bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Reactor Synthesis of Nanoscale Ceramic Powders using Organosilazane Aerosols
Authors: Xiao Tongsan D. , Strutt Peter R. , Gonsalves Kenneth E. , Shankar V.
Published: March 2011

This investigation involves the thermal conversion of an organosilazane precursors into ultrafine ceramic particles. In this process, aerosols of a reactive organosilazane precursor, [CH3SiHNH]nn = 3 or 4, are injected into a hot furnace to obtain Si3N4/SiC ceramic powders. One critical feature examined in this process was the rapidity of the powder synthesis, in a reaction which involves (i) elimination of ligand groups, (ii) formation of ceramic species, and (iii) condensation of ceramic species into ultrafine ceramic particles. Accompanying studies a model has been formulated to determine the gas cooling rate and particle size.
Dip Coating of Boron Nitride Thin Films on Nicalon Fibers
Authors: Shen Lu , Tan Beng Jit , Suib Steven L.
Published: March 2011

A process involving dip coating of ceramic fibers in H3BO3 solution followed by reaction with NH3 has resulted in the formation of a BN coating on Nicalon and a carbon coated Nicalon fiber. BN coated C-Nicalon fiber maintained its strength during the coating process, while the BN coated Nicalon did not.
Interpartical Attractions and the Mechanical Properties of Colloidal Gels
Authors: Rueb C. J. , Zukoski C. F.
Published: March 2011

The influence of the strength of interparticle attractions on the mechanical properties of colloidal gels is explored. As attractions increase, suspensions gel. At the gel point the zero shear rate viscosity diverges while the low frequency modulus becomes measurable. In addition at the gel point, storage and loss moduli were of the same order and displayed power law sealing on oscillation frequency. With much stronger attractions, the critical strain required to rupture the gel scales in a power law manner or elastic modulus. These observations are discussed in terns of recently developed models of gel fonnation and dynamics.
Synthesis and Useful Reactions of Organosilicon Polymeric Precursors for Ceramics
Authors: Seyferth Dietmar , Strohmann Carsten , Tracy Henry J. , Robison Jennifer L.
Published: March 2011

Inorganic and organometallic polymers are macromolecular systems in which the polymer backbone contains elements other than the carbon, oxygen and nitrogen usually found in organic polymers [1]. To take as an example silicon-containing polymers, in the silicones the polymer backbone is composed of the Si-O repeat unit; in polysilazanes, of the Si-N unit; in polysilmethylenes, of the Si-C unit. In the polysilanes there are only silicon atoms in the polymer backbone. Many of the other metalloids and metals among the elements in the Periodic Table have been or, in principle, can be incorporated into polymeric systems, so it is clear that the field of inorganic and organometallic polymers is a very large one. Inorganic and organometallic polymers have been of interest to chemists for a long time. It was the commercial development of the silicones in the 1940's that gave this field of research its modem impetus [2]. Once it was appreciated how useful these versatile organosilicon polymers could be, chemists became interested in the possibility of developing other organometallic (and also inorganic) polymers, ones that might complement or even surpass the silicones as far as useful applications were concerned. Research on inorganic and organometallic polymers became very active in the 1950's and 1960's. Work in this area became an international effort, prompted by the need for new materials that would meet the exacting demands of the jet age that had effectively commenced around the end of World War II. Even greater demands, in terms of materials that would still be useful under extreme conditions, came with the space age.
Three Dimensional Printing: Surface Finish and Microstructure of Rapid Prototyped Components
Authors: Lauder A. , Cima M.J. , Sachs E. , Fan T.
Published: March 2011

Three Dimensional Printing is a process for rapid prototyping of functional components. Thin layers of powder are bound in selected areas by ink-jet printing of a liquid binder. Layers are added sequentially until a three dimensional part is completed. The unbound powder is then removed. The raster scan pattern and layering used in forming has an observable effect on the surface finish and microstructure of the part, as does the chemistry of the particular materials system used. Important phenomena include ballistic interaction of the jet with the powder bed and wicking of the binder. Process parameters such as layer height, flow rate, and powder density were studied. Microstructural examination of the printed components is also reported.
Characterization of the Products of the Pyrolysis of Inorganic Polymers Used as Dispersants
Authors: Samuels William D. , Exarhos Gregory J. , Burton Sarah D. , Tarasevich Barbara J. , Stasko Daniel J.
Published: March 2011

A series of alumina particles coated with inorganic polymers, that have utility as preceramic dispersants, have been pyrolyzed and the products of the pyrolysis studied to help determine the possible decomposition routes. The inorganic polymers, bis(amino)polyphosphazenes and siloxanes, appear to undergo loss of the organic sidechains via a nucleophilic process which would incorporate inorganic backbone into the alumina matrix. The bis(alkoxy)polyphosphazenes decompose by nucleophilic attachment but also exhibit polymer loss by formation of cyclic oligomers.
Effect of Silicon Exposure on Pyrolysis of Preceramic Polysilazane
Authors: Han Helen N. , Lindquist David A. , Haggerty John S. , Seyferth Dietmar
Published: March 2011

