bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Leachate Generation at the Montour, Pennsylvania, Fly Ash Test Cell
Authors: Villaume J. F. , Bell J. W. , Labuz L. L.
Published: March 2011

The Pennsylvania Power & Light Company, in cooperation with the Electric Power Research Institute, is studying leachate generation at a large outdoor test cell of compacted coal combustion fly ash constructed at the Montour Steam Electric Station in north-central Pennsylvania. The test cell design is identical to that of the plant's active dry fly ash disposal facility. Leachate initially generated at the test cell contained concentrations of chromium and selenium approximately ten times above EPA's assigned Maximum Contaminant Levels (MCL's) for drinking water. Concentrations of these two parameters have since decreased approximately five-fold. Similar reductions have occurred in the concentrations of several of the other trace metals measured in the leachate. The dominant reaction mechanisms controlling leachate composition were examined in an attempt to explain these and other observations. Deterministic chemical modeling was performed to aid in the interpretation of the data. The dynamics of leachate generation were also examined through an evaluation of the infiltration and redistribution of moisture.
X-Ray Powder Diffraction For Studying the Mineralogy of fly ash
Authors: McCarthy Gregory I.
Published: March 2011

A brief summary of the use of x-ray powder diffraction for studying the mineralogy of fly ash is presented. Mineralogies of low-, intermediate- and high-calcium fly ashes are discussed and illustrated by results from XRD characterization of U.S. National Bureau of Standards fly ash Standard Reference Materials.
Single Crystal Silicon Membranes
Authors: Fernandez Andres , Hren P. , Lee K. C. , Silcox J.
Published: March 2011

Self-supporting, thin single crystal membranes can be fabricated from silicon wafers using ion implantation, anodic etching and subsequent annealing. Typically, membranes approximately 1200Å thick and about 250μm in diameter are formed in wafers 4 mil thick. Discs surrounding the membranes can be cut out to provide suitable TEM samples. In this paper, the steps for preparing such samples are presented with as much attention paid to experimental details as possible.
The Preparation of Mechanically Alloyed Powders for TEM Examination
Authors: Kamenetzky E. A. , Wall M. , Castro R , Tanner L. E.
Published: March 2011

TEM specimens of mechanically alloyed elemental Ni and Nb powders are prepared by a new procedure. The alloyed powders are mixed with smaller Al powders and fill an aluminum ring (3mm outer diameter). This composite is cold pressed together with the Al powders taking most of the deformation. The compacted specimen can be mechanically thinned. Electropolishing and ion milling can then proceed by standard methods with special precautions to minimize differential polishing or milling rates.

The microstructural aspects of the formation of an amorphous phase by high-energy ball milling these powders have been studied. After 6 h each particle transforms to a heterogeneous layered composite of particles of one element in the matrix of the other. Particle size ranges from 15 nm to 90 nm. Mechanical alloying for 36 h results in the formation of an apparently uniform phase interspersed with a few small (4 nm to 30 nm) elemental crystalline particles. The uniformity of composition and the presence of C, O, and Fe were studied by EDX and EELS.
Artefacts in Ceramics Produced During Preparation and Examination of TEM Specimens
Authors: Lee W. E. , McCoy M. A. , Mhaisalkar S. G.
Published: March 2011

A brief review of possible causes of artefacts in ceramic TEM specimens is illustrated with examples from oxide, silicate and titanate ceramics.
Tem Specimen Preparation by Mechanical Microthinning
Authors: Plummer H. K. , Shinozaki S.
Published: March 2011

Mechanical abrasion has been used by the authors to prepare a variety of materials, mainly ceramics, which have been thinned to electron transparency. The basic premise of this technique is the rotation of a spherically shaped wood tool at right angles to a rotating 3mm specimen disk (∼100 μm thick). A slurry of 1/2 μm diamond powder in a glycerin vehicle thins the specimen and carries away the abraded matter. In addition to the wood tool other materials such as brass, teflon and polyethylene have been tried without success. Abrasion “marks” left on the thin specimen surface can be ignored in some situations or removed by a touch up ion milling at 3 keV for ∼1/2 hr. Recently, attempts to thin N+ implanted Al from the un-implanted side using a wood tool were found to be extremely time consuming, i.e. 60 hr or more. It was found that a spherical stainless steel tool produced a suitably thin transmission electron microscopy (TEM) specimen using glycerin as the vehicle and no diamond powder. Depending upon the pressure applied to the tool these specimens could be thinned in as little as 3 hr. The turning marks left by the lathe tool proved to be sufficient to thin the soft aluminum. From this result It appears that soft tools will thin hard materials and hard tools can be used to thin soft materials efficiently. A number of other specimens recently prepared using mechanical microthinning will also be presented.
Preparation of Electropolished Transverse Sections of Thin Aluminum Sheet for Transmission Electron Microscopy
Authors: Smith Steve
Published: March 2011

The preparation of transverse section TEM foils from thin (0.2 mm to 1.5 mm) aluminum sheet would usually be accomplished by a combination of dimpling and ion milling. Both of these techniques are time consuming. A technique has been developed which allows these transverse section foils to be prepared by electropolishing, which greatly reduces the time required for specimen preparation. This technique also produces far more thin area for examination than a comparable foil which has been dimpled and ion milled, and eliminates artifacts produced by ion milling.
Simple Plan View Specimen Preparation Technique For Tem Investigation Of Semiconductors and Metals
Authors: Veirman A. De , Eysermans J. , Bender H. , Vanhellemont J. , Landuyt J. Van
Published: March 2011

This paper discusses a rapid and simple specimen preparation technique which was originally developed for plan view TEM investigation of processed silicon, but which afterwards was modified for the study of GaAs, Al/Al2O3 and Silicon-On-Insulator (SOI) structures. The major advantage of this poor man's method is that no specialised nor expensive equipment is needed.

