bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid Infiltration of MgO and Al2O3 Thin Films
Authors: Mallamaci Michael P. , Ramamurthy Sundar , Barry Carter C.
Published: March 2011

The deposition of glass films on thin ceramic substrates is a novel method for investigation of the initial stages of liquid infiltration into the grain boundaries of these materials. By maintaining electron transparency at all stages of the experiment, the transmission electron microscope (TEM) can be used to characterize individual grain boundaries before and after penetration by a liquid. The method has been tested for the MgO and AI2O3 systems, which have extensively studied experimental counterparts in which the corresponding bulk materials are infiltrated by a siliceous liquid.
Near Interface Oxide Degradation in High Temperature Annealed Si/SiO2/Si Structures
Authors: Devine R. A. B. , Mathiot D. , Warren W. L. , Fleetwoodi D. M.
Published: March 2011

Degradation of 430 nra thick SiO2 layers in Si/SiO2/Si structures which results from high temperature annealing (1320°C) has been studied using electron spin resonance, infra-red absorption spectroscopy and refractive index measurements. Large numbers of oxygen-vacancies are found in a region ≤ 100 nm from each Si/SiO2 interface. Two types of paramagnetic defects are observed following γ or X-irradiation or hole injection. The 1106 cm−l infra-red absorption associated with O interstitials in the Si substrate is found to increase with annealing time. The infra-red and spin resonance observations can be explained qualitatively and quantitatively in terms of a model in which oxygen atoms are gettered from the oxide into the under or overlying Si, the driving force being the increased O solubility limit associated with the anneal temperature.
Electrostatic Potentials for Metal Oxide Surfaces and Interfaces
Authors: Streitz F. H. , Mintmire J. W.
Published: March 2011

We discuss the development of interaction potentials which explicitly allow for charge transfer in metallic oxides. The charge transfer is calculated self-consistently using a charge equilibration approach, which allows the amount of charge transferred to respond to the electrostatic environment. We model the metal-metal, metal-oxygen, and oxygen-oxygen interactions with Rydberg function pair potentials. By fitting the Rydberg potential parameters to the elastic and structural constants of the material, we arrive at an efficient model for the simulation of metallic oxides. We demonstrate the applicability of the model by describing some preliminary results on the rutile phase of titanium dioxide.
Stress Driven Patterning of Epitaxial Films
Authors: Grinfeld Michael A.
Published: March 2011

We study possible morphologies of epitaxial films atop attractive substrates appearing as a result of competition of misfit stresses, van der Waals forces and surface energy. Corresponding formula for the critical thickness of the dislocation-free Stranski-Krastanov pattern is established for the isotropic deformable films and substrates. If the film thickness exceeds the critical magnitude the layer-by-layer pattern switches to islanding. At the first stage the islands have a shape of striae (i.e. long parallel trenches with periodic spacing). We discuss also i)the circumstances in which surface morphology of the film corresponds to a two-dimensional superlattice of islands rather than a one dimensional lattice of striae and ii)the influence of a buffer inter-layer.
The Structure and Stress State of Lamellar Interfaces in Two-Phase Titanium Aluminides
Authors: Appel Fritz , Christoph Ulrich , Wagner Richard
Published: March 2011

Titanium aluminide alloys with compositions slightly on the Ti-rich side of stoichiometry consist of the intermetallic phases α2 (Ti3Al) and γ(TiAl). The two phases form a lamellar microstructure with various types of coherent and semicoherent interfaces. The lattice mismatch occurring at the semicoherent interfaces is largely accommodated by networks of interfacial dislocations. Nevertheless, a significant homogeneous straining seems to remain at these interfaces, resulting in long-range residual stresses. The present paper reports an electron microscope study of the correlation between the misfit strain of adjacent lamellae and the atomic structure of the interfaces. The residual coherency stresses were determined by analyzing the curvature of dislocation loops which were emitted from the network of the interfacial dislocations. The estimated stresses are close to the shear stresses applied during macroscopic deformation experiments. The effects of these stresses on the deformation behaviour of the material are discussed.
Preparation of Amorphous Ti-Ni Films and Study on the Electrocatalytic Properties
Authors: Weikang Hu , Yunshi Zhang , Deying Song , Zuoxiang Zhou
Published: March 2011

The film electrodes of amorphous Tio.ssNi1.00 and Ti1.59Ni1.00 were prepared by means of ion beam sputtering method using TiNi and Ti3Ni alloy targets, respectively The surface microstructures and chemical states of elements of the two films before and after HF treatment were examined by SEM and XPS. The electrocatalytic properties for hydrogen evolution reaction were measured by the galvanost&tic steady-state method in 1M NaOH at 40°C. The results showed that the surface microstructures and compositions of the treated films obviously changed as compared with the untreated films. The electrocatalytic activities of the both films before treatment were lower, but the electrocatalytic activities and exchange current densities significantly increased after treatment.
X-Ray Studies of Low-Temperature Grown Sio2 on Si
Authors: Baribeau J.-M. , Landheer D. , Bardwell J.A. , Clark K.B. , Headrick R.L.
Published: March 2011

