bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of MoSi2-Based Composites
Authors: Yang J.-M. , Jeng S. M.
Published: March 2011

MoSi2-based composites reinforced with particles, whiskers and continuous fibers are fabricated using hot pressing and hot isostatic pressing techniques. The microstructure, interface compatibility, mechanical properties and failure behavior of the resulting composites are discussed.
Microstructure and Mechanical Bevavior of Ni3Al-Matrix Composites
Authors: Brennan P. C. , Kao W. H. , Jeng S. M. , Yang J.-M.
Published: March 2011

An aluminum oxide particulate-reinforced nickel-aluminide composite was fabricated by vacuum hot pressing and hot extrusion. Room temperature three point bend tests were conducted after 1 and 100 h at 1000 °C. The composite exhibited a decrease in yield strength from 772 to 517 MPa after 100 h while the ultimate fracture stress decreased from 1174 to 998 MPa. The strain to failure increased from 4.6% to 6.0% after the same exposure. Saphikon single crystal Al2O3 fibers were used to demonstrate the materials' compatibility. The fracture surfaces of the failed composites indicated ductile failures in the matrix and decohesion between the particles and matrix.
Creep Behavior and Microstructure of XD™ Titanium Aluminide
Authors: Feng C. R. , Smith H. H. , Michel D. J. , Crowe C. R.
Published: March 2011

The creep behavior of extruded XD™ Ti-47at%Al/7.5v%TiB2 composite was investigated together with extruded Ti-46at%Al alloy. Prior to creep testing, both materials received a duplex heat-treatment at 1200°C for 16h plus 900°C for 8h. The creep tests were conducted at 69, 103 and 138MPa at 760°C in air. The microstructures of both materials prior to and after the creep testing were examined by TEM. The microstructures suggest that the formation of the TiAl/Ti3Al two-phase lamellar structure was the predominant creep mechanism.
Structure/Property Comparisons in Particulate and Short Fiber γ-Based Titanium Aluminide Composites
Authors: Kampe S. L. , Clarke J. A. , Christodoulou L.
Published: March 2011

The effect of matrix microstructure on the mechanical properties of two model XD™ titanium aluminide composites containing 7 volume percent of either particulate (TiB2) or short-fiber ((Ti,Nb)By) reinforcement has been evaluated. Subsequent to wrought-processing via isothermal forging, heat treatments were performed to produce either a fully equiaxed or fully lamellar matrix microstructure. The synergism between matrix microstructure and reinforcement type has been evaluated for ambient-temperature tensile ductility and fracture toughness, and 800°C tensile strength and creep rate. Results indicate that overall composite performance is strongly dependent on reinforcement shape, the extent of which depends on the morphology of the matrix microstructure.
Microstructure and Interface Behavior in Diffusion Bonded Ni3Al+B Matrices Containing Continuous Al2O3 Fibers.
Authors: Lee C. , Grummon D. S. , Gottstein G.
Published: March 2011

Diffusion bonding is a well known method for fabricating metal matrix composites with continuous fiber reinforcements. However. little data yet exist regarding optimum processing conditions for production of such composites using intermetallic matrices. In this study, diffusion bonded couples were made from boron doped nickel aluminide slabs (vacuum arc remelted alloy IC-15 ) into which small numbers of continuous fibers of α-A12O3 were laid up. Diffusion bonding was carried out in vacuum at stresses between 20 and 50 MPa for 2 to 8 hours at 1273K to 1553K. The specimens were then fractured in uniaxial tension at room temperature and the microstructures and fracture surfaces examined. Preliminary data from optical and scanning electron microscopy showed complete metallurgical bonding of the IC-15 slabs occurred only when process temperatures exceeded 1533K. At these temperatures a 2-hour processing time resulted in considerable grain growth in both the matrix and in the fibers. Occasional fiber fracture was also found to have occurred during the bonding cycle. Auger electron spectroscopy revealed little interdiffusion between fiber and matrix after 2 hours at 1553K and no apparent fiber-matrix reaction zones were detected for any of the process conditions studied.
Cyclic Oxidation Resistance of a Reaction Milled Nial-AlN Composite
Authors: Lowell Carl E. , Barrett Charles A. , Whittenberger J. Daniel
Published: March 2011

Based upon recent mechanical property tests a NiAl-AlN composite produced by cryomilling has very attractive high temperature strength. This paper focuses on the oxidation resistance of the NiAl-AlN composite at 1473 and 1573 K as compared to that of Ni-47Al-0.15Zr, one of the most oxidation resistant intermetallics. The results of cyclic oxidation tests show that the NiAl-AlN composite has excellent properties although not quite as good as those of Ni-47Al-0.15Zr. The onset of failure of the NiAl-AlN was unique in that it was not accompanied by a change in scale composition from alumina to less protective oxides. Failure in the composite appears to be related to the entrapment of AlN particles within the alumina scale.
Ductile Phase Toughening of MoSi2-Chemical Compatibility and Fracture Toughness
Authors: Xiao L. , Kim Y. S. , Abbaschian Reza
Published: March 2011

