bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Spatial Resolution Microanalysis of Catalyst Particles
Authors: Lyman C. E. 
Published: March 2011

ABSTRACTQualitative and quantitative analysis of small catalyst particles is possible in the analytical electron microscope down to analysis areas on the order of 10 nm in diameter. The location of elements in the image field can be determined either by placing the electron probe on a particu-lar image feature or by forming a digital x-ray image showing the distribu-tion of various elements. In either case analysis of specimens of well defined thickness such as microtomed thin sections preserves spatial relationships in catalyst particles and simplifies interpretation of single element x-ray images. Electron energy loss spectroscopy can be combined with x-ray spectroscopy to reduce the ambiguity in x-ray spectra caused by spurious x-rays generated by electrons scattered from the analy-sis area to regions of high concentrations of elements removed from the analysis area.
The Local Atomic Arrangement in Amorphous Sixc1−x:H By Electron Energy Loss Spectroscopy and Electron Diffraction
Authors: Tafto J. , Kampas F. J. 
Published: March 2011

ABSTRACTWe have used electron energy loss spectroscopy (EELS) and electron diffraction to study the local atomic arrangement in amorphous SixC1−x:H in the composition range 0.37 < × < 1. In the thin films, which were pre-pared by radio-frequency glow discharge from a mixture of methane and sil-ane, the π at the K-edge of C does not show up even for the highest C-content, i.e., Si0.37C0.63, consistent with fourfold coordinated C in the whole composition range studied. Also the electron diffraction results suggest a tetrahedral network. Models where the minority element is sur-rounded by four atoms of the majority element, fit the experimental data better than models based on a random distribution of Si and C on the tetra-hedral network.
Grain-Boundary, Glassy-Phase Identification and Possible Artifacts
Authors: Simpson Y. Kouh , Carter C. B. , Sklad P. , Bentley J. 
Published: March 2011

ABSTRACTSpecimen artifacts such as grain boundary grooving, surface damage of the specimen, and Si contamination are shown experimentally to arise from the ion milling used in the preparation of transmission electron microscopy specimens. These artifacts in polycrystalline, ceramic specimens can cause clean grain boundaries to appear to contain a glassy phase when the dark-field diffuse scattering technique, the Fresnel fringe technique, and analytical electron microscopy (energy dispersive spectroscopy) are used to identify glassy phases at a grain boundary. The ambiguity in interpereting each of these techniques due to the ion milling artifacts will be discussed from a theoretical view point and compared to experimental results obtained for alumina.
Microstructural Changes in Deformed Silicon Nitride and Silicon Carbide
Authors: Tighe Nancy J. 
Published: March 2011

ABSTRACTThe microstructural changes that are associated with creep in silicon nitride and silicon carbide are described and related to the creep mechanisms. Creep in hot-pressed silicon nitride and sintered silicon carbide involves mechanisms of cavitation and crack propagation within the bonding phase when the temperatures are below those necessary to activate plastic deformation within the matrix grains. In hot-pressed, magnesia doped silicon nitride the bonding phase is amorphous magnesium silicate and the creep damage involves decohesion and sliding of the matrix grains within the soft bonding phase. In yttria-doped silicon nitride the bonding phase is crystalline and diffusional interactions between this phase, the matrix and the atmosphere dominate the creep process. A similar condition is found in siliconized silicon carbide whereby the creep is controlled by the behavior of the silicon phase.
TEM and SEM Studies of MOCVD-Grown GaP on Si
Authors: Ai-Jassim M. M. , Olson J. M. , Jones K. M. 
Published: March 2011

ABSTRACTGaP and GaP/GaAsP epitaxial layers have been grown on Si substrates by metal-organic chemical vapor deposition (MOCVD). These layers were characterized by SEM and TEM plan-view and cross-sectional examination. At growth temperatures ranging from 600° C to 800° C, the initial stages of growth were dominated by three-dimensional nucleation. TEM studies showed that at high temperatures the nuclei were generally misoriented with respect to each other yielding, upon coalescence, polycrystalline layers. The growth of single-crystal layers was achieved by nucleating a 30–50 nm layer of GaP at 500° C, followed by annealing and continued growth at 750 ° C. The defect density in these structures was investigated as a function of various growth parameters and substrate conditions. A high density of structural defects was generated at the Si/GaP interface. The use of 2° off (100) Si substrates resulted in GaP layers free of antiphase domains. These results and their implications are discussed.
The Potential of High-Resolution Transmission Electron Microscopy for Imaging Impurities at Dislocations and Grain Boundaries in Silicon
Authors: Rose Jamie H. , Gronsky R. 
Published: March 2011