X-ray reflectivity has been used to study properties of thin SiO2 films on (100) Si prepared by plasma-enhanced chemical vapor deposition (PECVD) or by anodic oxidation. Reflectivity curves were analyzed to obtain information concerning the thickness, density (p) and interface roughness (σ) of these oxide films. We found that the PECVD films have typically a density of 0.98 psi with a sharp Si/SiO2 interface (σ < 0.2 nm) and a surface roughness of -0.5 nm. Anodic oxide films have a lower density (p = 0.88 psi) and larger interface and surface roughness σ - 0.5 nm. High temperature annealing of the anodic oxides up to 900 °C resulted in no appreciable densification but caused an increase in the interfacial roughness. Considerable variations were observed in the reflectivity curves from a PECVD oxide film annealed in the 650-1050 °C range.-Modeling of these results suggests the existence of a thin interfacial layer (-0.5 nm) of less density (∼0.9psi) at the original silicon/PECVD oxide interface.
Characterization of thin Chemical/Native Oxides on Si (100) by Auger and Angle-Resolved XPS
Authors: Pylant Eddie D. , Hoener Carolyn F. , Arendt Mark F. , Witowski Bob
Published: March 2011

Chemical/native oxides grown on Si(100) after several standard wet cleans are characterized by Angle-resolved X-ray Photoelectron Spectroscopy (ARXPS), and Auger Electron Spectroscopy using sputter depth profiles. Target Factor Analysis (TFA) was used to separate the Si LVV Auger peak into three components identified by their lineshapes and positions as Si, SiO2, and SiOx- Auger depth profiles were used to quantify the thickness of the oxides, the depth distribution, and amount of SiOx in the interface region. ARXPS was used to study the chemical state distribution in the native oxides as a function of depth. The depth distribution function from the Auger data was converted to an angle-resolved format for direct comparison to the angle-resolved XPS data. With this comparison, the SiOx lineshape is correlated to a 3:1 mixture of Si 3+ and Si 2+ oxidation states.
Structure and Properties of Vanadium Pentoxide Gels
Authors: Livage J.
Published: March 2011

Transition metal oxide gels can be obtained, through a polycondensation process, by acidification of aqueous solutions. Thin layers can be easily deposited onto a substrate. Their electronic and ionic properties could lead to new developments of the sol-gel process. The semiconducting properties of V2O gels can be used for antistatic coatings or electrical switching devices. These gels exhibit a lamellar structure and can be described as particle hydrates. They are fast proton conductors and could behave as a host lattice for intercalation.
Electrical Properties of Na2O - SiO2 Dried Gels
Authors: Ravaine D. , Traore J. , Klein L. C. , Schwartz I.
Published: March 2011

Gels with compositions Na2O-(1-x)SiO2 were prepared from tetraethylorthosilicate (TEOS) with sodium acetate and from tetramethylorthosilicate (TMOS) with sodium methoxide or TEOS with sodium ethoxide. After gelation (10 min.) the samples were slowly dried for about one month at room temperature. Thermogravimetric analysis (up to 500°C) in air and O2 atmosphere was performed. The electrical properties were studied in air by impedance spectroscopy during successive temperature cycles starting from room temperature dried gels of composition 0.10 Na2O 0.90 SiO2. Protonic conductivity appears to be eliminated after reaching the 2nd stage of the drying process (200°C). The activation energies for conduction and the conductivities show small discrepancies from known values for homogeneous glasses of equivalent compositions. Considering the effect of water on the conductivity of glasses prepared by the melting procedure, one can estimate the residual water content in the so-called dried gels to be close to 0.5 wt %.
Preparation of Barium Titanate Films Using Sol-Gel Techniques
Authors: Dosch R. G.
Published: March 2011

Sol-gel techniques provide a convenient method of applying barium titanate films on solid substrates at ambient temperature. A significant advantage in using this technique is the capability of maintaining compositional homogeneity while coating large areas of surfaces with complex geometries. Solutions prepared by reacting a titanium alkoxide with barium hydroxide in methanol were used for preparing thin films (1000–3000Å) of barium titanate on silicon and metal substrates. Electrical properties of the films depended both on solution parameters and subsequent heat treatment of the films. Highest field strengths (8−9 × 106 V/cm) were observed in amorphous films prepared from partially hydrolyzed solutions.
Glasses and Ceramics from Colloids
Authors: Scherer G. W.
Published: March 2011

Flame-generated particles can be suspended in a nonpolar solvent, molded, and gelled. The microstructure obtained after solvent evaporation depends on the characteristics of the colloid. Higher solids loadings lead to denser green bodies and narrow pore size distributions. The mean pore size is proportional to the particle size. Sintering occurs at relatively low temperatures, producing amorphous or crystalline bodies of high purity.
A Comparison Between the Densification Kinetics of Colloidal and Polymeric Silica Gels
Authors: Brinker C. J. , Drotning W. D. , Scherer G. W.
Published: March 2011

Silica gels were prepared by three methods in which the original silicate species varied from extended linear or randomly branched polymers to more highly crosslinked clusters to colloidal particles of anhydrous silica. During isothermal sintering experiments, the viscosities of the two polymer gels increased significantly (up to 3 orders of magnitude) while the isothermal viscosity of the colloidal gel was constant. Viscosity increases were explained by crosslinking and structural relaxation of the polymeric gels.
Effect of Aging on Electrophoretic Behavior of Sol-Gel Derived Aluminas
Authors: Lee Burtrand I. , Hench Larry L.
Published: March 2011

