bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thickness Effect On The Crystallization Kinetics Of Electrolessly-Deposited Ni(P) Thin Films
Authors: Shi L. T. , O'Sullivan E. J. M. 
Published: March 2011

ABSTRACTIn order to understand thickness and interfacial effects on the crystallization kinetics of amorphous solids, Ni(P) thin films electrolessly deposited on Cu seed layers were annealed at constant heating rates or at constant temperatures in a DSC to obtain activation energies andAvrami exponents. It was found that the activation energy of crystallization in Ni(P) changes asa function of sample thickness when the sample thickness is less than 1.0 μm. Furthermore, the Avrami exponent was found to change not only as a function of thickness but also as a function of annealing temperature.
Crystallization Kinetics Of Fe80-yVyB12Si8 Amorphous Ribbons
Authors: Altúzar P. , V́zquez C , BañOS L. , Valenzuela R. 
Published: March 2011

ABSTRACTThe effects of vanadium in the crystallization kinetics amorphous ribbons Fe80-yVyB12Si8 (0.5 < y < 15) has been investigated by Differential Scanning Calorimetry, by using the Avrami, Kolmogorov-Johnson-Mehl-Avrami, and Calka and Radlinski equations. The addition of vanadium to Fe-B-Si alloys leads to an enhancement of stability against crystallization, as shown by an increase in the effective activation energy for crystallization (Eeff = 3.6eV) and an increase in the temperature for the first crystallization peak, as a function of vanadium content (from 780 to 855K). Results also show that the crystallization Mechanism, nucleation rate and dimensionality of growth are constant throughout the crystallization process in the composition range investigated.
DSC and Mössbauer Studies of Fe80B20 Crystallization
Authors: Malizia Federica , Ronconi Franco 
Published: March 2011

ABSTRACTDifferential Scanning Calorimetry has been used to investigate the mechanism of the isothermal crystallization kinetics in Fe80B20 Metallic glass. It is shown that the whole crystallization analysis must include, not only a crystal nucleation-and-growth process, but also a grain-growth process and that these two processes are separated in time during isothermal annealing. These processes have been studied directly finding the parameters which characterize their Mechanism. From the theoretical Johnson-Mehl-Avrami equation describing the nucleation-and-growth process, it was possible to calculate the evolution of the transformed fraction of the material as a function of the annealing time. To infer the meaning of the transformed fraction, samples subjected to different thermal treatments have been studied by Mössbauer Spectroscopy. Our results reveal that the transformed fraction is the sum of the crystalline component formed by all atoms located in the lattice of the grains and the interfacial component composed of atoms in the interfacial regions between grains.
Solid-Phase Epitaxial Crystallisation Of GexSi1−x Alloy Layers
Authors: Elliman Robert G. , Wong Wah-Chung , Kringhøj Per 
Published: March 2011

ABSTRACTThermally-induced solid-phase epitaxial crystallisation (SPEC) and ion-beam-induced epitaxial crystallisation (IBffiC) of amorphous GexSi1−x alloy layers is examined for three different starting structures: a) strain-relaxed alloy layers of uniform composition, b) strained alloy layers of uniform composition, and c) Ge implanted Si layers. Thermal annealing experiments show that the activation energy for strain-relaxed alloys is higher than that expected from a simple extrapolation between the activation energies of Si and Ge, and exceeds that of Si for x ≤ 0.3. Experiments on thin strained layers show that MBE grown strained layers which are stable during annealing at 1100°C for 60 s are also fully strained after SPEC, whereas layers which relax during annealing at 1100°C also relax during SPEC. Experiments on ion-implanted GexSi1−x structures show that fully strained Si/GexSi1−x/Si heterostructures can be fabricated for ion fluences below a critical fluence, and as for uniform alloy layers that this critical fluence is accurately predicted by equilibrium theory. Strain relaxation during SPEC of uniform alloys and implanted structures is shown to be correlated with a sudden reduction in crystallisation velocity which is believed to be caused by stress-induced roughening or faceting of the crystalline/amorphous interface. SPEC of thick (800 nm) implanted layers is shown to be limited by competition from ion-beam induced random crystallisation, while thin (120 nm) uniform alloys and implanted structures are shown to crystallise epitaxially and to exhibit similar behaviour to thermally annealed samples under certain conditions.
On the Determination of Partial RDFs for Amorphous Materials
Authors: Qin L. C. , Hobbs L. W. 
Published: March 2011