Chemical compatibility between oxide coated Nb filament reinforcements and MoSi2 was investigated. It was determined that ZrO2, Al2O3, and mullite coatings were chemically compatible with both Nb and MoSi2. Comparison between coated and uncoated filaments indicated that the coatings reduced the thickness of the interaction zone. The fracture toughness of the Nb filament reinforced composites showed an increase, while W filament reinforced composite showed a decrease, in the toughness compared to that of the matrix. The results are discussed in terms of the mismatches in the coefficients of thermal expansion and the bonding characteristics of the reinforcement/matrix interface.
Oxidation of Powder Processed NbAl3 Matrix Composites
Authors: Korinko Paul S. , Duquette D. J.
Published: March 2011

Niobium aluminide based composites fabricated by powder metallurgy techniques were tested for oxidation resistance between 1000 and 1400°C. The oxidation rate of these materials was improved over conventionally cast or pack aluminized NbAl3. The inclusion of oxide dispersoids decreased the rate constant by an order of magnitude at 1000°C compared to monolithic NbAl3 and to a value of the same order of magnitude as NiAl at 1170°C. The most heavily reinforced material studied had a rate constant an order of magnitude greater than NiAl at 1400°C.The oxide scale was generally adherent and compact but contained oxide nodules.
Interface Modification for Fiber-Reinforced Titanium Aluminide Composites
Authors: Boss Daniel E. , Yang J. M.
Published: March 2011

Candidate diffusion barrier coatings were applied to aluminum oxide and silicon carbide fibers, and consolidated in a gamma titanium aluminide alloy. Interfacial coatings of titanium carbide and titanium diboride were applied to the fibers using chemical vapor deposition, while calcium oxide coatings were applied from a solution. Sections of these specimens were vacuum encapsulated in quartz tubing and heat treated for 50 hours at 1100°C. The thermochemical stability of the fibers was evaluated using energy dispersive x-ray spectroscopy to compare the fiber-matrix interface of the specimens before and after heat treatment. Both the as-manufactured and the coated aluminum oxide fibers showed no discernable interaction with the titanium aluminide matrix. Titanium diboride effectively prevented the silicon carbide fiber from reaction with the matrix. The silicon carbide fiber which was coated with titanium carbide showed significant reaction between the fiber and the coating after heat treatment.
Effect of Thermomechanical Treatments on Solidification Inhomogeneity in Ingot Metallurgy Gammtait Anium Aluminides
Authors: Bryant J. D. , Semiatin S. L. , Maisano J. R. , Winter D. T. , Barrett A. R. H.
Published: March 2011

The addition of titanium diboride to near gamma titanium aluminides has been effective in reducing the initial grain size formed on solidification from the melt. Despite this refinement, however, significant constitutional inhomogeneity may be found due to segregation of alloying elements and reinforcement phases during solidification. The dendritic solidification of several XD'T alloys was studied to assess the extent of this segregation. Quantitative elemental analysis of dendritic and interdendritic regions indicates that a substantial chemical gradient is developed in aluminum and ternary alloying elements. The extent of chemical and reinforcement segregation and its relationship to overall aluminum content in the alloys is discussed. In a study to determine thermomechanical processing steps required to eliminate the casting inhomogeneity, homogenization heat treatments and isothermal forging were performed and the effect on microstructure determined. Remnant dendritic cell structures were seen to persist despite high-temperature heat treatments and mechanical working.
Synthesis and Characterization of Cellular SiO2 Materials by Foaming Sol Gels
Authors: Covino Josephine , Gehris Allen P.
Published: March 2011

A variety of cellular SiO2 materials have been synthesized using a foaming sol-gel process and their properties have been characterized. The process uses the rapid viscosity change during gelation to stabilize the structure of a foamed silica sol. It was found that the properties of these cellular materials are determined by method used. For example, the porosity and strength of these porous oxides depend on method of agitation and addition of Freon during the foaming process.

Density measurements, viscosity measurements as a function of pH, optical characterization, x-ray crystallography, ultimate compressive strength, dielectric constant measurements and thermal diffusivity were used to characterize these porous SiO2 materials. This paper will discuss the synthetic processes used to develop the porous silicas and properties of these materials.
Energy Absorption by Expanded Bead Polystyrene Foam: Dependence on Fracture Toughness and Bead Fusion
Authors: Stupak P. R. , Donovan J. A.
Published: March 2011

Increased energy absorption and load result when the contact area between an object and a foam cushion is less than the foam area because of an increased foam deformation volume (i.e. “Load Spreading”). The deformed volume is trapezoidal (i.e. not prismatic) and is a function of the foam dimensions and the object geometry. The load spreading effect is greatest when the ratio of the object area to the foam thickness is smallest; a common configuration in commercial packages (Figure 1).
Scaling Laws for Transport, Mechanical and Fracture Properties of Disordered Materials
Authors: Sahimi Muhammad , Arbabi Sepehr
Published: March 2011

We discuss scaling laws for scalar and vector transport properties of, and fracture processes in, disordered materials. Random resistor networks, and elastic and superelastic percolation networks are used to model the disordered material. While scalar transport properties of such systems (e.g. conductivity or diffusivity) obey universal scaling laws near the percolation threshold, vector transport properties (e.g. elastic moduli) may not follow such universal laws, and the critical exponents characterizing such scaling laws may depend on the microscopic force laws of the system. On the other hand, fracture processes in such systems appear to obey universal scaling laws. In particular, the external stress F for the fracture of the system scales with its linear size L as F ˜ Ld-1/(ln L)ψ, where d is the dimensionality of the system and ψ is a small critical exponent (ψ ≃ 0.1). Moreover, as the macroscopic fracture point of the system is approached, the ratio of various elastic moduli of the system approaches a universal fixed point, independent of the microscopic details of the system. Finally, the distribution of fracture strength in a randomly reinforced system, or in a system near its percolation threshold with a broad distribution of elastic constants, is in the form of a Weibull distribution, rather than the recently-proposed Gumbel distribution.
Optimal Selection of Foams and Honeycombs in Packaging Design
Authors: Zhang J. , Ashby M. F.
Published: March 2011