Sample alumina powder prepared with the procedures described by Yoldas [1,2] was suspended in 10−3 M NaCl and contained in precleaned polypropylene cups with air tight lids. Electrophoretic mobilities of the samples were measured at various pH's using a microelectrophoretic technique. The points of zero charge (PZC) were determined from plots of electrophoretic mobility vs pH of the sample suspensions. The initial values of PZC are 10.6 for γ-A12O3. and 8.3 for αAl-2O3 , The corresponding BET surface areas are 206 m2/g and 3m2/g respectively. Upon aging, the PZC decreased in 2 days and then increased by reaching maximum values of 10.4 for γ-Al2 O3 and 8.8 for α-Al2 O3 in 20 days. Aging of sol-gel derived aluminas and commercial alumina derived by precipitation are compared and differences are discussed.
Composition and Chemical Structure of Nitrided Silica Gel
Authors: Brow R. K. , Pantano C. G.
Published: March 2011

Sol/gel derived silica thin films were thermally treated in NH3for four hours at temperatures up to 1300C. The films were analyzed by ellipsometry, X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). Over 30 mol% nitrogen was incorporated in the film treated at 1300C. Using IR and XPS analyses, -NHxgroups were found to be present after low temperature treatments, while nitrogen was incorporated in an oxynitride structure after the higher temperature treatments.
Thermal Reaction of Silane with Acetylene and The Thermal Decomposition of Ethynylsilane
Authors: Ring M. A. , O'Neal H. E. , Erwin J. W. , Rogers D. S.
Published: March 2011

The volatile products from the thermal reaction (414°C) of silane in excess acetylene are hydrogen, ethylene, vinylsilane, ethynylsilane, vinylethynylsilane (possibly divinylsilane) and ethynyl-divinylsilane (1,2). We have reexamined this reaction using a 3 C2 H2/1 SiH4 reaction mixture and have obtained product yield curves for these products versus percent silane loss. We have also found that product curves are unaffected when propylene at pressures equal to that of acetylene is also present. Since only trace quantities of propylsilane are produced in the presence of propylene, we can rule out reactions involving silyl radicals. Thus the SiH4−C2H2 reaction involves silylene and silene intermediates. The products can be explained by a mechanism similar to one proposed by Barton and Burns (3).
Gel Structures in Leached Alkali Silicate Glass
Authors: Bunker Bruce C. , Headley Thomas J. , Douglas Sally C.
Published: March 2011

Transmission electron microscopy of leached NaOċ3SiO2 and K2Oċ3SiO2 glasses showed that the hydrateg glass surface is a silica rich gel which phase separates during leaching. Phase separation is initiated when pockets of an aqueous phase nucleate and grow in the hydrated silica matrix. The aqueous pockets eventually become a network of interconnected pores with a pore diameter of ∼30 nm. In advanced stages of leaching, the remaining interconnected silica rich phase resembles an aggregation of colloidal silica particles. The observed phase separation is consistent with literature models concerning the chemistry of silica in aqueous solutions and in leached glass.
Strength of Gel-Derived SiO2 Fibers
Authors: LaCourse William C.
Published: March 2011

Strengths of as drawn gel-derived SiO2 fibers are found to depend on H2O and alcohol content of the sol, as well as drawing viscosity. Additional factors, including fiber diameter and drying and consolidation schedules are found to dramatically influence strengths of the consolidated glass fibers.
Preparation, Structure, And Electronic Properties Of Amorphous Gaas By Tight-Binding Molecular Dynamics
Authors: Molteni C. , Colombo L. , Miglio L.
Published: March 2011

We investigate the short-range structural properties of a-GaAs as obtained in a computer experiment based on a tight-binding molecular dynamics simulation. The amorphous configuration is obtained by quenching a liquid sample well equilibrated at T=1600 K. A detailed characterization of the topology and defect distribution of the amorphous network is presented and discussed. The electronic structure of our sample is calculated as well. Finally, we discuss the reliability and transferability of the present computational scheme for large-scale simulations of compound semiconductor materials by comparing our results to first-principles calculations.
First Stages of Nano-Crystallization of Amorphous Fe75.5Cu1Si12.5B8 Studied by the Positron Annihilation Lifetime Technique
Authors: Kruk A. J. , Schut H. , Sietsma J. , Van Veen A.
Published: March 2011

The first stages of the nano-crystallization process of amorphous Fe75.5Cu1Nb3Si12.5B8 into a nano-crystalline structure are investigated by the positron annihilation lifetime technique. Samples have been isothermally annealed at 643 K for times varying between 600 and 105 seconds. The positron lifetime spectra have been analyzed allowing for three lifetimes. The shortest and the longest lifetime, τ1 = 150 ± 2 ps and τ3 = 1500–2000 ps respectively, are attributed to annihilation of positrons in the amorphous phase and to the formation and annihilation of ortho-positronium at the surface of the stacked foils and did not change significantly upon the annealing. The intermediate positron lifetime τ2 increased from 324 ps to 387 ps. The intensity of this component increased from 5 to 15%. Comparison with resistivity measurements indicates that the change of this lifetime component occurs at an early stage in the crystallisation process, i.e. when the fraction of crystalline material is on the order of 10−3. The increase of τ2 is attributed to positrons annihilating in a region with lower average density surrounding the small crystallite.
Intermediate Phase Nucleation at Diffusion Couple Boundaries
Authors: Hoyt J. J.
Published: March 2011

The nucleation of intermediate phases at the interphase boundary in diffusion couples is examined theoretically. A variational procedure is described which allows for a self consistent determination of the critical nucleus size and shape, the work of formation of the critical nucleus and the nucleation rate.
High Temperature Calorimetric Study of Mixing, Phase Separation, and Crystallization in Silicate Glasses
Authors: Navrotsky Alexandra
Published: March 2011