Preceramic polysilazane was added to high purity Si powders as a reactive binder during synthesis of reaction bonded Si3N4parts to improve the defect structures in both the unfired and nitrided parts. This study examined how the presence of Si powder affected the polymer-to-ceramic transformation of the polysilazane. Pyrolysis of both polysilazane and polysilazane+Si samples were characterized by TGA. Also, the gaseous volatiles evolved during pyrolysis were characterized by infrared and mass spectrometry. Results show that between 100- 550°C, silicon powder inhibits the loss of silazane oligomers from the polysilazane. However, for temperatures above 550°C, the weight loss differences between the pure polysilazane and the polysilazane+Si samples were less pronounced. Specific solvents used in the preparation of the polysilazane+Si mixtures affected the quantity and type of species in the volatiles during pyrolysis.
Microscopy Studies of Sol-Gel Derived Lithium Niobate
Authors: Joshi Vikram , Goo Grace K. , Mecartney Martha L.
Published: March 2011

Lithium niobate prepared by sol-gel techniques can crystallize at temperatures as low as 200°C, and achieve a high homogeneity. In this sutdy, nucleation, crystallization, and morphological development are examined by TEM for alkoxide derived LiNbO3. Preliminary studies show that the as-dried gel is completely amorphous and homogeneous. Between 150-200°C, crystallization begins with crystallites on the order of 10-20 nm appearing in the amorphous matrix. By 450°C, single crystal spheroidal particles (0.05 - 0.2 gm) form. By 600°C, facetted large crystallites on the order of 1 gtm develop. Grain size and porosity are strongly dependent on the amount of water of hydrolysis in thin films.
Sintering of Glass Powder Packings with Metal Inclusions
Authors: Jagota A. , Boyes E.D. , Bordia R.K.
Published: March 2011

The sintering of glass powder packings with metal inclusions has been studied using (a) a loading dilatometer, and (b) an in-situ SEM hot-stage. The addition of a small volume fraction of metal particles unexpectedly increases the sintering rate of the composite. With a further increase in the volume fraction of inclusions the sintering rate decreases rapidly to zero at a well-defined threshold. The in-situ sintering experiments have been used to observe the sintering mechanisms and to determine the parameters that contribute to this phenomenon: to assess the distribution of inclusions, and the nature of inclusion-inclusion and matrix-inclusion interaction. Predictions of the effective sintering rate are computed using a truss model with randomly distributed inclusions. The computations capture accurately the decrease in sintering rate (beyond the initial increase) with increasing volume fraction of inclusions. The initial increase is attributed to a reduction in viscosity of the glass due to chemical interaction with the metal.
Effect of Whisker Distribution on the Densification and Microstructures of AI2O3-Si3N4 Composites
Authors: Tseng W.J. , Funkenbusch P.D.
Published: March 2011

This study focuses on (1) the co-dispersion behaviors of dissimilar phases exhibiting different surface chemistry in ceramic suspensions and (2) the effect of local whisker distribution on matrix densification. Si3N4 whiskers and Al2O3 powders are mixed and slipcast in aqueous solution. Local whisker clusters are observed and remain stable even after prolonged sintering. High shear-rate agitation of the composite suspension does not eliminate the whisker agglomeration. Surface pre-treatment of whiskers, such as acid/base-washing, effectively reduces the clustering and sintered flaw size. From SEM observation it is found that the matrix powder densifies highly inhomogeneously because of the constraint imposed by the reinforcement. Matrix powder is inhibited from diffusing into “inter-whisker” voids.
Aluminothermic Synthesis of Al2O3/ZrO2/SiC Composite Powders
Authors: Erauw J.P.
Published: March 2011

The synthesis of Al2O3/ZrO2/ SiC composite powders by aluminothermic reduction of zircon in the presence of carbon is reported. The effect of the temperature on the progress of the reaction, as assessed by XRD analysis, is outlined. The morphological characteristics of the reaction products are described. Based on the experimental results, a reaction scheme is proposed. The possible propagation of the reaction is discussed in terms of the adiabatic temperature.
Synthesis of Inorganic Polymer-Ceramic Molecular Composites
Authors: Samuels William D. , Exarhos Gregory J. , Burton Sarah D.
Published: March 2011

The logical development of thermally stable polymers is based upon forming true molecular composites comprised of both polymer and ceramic components. This paper describes our initial studies on the synthesis of composite materials that are expected to produce films with thermal stability to 500°C.
Effect of Cu on Al-Transition Metal Reaction Kinetics
Authors: Huang H.-C. W. , Wittmer M.
Published: March 2011

The effect of Cu on the kinetics of compound formation between Al and transition metals such as Hf and Ti has been studied by resistivity measurement and Rutherford backscattering (RBS) in the temperature range of 325°C to 450°C. Thin film couples consisting of 150nm-thick transition metal film and 600nm-thick Al-Cu film were used, in which the Cu content was varied from 0 to 9 wt%. The intermetallic phases were found to grow as (time)1/2. Most interestingly, the reaction rate constants were found to decrease significantly with increasing Cu content, but to level off for Cu contents greater than about 2 wt%. The corresponding activation energy for a given Altransition metal reaction was found to increase with increasing Cu for Cu contents up to 2wt%. For example, when 4 wt% Cu is added to Al, the rate constant at 400°C for HfA13 is reduced by about a factor of 5, while the activation energy increases from 1.5 eV to 2.0 eV. RBS results indicate that the Cu addition seems to inhibit the diffusion of Hf into Al. Diffusive intermixing in the Al/Ti system is much smaller and, consequently, the effect of Cu additions in preventing Ti diffusion into the Al is also much smaller.
Electron and Ion Beam-Enhanced Adhesion
Authors: Mitchell I.V. , Williams J.S. , Sood D.K. , Short K.T. , Johnson S. , Elliman R.G.
Published: March 2011