A second technique is also described which is used in the case of unseeded SOI structures where the analysis of the top silicon layer is important.
A Controlled Method Of Preparing Plan-View Silicon Samples For Transmission Electron Microscopy Studies
Authors: Ellington Myrtle B.
Published: March 2011

Transmission electron microscopy (TEM) is an important technique for studies of extended defects and other microstructural features in semiconductor materials. An efficient, plan-view thinning technique is always desirable for these TEM studies. The problems associated with wet chemical thinning of silicon are often surface residues, pitting and rapid breakthrough. A controlled method for obtaining thin, plan-view TEM silicon samples by chemical thinning was developed and the method is described in this paper. Results indicate that the method minimizes the above cited problems and has several other advantages over previously reported thinning methods.
Techniques of Insulator/Semiconductor Heterostructure Specimen Preparation
Authors: Bahnck D. , Batstone J. L. , Phillips Julia M.
Published: March 2011

Techniques for the preparation of specimens for Transmission Electron Microscopy analysis are described. Cross-sectional specimens of insulator/semiconductor heterostructures have been successfully prepared. The problem of differential thinning rates and interface amorphization during argon ion-milling have been overcome using low argon ion accelerating voltages and shallow angles of incidence. Techniques for preparation of plan view specimens include the preparation of silicon substrates for in-situ crystal growth in an ultrahigh vacuum Transmission Electron Microscope.
Preparation of Vitrified TEM Samples for the Direct Observation of Sol and Gel Structures
Authors: Bailey Joseph K. , Bellare Jayesh R. , Mecartney Martha L.
Published: March 2011

Direct observation of structure in liquid phase materials is made possible by a cryo-vitrification technique in which a thin liquid sample is frozen at a high cooling rate to prevent crystallization. We have applied this technique to observe the evolution of structure in ceramic sols and gels using TEM. The sample preparation technique is described in detail and results obtained from colloidal and polymeric sols and gels are presented to show the usefulness of the technique. Artifacts arising from radiation damage and beam heating are also discussed.
GaAs/Si Nucleation and Buffer Layer Growth
Authors: Koch Stephanie M. , Hull Robert , Rosner S. Jeffrey , Harris James S.
Published: March 2011

We investigate two aspects of the initial stages of GaAs/Si growth: the effects of Si misorientation on GaAs island nucleation, and the structural changes occurring upon heating the buffer layer to the final deposition temperature. We observe that the GaAs islands tend to nucleate at Si surface steps and grow along them. The shape of the islands depends on the degree and direction of the Si misorientation from (100). Island coalescence occurs as the film grows, such that a 500Å film is almost completely continuous. In situ heating of a 30A film to 5750C for 15 minutes causes the islands to agglomerate, while similar treatment of the 500A film does not appear to expose more of the underlying substrate and in fact improves the film crystallinity.
The Role of thin Low Temperature Deposited GaAs Films on the two Step Growth of GaAs on Si By Mocvd
Authors: Inuzuka Hajine , Suzuki Yasutoshi , Awano Naomi , Hara Kunihiko
Published: March 2011

The structural change of the thin low temperature (~450°C) deposited GaAs films and the role for conventional temperature growth were studied by RHEED and cross-sectional TEN observation. The formation of the threedimensional high quality single crystalline islands from continuous twin GaAs layer deposited at low temperature (~450°C) was clarified. These three-dimensional islands act as the seeds for conventional temperature growth.
Photoluminescence Studies of Annealed GaAs Films Grown on Si Substrates
Authors: Bugajski M. , Nauka K. , Rosner S.J. , Mars D.
Published: March 2011

Low temperature (T - 5K) photoluminescence (PL) has been measured on a variety of as-grown and annealed GaAs films grown on Si substrates by the MBE technique. The PL spectra of the annealed GaAs layers showed an apparent difference between the nomigally undoped samples with free carrier concentrations below 1015 cm−3 and the layers with dopant concentrations exceeding 1017 atoms cm−3 . The annealing caused an increase of both excitonic and defect related PL intensities in low doped samples. In heavily doped layers the annealing suppressed excitonic emission and strongly enhanced defect related luminescence bands. Observed post annealed infrared shifts of the PL peaks in the excitonic region are explained assuming a tetragonally distorted GaAs lattice under tensile stress, and an increase in stress after high temperature annealing.
Heterostructures of GaAs and AlAs on Silicon: X-Ray Analysis and Excimer Laser Annealing
Authors: Georgakilas A. , Fatemi M. , Fotiadis L. , Christou A.
Published: March 2011

One micron thick AlAs/GaAs structures have been deposited by molecular beam epitaxy onto high resistivity silicon substrates. Subsequent to deposition, it is shown that Excimer laser annealing up to 120mJ/cm2 at 248nm improves the GaAs mobility to approximately 2000cm2 /v-s. Dislocation density, however, did not decrease up to 180mJ/cm2 showing that improvement in transport properties may not be accompanied by an associated decrease in dislocation density at the GaAs/Si interface.
High Quality GaP Growth on Si Substrates By Mocvd
Authors: Uchida K. , Kohama Y. , Tajima M. , Soga T. , Jimbo T. , Umeno M.
Published: March 2011