ABSTRACTThe application of HRTEM to the study of equilibrium segregation in linear and planar silicon defects is evaluated with image calculations. For this purpose, models for interstitial segregation in the Σ=9 grain boundary and donor segregation in the 30° partial dislocation are proposed. These models possess columns of impurity atoms.Systematic image simulations were first examined for an impurity column in an otherwise perfect <110> silicon crystal. Optimum contrast and exposure times require samples of thickness equal to the transmitted beam extinction distance. Arsenic and boron are detectable with a column concentration of about 5%. With diffuse phase contrast imaging, this limit is roughly halved.The above imaging conditions may be used to distinguish different defect core models.Observation of segregated impurities requires somewhat higher concentrations in addition to image comparisons with a clean defect. Quantitative analysis necessitates careful image simulation comparisons and improvements in knowledge of microscope parameters.
Electron Diffraction Study of Multilayer Structures with Partially Coherent Illumination
Authors: Otsuka N. , Choi C. , Kolodziejski L. A. , Gunshor R. L. 
Published: March 2011

ABSTRACTThe effect of partial coherency on electron diffraction patterns of Cd1−xMnxTe – Cd1−yMny Te superlattices has been investigated. Observed diffraction patterns are compared with intensity calculations performed using dynamical diffraction theory with a model of an extended incoherent monochromatic source. From this study, a new method of electron diffraction for characterization of multilayer structures can be developed. Under the condition that the lateral coherent distance of the incident beam covers two adjacent layers, diffraction beams arising from the two layers give rise to an interference fringe in a diffraction spot. With this type of diffraction pattern, one can determine the refractive index of a crystal in the multilayer structure.
Application of Analytical Electron Microscopy to Ion Implantation and Near Surface Microstructures
Authors: Sklad P. S. 
Published: March 2011

ABSTRACTSurface modification using ion beam techniques is recognized as an important method for improving surface controlled properties of metallic, ceramic, and semiconductor materials. Determination of the microstructure and composition in regions located within a few hundred nanometers of the surface is essential to gaining an understanding of the mechanisms responsible for the improved properties. Analytical electron microscopy (AEM), high resolution microscopy, and microdiffraction are ideally suited for this purpose. These techniques are powerful tools for characterizing microstructure in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer and annealing behavior. Such analyses allow correlations with theoretical models, property measurements and results of complementary techniques. The proximity of the regions of interest to the surface also places stringent requirements on specimen preparation techniques. The power of AEM in examining the effects of ion implantation will be illustrated by reviewing the results of several investigations. A brief discussion of some important aspects of specimen preparation will also be included.
Microcomputers in Teching Materials Science and Engineering: TK! Solver Models
Authors: Brostow Witold , Turner David P. 
Published: March 2011

ABSTRACTThis work is a part of a larger program, aimed at improving teaching of materials science and engineering (MSE) and also at better communication between teachers and learners. Since every incoming Drexel University student is provided with a microcomputer, the objective of this project was to develop learning tools for MSE usable with a microcomputer.We have used TK! Solver, a meta-expert system, capable among other things to solve overdetermined systems of simultaneous equations. In distinction to standard programming, interchanging the roles between unknown and known parameters does not require program changes. Various operations which ordinarily would involve attaching subroutines from a libraryare accomplished by simple choices from menus. We have developed a large number of TK! Solver models for MSE, covering various materials properties (mechanical, thermophysical, electrical…), as well as all important classes of materials.
Recruitment and Retention of Lower Division Metallurgy/Materials Students
Authors: Guard Ray W. , Stafford S. W. 
Published: March 2011