Helium ions of 2 MeV energy and electrons of 5 to 30 keV energy have been used to irradiate a variety of thin (10–330 nm) metal films after deposition on semiconductor and insulator substrates. Dose thresholds for increased adhesion were found following irradiation with either type of particle. It is argued that the stronger bonding arises from an electronic, rather than a collisional, process. Representative results are presented and discussed within the framework of a recent model for heavy ion-induced effects.
The Radiation Enhanced Adhesion of Gold on PTFE
Authors: Sofield C.J. , Woods C.J. , Wild C. , Riviere J.C. , Welch L.S.
Published: March 2011

The effect of γ-ray and electron irradiation on the adhesion of gold films to PTFE has been ascertained. The film adhesion has been found to undergo a sharp increase at a γ-ray dose of 5 × 106 to 1 × 107 rads. Qualitative ‘Scotch tape’ tests also show an increase in adhesion when the films are irradiated with electrons (250 eV - 3 keV).

Examination of the interface region of very thin (∼ 20 Å) gold films on PTFE by X-ray photo-electron spectroscopy indicates the increase in adhesion results from radiolytic processes and consequent chemical interaction with the gold.
Effects on Metal/Metal-Oxide Interface Adhesion Due to Electron and Ion Irradiation
Authors: Bøttiger J. , Baglin J. E. E. , Brusic V. , Clark G. J. , Anfiteatro D.
Published: March 2011

The influence of electron and ion irradiation on the adhesion at chromium-copper thin film interfaces has been studied. The measurements were carried out with different types and thicknesses of well-characterized oxides at the interfaces. The electron energies were varied between 5 and 10 keV, with doses up to 1018cm−2. lons of He+Ne+and P+were used in the range of energies between 150 keVand 1.0 MeV, with fluences ranging from 1015cm−2to 6× 1016cm−2. Substantial improvement of the adhesion is observed in cases where the beam has a significant nuclear stopping power component. Electronic processes may also play a role in improving adhesion, although they are not dominant in the case of the present films.
Modification and Study of Polymer Films Using High Energy Ion Beams
Authors: Venkatesan T.
Published: March 2011

Recent results on the effects of high energy ion beam irradiation in polymer films are reviewed in this paper. High energy ions (>10 keV/amu) deposit a large amount of energy (∼several cV/atom) in ionizing the electrons of the target atoms. This results in significant destruction of bonds in the films as a result of which polymers undergo rapid dissociation. Using a quadrupole mass spectrometer the study of transient emission of molecular species produced by an ion pulse has been shown to yield information about the diffusion and reaction kinetics of various molecules in the polymer. The fact that polymers undergo dissociation and those atoms which form volatile species are selectively depleted from the film could be utilized in producing useful inorganic composites by ion bombardment of polymers. For example, hard SiC composite films have been produced by ion beam irradiation of organo-silicon polymers. Eventually, polymer dissociation leads to a predominately carbon containing film which exhibits interesting electronic transport properties. Experiments on ion irradiated, pure carbon films indicate that a metallic form of carbon is produced from the polymer films at high irradiation
doses.
Formation of Alloy Phases at Fe-Al Interface by Ion Beam Mixing, asRevealed by Interface-Sensitive Conversion Electron Mössbauer Spectroscopic Measurements
Authors: Godbole V.P. , Bhide V.G. , Ghaisas S.V. , Kanetkar S.M. , Chaudhari S.M. , Ogale S. B.
Published: March 2011

The physical processes associated with the formation of various normal as well as metastable phases at an ion beam mixed Fe-Al interface are studied by using a novel interfacesensitive Conversion Electron Mbssbauer Spectroscopic (CEMS) technique.This technique which has been introduced and used for the first time in these investigations, is based on the deposition of a thin (less than 50 A°) layer of enriched Fe 5 7 isotope (95.45% by composition) at the interface between the aluminium substrate and a post-deposited 250A° film of natural iron (only 2.2% of Fe57), leading to a considerably enhanced spatial selectivity of the M~ssbauer information regarding the reactions occurring at the interface.A number of samples prepared in the manner mentioned above are subjected to an argon ion bombardment at an incident ion energy of 100 keV and a dose of ≃ 2 × 1016ions/cm2The ion beam mixed samples are annealed at different temperatures in the range between 300°C to 600°C for twenty minutes, to provide the thermal energy for the growth of different FexAlyphases at the interface.Conversion Electron Mössbauer Spectroscopy is employed at each stage of the ion beam processing and annealing of the samples, to characterize the phases formed. All the Mbssbauer spectra are least square fitted using the MOSFIT programme to obtain the best-fit values of Mössbauer parameters. The results indicate a substantial broadening of the Mössbauer lines for the as-implanted samples, a fact which can be attributed to the beam induced radiation damage. Subsequent annealing of the samples at different temperatures leads to annealing of damage and further to the formation of Fe3Al and FeAl solid solution. Mössbauer spectra of the samples annealed at 500°C indicate segregation of Fe at the interface along with the formation of Fe3Al phase, while annealing at 600°C results in the formation of Fe-Al solid solution phase with traces of effectively unreacted metallic Fe. The unimplanted composites heat-treated in an identical manner do not show these features. These results which are supported by RBS measurements, are interpreted and discussed in terms of the non-equilibrium nature of the ion beam processing of the interface.
On the Segregation of in Solutes to High-Angle (001) Twist Grain Boundaries in Al
Authors: Wolf D. , Lam N. Q.
Published: March 2011