The volume of foams used in packaging is enormous. Proper design requires identifying the right material and selecting the right density for each particular application. A new approach to package design is presented in the form of “the Packaging Selection Diagram”, from which the optimal density of a cellular material can be obtained once the maximum permitted stress of the packaging is known. This approach offers greater generality and simplicity than the existing methods such as the Janssen factor or the Energy Absorption Diagram.
Fracture Behavior of Open Cell Ceramics
Authors: Brezny Rasto , Green David J.
Published: March 2011

Cellular ceramics constitute a class of materials where the properties may be optimized against the weight. These materials may be potentially useful in both structural and non-structural applications. In order to broaden the utilization of the currently- available materials, the mechanical properties must be improved. The objective of this paper is to review several recent studies on the strength and toughness of open cell brittle materials. The work was aimed at understanding the mechanisms involved in the failure of these materials and the relationship between the properties and the microstructure.
The Indentation and Nailing of Cellular Materials
Authors: Vaz M. Fátima , Fortes M. A.
Published: March 2011

An experimental study was carried out on the indentation of cellular materials under quasi-static conditions. The study concentrated on a closed cell rigid polyurethane foam, but other cellular materials were tested. Load (F) - penetration depth (x) curves were obtained for various types of indenters which fall into two main types: sharp indenters (e.g. normal nails) and blunt indenters (e.g. flat ended nails). The F(x) curves are similar for the two types with an initial high slope region followed by a lower slope region in which F increases linearly with x. Nevertheless, the mechanisms of indentation are completely different, with a blunt indenter pushing the material under it and a sharp indenter pushing it radially as it penetrates. The effect of dimensions and shape of the indenters on the F(x) curves was investigated and scaling relations could be derived. Penetration-removal cycles clarify the differences between the two types of indenters, and give additional information on the mechanics of indentation. The experiments were complemented with scanning microscope observations of sections of the indented material. Two approaches are advanced for modelling indentation: a discrete approach in which the cellular structure is taken into account and a continuum approach.
Fracture Properties of an Anisotropic Biological Cellular Material - Apple Flesh
Authors: Khan Ali A. , Vincent Julian F. V.
Published: March 2011

The texture of apple flesh is important in assessing its eating qualities. The texture in turn is related to the structure of the parenchyma. The parenchyma cells of the fruit are arranged in radial quasi-columnar form with radial spaces in between. This anisotropy has a marked effect on the fracture properties such that it is much easier to drive a crack between the columns (radially) than to drive it across them (tangentially). The fracture tests used were simple crack-opening tests under tension or using a wedge. This difference was also detected by a taste panel. The radial spaces ease the passage of cracks travelling along them, and act as crack stoppers for cracks travelling at right angles to them. They also allow the cells to deform more in one orientation more giving the structure ductility and making the apple tougher in that orientation. It is possible to increase this effect by controlled damage such as slow freezing which causes the intercellular spaces to expand increasing the crack-stopping mechanisms and increasing the ductility, therefore increasing the fracture toughness. Toughness first increases, then decreases with increasing damage. This effect can be mimicked with brittle paper: fracture toughness of tracing paper initially increases if holes are punched randomly in it.
Fracture and Yield of a Porous Composite of Trinitrotoluene and Cyclotrimethylene Trinitramine
Authors: Wiegand Donald A. , Pinto J.
Published: March 2011

Composites of trinitrotoluene and cyclotrimethylene trinitramine have been studied in uniaxial compression and in triaxial confined compression. Failure by crack propagation and fracture was observed in all uniaxial studies while failure by yield and plastic flow was found for all triaxial confined compression work. The yield strength is approximately a factor of 2 greater than the uniaxial compressive fracture strength. The relationships between the fracture and yield strengths and Young's modulus indicate that all three decrease with increasing porosity. Based on this porosity interpretation, the compressive strength, the yield strength and Young's Modulus may be increased significantly by reducing the porosity.
Representation of the Microstructural Dependence of the Anisotropic Elastic Constants of Textured Materials
Authors: Cowin Stephen C.
Published: March 2011

This paper addresses the question of representing the dependence of the elastic coefficients in the anisotropic form of Hooke's law upon the microstructure of a material. The concern is with textured material symmetries, that is to say materials such as natural and man-made composites whose material symmetry is determined by microstructural organization. The approach is to relate the anisotropic elastic coefficients to local geometric or stereological measures of the microstructure. The predictions of micromechanical models and continuum mechanical models are compared and are found to be consistent with each other.
Digital-Image-Based Study of Circular Holes in an Elastic Matrix
Authors: Day A. R. , Thorpe M. F. , Snyder K. A. , GarBoczi E. J.
Published: March 2011