Several glass forming systems have been studied by in situ scanning calorimetry and by solution calorimetry in Molten 2PbO.B2O3 at 973 K. In systems which show macroscopic glass-glass phase separation on annealing, namely K2O-La2O3-SiO2 and Li2O-SiO2, the enthalpies of solution of optically clear quenched glasses and milky annealed glasses are almost identical. This behavior, coupled with a linear variation of heat of solution with composition along joins which have a large change in overall degree of polymerization, support the contention from spectroscopy that short range clustering dominates even in nominally single phase Materials, with exsolution observed as the initially present heterogeneous regions grow in size. Alkali titanosilicate melts show Cp anomalies consistent with breakdown of alkali titanate complexes or changes in Ti coordination. Calorimetry is a sensitive quantitative probe of crystallization as a function of time in both ceramic and geologic systems.
Nucleation And Growth Rates in Isothermal Crystallization Op Amorphous Si50Ge50 Films
Authors: Song J. H. , Im James S.
Published: March 2011

Isothermal crystallization behavior of as-deposited thin amorphous Si50Ge50 films (∼1000Å-thick) at 580°C has been investigated using transmission electron Microscopy (TEM). The crystal counting method was employed in order to obtain directly the two-dimensional steady-state crystal nucleation rate of 3.9×103 #/cm2sec (equivalent volumetric nucleation rate of 3.4×108 #/cm3sec). The Modified two-dimensional Johnson-Mehl-Avrami analysis, in which the growth rate of the crystals was the only adjustable parameter, and in which the time-dependent nucleation rate and the size effect associated with the onset of the observation are considered, was developed in order to extract the crystal growth rate of 16.5 Å/sec. When compared to the crystallization of a-Si films, these nucleation and growth rates confirm the observation that it is possible to achieve significantly faster crystallization at lower temperatures while producing substantially better Microstructures (i.e., > 5 μ grain-sized poly-Si50Ge50 obtained within two hours at 580°C vs. 1–2Μm grain-sized poly-Si obtained in about > 10 hours at 600°C).
Ion-Beam-Driven Amortization of Ca2La8 (SiO4)6O2 Single Crystals
Authors: Weber W. J. , Hess N. J. , Wang L. M.
Published: March 2011

Single crystals of Ca2La8(SiO4)6O2, with 1% Nd substituted for La, were irradiated with 0.8 MeV Ne+ and 1.5 MeV Kr+ ions over the temperature range from 15 K to 773 K. The irradiations were carried out using the HVEM-Tandem Facility at Argonne National Laboratory. The structural changes and the ion fluence for complete amorphization were determined by in situ transmission electron Microscopy. The ion fluence for complete amorphization increased with temperature in two stages associated with defect annealing processes. The critical temperature for amorphization increased from -360 K for 0.8 MeV Ne+ to -710 K for 1.5 MeV Kr+. During in situ annealing studies, irradiation-enhanced recrystallization was observed at 923 K. Spatially-resolved fluorescence spectra of the Nd ion excited with 488.0 nm laser excitation showed marked line-broadening toward the center of the amorphous regions. Initial Measurements indicate the subtle shifts of the 9I9/2 groundstate energy levels can be measured by pumping directly into the excited state 4F3/2 Manifold suggesting that the line broadening observed originates from a distribution of geometrically distorted Nd sites.
Ion Beam Induced Graphitization of Phenolformaldehyde
Authors: Ila D. , Evelyn A. L. , Jenkins G. M.
Published: March 2011

We have studied MeV ion beam induced phase transformation in phenolformaldehyde cured at 170°C by both Raman Microprobe spectroscopy and in situ resistance measurement of the irradiated area. Samples were irradiated using various doses of protons, alphas and nitrogen beams. Irradiated volumes in each sample were tested in situ for enhanced electrical conductivity and later on by Raman Microprobe spectroscopy. The results have shown changes in the resistance as much as seven orders of magnitude by alpha particles, six orders by nitrogen bombardment and three orders by hydrogen. Raman Microprobe spectroscopy of the darkened phase shows development of the D- and G-lines which are characteristic of the production of a carbonized resin. These spectra indicate that maximum carbonization was caused by the nitrogen beam.
The Effect of Strain and Strain-Gradients on the Crystallisation Kinetics of S1−xGex Alloy Layers
Authors: Kringhøj Per , Elliman Robert G. , Hansen John L.
Published: March 2011

A comparison of strain relief in SiGe alloy layers during high temperature annealing and solid phase epitaxial crystallisation (SPEC) has shown that layers which are thermodynamically stable are also fully strained following SPEC, whereas metastable layers that relax at high temperatures also relax during SPEC. This is illustrated by the fact that a uniform SiGe layer with x=0.085 is stable during annealing at 1100°C for 60 sec and is fully strained following SPEC. In contrast, a uniform layer with x=0.17, which was fully strained as-grown by molecular beam epitaxy (MBE), is shown to relax during high temperature annealing and during SPEC.