The energies of the Σ = 5, 13, and 17 (001) coincidentsite lattice (CSL) twist boundaries in Al containing small amounts of Zn solutes have been calculated using an iterative energy minimization technique in conjunction with interatomic potentials derived entirely from first principles. By determining both the energies of substitution in the bulk and in different sites in the boundary, the site selectivity for Zn segregation at the grain boundary has been investigated. In the lattice plane immediately near the grain boundary, Zn solutes were found to prefer the lower-symmetry non-coincidence sites while, in the next plane, substitution in the coincidence sites is preferred. The effect of Zn-Zn interactions has also been considered for small solute concentrations. It is found that the magnitude of the Zn-Zn interaction energy is remarkably insensitive to the particular sites occupied by the Zn atoms as well as the detailed geometry of the interface.
Structure and Dissociation of 15° <110> Tilt Boundaries in Germanium
Authors: Skrotzki W. , Wendt H. , Carter C. B. , Kohlstedt D. L.
Published: March 2011

The structure and dissociation of grain boundaries in Ge bicrystals, grown by the Czochralski method, have been analyzed by visible light and transmission electron microscopy. The seed crystals were oriented to yield either a symmetric or an asymmetric grain boundary plane with a 15° rotation about a common <110> direction. The asymmetric boundary, with a {111} boundary plane, dissociated along most of its length into a first order twin boundary (Σ 3) and a symmetric 55° grain boundary (Σ 41c). The symmetric 15° boundary is composed of an array of Lomer dislocations. Contrary to theoretical predictions, this boundary is stable.
Nucleation Phenomena in Transitions from two to three phases, diffusion Couples, Phase Stability,the thin film formation of some silicides
Authors: D»Heurle F. M.
Published: March 2011

EXTENDED ABSTRACT

Nucleation is generally understood to refer to the initial process of creating a new phase, for example, liquid water, from another phase, water vapor, as a result of a temperature excursion which carries the system through some critical temperature (in the case at hand, at normal atmospheric pressure, 100°C). The processes involved in such transformations have been the object of careful observations for a long time, at least two centuries; a very good historical perspective on this subject is found at the beginning of Ref. 1. The special case of metal vapors condensing on substrates in order to form thin films is considered in all texts dealing with thin film preparation [2]. The precipitation of a new phase, such as CuAl2, from a supersaturated solution (of copper in aluminum) has immense technological importance which motivates the attention being paid to nucleation phenomena in all metallurgical treatises [3,4].(A particularly thorough discussion is found in Ref. 5.) In all cases, nucleation phenomena are controlled by the necessity of creating an interface between the nucleated phase and the original matrix. The energy of the interface imposes special thermodynamic constraints on the evolution of the system.
Photoemission Studies of the Ag/InP(110) Interface: Interfacial Reactions and Schottky Barrier Formation
Authors: Petro W. G. , Kendelewicz T. , Babalola I. A. , Lindau I. , Spicer W. E.
Published: March 2011

Room-temperature interfacial reactions at the Ag/InP (110) interface have been studied using soft x-ray photoemission spectroscopy of the In 4d and P 2p core levels. For low Ag coverages (less than 1 monolayer (ML)) no measurable change in core level shapes is observed, and the shift in core level position is due solely to band bending. At high Ag coverages (up to 72 ML) we observe dissociated In metal, P atoms near the surface, and Ag clustering. Fermi level movement is deduced from these spectra using a deconvolution technique, and pinning positions of 0.40 ± 0.05 eV below the conduction-band minimum for n-type and 0.5 ± 0.l eV above the valence-band maximum for p-type are found. These positions are in close agreement with calculations of native defect levels.
Selective Growth, Diffusion Layers and the Schottky Barrier Height in Nickel Silicide-Silicon Interfaces
Authors: Erskine J. L. , Chang Yu-Jeng
Published: March 2011

Selected interface phenomena associated with metal semiconductor contacts are discussed in relation to recent experimental and theoretical work on the electronic properties, interface formation and structure, and device characteristics of nickel-silicon interfaces. Evidence is presented which suggests that a well-defined interfacial phase is present at all nickel silicide-silicon boundaries formed by deposition of nickel atoms onto silicon surfaces. The existence of this phase is shown to account for several important interface properties of the nickel silicide system including selective growth, the rotational twin structure of epitaxial films and the observed invariance of the nickel silicide-silicon Schottky barrier height as the silicide contact stoichiometry is varied.
Shallow Contact Formation of Gadolinium Silicide
Authors: Cheng I. C. , Lau S. S. , Thompson R. D. , Tu K. N.
Published: March 2011

Gadolinium silicide with its attractive features of low formation temperature of about 350°C and low Schottky barrier height on n-type single-crystal silicon substrates (ϕnB1∼O.4ev,ϕpB ∼ 0.7ev) was chosen for studying the feasibility of forming shallow uniform contacts. Samples with various compositions prepared by both bilayer evaporation with a configuration of Si(α)/Gd/Si(xtl) and coevaporation with a Si−Gd /Si(xtl)structure were used for studying the contact formation as a function of composition and heat treatment. We found that shallow contact formation can be achieved provided that the following conditions are met: (a) for bilayer evaporation, the atomic ratio of Si(α)/Gd ≥ 2 should be maintained, (b) for coevaporation, the Si to Gd atomic ratio between 1.7 and 2.0 is desired. The bilayer deposition scheme appears to be a more convenient technique to use in practice.
Epitaxial Growth of FeSi2 on (111)Si
Authors: Cheng H.C. , Chen L.J. , Your T.R.
Published: March 2011