GaP crystals are grown on Si substrates by MOCVD. Double crystal X-ray diffraction indicates that the crystal quality of GaP layers greatly improves when AsH3 is supplied before growth. The FWHM of (400) diffraction peak of the GaP layer decreases as the thickness increases and the best FWHM of 112.5 arcs is obtained at a thickness of 5 μm. The GaP/Si interface is characterized using secondary ion mass spectroscopy (SIMS) to demonstrate the effect of AsH3.
Oriented Growth of SrTiO3 Films on Si(100) Substrates Using In—situ Cleaning By Excited Hydrogen
Authors: Ishiwara Hiroshi , Azuma Kazumutsu
Published: March 2011

In—situ cleaning of Si surfaces in vacuum was successfully performed using excited hydrogen and it was applied to epitaxial growth of SrTiO3 films on Si(100) substrates. Epitaxial growth of SrTiO3 films was observed under optimum cleaning conditions, however, the epitaxial nature was found to be destroyed for films thicker than 50 nm, which is probably due to the non—stoichiometry of the films. The electrical properties of the initially epitaxial SrTiO3 films grown on the cleaned Si substrates were better than those of polycrystalline ones.
Heteroepitaxial Growth of A1203 Thin Films on Si By Lpcvd
Authors: Ishida M. , Katakabe I. , Ohtake N. , Nakamura T.
Published: March 2011

Heteroepitaxial A1203 thin films were grown successfully on Si(lO0) substrates by low—pressure chemical vapor deposition (LP—CVD). The growth was performed at a pressure of 30 Torr by pyrolysis of N2 bubbled AI(CH3)3 and N20 at substrate temperatures above 1000ºC.RHEED patterns indicated that the grown films were ɤ—Al203 single crystals with an orientation relationship of ɤ—Al203(l00)//Si(l00). The ɤ—A1203 films were stable and did not show phase transition after a 1140ºC heat—treatment for 2hr. MOS capacitors with 500—Å—thick A1203 films as a gate insulator showed highfrequency capacitance—voltage (C—V) curves without hysteresis. The A1203 interface state density determined from quasi—static C—V measurements was 1.7 X 1011cm-2eV-1. It can be seen that ɤ—Al203 film is a promising new insulator for Si on Insulator (SOI) structures.
The Effect of Substrate Annealing on Epitaxial Growth in Mbe—Grown Silicon on Sapphire.
Authors: Pellegrino Joseph G. , Richmond Eliezer D. , Twigg Mark F.
Published: March 2011

We have continued our investigation1 of the effects of pre—deposition substrate annealing for the case of MBE grown silicon on sapphire. Three identical series of samples were grown with film thicknesses ranging between 65 and 1500 angstroms. Each series of samples was grown upon sapphire which had been annealed at either 1450ºC, 1300ºC, or 900ºC. The growth temperature and growth rate were the same for each series. The anneal time for each sample was 30 minutes.
New Directions in the Growth of Epitaxial Insulators and Metals on Silicon
Authors: Phillips Julia M. , Batstone J. L. , Hensel J. C.
Published: March 2011

By nature of their high degree of crystalline perfection, epitaxial insulators and metals on semiconductors are structurally characterizable to a considerably greater extent than are polycrystalline or amorphous materials. This offers the possibility of correlating the detailed structure of these thin epitaxial films and their interfaces with their electrical properties. We have recently found evidence for the influence of the atomic structure of the CaF2/Si(ll1) interface on its electrical properties. Wehave also studied the structural and electrical properties of ultrathin epitaxial cobaltsilicide layers on Si(111).
Growth of Thin Epitaxial CoSi2 Layers on Si(100)
Authors: Yalisove S. M. , Tung R. T. , Batstone J. L.
Published: March 2011

The growth of high quality, thin (14-70 Å) epitaxial CoSi2 layers on Si(100) substrates have been observed. Three types of films have been grown on the Si(100) substrate; pure CoSi2(100), pure CoSi2(110), and mixed CoSi2(100)+CoSi2(110). The CoSi2(110) can exist in two 90º rotated variants on the Si(100) surface and these are observed. Methods to isolate the epitaxial orientations are described. Results from in-situ LEED and AES as well as ex-situ RBS and plan view TEM are presented.
Electrical & Structural Properties of TiSi2 Films
Authors: Ravindra N.M. , Fink T. , Moerkirk R.P. , Fathy D.
Published: March 2011

Studies of the electrical and structural properties of TiSi2 films formed during the fabrication of shallow junctions by ion implanting As+ into p–Si through Ti films are reported here. Electrical measurements of the temperature dependent specific contact resistance and structural measurements such as transmission electron microscopy have been performed on these device structures. The specific contact resistance is seen to decrease with increasing measurement temperature. These studies have been carried out on furnace and rapid thermally annealed films.
Propagation of Dislocations Through GeSi/Si Strained Layers and Superlattices
Authors: Hull R. , Bean J.C. , Leibenguth R.E.
Published: March 2011