A depth dependent SPEC velocity is observed for metastable layers, with a decrease in velocity as the alloy layer begins to crystallise and an increase in velocity as strain relaxation proceeds.
A Positron-Annihilation-Lifetime study of Polymer Blends
Authors: Liu J. , Jean Y. C. , Yang H.
Published: March 2011

Positron-annihilation-lifetime (PAL) spectroscopy has been utilized to investigate the free-volume properties of two types of polymer blends, a miscible blend of bisphenol-A polycarbonate (PC) and tetramethyl bisphenol-A polycarbonate (TMPC), and an immiscible blend of PC and polystyrene (PS). In the miscible blend, the free-volume hole size and its fraction follow a linear relationship with respect to the weight fraction while in the immiscible blend, the relationship is not linearly additive. The free-volume hole distributions in the immiscible blend are found to be significantly broader than those in the pure polymers. The difference is thought to be a result of the free volume formed and associated with the conformation and interchain packing between the dissimilar chains in incompatible polymers.
Solid Phase Epitaxy Process Of Ar-Ion Bombarded Silicon Surfaces and Recovery of Crystallinity by Thermal Annealing Observed With Scanning Tunneling Microscopy
Authors: Uesugi Katsuhiro , Yoshimura Masamichi , Yao Takafumi
Published: March 2011

The solid-phase epitaxy (SPE) process of Ar+-ion bombarded Si (001) surfaces and recovery of crystallinity by thermal annealing are studied “in situ” by using a scanning tunneling Microscope (STM). As-bombarded surfaces consist of grains of 0.63–1.6 nm in diameter. The grains gradually coalesce and form clusters of 2–3.6 nm in diameter at annealing temperature of 245° C (2×1) and (1×2) reconstructed regions surrounded by amorphous regions are partially observed on the surface by prolonged annealing, which suggests the onset of SPE. Successive observation reveals that the smoothing of the surface occurs layer by layer. As annealing temperature is raised up to 445 °C, the amorphous layer epitaxially crystallizes up to the topmost surface, and (2×1) reconstructed surface with Monatomic-height steps is observed. The smoothing of the surface structures and the formation of nucleation of Si islands are observed during annealing at 500 °C.
Bulk Semicrystalline Polymers: A Status Report
Authors: Keith H. D.
Published: March 2011

Discovery several decades ago that long-chain molecules crystallize by folding prompted vigorous basic research on structure-property relations in bulk semicrystalline polymers with expectation of insights that, paralleling experience in metal physics, would lead to better materials for technology. However, complexity of the crystallization process and difficulty in exploring morphology in adequate detail were both underestimated. Important aspects of behavior were recognized but improved polymeric materials have resulted more from exploratory engineering with composites and blends than from basic research on homopolymers. A summary of this research is presented with emphasis upon developments key to present status; also upon the truly formidable challenges that remain, Most readily accessible questions for research being of limited technological significance.
Shear Induced Morphology Of Semicrystalline Block Copolymers
Authors: Kofinast Peter , Cohen Robert E.
Published: March 2011

A series of semicrystalline diblock copolymers of poly (ethylene) / poly (ethylene-propylene) (E/EP) were subjected to high levels of plane strain compression using a channel die. Deformations were imposed both below and above the melting point of the E block. The crystallographic and morphological textures were examined using wide-angle x-ray diffraction pole figure analysis and two dimensional small-angle x-ray scattering. The lattice unit cell orientation of the crystallized E chains with respect to the lamellar superstructure was determined, as well as the lamellar orientation relative to the specimen boundaries. When the diblocks are textured above the E block melting point at various compression ratios, the lamellae orient perpendicular to the plane of shear, while texturing below Tm causes the lamellae to orient parallel to the plane of shear. The orientation of the crystallized E chains was perpendicular to the lamellar normal, irrespective of the texturing temperature. The various shear-induced lamellar morphologies have potential applications in gas transport control to develop membranes for use in gas separations or as barrier Materials.
In-Situ TEM Crystallization of Anorthite-Glass Films on α-Al2O3
Authors: Mallamaci Michael P. , Bentley James , Barry Carter C.
Published: March 2011

Anorthite-glass films have been grown by pulsed-laser deposition on single-crystal α-Al2O3 substrates which were pre-thinned to electron transparency. The glass films were crystallized in the transmission electron Microscope (TEM), which allowed direct observation and video-recording of the crystallization process. Crystallization of these films in the TEM resulted in the formation of hexagonal and orthorhombic anorthite. The orthorhombic phase was the predominant product of glass films grown at elevated substrate temperatures and displayed strong epitaxy with the underlying substrate. In contrast, the hexagonal phase was the major constituent of films grown at ambient substrate temperature and displayed no clear epitaxy with the substrate. The differences in degree of epitaxy and phase structure may be evidence of ordering at the original glass/oxide interface.
High Resolution In Situ TEM Studies of Silicide-Mediated Crystallization of Amorphous Silicon
Authors: Hayzelden C. , Batstone J. L.
Published: March 2011

We report in situ high resolution transmission electron microscopy studies of NiSi2-Medi-ated crystallization of Amorphous Si. Compared to conventional solid phase epitaxy of (111) Si, an enhancement of the growth rate by three orders of magnitude was observed and high quality twin-free needles of <111> Si were formed. Crystallization occurred via a ledge growth mechanism at the epitaxial Type A NiSi2/crystalline Si (111) interface. A Model for NiSi2-Mediated crystallization of Amorphous Si involving the passage of kinks along <110> ledges at the NiSi2/crystalline Si (111) interface is proposed.
Crystallization of Glass Films on Single-Crystal MgO Substrates
Authors: Ramamurthy Sundar , Mallamaci Michael P. , Barry Carter C.
Published: March 2011