Isothermal annealing, two step annealing and ion beam mixing were performed to induce interfacial reactions between iron thin films and silicon substrate. Both orthorhombic and tetragonal FeSi2 were found to grow epitaxially on (lll)Si with orthorhombic FeSi2 being the predominant phase. No epitaxial growth of FeSi2 on (001)Si was detected. Epitaxial islands as large as 40 μm in size were formed by a scheme combining ion beam mixing and two step annealing.
Material Properties of Semiconductor Strained-Layer Superlattices
Authors: Osbourn G. C.
Published: March 2011

High quality superlattices can be grown from semiconductor materials with lattice mismatches of several percent if the layers are kept sufficiently thin. The mismatch in these structures is accommodated by coherent layer strains, so that misfit defects are not generated at the superlattice interfaces. These strained-layer superlattices have unique structural, optical, and electrical properties due to both the large layer strains and the flexibility in the choice of lattice mismatched layer materials. Recent results which demonstrate the high crystalline quality of these mismatched heterostructures are reviewed. Further results are presented which illustrate some of the unique material properties of these structures, and potential applications associated with such properties are discussed.
Ion Channeling Analysis of GaAsxP1-X/Gap Strained-Layer Superlattices
Authors: Picraux S. T. , Biefeld R. M. , Osbourn G. C. , Chu W. K.
Published: March 2011

Axial ion channeling and backscattering with 2 MeV 4He are used to probe the strain in GaAs. 16P.84/GaP strained-layer superlattices (SLS) by two methods. The tetragonal distortions in the growth direction of SLS's give rise to alternating tilts in inclined crystal directions at each interface. In the first method the large increase in dechanneling along <110> directions containing the angular tilts is measured relative to the negligible increase in dechanneling along the <100> growth direction. This method provides a sensitive depth-dependent measure of strain but requires computer simulation for quantitative analysis. In the second method, channeling angular scans are used to directly measure the lattice strain by the shift in the <110> crystal direction in the top layer relative to the average <110> direction. These results demonstrate the validity of the strain accommodation model for the interpretation of the dechanneling and indicate that GaAsxP1-x/GaP SLS structures of high crystalline quality can be obtained with strains somewhat lower than that predicted theoretically from bulk lattice properties.
Tetragonal Distortion in VPE and LPE In1-xGaxAs Grown on (100) Inp
Authors: Macrander A. T. , Chu S. N. G.
Published: March 2011

The tetragonal distortion present in both VPE and LPE In1-xGaxAs was measured from X-ray rocking curves of the (511) reflection. These measurements were then used to establish coherency limits. In addition, wafer curvature was measured and compared to that calculated via an expression which incorporates both tetragonal distortion and misfit dislocations. Agreement was found except for a case in which stacking faults were present.
Marker Experiments for the moving Species in Silicides During Solid Phase Epitaxy of Evaporated Si
Authors: Lien Chuen-Der , Bartur Meir , Nicolet Marc-A.
Published: March 2011

Evaporated W, implanted Xe, and implanted 18O were used as markers to study the dominant moving species during (a) solid phase epitaxy (SPE) of evaporated Si, (b) silicide formation, and (c) oxidation of silicides on Si substrate.

MeV 4He+ backscattering spectrometry and 18O (p, α)15 N nuclear reaction were used to monitor the evolution of elemental profiles as well as the change in the marker position. In most cases, the dominant moving species in SPE is the same as that observed in the formation and oxidation of that silicide. However, in CrSi2 the dominant moving species is Si during silicide formation, but Cr during SPE or oxidation.
Nitrogen Ion Implantation in Silicon: Structure of the Subsurface Region
Authors: Liliental Z. , Carpenter R.W. , Fathya D. , Kelly J.C.
Published: March 2011

Subsurface dielectric layers in silicon formed by oxygen ion implantation have been the subject of various investigations, as an attractive alternative to building devices and integrated circuits on insulating substrates. More recently, the methods of high resolution analytical electron microscopy (HRAEM) have been applied to the analysi off these buried dielectric layers with significant results.(1,2 When oxygen is implanted into silicon, the interface between the amorphous oxide and the silicon is sharp on an atomic scale, but islands of silicon exist in the oxide for some distance from the interface. The effect is ion implantation condition dependent. Dielectric layers formed by nitrogen ion implantations are expected to be similar to those formed by oxygen implantationbut offer advantages from the materials science viewpoint in terms of thermodynamic stability and mechanical strength.(3,4In this paper we report observations of the structure of silicon after two different implantations conditions which are the first part of an investigation to determine effect of implantation variables on microstructure.
Analysis of the Si-ON-Insulator Structure by Modeling of the Interface Atomic Arrangement
Authors: Saito T. , Yamakoshi Y. , Ohdomari I.
Published: March 2011

A structure of interface between crystalline Si (c-Si) and underlying SiO2 film formed by Si-on-Insulator technique has been analyzed by modeling of interface atomic arrangement. A ball-and-spoke model of a stoichiometrically abrupt c-Si/SiO2 interface has been constructed by connecting a (100) c-Si lattice and a continuous random network model of amorphous SiO2 . A Keating-type potential has been used for the interatomic interactions. The bond bending distortion energy of both Si and O atoms increases at the interface, while the bond stretching energy is negligibly small. The amount of interface energy due to bond distortion is 0.20J/m2.
Metallurgy and Morphology of the Interface of AuGe Ohmic Contact to GaAs
Authors: Lakhani Amir A. , Urech David R.
Published: March 2011