ABSTRACTRadial distribution functions (RDFs) for vitreous silica (V-SiO2) have been obtained from energy-filtered electron diffraction data obtained in the HB5 scanning transmission electron Microscope. Results have been compared with those obtained from high-resolution neutron diffraction experiments, and are in good agreement within experimental errors. It was found to be impractical to obtain partial RDFs for this material from combined neutron, X-ray and electron diffraction data, because the similarities in characteristics of X-ray and electron scattering cause indeter-Minacies. A criterion equation has been given to determine feasibility.
Density Reduction: A Mechanism For Amortization at High Ion Doses
Authors: Specht E. D. , Walko D. A. , Zinkle S. J. 
Published: March 2011

ABSTRACTAt cryogenic temperatures, the accumulation of vacancy-interstitial pairs in Al2O3 from atomic displacements associated with ion implantation produces amorphization. At room temperature, these pairs recombine, and amorphization occurs only at high doses. X-ray reflectivity measurements show that amorphization of the surface of Al2O3 implanted at room temperature with 160 keV Cr+ ions is preceded by a progressive reduction in near-surface density. Monte Carlo simulations show that this density reduction can be accounted for by high-energy-transfer collisions which knock atoms deep into the target, leaving widely separated vacancies and interstitials, which do not recombine. Electron Microscopy shows that at least some of these vacancies condense into voids. We propose that this reduction in near-surface density can lead to amorphization at high doses. We present simple approximations for the density reduction expected for different ions and targets.
Dopant Activation And Epitaxial Regrowth in P-Implanted Pseudomorphic Ge0.12Si0.88 Layers on Si (100)
Authors: Lie D. Y. C. , Cams T. K. , Theodore N. D. , Eisen F. , Nicolet M.-A. , Wang K. L. 
Published: March 2011

AbstractA pseudomorphic Ge0.12Si0.88 film 265 nm thick grown on a Si (100) substrate by molecular beam epitaxy was implanted at room temperature with a dose of 1.5 × 1015 cm2 of 100 keV P ions. The projected range of the ions is about 125 nm, which is well within the film thickness. Only the top portion of the Ge0.12Si0.88 layer was amorphized by the implantation. Both implanted and non-implanted samples were subsequently annealed in vacuum for 30 Minutes from 400 °C to 800 °C. Values of electron Hall sheet mobility and concentration in the implanted Ge0.12Si0.88 epilayer were measured after annealing. The solid phase epitaxial regrowth is complete at 550 °C, where the implanted phosphorus reaches - 100 % activation. The regrown Ge0.12Si0.88 layer exhibits inferior crystalline quality to that of the virgin sample and is relaxed, but the non-implanted portion of the film remains pseudomorphic at 550 °C. When annealed at 800 °C, the strain in the whole epilayer relaxes. The sheet electron mobility values measured at room temperature in the regrown samples (Tann ≥ 550 °C) are about 20% less than those of pure Si.
Nonequilibrium States of Symmetric Tetraalkylammonium Halides
Authors: Xenopoulos A. , Mucha M. , Wunderlich B. 
Published: March 2011

ABSTRACTThe nonequilibrium behavior of symmetrical tetra-n-alkylammonium halides is described from a study of the transition behavior using thermal analysis and hot-stage optical Microscopy. Results are discussed in terms of reversibility, supercooling, sharpness of transitions on thermal cycling, and glass transitions. The transitions of plastic to rigid crystals have the largest supercoolings. Gradual disordering on heating and incomplete ordering on cooling are found for some of the salts and represent interesting examples of order/disorder and glass transitions with reduced cooperativity.
Crystallization From Polymer Blends
Authors: Stein Richard S. 
Published: March 2011