Thin, calcium magnesium silicate glass films have been deposited onto (001) -oriented single-crystal MgO substrates by pulsed-laser deposition (PLD). The substrates were thinned to electron transparency and characterized in the transmission electron Microscope (TEM) before and after the deposition and following different heat treatments. Energy Dispersive X-ray Spectroscopy (EDS) was used in the TEM to characterize the chemistry of the films. The heat treatments were performed both in situ and ex situ. Direct evidence for crystallization was obtained by in-situ experiments at 950°C. Subsequent heat treatments were performed for longer times in air between 950°C and 1100°C. The crystallized phase was found to be Monticellite (CaMgSiO4) and the crystallites show moderate epitaxy with the underlying substrate. Films contaminated with aluminum resulted in the growth of magnesium aluminate spinel (MgAl2O4) epitaxially from the substrate. These observations of epitaxy indicated that crystallization initiated at the surface of MgO.
Crystallization Of Silicon Thin Films Prepared By Ecr Pecvd
Authors: Lee Seok-Woon , Jeon Yoo-Chan , Joo Seung-Ki
Published: March 2011

Silicon thin films were deposited by Electron Cyclotron Resonance PECVD using silane as a source gas at room temperature. Deposited films were crystallized either by conventional furnace annealing(FA) or by rapid thermal annealing (RTA) process. The films deposited on SiO2/Si wafer substrates were Amorphous or microcrystalline depending on the microwave power. Deposited films were annealed at 600TC in a furnace. As expected, higher crystallinity was obtained in the case of the Amorphous films than the microcrystalline films after 7.5 hours annealing. It took 15 hours at 600δC for the Amorphous films to reach their maximum crystallinity in case of FA, but it only took 1 second at 900 δC for RTA. In addition, it was shown that RTA can be applied to the rapid crystallization of Amorphous silicon thin films deposited on a fused quartz substrate utilizing a new film structure.
Solid State Ordering of Wholly Aromatic Copolyesters of Random Monomer Sequence
Authors: Blackwell J. , Schneider A.-I. , McCullagh C. M.
Published: March 2011

X-ray diffraction and computer molecular modeling Methods are being used to investigate the ordering of random sequence copolyesters when cooled for the nematic Melt. Data will be presented for the copolymers prepared from p-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid. The non-periodic diffraction patterns arising from the random monomer sequences are also indicative of the presence of limited three dimensional order. For both polymer systems, we can generate the qualitative feature of the x-ray data using models in which short non-identical segments of 10–12 Monomers on adjacent chains are approximately in register at their center. Molecular Mechanics calculations show that mese non-identical sequences can be packed on the observed hexagonal lattice with only small energy differences when compared to analogous homopolymer structures. Data will also be presented showing how x-ray diffraction can be used to follow transesterification of copoly (HBA/HNA) in the nematic MelL
Reliability of Flex Coatings for High-Performance Applications
Authors: Tong H. , Wilson C. , Graham T. , Shi L.
Published: March 2011

A study was undertaken to select a suitable coating for a high-pin-count flexible edge connector (Flex) that interconnected a multichip thin-film silicon carrier to a printed circuit board. The Flex with cantilevered inner leads were joined to the contact pads at the perimeter of the carrier. 15 polymeric coatings were evaluated by subjecting coated Flexes to tests consisting of inner lead bending, temperature/humidity/bias (85°C/80%/15 V/350 hours), corrosion, line peel, and/or pressure cooker (126°C/20 psig/120 hours). Inner lead bending measurements were performed to assess the potential of lead shorting at the inner lead bonding sites during thermal cycling. From this study, a low-stress silicone evolved as the best candidate. The results leading to this conclusion will be shown and discussed.
A Study of Sn-Pb-Re Solder
Authors: Ying Zhu , Hongyuan Fang , Yiyu Qian
Published: March 2011

One of the important way to improve the property of solder joints is to improve the property of solders, This paper is about a study of Sn-Pb-RE solder(RE-Rear Earth, mainly contains Ce and La). It has been shown that the final form of RE in SnPb60/40 solder is Sn-RE intermetallic compound, and a very little RE can change the solder microstructure greatly. The influence of RE on solder life of creep rupture is that Sn-Pn-RE solder has much long life than that of SnPb60/40, and the solder life increases with the increase of RE content.
Characterizing Soldering Fluxes
Authors: Turbini Laura J. , Freeman Garth B. , Cauffiel David
Published: March 2011

For a number of years electronic manufacturers of printed circuit assemblies have used rosin-based soldering fluxes. Post-solder cleaning was accomplished with chlorinated or chlorofluorocarbon (CFC) solvents. With the elimination of these solvent options due to their destructive effect on the stratospheric ozone layer, manufacturers are looking to alternative cleaners for rosin flux or to new flux choices which can be cleaned with water, or left uncleaned.

Many of the flux formulations are new and their long-term effect on the performance of product manufactured with them is unknown. Although ionic contamination testers can alert one to the ionic levels remaining on an assembly, the corrosivity of the residues is not directly related to the total ionic level, but only to certain ionic species. Surface insulation resistance testing is used by many in the industry, but the results are complex and often misunderstood.