Scanning electron microscopy and energy dispersive x-ray analysis have been used to study the formation of AuGe ohmic contacts to GaAs. Both sintering and alloying of the metallization result in deep trenches and spikes. Lateral growth of the metallization at the perimeter of the contact is also reported. In situ analysis during the formation of the ohmic contact has demonstrated the formation of a solid phase complex of Au-Ge-As and the rapid loss of As at 450°C. The influence of the Au-Ge-As complex and the loss of As on the specific contact resistivity is discussed.
Transport Studies in Single-Crystal Films of Cosi2 and Nisi2
Authors: Hensel J. C. , Tung R. T. , Poate J. M. , Unterwald F. C. , Jacobson D. C.
Published: March 2011

Transport studies have been performed on thin films of CoSi 2 and NiSis2 in the temperature range 1 to 300 K. The conductivities are metallic with essentially the same temperature dependence; however, the residual resistivities are markedly different even though the two silicides are structurally similar (the room temperature resistivity of NiSi2 being at least twice that of CoSi2 of 15 μΩ cm). The difference is attributed to intrinsic defects in NiSi2. This defect has been simulated by ion bombardment of the film where it is also shown that Matthiesen's rule is obeyed over a remarkable range of bombardment doses.
Interface Reactions In Tasi 2/Si Contacts at High Temperature
Authors: Oppolzer H. , Neppl F. , Hieber K.
Published: March 2011

The influence of deviations from TaSi2 stoichiometry in co-sputtered,amorphous Ta-Si films on interface reactions in contacts to silicon at 900°C was investigated by TEM of thin cross sections through the contact windows. Excess silicon precipitates epitaxially in the contacts, pits are formed for silicon deficiency. The involved lateral silicon transport ranges over several tens of microns. The effects of interfacial oxides and a crystalline TaSi 2 pad layer were studied.
Introduction of Electrical Defects in P-Type Silicon due to Electron-Beam and RF Sputtering Metallization Processes
Authors: Paz O. , Auret F. D.
Published: March 2011

Defects introduced in p-type silicon during RF sputter deposition of Ti-W and electron-beam evaporation of hafnium were investigated using I-V, deep level transient spectroscopy and electron-beam induced current techniques. DLTS measurements indicate the presence of several deposition and evaporation induced defect states. H(0.35) at EV + .35 eV and H(0.38) were the most prominent defects. Minority carrier diffusion length results taken after annealing showed that in the case of the Hf contacts the damage was annealed out while in the case of Ti-W it was not. These differences in carrier recombination are traced to the concentration of H(0.35). Sputtering or evaporation induced damage also increased the barrier height. This observed increase was modeled assuming the introduction of donor-like defects.
SI Contacts Formed from Spun-on Metallo-Organic Solutions
Authors: Pai C. S. , Zhang B. , Scott D. M. , Lau S. S. , Bartur M. , Tseng W. F.
Published: March 2011

The use of spun-on liquids to form ohmic and Schottky barrier contacts on Si has been investigated. Two commercially available metallo-organic solutions containing Au or Pt were applied to Si substrates by spinning techniques. The Au or Pt contacts were then formed by annealing at 250°C or 450°C respectively. The metallurgical interactions between the spun-on Au or Pt layers and the Si substrate were investigated by MeV backscattering spectrometry and X-ray diffraction as a function of the annealing temperature. The resulting electrical characteristics were investigated with four point probe, I-V and C-V techniques. It was found that the spun-on Au or Pt films react with Si substrates at much higher temperatures than those deposited by vacuum evaporation. The diode characteristics of the spun-on Au films are comparable to those of evaporated Au films ( φB ∼0.85V, n ∼1.08), whereas diode characteristics of spunon Pt films show no linear region on the ln I-V curve. The application of spun-on Au also improves the bondability of Si chips on Mo headers.
The Measurement of Silicide Schottky Barrier Heights by Use of Photovoltaic Techniques
Authors: Kuech T.F. , Wu C.S. , Lau S.S.
Published: March 2011

Schottky barrier structures often exhibit forward bias current voltage characteristics possessing a marked deviation from ideal behavior. In many cases, this deviation can be attributed to the influence of an appreciable series resistance on the diode characteristic making the determination of the actual Schottky barrier height from this characteristic difficult. In a study of rare earth silicides on Si, the present authors have successfully employed an alternative technique which overcomes this series resistance effect. This technique is derived from the conventional methods for obtaining barrier height and series resistance values in photovoltaic devices, although not necessarily requiring transparent metallizations. Photogenerated current from the device periphery is utilized here in the determination of the barrier height. The measurement of both open circuit voltage and the short circuit current at varying illumination intensities allows the junction characteristic to be determined essentially free from series resistance effects. A comparison will be made between the values of the barrier height derived from conventional J-V and photoresponse measurements, with photovoltaic measurements made on structures possessing either a semi-transparent or opaque metallization.
Lateral Silicide Growth
Authors: Zheng L. R. , Zingu E. , Mayer J. W.
Published: March 2011