We describe in-situ transmission electron microscope observations of the relaxation of strained layer GeSi/Si epitaxy. Dynamic observations of misfit dislocations in these structures reveal that dislocation nucleation and growth activation barriers, as well as interactions, limit the rate at which strain is relieved. The equivalence of threading and misfit dislocations in this system is demonstrated. Extension of the principles learnt from these single layer experiments to threading dislocation propagation through multilayer structures, enables us to understand the relative inefficiency of GeSi/Si strained layer superlattices in blocking threading dislocations.
The Influence of Substrate Surface Chemistry on GaAs - on - Si Growth
Authors: Bringans R. D. , Olmstead M. A. , Ponce F. A. , Biegelsen D. K. , Krusor B. S. , Yingling R. D.
Published: March 2011

Several surface treatment techniques have been used to study the effect of the Si surface on subsequent GaAs-on-Si epitaxy. In particular, the effect on the degree of island formation is addressed. Experiments have been carried out with GaAs film thicknesses in the range from one monolayer to around 50nm. Core level spectroscopy results for the monolayer films give information about the bonding character at the interface and suggest methods of improving the degree of two-dimensional growth. A particular Ga-prelayer technique is examined with high resolution TEM and found to give significantly different results than the standard MBE growth technique.
Electronic Properties of Si - Ge Micro Nipi Structures
Authors: Yang L. H. , Fong C. Y. , Nelson J. S.
Published: March 2011

Electronic properties of the n-doping--insulator--p-doping--insulator structures in ultra thin strained [001] Si - Ge superlattice have been studied theoretically. The Ge - layer is used as one of the insulating region. The Al and As atoms are treated as impurities. The superlattice ((Si)10 -(Ge)2) exhibits an indirect gap in reciprocal space and the staggered band alignment in real space. With doping, the samples show a direct band gap and staggered band alignment. The acceptor state is associated with the Al-Si bonding state, while the donor state is derived from the As s-like state. The separation of the charge carriers in the real space can be obtained.
New Approach to Growth of High-Quality GaAs Layers on Si Substrates
Authors: Varrio Jukka , Salokatve Arto , Asonen Harry , Hovinen Minna , Pessa Markus , Ishida Koichi , Kitajima Hiroshi
Published: March 2011

GaAs layers were grown on Si (001) substrates by molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). They were examined by transmission electron microscopy, doublecrystal X-ray diffraction and Rutherford backscattering/channeling technique. Initial layer growth in both MEE and MBE was governed by three-dimensional nucleation but a stronger tendency for GaAs islands to align along the surface steps of Si was observed in the case of MEE. There was no measurable tilt between the (001) planes of GaAs and Si if growth was initiated by MEE at low temperature, prior to further growth by MBE at higher temperatures. On the contrary, the tilt angle was 0.34• when the entire structure was prepared by conventional two-step MBE. Rutherford backscattering measurements indicated a significant reduction in the density of defects throughout MEE/MBE GaAs in comparison with MBE GaAs.
Advanced Sensing of Materials Processing
Authors: Wadley Haydn N. G. , Kahn Arnold H. , Johnson Ward
Published: March 2011

To implement new process control strategies including Intelligent Processing of Materials, advanced sensors are required to nonintrusively evaluate process and microstructure variables. Researchers increasingly are looking to innovative extensions of traditional nondestructive evaluation technologies, such as ultrasonics, acoustic emission, and eddy current methodologies for this. Here, the nature and characteristics of emerging sensors based upon these new measurement methods are described and examples of their application discussed.
Non-Contact True Temperature Measurements for Process Diagnostics
Authors: Khan Mansoor A. , Allemand Charly , Eagar Thomas W.
Published: March 2011

The accurate measurement and control of temperature can be of great importance in most materials manufacturing and processing applications. With present-day technology such measurement almost always requires either physical contact with the subject or an extensive calibration procedure. In many cases contact is either not desirable, because such contact may significantly alter the temperature or other characteristics of the subject, or is not possible because the subject is moving, is too far away, is too hot or is in an otherwise hostile environment. Similarly calibration may not be possible if the characteristics change too much.
Optical Diagnostics for a High.Power, RF-Inductively Coupled Plasma
Authors: Nogar N. S. , Keaton G. L. , Anderson J. E. , Trkula M.
Published: March 2011

Emission spectroscopy and laser-induced fluorescence have been used to monitor the field and tail-flame regions of a Hull-design1inductively coupled plasma. This plasma is used for a variety of syntheses2,3including SiC, TiC, BN, AlN and diamond. Temporallyand spatially-resolved spectra of both pure Ar and Ar/gas mixtures have been studied as a function of RF power, pressure and flow rate. Preliminary data suggest that the system is far from local thermodynamic equilibrium.
Laser Diagnostics for Investigation of Particle Formation Processes
Authors: Semerjian H. G. , Zachariah M. R. , Presser C.
Published: March 2011

Formation, growth and deposition of particles represent a critical part of several important industrial processes, such as production of carbon black, optical fibers, micro-electronic components, and metal and ceramic powders. Laser diagnostic techniques are utilized to develop a fundamental understanding of these processes.