Using a digital-image-based representation of a continuum composite, we apply computer simulation techniques to obtain the elastic moduli of a matrix containing randomly-centered circular voids. As the area fraction of the voids increases, the elastic moduli of the composite decrease until they eventually vanish at the percolation threshold. We compare our results with an effective medium theory, which predicts that Poisson ratio tends to a fixed value as the percolation threshold is approached, independent of the values of the elastic moduli in the pure system. Our results are also compared with recent experimental results.
Impact Resistance of Post-Tensioned Concrete
Authors: Wang Nianzhi , Mindess Sidney
Published: March 2011

Impact tests were carried out on post-tensioned beams, prepared both with plain concrete and fibre-reinforced concrete. It was found that post-tensioned beams might be less resistant to impact loading than were ordinary reinforced concrete beams. However, the addition of fibres to the concrete greatly increased the impact resistance of these beams.
Fracture Properties of Fiber Reinforced Concrete Subjected to Impulsive Loading
Authors: Ansari Farhad , Navalurkar Rajendra K.
Published: March 2011

The need to accurately predict the response of structures under impact loadings has led to an interest in the mechanical properties of component materials at high rates of loading. The mechanism of cracking and its propagation play an important role in evaluation of the response of fiber reinforced concrete structures subjected to impulsive loading. In the present study, single–edge notched beams were tested under high velocity impact loads. A computer assisted instrumented Charpy test system was employed in performing the impact tests. Development and testing of a new fiber optic sensor, for the determination of internal Crack Opening Displacements (COD) in fiber reinforced concrete is described.
Testing of SFRC by the Schmidt Rebound Hammer
Authors: Šušteršič Jakob , Rebić Milenko , Urbančič Stanislav
Published: March 2011

The rebound number, its relationship to fundamental frequency and correlations with compressive strength and erosion - abrasion resistance are discussed. Nine mix proportions were used. The w/c ratios were varied from 0.30 to 0.65. The volumetric percentage of hooked steel fibres was varied from 0.25 to 2.0 vol.% at the w/c of 0.30; at the others the quantity of fibres was constant. In addition, mixes without fibres were made at each w/c.

The rebound number and the fundamental frequency are decreased by an increase of steel fibre content. The rebound number correlates with erosion - abrasion resistance. It does not correlate with compressive strength of concretes with constant w/c and different contents of fibres.
Ceramic Fiber Composites, Processing and Performance
Authors: Rice Roy W.
Published: March 2011

Ceramic fiber composites (mainly with continuous fibers) are reviewed, in part, from the perspective of the pertinence of such results to cementitious construction materials. While there is a large gap in the density, stiffness, etc., of the matrices and of the types and volume fraction of fibers used in these two types of material systems, the fact that for any of these systems fiber-matrix friction/pull-out are important suggests some useful transfer of information. Fiber coatings, which can have spectacular benefits in ceramic fiber composites by controlling fiber-matrix interfaces are discussed. Matrix conformance to the fibers and fiber bending and shape are also probable factors about which less is known, but are discussed because of their potential importance. Similarly, issues of fiber size and fibermatrix property differences are briefly discussed, as are effects of matrix porosity.
Fracture Energy Optimization in Synthetic Fiber Reinforced Cementitious Composites
Authors: Li Victor C. , Wang Youjiang , Backer Stanley
Published: March 2011

A study has been carried out on cementitious composites reinforced with various synthetic fibers, focusing on their tensile behavior, toughness, and fracture mechanisms. A model is formulated to predict the tensile behavior and fracture energy of fiber reinforced cementitious composites (FRC) with short, randomly distributed fibers. The model accounts for the pull-out of fibers oblique to the fracture surfaces (including snubbing friction effect), and the variation of the fiber/matrix interfacial shear stress during pull-out. Experimental and analytical results are shown to be in close agreement for the one class of fiber reinforcement which best satisfies the assumptions of the model. Systems which violate the assumptions exhibited different failure mechanisms and were observed to show less satisfactory reinforcement performance, especially the composite fracture energy. The model is used to examine the effect of fiber properties on composite post-cracking behavior and is useful in design of such material systems with optimum performance and cost effectiveness.
Dependence of Substrate Orientation on the Synthesis of CoSi2 Layers Formed by Ion Implantation & Rapid Thermal Annealing
Authors: Gwilliam Russell M , Reeson Karen J , Webb Roger P , Spraggs Russell S , Sealy Brian J
Published: March 2011

200 keV Co+ ions have been implanted into (100), (110) and (111) single crystal silicon substrates to doses of 2 × 1017 Co+ cm−2 and 5 × 1017 Co+ cm−2. During implantation the substrates were tilted at an angle of 70 to the incident ions and maintained at a temperature of 350°C. The experimental results, after implantation, are in close agreement with those obtained by computer simulations, which allow the single crystal orientation of the target and its position with respect to the incident ions to be specified. 5s RTA treatment at 1100°C was found to give CoSi2 layers of similar crystalline quality and resistivity to those produced by conventional furnace annealing.
Low Resistivity CoSi2 Surface Layers for Use as Contacts in CMOS Processes
Authors: Audet Sarah A. , Rafferty Conor S. , White Alice E. , Short Ken T. , Hsieh Yong-Fen
Published: March 2011