Silicide formation and growth kinetics have been investigated with lateral diffusion couples formed by deposition of Ni and Cr layers on patterned Si substrates and by deposition of Ni patterns on Si films. For annealing temperatures between 520 and 650°C the growth of CrSi2follows a (time)½ dependence with an activation energy of 1.4± 0.1 eV. In Ni-silicide formation at temperatures below 600°C, Ni was the predominant moving species. As the temperature increased, the motion of Si became significant. The apparent activation energy for silicide formation varied from Ea ≅ 1.4 eV for Ni motion at relatively low temperatures to Ea≅ 2.3 eV for Si motion that occurs at high temperatures. Lateral diffusion in device geometry structures resulted in degradation of contact planarity due to the penetration of metal silicides in Ni-Si structures or the erosion of silicon in Cr-Si structures.
The Kinetics of Platinum Silicide Formation Using CW Lamp Annealing
Authors: Hopkins C. G. , Baumann S. M. , Blattner R. J.
Published: March 2011

The reaction of a metal film with polycrystalline silicon to form a metal silicide has been shown to occur very rapidly when using cw lamp annealing in contrast to conventional furnace annealing. The faster reaction kinetics implies a more efficient energy coupling (radiative heating) versus the conductive/convective heat transfer processes which dominate furnace annealing. From Rutherford backscattering determinations of the thickness of PtSi formed as a function of anneal time (t), we have found the relationship to be linear in t with growth rates in the rangg 10−7–10−6 cm/sec (10 – 100Å/sec) for the temperature range 375 – 450° C. From these data the activation energy for the formation of PtSi was calculated to be 1.8± 0.2eV for cw lamp annealing, in reasonable agreement with literature values from conventional furnace annealing experiments.
Properties of In Situ Reinforced Silicon Nitride Ceramics
Authors: Li C.-W. , Yamanis J. , Whalen P.J. , Gasdaska C.J. , Ballard C.P.
Published: March 2011

In situ reinforced (ISR) silicon nitride ceramics have been developed to have microstructures that mimic the best whisker containing ceramic matrix composites. Large, interlocking needle-like grains of beta silicon nitride can be produced throughout these materials to create an isotropic, high-temperature ceramic with high fracture toughness (˜9 MPa√m), good high-temperature strength (4 Pt MOR = 750 MPa at 25°C and 500 MPa at 1375°C), high Weibull modulus (m >20), and low creep at high temperature. Since these materials do not rely on transforming metastable phase inclusions as a toughening mechanism, their fracture resistance is virtually insensitive to temperature. The high crack growth resistance of these ceramics also yields a material which is extremely defect tolerant. Residual MOR strengths of 300–400 MPa are typical after multiple 50-kg Vicker's indentations of the sample tensile surface. After abrasive particle impact, the biaxial strengths of the in situ reinforced ceramics are typically more than twice that of traditional, fine-grained silicon nitrides.

Unlike ceramic composites toughened using whisker additives, the in situ reinforcement approach to silicon nitride development does not require the use of complicated whisker dispersion techniques for green processing, nor is shape-limiting hot pressing required for densification during sintering.
Porous Alumina by Hot Isostatic Pressing
Authors: Kuzjukevics Anatolijs , Ishizaki K.
Published: March 2011

Production of porous alumina ceramics by capsule-free hot isostatic pressing of bimodally distributed alumina powders with a large size difference (>10) and reaction sintering of alumina powder and boron oxide formed by oxidation of boron nitride during sintering were investigated. The influence of the composition of bimodally distributed alumina and alumina-boron nitride mixture of powders on open and closed porosity was studied.

HIP treatment at 1600°C provided sintering of only fine-grained powder. A small loss in open porosity (about 4%) is observed with increasing of the fine powder weight fraction up to 0.4.

Reaction sintering of a fine-grained alumina powder with boron oxide gives significant (about 30%) increase of open porosity.
New Processing and Evaluation of Porous PZT with High Connectivity Using Capsule-Free O2 HIP
Authors: Sugihara Sunao , Hayashi Takashi , Okazaki Kiyoshi
Published: March 2011

New processing of porous PZT ceramics with high connectivity was investigated using capsule-free O2 HIP technology. Porous PZT bodies were prepared by pressureless-sintering of green compacts with various amounts of spherical PMMA particles, followed by hot isostatically pressed at 1100°C and 200 MPa for 1 hour in 5%O2/Ar mixture gas atmosphere. The densification of porous PZT sintered bodies hardly occurred by capsule-free O2 treatment, resulting in the formation of well-developed neck growth between PZT grains. They exhibted a homogeneous microstructure with a bimodal pore size distribution consisting of both several ¼m and 50–80¼m pore sizes.

The capsule-free O2 HIPed porous PZT bodies have a larger permittivity and a smaller depolarizing factor about a half than the specimens before O2 -HIPing, suggesting that the HIPed PZT has a higher connectivity. Piezoelectric g33 constant-porosity relations were also described and mechanical property was discussed to indicate an increase of bending strength more than 20% compared to conventional sintering.
Influence of Hipping Pressure on the Strength and the Porosity of Porous Copper
Authors: Takata Atsushi , Ishizaki K. , Kondo Y. , Shioura T.
Published: March 2011

Open porous copper metals, which have high strength, high open porosity and well controlled pore size distribution, were produced by a hot isostatic press (HIP) process. They were sintered at different temperatures from 973 to 1273K under various HIPping pressures up to 200MPa. Pore size distribution and Young's modulus of the sintered samples were analyzed. The HIPped products have greater strength and higher open porosity than those of the normally sintered ones. The internal structural parameters such as pore size distribution were controlled by changing the HIPping pressure.
The Production of Porous Si3N4 Ceramics with 100% β Phase
Authors: Saito Naruki , Ishizaki K. , Kuzjukevics A.
Published: March 2011

