-crystal ScN(001) layers grown on MgO(001) 1 × 1 in a multichamber ultrahigh vacuum (UHV) system. A turbomolecular-pumped magnetron sputter deposition chamber was attached to a Physical Electronics model 660 scanning Auger system to allow spectra to be collected on the as-deposited film without exposure to air. The spectra show that the film surfaces are free of O and C. Spectra are also presented following sputter etching with a 3 keV Ar+ beam at an incident current density of 0.3 mA cm−2. The film was sputtered until the N/Sc peak height ratio reached equilibrium, then spectra were acquired for the after sputter condition. AES spectra were collected for both the as-deposited and the Ar+ sputter etched films using primary beam energies of 3, 5, 10, and 20 keV. The as-deposited bulk film composition was analyzed by Rutherford backscattering spectroscopy (RBS) and found to be stoichiometric with a N/Sc ratio of 1.06 ± 0.03.
Epitaxial TiN(001) Grown and Analyzed In situ by AES After (1) Deposition and (2) Ar+ Sputter Etching
Authors: Finnegan N. , Lee T.-Y. , Haasch R. T. , Greene J. E. , Petrov I.
Published: July 2002

In situ Auger electron spectroscopy (AES) spectra were obtained on single-crystal TiN(001) layers grown on MgO(001)1 × 1 in a multichamber ultrahigh vacuum (UHV) system. A turbomolecular-pumped magnetron sputter deposition chamber was attached to a Physical Electronics model 660 scanning Auger system to allow spectra to be collected on the as-deposited film without exposure to air. The spectra show that the film surfaces are free of O and C. Spectra are also presented following sputter etching with a 3 keV Ar+ beam at an incident current density of 0.3 mA cm−2. The film was sputtered until the N/Ti peak height ratio reached equilibrium, then spectra were acquired for the after sputter condition. AES spectra were collected for both the as-deposited and the Ar+ sputter etched films using primary beam energies of 3, 5, 10, and 20 keV. The as-deposited bulk film composition was analyzed by Rutherford backscattering spectroscopy (RBS) and found to be stoichiometric with a N/Ti ratio of 1.02 ± 0.02.
Adsorption, decomposition, and stabilization of 1,2-dibromoethane on Cu(111)
Authors: Chan Ally S. Y. , Jones Robert G.
Published: July 2002

The molecular adsorption and thermal reaction of 1,2-dibromoethane (DBE) on Cu(111) has been studied using ultraviolet photoelectron spectroscopy, work function change (ΔΦ) measurements, low energy electron diffraction, and line-of-sight temperature programmed desorption. At 100 K, DBE adsorbs molecularly, exhibiting a decrease in work function of 0.86 eV at the completion of the monolayer. Layer-by-layer growth is observed up to two molecular layers, with further adsorption leading to the growth of tower crystallites. The first layer of DBE undergoes thermal decomposition at 125 K to give gaseous ethene and chemisorbed bromine in a (√3×√3)R30° structure, which increases the work function of the surface by 0.58 eV. Chemisorbed bromine from partial decomposition of the first layer is found to stabilize the remaining DBE molecules in the decomposing layer, thereby arresting complete decomposition until a higher temperature. Subsequent decomposition of the stabilized DBE leads to ethene emission at 145 and 160 K for initial DBE coverages in the submonolayer and multilayer regime, respectively.
Compact focusing system for ion and electron beams
Authors: Reijonen J. , Ji Q. , King T.-J. , Leung K. N. , Persaud A. , Wilde S.
Published: July 2002

A compact ion and electron beam focusing column design has been developed in Plasma and Ion Source Technology Group at Lawrence Berkeley National Laboratory. The electrostatic ion beam-focusing column was simulated using 2D IGUN [R. Becker and W. B. Herrmansfeldt, Rev. Sci. Instrum. 63, 2756 (1992)] ion extraction and beam transport code. A new method has been developed to include finite ion temperature to the IGUN simulation (Reijonen et al., Proceedings of the LINAC Conference, 2000). The focused ion beam system includes an ion temperature collimator, which eliminates the large angle beam trajectories resulting in a small beam spot size. The small holes in the column electrodes are laser drilled, and are aligned by an optical comparator. Simulations show that focused beam spot size as small as 147 nm is achievable for a 40 keV argon beam. The compact electron beam focusing system consists of three elements: the plasma cathode, an electron temperature collimator (similar to the ion beam temperature collimator), and the focusing electrode elements. The total length of the system is less than 10 mm. The column design is performed using EGUN (W. B. Herrmansfeldt, Slac Report No. 331, 1988), electron beam computation code, and IGUN. Space charge effects as well as the electron temperature are incorporated in the computation. The simulations show that focused beam spot size of 60 nm can be achieved. Both columns use similar type rf-induction plasma generator. P+, BF2+, and O2+ ion species production by such source is also demonstrated.
Atomic force microscopy study of the growth and annealing of Ge islands on Si(100)
Authors: Liu Bing , Berrie Cindy L. , Kitajima Takeshi , Bright John , Leone Stephen R.
Published: July 2002

Atomic force microscopy is used to study the growth and annealing of Ge islands on Si(100) by molecular beam epitaxy. The Ge island shape, size distribution, number density, and spatial distribution under various growth conditions, such as different substrate temperatures, Ge beam fluxes, and annealing times, are investigated. By limiting the growth to a low coverage of 6 ML of Ge, we find that either a low growth temperature (⩽875 K) or a high beam flux can produce films dominated by pyramids of {105} facets. Domes of higher aspect ratios only appear at high growth temperatures or after a long time of annealing at low temperatures. This indicates that in the competition between the different kinetic processes responsible for the pyramid and dome formation, the domes require a higher activation energy and grow slower. We also demonstrate that appropriate annealing at low temperature can form locally ordered arrays of pyramids with a narrow size distribution.
The Stanford Two-Mile Linear Electron Accelerator
Authors: Neal R. B.
Published: July 2002

A two-mile linear accelerator under construction at Stanford University will, upon completion in 1966, accelerate electrons to energies of 20 BeV for purposes of physics research. The accelerator consists of an evacuated disk-loaded waveguide through which an electromagnetic wave at 2856 Mc/sec propagates at the velocity of light. Electrons, injected at one end, are accelerated by the traveling wave along the axis of the structure, gaining energy in the process. Radio-frequency power is supplied by 240 klystron amplifiers each producing 24 MW peak and 22 MW average at 360 pulses/sec and 2.5-μsec pulse length. The accelerator and the waveguides are evacuated to 10−7 Torr by 120- to 500-liters/sec ion getter pumps connected to an 8-in. longitudinal manifold in an upper gallery. Vacuum “finger” manifolds extend transversely at 80-ft intervals to the lower accelerator housing. All-metal seals are used throughout the vacuum system.