ABSTRACTOpportunities in the materials science and engineering field appear quite plentiful into the next century. An increasing number of materials engineers will be needed by industry to develop new materials as well as adapt current ones to new needs. Is there a shortage of metallurgical/materials engineers? Academic institutions with existing or developing programs in materials may affect significant increases in enrollment by “marketing” materials high technology. The Department of Metallurgical Engineering at The University of Texas at El Paso has made exceptional progress in recruiting and retaining prospective engineering students into this technical area. What has been successful at UTEP may also benefit other academic programs.
Concentration Measurements of Chlorine Atoms in A Plasma Reactor
Authors: Wormhoudt Joda , Stanton Alan C. , Richards Albert D. , Sawin Herbert H. 
Published: March 2011

AbstractInfrared absorption spectroscopy has been used to measure atomic chlorine concentrations over a range of plasma conditions in both Cl2 and CF3Cl discharges.These measurements were made utilizing the spin-orbit transitions in the ground state of atomic chlorine near 882 cm−1.The concentration studies were performed by passing light from a diode laser through a multi-pass (White) cell set in two opposed windows of a parallel plate plasma etching reactor.The plasma work was preceded by a laboratory measurement of the infrared absorption line strengths of the 2P1/2 ← 2P3/2 transition.This measurement was done in a known concentration of atomic chlorine produced in a low pressure discharge flow system by the reaction of Cl2 or HCl with excess fluorine atoms.These measurements resulted in an integrated line strength of 4.14 (±0.89) × 10−21 cm2-molecule−1-cm−1 for the strongest hyperfine component of the transition at 882.3626 cm−1.Measured atomic chlorine concentrations in Cl2 discharges varied between 0.2 and 8.0 × 1014 atoms/cm3, representing atomic chlorine fractions on the order of a few percent.The measured atomic chlorine concentrations increased approximately linearly with increasing power and pressure, and increased with increasing frequency above approximately 1 MHz.Below 1 MHz, the atomic chlorine concentration was relatively independent of frequency.
Spectroscopic Diagnostics and Kinetics of Low Pressure Processing Plasmas
Authors: Garscadden Alan 
Published: March 2011

AbstractA review is presented of a negative glow model of low frequency, low pressure plasma reactors and the salient features are described using silane mixtures as the example.The input requirements for this model and similar models are also discussed in order to establish the sensitivity of the homogeneous plasma reactions to operational conditions.Calculations are presented to demonstrate the sensitivity to mixture ratios, buffer gas type and power loading.
An Investigation of the Cathode Fall
Authors: Doughty D. A. , Lawler J. E. 
Published: March 2011

AbstractSpectroscopic diagnostics are used to map key parameters of the cathode fall of a He glow discharge.Optogalvanic spectroscopy on Rydberg atoms is used to perform spatially resolved electric field measurements.The resulting E/N maps provide the ion and electron current densities, which are used to determine the local ionization rates.Local excitation rates are mapped by observing the spectral emission from the discharge.Optogalvanic spectroscopy is also used to observe electron avalanches starting from a well defined position in the cathode fall.These detailed experimental maps will be essential in studies of the nonhydrodynamic electron distribution function.Various theoretical models of the cathode fall will be compared to the experimental results.
Silicon Nitride from Microwave Plasma: Fabrication and Characterization
Authors: Tessier Yves , Klemberg-Sapieha J. E. , Poulin-Dandurand S. , Wertheimer M. R. 
Published: March 2011

AbstractPlasma silicon nitride (P-SiN) films were prepared from SiH4/NH3 mixtures in a large volume microwave plasma (LMP) apparatus, at substrate temperatures T2 ranging from ambient to 250°C.Under otherwise nominally identical fabrication conditions, deposition rates were 10 to 25 times greater than those reported by others for radio- or audio-frequency plasmas.Based on film compositions, determined by elastic recoil detection (ERD), and measurements of such properties as density, refractive index, etch rate in dilute HF, and moisture permeation coefficient, our best P-SiN films (produced at T2 ≥ 200°C) are very similar to those reported in the literature.
Characterization of Hydrocarbon Plasma used for a-C:H Deposition
Authors: Wagner J. , Wild Ch. , Bubenzer A. , Koidl P. 
Published: March 2011