Uniform CoSi2 surface layers 30nm thick have been realized through room temperature implantation of Co+ through a resist or an oxide mask and low temperature (600°C) annealing. TEM studies show that the surface layers are polycrystalline with large, uniformly thick grains. Resistivity values as low as 181µΩ-cm have been obtained. Surface layers of TiSi2 have also been synthesized using a similar process. The ease of formation, the low resistivity and the smooth interfaces of the CoSi2 and TiSi2 surface layers make this technique a promising candidate for contacting source and drain junctions in sub-half-micron CMOS processes.
Nucleation, Transformation and Agglomeration of C54 Phase Titanium Disilicide
Authors: Mann R.W. , Racine C.A. , Bass R.S.
Published: March 2011

The transformation of TiSi2from the C49 phase to the C54 crystallographic phase is an irreversible, polymorphic transformation that occurs by a nucleation and growth process. Typical of polymorphic transformations, the transition occurs readily once a stable embryo of the thermodynamically favored phase is formed. Future VLSI applications requiring control of the resistivity and thermodynamic stability of thin TiSi2films formed on submicron features will necessitate understanding this nucleation and transformation process to a greater extent. We have found that the C54 phase nucleation site density, the resulting microstructure and thermal stability of the film can be strongly influenced by the initial silicide formation conditions. Rapid thermal processing (RTP) has been found to offer a significant advantage over conventional furnace annealing for the silicide formation process.
Rapid Thermal Annealing of Titanium in an Ammonia Ambient: Kinetics and Film Properties
Authors: Srikrishna K. , Jairath R. , Huglin G.
Published: March 2011

The reaction between titanium and ammonia to form titanium nitride in a rapid thermal annealer has been studied as a function of process temperature and substrate conditions. The films produced have been characterized by Rutherford Backscattering, Sputtered Neutral Mass Spectroscopy and four point probe electrical resistivity measurements. On oxide substrates, below 720°C only dissolution of nitrogen within the titanium is observed leading to an increase in the specific resistance of the film. Above 720°C, stoichiometric titanium nitride begins forming leading to a drop in the specific resistance of the film. Only in the vicinity of 800°C is all the titanium consumed to form TiN. However, temperatures beyond 700°C cause dissolution of oxygen within the titanium. On silicon substrates, the competing reactions of nitridation and silicidation at the two interfaces govern the extent of nitridation.
Optical Properties of Growth Phases Formed by Rapid Thermal Annealing of MoSix thin Films on Si (100)
Authors: Srinivas G. , Rastogi R.S. , Vankar V.D.
Published: March 2011

Amorphous thin films were deposited by co-sputtering Mo and Si on Si(100) single crystals. Rapid thermal annealing at 700, 800 and 1050°C for 30 sec. resulted in the growth of hexagonal and tetragonal phases of MoSi2 as revealed by glancing angle x-ray diffraction. The optical properties of these films were studied by spectroscopic ellipsometry in the range 1.0 to 5.0 eV. As deposited films showed both metallic and semiconducting features in the <ε1> and <ε2> spectra. As a result of annealing at 700 and 800°C, pronounced increase in <ε1> was obtained. Annealing at 1050°C resulted in decrease of the values of <ε2>. Surface morphology, density changes and stress variations associated with recrystallization and compound formation are proposed to account for these observations. The peaks in <ε2> spectra are found to be interband transitions in the MoSi2 structures. These results are in confirmity with the EELS and UPS studies and theoretically calculated band structure of MoSi2.
In-Situ Fabrication and Process Control Techniques in Rapid Thermal Processing
Authors: Moslehi Mehrdad M. , Kuehne John , Yeakley Richard , Velo Lino , Najm Habib , Dostalik Bill , Yin David , Davis Cecil J.
Published: March 2011

Advanced rapid thermal processing (RTP) equipment and sensors have been developed for in-situ fabrication of semiconductor devices. High-performance multi-zone lamp modules have been applied to various processes including rapid thermal oxidation (RTO), chemicalvapor deposition (CVD) of tungsten and amorphous/polycrystalline silicon, silicide formation, as well as high-temperature rapid thermal annealing (RTA). Concurrent use of multizone lamps and multi-point temperature sensors allows real-time wafer temperature control and process uniformity optimization. Specific experimental results will be presented on the multi-zone lamp modules, in-situ process control sensors, and single-wafer fabrication processes.
Impacts of Temperature and Reactant Flow Rate Transients on LPCVD Tungsten Silicide Film Properties
Authors: Cale T. S , Park J.-H. , Raupp G. B. , Jain M. K.
Published: March 2011

A transient model of a stagnation point flow, single wafer reactor is used to predict the concentrations of tungsten hexafluoride and dichlorosilane as a function of position along the surface of a six inch wafer during the transient and steady state operating phases of tungsten silicide deposition in trenches having an initial aspect ratio of five. We analyze two startup protocols: 1. The susceptor temperature setpoint is changed from just above room temperature to its steady state value after the reactant flows are established. 2. The reactant flowmeter setpoints are changed to their steady state values after the wafer temperature is established in a flow of inert gas. A ballistic transport and reaction model is used to predict film thickness and composition profiles of these tungsten silicide films as a function of deposition time. The transient portions of the two startup protocols do not affect film profiles or average composition as much as the inherent increase in aspect ratio as the fill proceeds.
Role of Photoeffects in Integrated Rapid Isothermal Processing
Authors: Singh R. , Sinha S. , Thakur R.P.S. , Hsu N.J.
Published: March 2011