Porous silicon nitride ceramics with open porosity fraction of about 0.25 were obtained by capsule-free hot isostatic pressing from as-received and aqueous Soxlet washed powders. Particle surface modification by aqueous washing increases green density of cold isostatically pressed bodies and leads to a decrease in open pore fraction. At the same time, the α–β transition rate of the treated powder decreases.
Efficient Densification of Fine-Grained Ceramics by Hybrid (RCS-Plus-HIP) Processing
Authors: Palmour Hayne , Hare Thomas M. , Russell Roger L.
Published: March 2011

In this paper, we consider certain technological and economic advantages associated with rate controlled sintering (RCS) as the critical first step in a two-step hybrid densification cycle: RCS-plus-HIP. With proper combinations of(a) powder processing (to obtain narrow initial particle size distribution and high green density) and (b) carefully optimized RCS sintering profile (to assure effective pore closure with minimal grain growth), one can readily produce technically dense (gas-tight) sintered ceramic components that can then be rather easily HIPed to full density with very little additional grain growth.

The experimental background and underlying concepts for RCS are briefly reviewed, and are related to the broader issue of establishing and maintaining control of microstructural evolution during densification processes, including those that are best concluded in the high pressure gas atmospheres typically employed for hot isostatic pressing (HIP). To illustrate these points, some examples of RCS-plus-HIP processed oxide ceramics – dense, optically translucent and/or transparent, yet also quite uniformly fine-grained – are shown and discussed.
Influence of High Oxygen Partial Pressure on the Positive Temperature Coefficient Resistivity of BaTiO3
Authors: Huybrechts Ben , Ishizaki K. , Takata M.
Published: March 2011

The influence of high oxygen partial pressures on the PTC behavior of non acceptor doped BaTiO3 is studied by using oxygen-hot-isostatic-press (O2-HIP). Annealing in high oxygen partial pressures increased the maximum resistivity with a factor 3, also the minimum resistivity and the gradient in the Arrhenius plot, i.e. resistivity versus the reciprocal of the temperature, increased. The results are analyzed using the well accepted Heywang model. The changes after O2-HIPping can be explained with an increase in acceptor density at the grain boundaries.
Densification of Glass by HIP
Authors: Yamashita Hiroshi , Kitamura Naoyuki , Kondoh Isao
Published: March 2011

Densification of glass under high pressure and high temperature are shortly reviewed from the points of view of glass structure and densification mechanism. Some of characteristic properties of the densified state are promising for use in the fields of optics and ultra-sonic waves.
Single Crystal Growth of YBa2Cu4O8 and Y2Ba4Cu7O15 Under High Oxygen Pressure
Authors: Miyatake T. , Takata T. , Yamaguchi K. , Takamuku K. , Koshizuka N. , Tanaka S. , Shibutani K. , Hayashi S. , Ogawa R. , Kawate Y.
Published: March 2011

We investigate the crystal growth of YBa2Cu4O8 (124) and Y2Ba4Cu7O15 (247) in Al2O3 crucibles at an oxygen partial pressure of 20MPa employing an O2- HIP apparatus in a mixed gas environment of Ar-20%O2. Various melts compositions, rich in Ba and Cu, are explored to optimize crystal growth of 124. Large 124 single crystals up to a size of 1×0.5×0.05mm3 are obtained from compositions with about 65˜67%CuO. 247 single crystals having a maximum size of 3×1.5×0.05mm3 are grown from the same composition of melts. 124 crystals exhibit superconductivity at 75K. 247 crystals show Tc of 20K.
AgO Doped YBa2Cu4O8 Superconductor Under High Oxygen Partial Pressure
Authors: Sawai Yuichi , Ishizaki K. , Takata M. , Kuzjukevics A.
Published: March 2011

Generaly silver doping into YBa2Cu3O7 superconductor improves the critical temperature and critical current density. In this work the silver peroxide was doped into YBa2Cu4O8 superconductor and sintered by the Oxygen Hot Isostatically Pressing method. The critical temperature of the 124 phase increased by silver peroxide doping.
High Nitrogen Concentration in Fe-Cr-Ni Alloys
Authors: Rawers James C. , Gokcen Nev A. , Pehlke Robert D.
Published: March 2011

Increasing the nitrogen concentration in iron and iron alloys significantly improves their mechanical properties. A recent technique for melting in a hot-isostatic pressure furnace using nitrogen as the pressurizing gas has been developed by U.S. Bureau of Mines researchers for making massive nitrogen additions to iron (up to 1.6 weight percent nitrogen) and iron-chromium-nickel alloys (up to 6.6 weight percent nitrogen). The total nitrogen concentration measured at atmospheric pressure and room temperature was determined to be the equilibrium nitrogen concentration in the molten alloy. Statistical correlations were derived to explain the effects of melt pressure and alloy composition on the resulting nitrogen concentration. Nitrogen concentrations measured in solidified alloys made by high pressure melting techniques at lower pressures are consistent with previous published data. Computer generated phase diagrams for high nitrogen-chromium concentrations are also consistent with nitride microstructure observed after high-pressure melting. Extension of existing atmospheric nitrogen concentration data to higher pressure nitrogen concentrations shows Sievert's law (nitrogen concentration is proportional to the square root of the nitrogen melt pressure) to be valid for pure iron. However, substantial deviations from Sievert's law are observed for higher alloy compositions. Statistical fits of thermodynamic concentration data to the high-pressure melt nitrogen data requires evaluating element concentration terms, interaction effect terms, pressure terms, and pressure-composition effects terms. Examination of the nitrogen concentration data suggests several methods of correlation.