ABSTRACTBinary polymer blends in which one or both components crystallize have been considered. These May be miscible or immiscible in the amorphous state, and phase separation may occur along with crystallization. The rates of these two processes vary differently with temperature, so the consequent morphology and properties depend upon the temperature history. For Miscible blends, the glass transition temperature depends upon composition. This affects diffusion so that crystallization kinetics varies as composition changes. If only one component crystallizes and the other is rejected, this rejected component diffuses away from the growing crystalline regions in a manner dependent upon the interaction between components.These phenomena are studied using a variety of techniques such as calorimetry, x-ray diffraction and scattering, and small-angle light and neutron scattering for a number of polymer systems.
Small Angle X-Ray Scattering of Crystalline Polymer Blends
Authors: Huo Peter P. , Cebe Peggy , Capel Malcolm 
Published: March 2011

ABSTRACTBinary blends of a semicrystalline polymer, poly (butylene terephthalate), PBT, with an amorphous polymer, polyarylate, PAr, were studied for a wide range of compositions. SMall angle x-ray scattering, thermal and mechanical analyses were conducted to determine the location of the uncrystallizable PAr relative to the crystal lamellae of PBT, for blends crystallized by heating from the quenched state. Comparison of experimental and calculated long periods indicates that interlamellar PAr placement becomes less probable as the PAr composition increases. When PBT crystallizes in these blends, Most PAr is rejected from the regions near the crystal surfaces when PAr fraction exceeds about 0.40.
Silicon Crystallization from Annealed Cu/A-Si:H Bilayers: A Multitechnique Study
Authors: Achete C. A. , Bernardino L. , Freire F. L. , Mariotto G. , Niehus H. 
Published: March 2011

ABSTRACTSilicon crystallization has been observed to occur in copper/a-Si:H thin film bilayers annealed at 280 °C. Copper-silicide formation was observed after annealing at 200 °C. Samples characterization was made by a combination of several analytical techniques: scanning electron Microscopy, Raman spectroscopy through a microscope probe, Auger electron spectroscopy, elastic recoil detection analysis and Rutherford backscattering spectrometry. The possible role of hydrogen in this process is discussed.
Effect of Pb Content on the Transformation of Sputtered PbxZr0.4Ti0.6O3 Thin Film
Authors: Joo Jae-Hyun , Kill Deok-Sin , Joo Seung-Ki 
Published: March 2011

ABSTRACTPZT (PbxZr0.4Ti0.6O3) thin films were prepared by reactive co-sputtering and annealed by RTA (Rapid Thermal Annealing). Transformation kinetics and effect of Pb content on the transformation were intensively studied using EMA (Effective Medium Approximation). It has been found that depending on Pb content as well as RTA temperature, the crystal structure of PZT films changed greatly. It turned out that the transformation temperature for the perovskite phase can be lowered and the width of transition temperature region was reduced by increasing Pb content in the films. Dependence of transformation path on the Pb content has been studied.
Conduction Mechanisms In Crystallized Silicon Films On Molybdenum Substrates
Authors: Palmer J. , Yi J. , Wallace R. , Anderson W. 
Published: March 2011

ABSTRACTHydrogenated Amorphous silicon films deposited on molybdenum sheet metal substrates have been crystallized by thermal annealing at 850°C for 4 hours in a nitrogen atmosphere. X-ray diffraction and scanning electron microscopy results indicated that the average grain size in the crystallized films was approximately 200A. Palladium contacts were fabricated and the resulting Pd/Si/Mo structures were electrically characterized. Current-voltage-temperature measurements for phosphorus doped and undoped annealed samples resulted in a J “V characteristic consistent with space-charge-limited current. Using this data, Mobility as a function of temperature from 100K-300K was obtained. In phosphorus doped samples, the mobility appeared to be limited by energy barriers at the grain boundaries. In undoped samples, a σ “T’ exp (-b/T’) temperature dependence consistent with variable-range hopping conduction was observed.
Amorphous Silicon Crystallization For Tft Applications
Authors: Yi J. , Wallace R. , Sridhar N. , Chung D. D. L. , Anderson W. A. 
Published: March 2011