All of these factors have been the driving force to develop a quantitative screening test for soldering flux residues. This test, originally conceived by Dr. David Bono, has been modified and developed at Georgia Tech to provide a quantitative evaluation of flux residue corrosivity. This work, in collaboration with the work being performed by the French standards group, will result in a new international industry standard. This paper reports the latest data on this important test development.
An Experimental and Modeling Study of Thermal Cyclic Behavior of Sn-Cu and Sn-Pb Solder Joints
Authors: Pao Y.-H. , Badgley S. , Govila R. , Jah E.
Published: March 2011

Thermal cyclic shear stress/strain hysteresis response of 97Sn-2Cu-0.8Sb-0.2Ag, 95.5Sn-4Cu-0.5Ag, 63Sn-37Pb, and 62Sn-36Pb-2Ag solder joints have been determined using a double beam specimen. The temperature cycle had a period of 40 minutes and extreme temperatures of 40°C and 140°C.The steady state creep properties of these solders were determined, and the associated Norton's law was implemented in a finite element program to simulate the experiment. The fatigue life of these solders joints and failure mechanism are also discussed.
In-Situ Tem Study of Copper-Tin Intermetallic Formation
Authors: Wu Yujing , Jacobs Elizabeth G. , Pouraghabagher Cyrus , Pinizzotto Russell F.
Published: March 2011

The formation and growth of Cu6Sn5 and Cu3Sn at the interface of Sn-Pb solder/copper substrate are factors which affect the solderability and reliability of electronic solder joints. The addition of particles such as Ni to eutectic Sn-Pb solder drastically affects the activation energies of formation for both intermetallics. This study was performed to understand the mechanisms of intermetallic formation and the effects of Ni on intermetallic growth. Cu/Sn and Cu/Sn/Ni thin films were deposited by evaporation and observed in the TEM in real time using a hot stage. The diffusion of Sn through Cu6Sn5 and Cu3Sn followed by reaction with Cu must occur for intermetallic formation and growth to take place. Ni is an effective diffusion barrier which prevents Sn from diffusing into Cu.
The Oxygen-Related Defect in Aluminum Nitride Ceramics: a Thermal Conduction Limiting Defect in a Technologically Important Material
Authors: Harris Jonathan H. , Youngman Robert A. , Enck Rudy
Published: March 2011

Aluminum nitride (AlN) sintered ceramics are a critical new material for electronic packaging applications, principally because of AlN's high thermal conductivity and close thermal expansion match to silicon. AlN is expected to play a key role in the next generation of high powder electronic packages, in applications ranging from high power discrete component substrates to co-fired, multilayer packages for integrated circuits. In the following paper, a detailed picture of the oxygen-related defect in AlN ceramics is presented. This impurity is of critical technological importance, because vacancies associated with oxygen severely limit thermal conduction when present in high concentrations. The results of thermal conductivity measurements, luminescence studies, optical absorption experiments, photo-induced absorption studies and electrical measurements on both ceramic and single crystal samples will be presented in order to understand the detailed nature of this defect and to model its control over a number of important technological properties.
Fabrication of Cofired ALN Multilayer Substrates at Low Temperature Sintering
Authors: Terao Koichi , Uchiyama Ichiro , Hamano Akihiro
Published: March 2011

In order to lower the firing temperature of W cofired AlN multilayer substrates, sinterabilities of AlN substrate material and W conductor were investigated at low sintering temperatures around 1650 •C.

In case of AIN substrate material, the effect of AIN powder properties on sinterability and thermal conductivity was evaluated. The powders, with specific surface area between 2.3 and 8.2m2• g−1 and oxygen content between 0.7 and 3.2 wt%, were sintered with CaO and Y2O3 as sintering additives. The finer powder promoted the densification below 1600°C and each powder was fully densified at 1650°C. However thermal conductivity sintered at 1650°C decreased with decreasing particle size due to increasing oxygen content inside AlN grains. The thermal conductivity of optimized AlN substrate sintered at 1650°C had over 100W • m−1 K−1.

W conductor is required dense microstructure for high adhesion strength to AlN substrate. Shrinkage mismatch between AlN and W during sintering caused porous microstructure for coarse W powders or detaching for fine W powders. The optimized W paste was developed for low temperature sintering.
Aluminum-Matrix Aluminum Nitride Particle Composite as a Low-Thermal-Expansion Thermal Conductor
Authors: Lai Shy-Wen , Chung D. D. L.
Published: March 2011

Aluminum-matrix composites containing AIN or SiC particles were fabricated by vacuum infiltration of liquid aluminum into a porous particulate preform under an argon pressure of up to 41 MPa. Al/AIN was superior to Al/SiC in thermal conductivity. At 59 vol.% AIN, Al/AlN had a thermal conductivity of 157 W/m. °C and a thermal expansion coefficient of 9.8 × 10−-6°C−1 (35–100 °C). Al/AlN had similar tensile strength and higher ductility compared to Al/SiC of a similar reinforcement volume fraction at room temperature, but exhibited higher tensile strength and higher ductility at 300–400°C. The ductility of Al/AlN increased with increasing temperature from 22 to 400°C, while that of Al/SiC did not change with temperature. The superior high temperature resistance of Al/AlN is attributed to the lack of a reaction between Al and AIN, in contrast to the reaction between Al and SiC in AI/SiC.
A Damage Integral Based Analysis and Simulation of the Thermal Fatigue of Diebonds
Authors: Lilienfeld David A. , Børgesen Peter , Li Che-Yu
Published: March 2011

Microelectronic packages undergo substantial thermal excursions during processing and often in service. Differences in the thermal expansion of the various components may therefore lead to fatigue of the interconnects. A computer simulation has been developed which is based on a damage integral approach for the modeling of damage and failure in the various bonding layers found throughout such a package. This code should apply equally well to solder die bonds and polymeric or epoxy adhesive layers, assuming that the corresponding crack growth parameters and constitutive relations are known. Using literature values for these properties, predictions have been compared to experimental thermal cycling data for solder die bonds. Consequences for the extrapolation of accelerated test results to service conditions are discussed.
Low Stress, High Resolution Photosensitive Polyimide Based on a BPDA/PDA/6FDAm Copolymer
Authors: Angelopoulos Marie , Gelorme Jeff , Swanson Sally , Labadie Jeff
Published: March 2011