AbstractOptical emission analysis and mass spectroscopy was applied to study the rf-glow discharge in hydrocarbons used for the deposition of amorphous hydrogenated carbon (a-C:H).The mass spectra of the positively charged ions in the plasma are characteristic for the hydrocarbon used - e.g.benzene, hexane, or methane.In contrast, the properties of the deposited a-C:H film, such as refractive index, are independent of the precursor gas.Spatially resolved optical measurements show strong emission from C, C2, and CH in the vincinity of the negatively self-biased cathode (substrate) irrespective of the precursor used.Based on these findings we conclude that the fragmentation of the impinging energetic hydrocarbons is one of the key mechanisms for the formation of hard, strongly cross-linked a-C:H films.
Theoretical and Computational Problems in Modeling Glow Discharges
Authors: Graves David B. , Jensen Klavs F. 
Published: March 2011

AbstractIt is desirable to develop detailed models of glow discharge chemical reactors in order to understand the many complex interactions that govern reactor performance.One important part of an overall model of the plasma reactor is the description of the discharge physical structure including charged particle densities, energies and the self-consistent electric field.The continuum or fluid equation approach to this problem is presented in this paper and potential problems with this approach are discussed.Results from recent simulations of a 13.56 MHz rf discharge are presented.The behavior of the electrons in the quasineutral plasma and their interaction with the self-consistent field are highlighted.It is shown that the rf power dissipation peaks at the plasma-sheath boundary, and the implications of this for the validity of estimates of mean electron density from equivalent rf rcircuit models is discussed.
Continuum Modeling of Charged Particle Transport: RF Breakdown and Discharges of SF6
Authors: Thompson Brian E. , Sawun Herbert H. , Owens Aaron 
Published: March 2011

AbstractContinuity equations for the concentration of electrons, positive ions, and negative ions were constructed and solved to predict rf breakdown voltages and the electrical properties of SF, discharges.These balances for the three types of charged species include terms for convection (electric field-driven fluxes), diffusion, and reactions (ionization, electron attachment, and negative-positive ion recombination).The mobilities, diffusivities, and reaction rate coefficients necessary for the rf discharge model are based on reported measurements and calculations of these parameters in dc electric fields.The electric fields developed in the rf discharge are calculated from Poisson's equation and applied voltage conditions.Predictions based on this model are compared with measured rf breakdown characteristics of SF6.
Kinetics of Plasma Etching Silicon with Nitrogen Trifluoride
Authors: Stenger Harvey G. , Akiki G. S. 
Published: March 2011

AbstractA kinetic model, composed of elementary chemical reactions, is derived to predict the etch rate of crystalline silicon with NF3 in a plasma discharge.Experimental data taken from a radial flow plasma etching reactor is used to determine the model's kinetic parameters.The rate constant for atomic fluorine reacting with <100> silicon was determined to be 1410 cm/min at 25 °C, in good agreement with a value obtained by other investigators.
Directional Plasma Etching of Polysilicon in SF6/CFCL3 discharges
Authors: Mocella Michael T. , Thompson Brian E. , Sawin Herbert H. 
Published: March 2011

AbstractThe directional etching of P-doped polysilicon has been studied as a function of power (0.2 – 0.8 W/cm3), pressure (0.2 – 0.4 torr), and CFC13 (FreonR-11) fraction (1 – 20%) in SF6 discharges.Over this parameter space, experimental measures of the etching rate, directionality, plasma impedance, optical emission, and ion-bombardment energy and flux were made.Through Ar actinometry, the concentrations of F and Cl were estimated.Response Surface Methodolgy was used to fit the measurements to polynomial models which were used in the subsequent kinetic modeling of the process.As the fraction of CFCl3 was increased from 1 to 20%, the F concentration fell by a factor of 3 while the Cl concentration increased by a factor of approximately 20.The mask undercut and etching rate, however changed less than a factor of two with the CFCl.increase.The measured average ionbombardment energies were well correlated using discharge currents.
Electron Energy Distribution Functions in RF Molecular Plasmas
Authors: Dilonardo M. , Capitelli M. , Winkler R. , Wilhelm J. 
Published: March 2011