ABSTRACTThin film hydrogenated Amorphous silicon (a-Si:H) was deposited on Molybdenum (Mo) substrates by d.c. glow discharge. We investigated the a-Si:H crystallization using four anneal techniques; nitrogen atmosphere furnace, vacuum, rapid thermal anneal (RTA), and excimer laser anneal. Anneal temperature ranged from 100 to 1200 °C. Excimer laser energy per pulse ranged from 90 to 340 M.J. Transmission electron Microscopy (TEM) revealed microstructure of crystallized Si film with grain size over 0.5 μm. X-ray diffraction (XRD) and Raman spectroscopy were employed to determine the degree of crystallization. The a-Si:H started to crystallize at temperatures over 600 °C. An 850 °C anneal reduced film resistivity to 10s (ω-cm) for intrinsic and 1 (ω-cm) for n-type. Coplanar type thin film transistors (TFT) with gate channel length of 25 μm and width of 220 μm were fabricated with various insulating layers; if sputtered SiO2, Si3N4, BaTiO3, MgO, and evaporated SiO. The first two exhibited the least leakage current. The as-grown intrinsic a-Si:H field effect mobility was around 0.03 (cmVV.s) and delay time was 5×10−7 s. The solid phase crystallized silicon film exhibited high leakage current. The delay time of an excimer laser anneal treated TFT was reduced to 2.5×10−7 s. Crystallized Si film mobility was improved to 15 (cm2 /V.s).
Laser Annealing of Hydrogenated Amorphous Silicon Thick Films
Authors: Sridhar Nagarajan , Chung D. D. L. , Anderson W. A. , Fu L. P. , Petrou A. 
Published: March 2011

ABSTRACTHydrogenated amorphous silicon thick films deposited by dc glow discharge on molybdenum substrates were annealed by a pulsed Nd:glass laser. Mass spectrometry showed hydrogen remaining in all the laser annealed films. The amount of hydrogen remaining decreased with decreasing scan rate. The hydrogen evolved upon heating at 365 °C and mainly at 658 °C before laser annealing, but at 365, 575 (Mainly) and 645 °C after laser annealing, indicating weakening of the silicon-hydrogen bonding after laser annealing. The presence of hydrogen inhibited crystallization, as indicated by Raman scattering. The photo and dark conductivity of the film increased by one and three orders of magnitude respectively with increasing laser energy density up to 12 J/cm2 at a fixed scan rate. This Means that the photoresponse was decreased with laser annealing, in spite of the associated increase in crystallinity. This photoresponse decrease is attributed to the hydrogen evolution.
Transient Phases and their Transition Temperatures of A-Si in Non-Isothermal Processes
Authors: Suzuki Masakuni , Kitagaffa Akio 
Published: March 2011

ABSTRACTThe heating rate dependence of the phase transition temperature was formulated based on the temperature dependence of nucleation of a new phase. The glass transition temperature of a-Si was explained in terms of van der Waals fluid of a-Si pseudo-Molecules which are produced by the fragmentation of continuous random networks of Si atoms. Transient phases and their transition temperatures as a function of the heating rate are summarized in the phase diagram.
Physical Studies of A Series of Main-Chain Liquid Crystalline Polymers With Long Soft Segment
Authors: Wu Bing , Lillya C. Peter , Stein Richard S. 
Published: March 2011

ABSTRACTA series of Main-chain liquid crystalline polymers with long and polydisperse soft segments has been synthesized. The thermal properties of these polymers have been characterized by differential scanning calorimetry, optical microscopy and wide angle X-ray diffraction. Unexpectedly, these polymers have a strong tendency to form purely smectic Mesophases. The degree of ordering of these polymeric mesophases is Much higher than that of the mesophase formed by a low molecular weight Model compound with the same Mesogen. The soft segment length effects on thermal behavior of such segmented copolymers have been elucidated. A semi-quantitative theory has been formulated to interpret these observations. A phase diagram relating thermal properties to soft segment length has been proposed.
Copper-Matrix Molybdenum Particle Composite as a Low-Thernal-Expansion Conductor
Authors: Yih Pay , Chung D. D. L. 
Published: March 2011