A novel series of BPDA/PDA/6FDAm polyimide copolymers have been developed. These materials are more flexible, soluble, and more optically transparent than the homopolymer BPDA/PDA. A negative acting PSPI has been developed based on one of these copolymers. This PSPI exhibits high resolution. 6 μm lines can be delineated in a 19 μm thick film. In addition, the PSPI exhibits high performance mechanical/physical properties such as a low CTE, low stress, and high elongation at break.
Micro-ATR-IR as a Probe of BCB Layers for MCM-D/L Applications
Authors: Mohler C. E. , Strandjord A. J. G. , Castillo D. W. , Stachowiak M. R. , Heistand R. H. , Garrou P. E. , Tessier T. G.
Published: March 2011

To lower the cost of multichip module packaging, hybridized substrate technologies have recently been reported which blend the desirable aspects of D and L fabrication (MCM-D/L). High performance dielectrics such as Cyclotene™3022 and photosensitive BCB have been shown to be compatible with laminate substrates used in MCM-DIL, however the cure levels of the dielectric on the laminates must be known for optimum processing.

In this paper, the capability of attenuated reflection IR microscopy (micro-ATR-IR) to probe thin films of BCB polymers is demonstrated. This technique enables the polymer layer to be probed regardless of the characteristics of the substrate. Cure levels of both Cyclotene™ 3022 and photodefinable BCB polymer films are obtained with micro-ATR-IR on both silicon and laminate substrate. Micro-ATR-IR is also used to probe a rapid thermal cure of Cyclotene Tm 3022 and photodefinable BCB layers on copper-clad polyimide laminate; these measurements cannot be made with transmission IR due to the high reflectivity of the substrate.
Optoelectronic Packaging for Computer and Communication Systems
Authors: Lockwood H. F. , Armiento C. A.
Published: March 2011

The principal driver behind advanced hardware development in the communications and computer industries can be reduced to an optimal set of parameters related to performance, cost and reliability. High performance systems typically have high functional density. For example, the continuing trend of VLSI is toward reduced feature size, increased wiring density and larger chip size to achieve increasingly higher levels of on-chip functionality. At some point in the cost structure, however, the single chip solution is no longer viable, and monolithic integration gives way to hybrid integration. In this respect, the multichip module fills a void in the packaging/ integration hierarchy between the ever-larger single chip and the printed wiring board.

An analogous situation is emerging in optoelectronics. The single chip package with its relatively low system functionality and high cost is giving way to the multi-technology module that integrates optical and electronic functions within a single package. One of the most interesting approaches to the multi-technology module uses a silicon substrate as the platform for hybrid integration of electronics and optoelectronics. It will be argued that this “silicon waferboard” approach is the cost-effective route to manufacturability of high-performance modules for communications and computer systems. Enhanced reliability follows from applying standard IC processing technology at the platform level in the packaging hierarchy.
X-Ray Absorption Study of Ti and Cr Reactions with Triazine and Polyimide
Authors: Konstadinidis K. , Opila R. L. , Marcus M. A. , Short K. , White A. E. , Ibidunni A. O. , Davenport A. , Isaacs H.
Published: March 2011

In this paper we present results on the use of x-ray absorption spectroscopy and in particular extended x-ray absorption fine structure (EXAFS) to study non-destructively buried interfaces between polymers and metals. In particular we study the interaction between isolated metal atoms (Ti or Cr) and the surrounding polymer matrix (polyimide or triazine). The metal atoms have been introduced into the polymer matrix using ion-implantation. We find that Cr forms a π complex with the aromatic structures of polyimide and triazine in agreement with model compound and XPS data. Ti on the other hand seems to form Ti-O-C bonds with both polymers.
Interfacial Debonding in PWBs
Authors: Li Junhui , Pecht Michael
Published: March 2011

Glass fiber reinforced epoxy laminates have been widely applied in the electronic packaging industry as multilayer printed wiring boards (PWBs). Previous investigations indicate that, the electric insulation between printed through hole (PTH) and conductive lines can be lost if the boards are subjected to certain environmental conditions [1,2,3]. The insulation breakdown is caused by copper filament formation along the glass fibers once the filament bridges any two nearby circuittraces, such as a PTH and a power plane, or between two PTHs. The conductive filament formation is a two step process: path formation and electrochemical reaction. The path formation is caused by degradation of the glass-epoxy interface, which provides the copper ion migration path for the second step. Humidity and temperature are the key factors leading to interfacial degradation. Usually, humidity is of more concern because water absorption helps the path formation. Among board materials, epoxy resin, as the matrix material, is more susceptive to moisture absorption than glass fiber or copper [3,4]. Operating temperature that changes the degree of moisture absorption [5,6], and thermal cycling that enhances water absorption, and stress induced from thermal-mismatches [7], are also considered as the important factors to the interface degradation.

Epoxy/glass interfacial debonding can be introduced near PTHs by thermal cycling [8]. The interfacial debonding between glass fibers and the epoxy matrix near PTHs accelerates the electromigration process. In order to study the interfacial debonding mechanisms, thermal cycling tests of PWBs were conducted and the dynamic process of interfacial debonding was characterized using environmental scanning electron microscope (ESEM). This paper presents the experimental results with discussion of the possible interfacial debonding mechanisms.