Formation of carbonaceous soot particles has been studied in laminar, coannular, hydrocarbon diffusion flames. Laser extinction/scattering, laser scattering dissymmetry, and velocimetry measurements have been used to determine particle volume fraction, size, number density and velocity. From this set of data, particle formation and growth rates have been determined for different fuels and at different temperatures. Similar techniques have been used to study silica particle formation in an opposed jet diffusion flame, where silicon is introduced in the form of silane (SiH4) into the fuel stream (H2/Ar); the oxidant is an O2/Ar mixture. The advantage of this geometry is that, along the stagnation point streamline, the flow may be considered one-dimensional. This should allow the extension of the results of this study to practical CVD or MCVD processes for optical fibers. Laser diagnostic techniques are also being used to investigate metal powder atomization processes, and the effect of operating conditions on particle size distribution.
Optical Measurements of Soot Particles in Flames
Authors: Santoro Robert J.
Published: March 2011

The formation and growth of soot particles in combustion systems represents an area of significant research interest. Critical to progress in this area has been the development of suitable optical diagnostic techniques. Principal among these has been the utilization of laser light scattering techniques to obtain particle size and concentration information. When combined with measurements of other quantities such as the velocity, the resulting spatially and temporally resolved measurements can be used to examine particle processes such as coagulation and surface growth. In the present work, the results from studies conducted in laminar diffusion flames involving laser based measurements of the soot particle and velocity fields are reviewed. As an example of the utility of such an approach, these results are used to examine the evolution of the particle surface area for a series of simple hydrocarbon fuels. The results indicate that the available surface area varies strongly with the fuel molecular structure. However, the specific surface growth rate is observed to be similar for all the fuels studied.
High Sensitivity Measurement of Flame Radicals by Frequency Modulation Spectroscopy
Authors: Woody Bernard A.
Published: March 2011

Frequency modulation spectroscopy (FMS) is a new combination of optical absorption spectroscopy and radio technology which increases absorption sensitivity by orders of magnitude. Extremely weak atomic and molecular lines and stronger absorbers at low number densities, previously accessible only to fluorescence techniques, are readily detected.

Information obtainable through FMS include species number density, lineshape and temperature. Data interpretation is straightforward without regard to such problems as quenching, alternate excited state reaction channel loss and source/absorber solid angle and spectral response calibration, since the technique probes the lower state population via line of sight, volume integration. Application of the technique to the study of radical species such as CH, CN, and NO2 produced in flames and low pressure reactor vessels has made absorption studies of these systems feasible for the first time. The technique has also been used to study such diverse problems as the effect of fuel additives on the production of soot, and the concentration and distribution of the chemical intermediates, BH, BO, and BO2, in microwave driven reactive flows. Feasibility studies to determine if FMS can assist in the diagnostic and control problems of chemical vapor deposition in the semiconductor industry have recently been initiated.
Laser-Induced Fluorescence Measurement of Free Radical Intermediates
Authors: Crosley David R.
Published: March 2011

Laser-induced fluorescence (LIF) provides a means for sensitive, selective and nonintrusive measurements of reactive intermediates, often free radicals, which control the chemistry of combustion. The same approach can be used to detect in the gas phase, atoms, radicals and ions which are reactive intermediates in materials processing. This article briefly examines the use of LIF in combustion. It includes a description of the LIF spectroscopic method as employed for quantitative measurements, and the use of LIF in a semiquantitative manner with extension to the simultaneous detection of more than one species.
Digital Fluorescence Imaging of Gaseous Flows
Authors: Hanson Ronald K. , Paul Phillip H. , Seitzman Jerry M.
Published: March 2011

The current status of planar laser-induced fluorescence (PLIF) imaging is reviewed, and example imaging results obtained in subsonic and supersonic jet-mixing flows with a new intensified high-resolution CCD-array camera are presented.
Optical Methods for Plasma Edge Diagnostics in Magnetic Confinement Experiments
Authors: Hintz E. , Bogen P.
Published: March 2011

The radial extension of the plasma edge being determined by the ionisation length of the atomic hydrogen, the rtanges of the main plasma parameters to be covered are: 1010 cm-3 < ne <. 1013cm-3 5 eV < Te- < 100 eV, density of neutral particles below 1010 cm-3. Physical quantities to be measured are the electron density ne and temperature Te, the density and temperature (velocity distribution) of hydrogen and of the main impurities (oxygen, carbon, metals). Relying mainly on emission spectroscopy, laser induced fluorescence and atomic beam methods, most of these quantities can be determined with the desired space and time resolution. Experimental arrangements will be described and typical results will be presented.
Self Bias of an R.F. Driven Probe in an R.F. Plasma
Authors: Benjamin N M P , Braithwaite N St J , Allen J E
Published: March 2011

An effect of sinusoidal r.f. voltages between a plasma and a floating Langmuir probe (or other electrode) is to produce a d.c. self bias voltage. This effect has previously been studied with r.f. applied to probes in d.c. plasmas, and the results have often been referred to in connection with d.c. probes in r.f. plasmas, although the situation is slightly different. In the current work a ‘d.c.’ probe in an r.f. plasma is examined. However, the r.f. potential difference between probe and plasma is first compensated for by superimposing a synchronous signal of appropriate amplitude and phase on to the d.c. circuit. Thus the probe can perform essentially d.c. type measurements on the r.f. plasma. The deliberate reintroduction of a measure of r.f. between probe and plasma is accomplished by overdriving the compensation signal thereby generating a controlled amount of self bias.