Rapid isothermal processing (RIP) based on incoherent radiation as the source of energy is emerging as a practical alternative to furnace processing. In this paper, we show that in addition to the well established short time processing feature, RIP can also be used as a reduced substrate temperature processing technique.
Microstructure and Kinetic Analysis of the Initial Stages of SiC Formation in a Rapid Thermal Processor
Authors: Kim Ki-Bum , Liao Jimmy C. , Burrow Brad J. , Sullivan Eileen A.
Published: March 2011

We have investigated the evolution of the microstructure, growth modes, and growth kinetics of β-SiC in a rapid thermal processor using FTIR, ESCA, and TEM. SiC layers were formed by reacting C2H4 with Si substrates between 900 and 1300°C at 5 torr. We found that SiC forms discrete nuclei at 900°C, a mixture of discrete nuclei with a thin β-SiC layer in between those nuclei at around 1000°C, and a continuous β-SiC layer above 1100°C. In all cases, β-SiC grows epitaxially on Si substrates. In addition, we identified that a graphitic carbon layer is formed on top of a continuous β-SiC layer. The thickness of the SiC layer was deduced from the integrated absorption spectra of FTIR and measured from the high resolution cross-sectional TEM micrographs. Kinetic data indicate that SiC grows rapidly at the initial stages of reaction. The growth rate, however, is retarded significantly as the reaction proceeds.
Single-Wafer RTCVD of Polysilicon: a Complementary Step in Front-End Integrated Processing
Authors: Kermani Ahbmad
Published: March 2011

Polycrystalline silicon is used in the fabrication of integrated circuits in various applications. These include a MOS gate material, bipolar emitter and base contacts, trench refill, complementary material for elevated source / drain structures, solid diffusion source for formation of shallow junctions and the active material in thin film transistors. The deposition of polysilicon as the MOS gate electrode or the bipolar emitter contact follows the most critical processing steps in fabrication of these devices. Maximum reproducibility and highest device performance are achieved when the interfaces between the polysilicon and the underneath substrate are well controlled. This level of control can be obtained by combining the compatible processing steps under a controlled environment. Single-wafer RTCVD of polysilicon was introduced to complement the emerging front-end integrated processing technology for MOS, bipolar and BICMOS devices.
Demonstration of Multiprocessing by Silicon Epitaxy Following In-Situ Cleaning
Authors: Apte Pushkar P. , Venkatraman Ramnath , Saraswat Krishna C. , Moslehi Mehrdad M. , Yeakley Richard
Published: March 2011

Conventional semiconductor manufacturing techniques may be unable to meet technological demands in certain cases, and alternatives need to be investigated. We propose in situ sequential processing, which we define as ‘multiprocessing’, as a possible innovation. We demonstrate a specific manifestation of multiprocessing, namely the integration of a novel in situ pre-clean using anhydrous hydrogen fluoride with chemical vapor deposition of silicon, leading to the growth of high-quality single-crystal silicon epitaxy. Further, we show that the multiprocessing technology is viable for manufacturing, since it is simple, rapid, has a low thermal budget and does not suffer from cross-contamination. Finally, we discuss the possible role of multiprocessing in semiconductor manufacturing.
In Situ Wafer Emissivity Variation Measurement in a Rapid Thermal Processor
Authors: Dilhac J-M. , Ganibal C. , Nolhier N.
Published: March 2011

Wafer backside reflectivity measurements at room temperature have been performed in a rapid thermal processor equipped with two rows of heating lamps by measuring, with the process optical pyrometer, the light emitted by the lower row of the heating lamps and reflected by the wafer. The differences in reflectivity have been correlated with the process temperature variations induced by emissivity changes. Optical pyrometer recalibration procedures have then been established. It has been demonstrated that the reflectivity measurement, performed automatically for each wafer prior to the thermal cycle, may drastically improve the accuracy of temperature control.
Rapid Thermal Processing and Properties of Sol-Gel Derived Ferroelectric Thin-Films for Non-Volatile Memories.
Authors: Barlingay C. K. , Dey S. K
Published: March 2011

Ferroelectric Pb(Zr0.52Ti0.48)O3 or PZT (52/48) thin-films (0.5 μm) were integrated onto Pt passivated Si wafers (3–4 inches) by polymeric solgel processing followed by rapid thermal annealing. Dense and crack-free perovskite microstructures were obtained by densification of the amorphous gel-matrix prior to crystallization. The films exhibited submicron grains (0.2–0.6 μm) with a columnar growth habit. High field measurements on thin-films determined Pr, Psp, and Ec in the ranges of 29–32 μC/cm2. 44–58 μC/cm2, and 50–60 kV/cm, respectively, and ferroelectric switching times below 3 ns.
The Nature of Electrically Inactive Implanted Arsenic in Silicon after Rapid Thermal Annealing
Authors: Altrip John L. , Evans Alan G.R. , Young Nigel D. , Logan John R.
Published: March 2011

The electrical activation of As implanted Si has been investigated on rapid thermal annealing timescales using sheet resistance, spreading resistance and Hall Effect techniques. For high dose implants (>1015 As cm-2) differential Hall Effect and spreading resistance profiles confirm the existence of a temperature dependent electrical solubility limit. However for low dose implants, annealing schedules chosen such that the electrical solubility limit is not exceeded reveal electrical deactivation which is not accounted for in the clustering theory. Hall Effect measurements performed as a function of temperature have enabled us to reveal directly electrically inactive As which is not observable at room temperature using standard electrical techniques. The results indicate that As atoms in Si introduce deep trapping levels within the bandgap which are responsible forremoving As from the conduction process at room temperature. This temperature activated process is characterized with an activation energy of 0.4eV.
Rapid Isothermal Processing of Strained GeSi Layers
Authors: Nayak D. K. , Kamjoo K. , Park J. S. , Woo J. C. S. , Wang K. L.
Published: March 2011