AbstractElectron energy distribution functions in molecular rf plasmas (CO, SF6) have been calculated by numerically solving the time dependent Boltzmann equation in a wide range of field frequencies up to the establishment of the periodic state.Particular attention is given to the reduction of the modulation degree and phase shift with respect to the rf field of the isotropic distribution function and of some macroscopic quantities as a function of frequency.Time averages of distribution functions and of some macroscopic quantities are then compared with the corresponding results obtained by using the effective field approximation.Finally we discuss the role of the second kind collisions in affecting the results.
Single Wafer, Anisotropic Etching of Polysilicon with C12/SF6 and Trielectrode Reactor Operation
Authors: Nulty James E. 
Published: March 2011

AbstractA totally anisotropic, highly selective dry poly etch process has been developed that is capable of etching sub-2.0 micron linewidths.Doped poly etch rates of 10,000 A/min.are obtained using C12-only chemistry.Standard novolac or bilevel photoresist is used, depending on the lithography requirements.Anisotropy is achieved without the use of carbon-containing gases; as a result, minimal proximity effects are observed between dense and stand alone etched lines.Wafer maps of etched linewidths on 4-inch wafers are presented, showing mask to final bias and uniformity results.A commercially available triode dry etching system was used for the work.The self-induced dc bias voltage can be selected regardless of the applied rf power.The effect of variable self-induced dc bias versus applied rf power is presented for selectivity, upper and lower electrode interactions, and etch rate uniformity.Characterization by the use of spectroscopy is also presented, showing changes due to varying the self-induced dc bias at a constant rf power.
Homogeneous and Heterogeneous Chemistry of Methane Deposition Plasmas
Authors: Partlow W. O. , Kline L. E. 
Published: March 2011

AbstractExperimental measurements and theoretical modeling of methane deposition plasmas have made it possible to determine the most likely homogeneous and heterogeneous chemical reaction paths leading to deposition of hydrogenated carbon from the fragments of electron dissociated methane.The methane plasma was modeled as a plug-flow reactor.Gas phase reactions, diffusive transport, variable surface reflection coefficients, and surface chemical reactions are included in the model which follows a “plug” of gas as it flows through the reactor.Boltzmann equation and Monte Carlo calculations were used to determine the electron energy distribution and the resulting dissociation and ionization rate coefficients averaged over space and time.Experimental measurements of the time dependent electrical properties of the plasma are used as input to the model.Deposition rates, deposition uniformity, downstream mass spectroscopy, and the dependences of these quantities on power and mass flow rates are compared to the model to arrive at a consistent representation of the deposition chemistry.
Characterization of Plasma-Enhanced Chemical Vapour Deposition of Silicon-Oxynitride
Authors: Hoek W. G. M. Van Den 
Published: March 2011

AbstractThe plasma-enhanced chemical vapour deposition (PECVD) of siliconoxynitride from silane, ammonia and nitrous oxide was studied using an ASM vertical parallel plate reactor.Films varying from PECVD oxide (refractive index no1.50) to PECVD nitride (n=2.00) were analyzed using ellipsometry, UV-visible reflection spectroscopy, Fourier-transform infrared transmission spectroscopy (FTIR), nuclear reaction analysis (NRA), Rutherford backscattering (RBS) and electron spectoscopy for chemical analysis (ESCA).Stress measurements were performed using a Fizeau interferometer.
Influence of Substrate Temperature on the Structure of Tin-Films
Authors: Molarius J. M. , Korhonen A. S. , Erola E. , Nykanen E. 
Published: March 2011

AbstractThree series of Ti-N films with varying nitrogen contents from about 8 to 52 at.% N were deposited by triode ion plating at temperatures of 773, 623 and 373 K, respectively.Marked changes in the structures of the films with decreasing temperature were observed by x-ray diffraction.Stoichiometric δ-TiN which showed (220) preferred orientation at 773 K changed to (111) at lower temperatures.At intermediate nitrogen concentrations α-Ti (002) decreased and a new ε-Ti2N (002) developed with decreasing temperature.Very smooth and dense films could be produced at the lower temperatures.