The observed variation of probe bias with r.f. overdrive is in good agreement with analytic theory based upon modified Bessel functions as used for d.c. generated plasmas. This work is of general interest in probe diagnostics of r.f. generated plasmas, and understanding the self bias of isolated electrodes.
Optical Imaging Diagnostics for Fusion Plasmas
Authors: Allen S. L.
Published: March 2011

Imaging diagnostics are used for spatially-and temporally-resolved quantitative measurements of plasma properties such as the ionization particle source, particle and energy loss, and impurity radiation in magnetically confined fusion plasmas. Diagnostics equipped with multi-element solid-state detectors (often with image intensifiers) are well suited to the environment of large fusion machines with high magnetic fields and x-ray and neutron fluxes. We have used both conventional (16 ms/frame) and highspeed video cameras to measure neutral deuterium Hα, (6563 Å) emissions from fusion plasmas. Continuous high-speed measurements are made with video cameras operating at 0.1–0.5 ms/frame; gated cameras provide snapshots of 10–100 μs during each 16-ms video frame. Digital data acquisition and absolute intensity calibrations of the cameras enable detailed quantitative source measurements; these are extremely important in determining the particle balance of the plasma. In a linear confinement device, radial transport can be determined from the total particle balance. In a toroidal confinement device, the details of particle recycling can be determined. Optical imaging in other regions of the spectrum are also important, particularly for the divertor region of large tokamaks. Absolutely calibrated infrared cameras have been used to image the temperature changes in the walls and thereby determine the heat flux. Absolutely calibrated imaging ultraviolet spectrometers measure impurity concentrations; both spatial and spectral imaging instruments are employed. Representative data from each of these diagnostic systems will be presented.
Spectroscopic Study and Amorphous Film Deposition in RF and Pulsed Plasma Processings
Authors: Ebihara Kenji , Kanazawa Seiji , Maeda Sadao
Published: March 2011

Processing plasmas generated by three types of discharges are diagnosed spectroscopically in order to estimate the quantitative relationship between plasma parameters and electrical and optical properties of deposited materials. An rf discharge is capacitively produced by a 13.56 MHz rf oscillator. A microwave generator operating at 2.45 GHz is used to supply power to a discharge cavity. Further a pulsed plasma which is inductively generated by pulsed current ( 70 kA peak ) is applied to study dissociation process in the transient plasma and possibility of a novel processing system. The gases used are methane for amorphous carbon formation and silane for amorphous silicon deposition. Measurements of optical emission spectrum are performed to estimate the processing plasma state by the relative spectral intensity method and the Doppler-broadening method.
The Effect of Ar+ Ion Implantation on the Impact-Abrasive Wear Property of Cu-Polyimide System
Authors: Koh S. K. , Pae K. D.
Published: March 2011

A thin Cu film(400 Å) was deposited on a smooth polyimide(PI) substrate. Ar+ ion implantation onto the Cu/PI film has been shown to mix Cu and PI and to modify the impact-abrasive wear property. Ar+ ions with energies of 200 keV, and dosage between 1015 to 4×1016 ions/cm2 were used. The surface analyses were carried out with RBS, X-ray and Optical Microscope. The wear properties of the Cu-PI system were determined by a newly constructed Impact-Abrasive Wear Tester. An X-ray diffraction study shows an increase in Cu( 111 )peak with Ar+ ion dosage. The wear property was found to be a function of ion energy, ion dosage, crystallinity of Cu, the amount of mixing of Cu and PI, and the damage of PI substrate due to ion implantation.
On the Adhesion of LPCVD WSi2 to Doped and Undoped Polysilicon
Authors: Shenai K. , Piacente P. A. , Lewis N. , McConnell M. D. , Smith G. A. , Baliga B. J.
Published: March 2011

We report on the adhesion characteristics of Low Pressure Chemical Vapor Deposited (LPCVD) WSi2 to doped and undoped polysilicon when used for fabricating silicon discreie and integrated devices. About 3000Å of silicon rich (Si:W atomic ratio of 2.6) LPCVD WSi2 was deposited on 6 kÅ of polysilicon and annealed in nitriding and oxidizing ambients at various temperatures from 1000°C to 1100°C to lower the sheet resistance. Detailed material analyses of as-deposited and annealed polycides were performed using Auger, SIMS, RBS, TEM, and SEM and electrical conductivities of the films were measured using the four point probe. In some samples, the oxide grown on the silicide film was wet etched prior to implanting and diffusing As corresponding to the source/drain diffusions in power FET's. It was observed that polysilicon doping, WSi2 deposition and annealing, oxide or nitride etching, implantation and diffusion of As - all had significant impact on the grain structures of silicide and polysilicon, adhesion of the silicide film to polysilicon, and the electrical conductivity of the silicide. In samples where the oxide grown on the silicide was wet etched, enhanced grain boundary related oxidation of the silicide and polysilicon and seepage of the wet etchant through sequential etching of grain boundary oxide resulted in poor adhesion of WSi2 grains to polysilicon and eventual silicide peeloff. This problem was severe in samples which were not implanted with As but subjected to 900°C, 60 min. source drive.
Computer Simulation of Elastic Properties of Grain Boundary Materials
Authors: Wolf D. , Lutsko J. F.
Published: March 2011

Lattice statics and lattice dyanamics computer simulation methods are applied to investigate the elastic properties of grain boundaries in fcc metals. The elastic constants in the GB reigon are found to differ significantly from their bulk ideal-crystal values. Due to the broken symmetry in the GB region a pronounced anisotropy of the elastic properties is observed. Whereas Young's moduli are found to increase in the GB region, the shear moduli and Poisson's ratios generally decrease. The magnitude of these effects is shown to depend sensitively on the GB structure.
Auger Analysis of a Fiber/Matrix Interface in a Ceramic Matrix Composite
Authors: Honecyt Frank S. , Pepper Stephen V.
Published: March 2011