The effects of high temperature-time thermal cycles on the structural stability of GexSi1−x/Si and Si/GexSi1−x/Si layers are studied, using double-crystal x-ray diffraction. The temperature-time cycles chosen in this study are useful for the fabrication of submicron Si MOSFETs. The electrical characteristics of GeSi/Si p-n heterojunctions as a function of annealing temperature and time are also presented.
A Continuous Heterogeneous Model for the Crystalline to Amorphous Transition in Ion Implanted Semiconductors : Relationship to the “Critical Damage Energy Density” Model
Authors: Vieu C. , Claverie A. , Faure J. , Beauvillain J.
Published: March 2011

A method is presented for calculating amorphization doses of ion implanted semiconductors, based on a continuous heterogeneous description of damage accumulation. This new approach is compared to the classical “critical damage energy density” (CDED) model. For high dose implantations the equivalence of both descriptions is formally established. It is proposed that the main limitation of the CDED model lies in the linear additivity of damage rather than the homogeneous damage build-up.
Effect of Processing Conditions on the Surface Morphology of thin Polysilicon Films Used for Dram Cell Capacitors
Authors: Mathews Viju K.
Published: March 2011

The surface texture of polysilicon films, used for capacitor storage nodes, have been investigated for various deposition conditions. An increase in capacitance of approx. 70% has been observed in this work. The reproducibility of the surface texture and the resulting capacitance can be improved by optimizing the deposition pressure. The gain in capacitance was also observed to be affected by the thickness of the film. In the mass flow controlled regime the increase in capacitance was 12%. The increase in surface roughness and the gain in capacitance for the hot wall process provides a simple alternative for satisfying the charge capacity requirements in high density dynamic random access memories.
Real Time X-Ray Studies of Interface Kinetics in Epitaxial Strained Layers
Authors: Clarke Roy , Passos Waldemar Dos , Lowe Walter , Rodricks Brian , Brizard Cristine
Published: March 2011

A new time-resolved x-ray method of probing the kinetics of interfacial strains in semiconductor heterostructures is presented. High-resolution synchrotron radiation measurements of the strain relaxation during rapid thermal annealing (RTA) show that the lattice strain of an as-grown strained layer structure GaAs-Inx.Ga1−x-As-GaAs/GaAs is relieved cooperatively by a series of sluggish discontinuous transitions. We find that ion implantation enhances the annealing kinetics of InAlAs strained layers.
Characterization of Lead Zirconate-Titanate Thin Films Prepared by Pulsed Laser Deposition
Authors: Chiang C. K. , Wong-Ng W. , Schenck P. K. , Cook L. P. , Vaudin M. D. , Brody P. S. , Rod B. J. , Bennett K. W.
Published: March 2011

Dense smooth lead zirconate-titanate thin films have been prepared by excimer laser deposition. The as-deposited films are amorphous as indicated by x-ray powder patterns. Differential scanning calorimetry studies show that the film has a glass transition at 301 °C, and the amorphous to crystalline transformation takes place above 350°C to 650°C. Phase formation as a result of post-deposition heat treatment is described.
Analytical Electron Microscopy Studies of Bi-Substituted Garnet Films
Authors: Crozier P. A. , Labun P. A. , Suzuki T
Published: March 2011

In-situ heating in an electron microscope, together with EDX and EELS analysis, was used to characterize as-deposited amorphous and transformed garnet films. It was found that upon initial crystallization, a non-uniform precipitation of a second phase occurred, altering the local chemistry and microstructure of the transformed film. In addition, to study the transformation kinetics in more detail some experiments were conducted at slower heating rates and lower temperatures. It is hoped that the data obtained can be correlated to magnetic property measurements and contribute to the development of improved processing conditions.
Characterization of Contaminants by S-Sims Mapping for Magnetic Recording Devices
Authors: Viswanathan K. V. , Wadkins P. J.
Published: March 2011

The magnetic storage industry moved from particulate to thin fdm disks during the 1980's due to the trend toward higher density media. The disk dimensions also shrunk, from 350 mm to 95 mm and are expected to go down to 62.5 mm. The head-disk fly height will be reduced from 35 nanometers to below 10 nanometers during the coming decade. Contamination build-up on the disk, the head, and at the head-disk interface can create problems and may ultimately lead to head crashing. Therefore, it is important to build hard disk drives using very clean components. Some of the important components are the disk, the bearing, the head, the actuator, the comb, and the spindle. Hydrocarbon contamination is ubiquitous. Lubricants used can be collected by the head and may cause head print problems. Depending upon the curvature of the head and asperities on the disk, there will be head-disk interactions which can lead to smears on the disk surface. Build-up of such smears on the head and disk can reduce fly height and cause performance problems.