Auger electron spectroscopy (AES) with depth profiling was used to characterize the fiber/matrix interface of SIC fiber, reaction bonded Si3N4 matrix composite. Depth profiles of the “as received” double coated fiber revealed concentration oscillations which disappeared after annealing the fiber in the environment used to fabricate the composite. After the composite was fractured, the Auger depth profiles indicated that failure occurred in neither the ß-SiC fiber body nor in the Si3N4 matrix but in the fiber coating itself.
Fracture Mechanics of Low Molecular Weight Polymers
Authors: Mikos Antonios G. , Peppas Nikolaos A.
Published: March 2011

A novel analysis is presented to explain mechanistic aspects of the fracture of low molecular weight polymers. The fracture energy is calculated as a function of the mean interpenetration distance of a polymer chain which has been derived from the solution of the Fokker-Planck equation. Experimental results with monodisperse polystyrene have been used to validate the theory.
Monocarbide Characterization In Nickel-Base Mc Aligned Eutectics
Authors: Jackson M.R. , Gigliotti M.F.X. , Yang S.W. , Walter J.L.
Published: March 2011

In the aligned Ni-MC eutectic alloys being developed for jet engine blade applications, the fibers are considered to be Tac, Tic, etc. In fact, these fibers will contain Cr, Mo, W and possibly other elements as substitutions for the “M” constituent, and often will not be stoichiometric. Quantitative chemical analysis of fibers is difficult because of their size. However, lattice parameter measurements can be used to learn much a out the carbide chemistry and stoichiometry. Results will be described in detail for fibers extracted from simple Ni-TaC, Ni,Cr-TaC and Ni,Cr,AI-Tac systems. In addition, experiments on mixed (Ta,V)C and (Ta,Ti)C carbides will be discussed. Carbide lattice parameters can be understood in terms of the free energies of formation of the various carbides.
Selective Etching and Laser Melting Studies of Monotectic Composite Structures
Authors: Angers L. M. , Grugel R. N. , Hellawell A. , Draper C. W.
Published: March 2011

Thin slices of directionally solidified, fibrous composite, monotectic alloy samples have been selectively etched to remove the fibrous phase, so to produce fine sieves of filters having pore diameters ≲10μm. Alloys in systems Al-In, Al-Bi and CuAl-Pb have been examined using as etchants aqueous nitric acid (Al-In, Al-Bi) and aqueous citric acid (CuAl-Pb) without applied anode voltages. These alloys and etchants illustrate examples in which fiber and matrix are attacked to different extents (Al-In), the phase interface is selectively attacked (Al-Bi) or only the fibers are attacked (CuAl-Pb). Hole sizes and perfection are compared for etching times, concentrations and anode voltage.

Laser melting of the surface of CuAl-Pb samples has been used to screen or frame areas of the composite microstructure and also shows how local melting of the fibrous Pb phase can be used to assess the heat affected zone.
Microstructural Perturbations in Directionally Solidified Al-In, Al-Bi and Zn-Bi Monotectic Alloys
Authors: Toloui B. , Macleod A. J. , Double D. D.
Published: March 2011

Studies have been made of the microstructures developed in directionally solidified monotectic Al-In, Al-Bi and Zn-Bi alloys, as a function of growth velocity and temperature gradient. With increasing growth velocity and decreasing gradient the microstructures show transitions from regular rod-like arrangements of the lower melting point phase, through arrays of aligned droplets to coarse irregular droplet dispersions. Intermediate stages show rods with longitudinal shape perturbations of a classic Rayleigh-type instability. The changes are discussed in terms of oscillatory instabilities at the solid-liquid interface (enhanced by increasing growth velocity and decreasing temperature gradient) coupled with ripening effects in the solid + liquid region behind the interface.
Quantitative Evaluation of the Interfacial Free Energies at A Solid-Liquid Lamellar Eutectic Interface
Authors: Kaukler W. F. , Rutter J. W.
Published: March 2011

The solid-liquid interfacial free energies of each of the individual phases comprising the eutectic system, Carbon Tetrabromide-Hexachloroethane, were measured as a function of composition using a “grain boundary groove” technique. Thermodynamic data were combined with groove shape measurements made from high resolution optical photomicrographs of the solid-liquid interfaces to give the interfacial free energy data. An interfacial free energy balance at the eutectic trijunction was performed to obtain all the forces acting on that point. The three interphase interfacial free energies at the eutectic trijunctions as well as a solid-solid phase boundary torque were evaluated.