Static Secondary Ion Mass Spectrometry (S-SIMS) is a powerful technique used to analyze both organics (characteristic fragmentation pattern) and inorganics (by mass number, including isotopic ratio). This approach is not possible with other analytical techniques. Further, the technique is surface sensitive and the detection limit is very low. This paper discusses S-SIMS mapping of smears and head prints following contact/start/stop (CSS) testing. The roles played by individual file components in generating smears are identified. S-SIMS can also be extended to contaminant analysis on silicon wafers, printed board circuits, etc.
Effective Magnetic Permeability of Composite Materials Near the Percolation Threshold
Authors: Lagar'kov A. N. , Panina L. V. , Sarychev A. K.
Published: March 2011

A proposed cluster model is used to determine analytically the effective magnetic permeability of ferromagnetic percolating systems. It is shown that on the approach to the percolation threshold the real part of the magnetic permeability tends to zero in spite of the increase of ferromagnetic component. This anomaly is due to the formation of large conducting clusters.
Pseudomorphic Growth of Fcc FeMn Thin Film on NiFe and its Interfacial Structure
Authors: Hwang Chcrngyc , Nguyen Thao A.
Published: March 2011

Thin film couple of NiFe/FeMn has been used in the magnetoresistive read head design in the magnetic recording industry. The strong magnetic coupling between FeMn and NiFe is of most importance in providing the stability of the MR head. FeMn has been shown to grow epitaxially on NiFe surface and form a metastable fcc structure. The existence of this fcc structure is believed to be the source of the magnetic coupling. It has also been shown that the grain to grain epitaxy exists in this polycrystalline thin film couple, however with only indirect evidence such as Moiré fringes across the interface boundary. To further study this pseudomorphic growth phenomenon, a specially prepared large grain FeMn/NiFe thin film couple was used. Lattice imaging of the interfacial structure was obtained by high resolution cross-section transmission electron microscopy. The plan-view TEM imaging and electron dilfraction patterns also show clear evidence of the grain to grain epitaxy in almost all the grains. The epitaxial strain associated with each coupled grain was also evidenced by the isolated strain contours within each grain. Detailed interfacial structure analysis will be given to elucidate the mechanism(s) by which the interfacial strain is accommodated.
Soft Magnetic Properties and Microstructures for the Fe Based Sputtered Films with High Bs
Authors: Takahashi Migaku , Shimatsu T.
Published: March 2011

Physical origin of high initial permeability, μi, in Fe based films with large magnetocrystalline anisotropy and magnetostriction is systematically discussed in connection with the microstructure of the films. In order to decrease the local anisotropy fluctuation to determine μi in these films, decrease of effective magnetic anisotropy, Ueff, of each grain mainly caused by the sufficient reduction of grain size is required. Induced uniaxial magnetic anisotropy energy, Ku, in film plane plays an important role to decrease Ueff through the micromagnetic interaction. The ratio of Ueff /Ku proposed as the important key to analyse the magnetization process. The dependence of μi Ku is classified concerning for Ueff/Ku.
Soft Magnetic Properties and Brittleness of Boron-Doped Sendust Alloy
Authors: Shoa Yuan-Zhi , Gu Shou-Ren , Chen Nan-Ping
Published: March 2011

Sendust is limited in its application due to its brittleness. This paper shows the brittleness of sendust ribbon made by rapid quenching can be improved by microalloying of boron with negligible influence on its magnetic properties. The mechanims of boron effect on its properties is discussed.
Magnetic Anisotropy of FeAlSi Sputtered Films
Authors: Ohta Toshihiko , Ohsawa Yuichi , Iwasaki Hitoshi
Published: March 2011

The FeAlSi film magnetic anisotropy has been studied in relation to the residual stress and crystalline orientation. Experiments show that the magnetic anisotropy behavior depends on the geometrical location of the substrate with the target during the deposition. The main origin of the magnetic anisotropy is attributable to the magnetoelastic effect due to the residual stress anisotropy, which may be induced by the anisotropic incidence of sputtered particles to the substrate.
Microstructure and Coercivity of Rapidly Quenched ND-FE-B Magnets
Authors: Pinkerton Frederick E.
Published: March 2011

Rapidly quenched Nd2Fe14B-based permanent magnets owe their high intrinsic coercivity Hci to their unique submicron-sized grain structure. While no clear consensus has yet emerged regarding the microscopic origin of coercivity in these fascinating materials, magnetic and structural data suggest pinning of magnetic domain walls at or in an intergranular phase between Nd2Fe14B grains as the most likely mechanism. The small, randomly oriented grains in isotropic melt-spun ribbons produce a magnetic structure wherein each Nd2Fe14B grain is a single magnetic domain, with the domain walls expelled to the grain boundaries. The magnetic interaction between neighboring grains plays an important role in the magnetization reversal of individual grains, as revealed, for example, by detailed examination of the initial magnetization and demagnetization processes. The formation of large domain structures via these interactions is frustrated by the random grain orientation in ribbons, but short range magnetic correlations between grains (“interaction domains”) are observed locally.

The oriented grains in aligned die upset magnets produce a very different magnetic structure having large scale coherent domains which extend through many grains. A variety of experiments, including studies of the temperature dependence of Hci, suggest that coercivity arises from pinning of the extended domain walls at Nd2Fe14B grain edges.
Dynamics of a Superparamagnetic Ensemble
Authors: Garanin D. A. , Panina L. V. , Ischenko V. V.
Published: March 2011

We have completed a detailed consideration for dynamics (the processes of remagnetization and linear susceptibility) of a superparamagnetic ensemble. The results were obtained using analytical and numerical solutions of the initial Fokker-Plank equation.