It was found that the solid-liquid interfacial free energies of the two phases of the eutectic could be evaluated from photomicrographs of growing or stationary eutectic interfaces. In addition, it was found that for a substantial range of freezing conditions the eutectic interface shape can be predicted from a knowledge of the interfacial free energies alone.
The Quaternary System Fe-Cr-Mn-C and Aligned Ferrous Superalloys
Authors: Lemkey F. D. , Thompson E. R. , Schuster J. C. , Nowotny H.
Published: March 2011

A challenge exists for wider application of low cost iron-base alloys in the extreme conditions of high temperature, hot corrosion, and high stress experienced in gas turbine engines. In response to this challenge the constitution of the quaternary, Fe-Cr-Mn-C, and to a lesser extent the quinary, Fe-Cr-Mn-Al-C, systems were examined for in situ composite alloy candidates. Multivariant eutectic compositions, determined from phase equilibria, were directionally solidified to produce aligned composites consisting of M7C3carbides within a gamma iron matrix. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities. Stress rupture tests in the direction of phase alignment for certain compositions (e.g., Fe-20 wt% Cr-lO wt% Mn-3.2 wt% C) indicated strength values comparable to cast nickel-base superalloys and exceeded those of the strongest iron-nickel superalloys developed for automotive turbines. Results of cyclic sulfidation testing at 9000 indicated a balance of Cr and Al content to be important to the achievement of outstanding surface stability.
Off-Axis Mechanical Properties of A Cellular Al-Al 3Ni Directionally Solidified Eutectic
Authors: Hetzner Dennis W. , Oliver Ben F. , Becker William T.
Published: March 2011

Ingots having a cross-sectional area of 1.27 cm × 10.8 cm were directionally solidified for testing off-axis tensile properties. To avoid macroscopic banding due to inductive melting and thermal convection, growth rates of 2.2 cm/min were required. The resulting solidification structures were cellular.

The macroscopic tensile behavior of the eutectic alloy was similar to that observed for mechanically formed fiberreinforced composite materials; in particular, three distinct modes of fracture occurred. In Region I, where the angle(ϕ) between the growth direction and the tensile axis was small, the tensile strength of the composite was inversely proportional to cos2 ϕ. In Region II (20° ≤ ϕ ≤ 55°) and Region III (60° ≤ ϕ ≤ 90°), the tensile strength of the composite was inversely proportional to sin ϕ, cosϕ, and sin 2ϕ, respectively.

For all regions, failure was initiated by the fracture of large Al3Ni intercellular blades. In Region I, fracture was by a combination of tensile overload on a plane perpendicular to the tensile axis or shear on a plane inclined to the tensile axis at approximately 45°. In Region II, failure was by shear in a plane containing the growth direction and in a direction parallel to the fibers. For Region III, failure was by plane strain constraint with shear perpendicular to the longitudinal axis of the fibers.

The fracture of large intercellular Al3Ni blades can be explained by the variation of S13 about the tensile axis, and the corresponding intercellular tensile strains which result. In Region II, metallographic examination of tensile specimens shows a Poisson's ratio effect to be contributing to the strength of the composite; occasionally shear between adjacent cells is observed. By using the yield strengths of specimens having fibers oriented parallel to and perpendicular to the tensile axis, an approximate yield surface can be constructed. This yield surface accurately predicts the transition in failure mode from Region II to Region III.
Processing of Polymeric Precursor, Ceramic Matrix Composites
Authors: Diefendorf R. J. , Boisvert R. P.
Published: March 2011

Ceramic matrix composites have been produced by utilizing polymer pyrolysis as the processing technique. The precursor, polyvinylsilane, is a viscous, thermosetting polymer which yields a predominantly SiC ceramic material when pyrolyzed. This organometallic polymer in combination with SiC fibers and SiC whiskers was used to fabricate ceramic matrix composites. One of the major problems with a brittle/brittle composite system in which strong coupling exist between the fibers and matrix is the characteristic catastrophic failure that occurs once the strain to failure of one of the constituents is exceeded. This brittle behavior can be altered by the application of a suitable barrier layer between the fiber and matrix. Due to the success of a barrier layer between fiber and matrix in producing higher performance composites, multiple barrier layers were used to further improve the performance of the ceramic composite.
Theoretical Analysis of Chemical Vapor Infiltration in Ceramic/Ceramic Composites
Authors: Tai Nyan-Hwa , Chou Tsu-Wei
Published: March 2011

A model for the deposition of alumina and titanium carbide within a ceramic fiber bundle from the chemical reactions has been examined in this paper. The model considers vapor diffusion, chemical reaction on the inner surface of the capillary, deposition film growth, porosity, and effects of reactants composition at various reactor temperature and pressure. Binary, multicomponent diffusion and Knudsen diffusion have been taken into account for the different stages of the CVI process. Furthermore, both diffusion controlled and reaction controlled processes have been examined in order to determine the dominating process in chemical vapor infiltration.
Synthesis of Titanium and Boron Containing Polymers: Potential Precursors for Advanced Ceramics
Authors: Gonsalves Kenneth E. , Kembaiyan K. T.
Published: March 2011

Titanium containing fibers have been synthesized via the modification of organic materials. Thermal processing of these chemically modified organic fibers in reactive/inert atmospheres, has produced materials containing Ti (C,O). Materials analysis was performed using SEM-EDS, ESCA and Auger spectroscopy. Novel monomeric titanium materials were synthesized for the above mentioned modification of organic materials. Boron containing monomers and polymers were also synthesized as possible precursors for B-N-C materials.
The Mechanical Performance of Fiber Reinforced Ceramic Matrix Composites
Authors: Evans A. G. , Marshall D. B.
Published: March 2011

This article evaluates the current understanding of relationships between microstructure and mechanical properties in ceramics reinforced with aligned fibers. Emphasis is placed on definition of the micromechanical properties of the interface that govern the composite toughness. Issues such as the debond and sliding resistance of the interface are discussed based on micromechanics calculations and experiments conducted on both model composites and actual composites.