AbstractPowder metallurgical fabrication of Cu/Mo composites containing 33–73 wt.% Mo was carried out by using either Cu coated Mo powder or a mixture of Cu and Mo powders. The former yielded Cu/Mo composites of greater density, hardness, compressive yield strength and abrasive wear resistance, and lower electrical resistivity and coefficient of thermal expansion than the latter. This is attributed partly to the lower porosity of the former composites and partly to the separation of the adjacent Mo particles in the former composites and the partial linkage of the adjacent Mo particles in the latter composites.
Au/Ti and Au/Ni-Cr Metallization of CVD Diamond Substrates for Multichip Module Applications
Authors: Chilakamarri Prasad , Meyyappan Ilango , Naseem H. A. , Brown W. D. 
Published: March 2011

AbstractMultichip Modules (MCMs) have recently received widespread attention in the electronics industry. Owing to its high thermal conductivity, CVD diamond holds great promise for solving thermal management problems in MCMs. Also, large diameter free standing diamond substrates have recently become available. It is thus necessary to develop a reliable metallization for diamond substrates. As Au does not adhere to diamond, refractory metals, viz., Ti, W and Mo have been used as glue layers, as they form carbides above 800 °C. Since CVD diamond looses its properties at these temperatures, there is a need to obtain adherent metallizations at much lower temperatures. In the work reported here, tenaciously adherent Au/Ti and Au/Ni80-Cr20 metallization systems were sputter deposited on CVD diamond substrates for potential use as interconnects in MCMs. The adhesion values obtained by Sebastian V stud pull tester were in the range of 12 Kpsi, with post-deposition anneal temperature as low as 150 °C. The key to good adhesion was preconditioning of the diamond surface using in-situ sputter-etch technique. The effect of post-deposition annealing (up to 450 °C) on the interdiffusion of Au with the underlying metals was studied using AES, EDX, Optical Microscopy and sheet resistance measurements. Results indicate mixing of C from diamond with refractory metals at low temperatures which may be contributing to strong adhesion.
Z-Axis Anisotropic Electrically Conducting Polymer-Matrix Composite Film
Authors: Li Lin , Chung D. D. L. 
Published: March 2011

AbstractA z-axis anisotropic electrically conducting polymer-matrix composite film was developed. It comprised 25 vol.% copper coated polyether sulfone particles and a polyimidesiloxane matrix. Each particle protruded from both sides of the film and provided a conducting path along the z-axis. A z-axis pressure of 40 kPa resulted in a z-axis electrical resistivity of 2 ohm.cm for the overall film (i.e., 5 × 10-2 ohm.cm for a conducting path); subsequent pressure removal caused the resistivity to rise to 7 ohm.cm only. The film exhibited negligible stress relaxation and a low modulus of 1.67 GPa.
Optical Properties of Low Dielectric Constant Polyimides and Effects of Orientation
Authors: Rich David C. , Cebe Peggy , Clair Anne K. St. 
Published: March 2011

AbstractControl of the refractive index in low dielectric constant polyimides through modification of chemistry and structure was investigated. The optical refractive indices of several low dielectric constant polyimides were measured, and the effects of orientation on optical anisotropy were determined. Refractive index in these polyimides was found to decrease with increasing fluorine content due primarily to the low electronic polarizability of the fluorine-carbon bonds. In zone drawn polyimides, refractive index was found to increase substantially in the direction of the draw, but decrease substantially normal to the draw direction. This was explained in terms of the preferential alignment of the polymer chains.
An Assessment of Au Wire Bump Thermo-Mechanical Integrity in GaAs/Al2O3 Flip Chip Modules
Authors: Lin Jong-Kai , Hileman Bennett , Lee Russ , O'brien Richard , Sharma Ravi 
Published: March 2011

AbstractThe flexibility and cost advantages of the wire bumping process are making it increasingly attractive as an alternative bumping method for low I/O flip chip technologies. In this study, electrical measurements from DC to 8.1 GHz and die shear experiments are used to assess the thermo-mechanical integrity of Au/2%Pd wire bumped GaAs/Al2O3 flip chip modules. Finite Element Modeling results for in-process and in-service temperature cycling indicated that the maximum stress of the flip chip module is well below the failure stresses for GaAs, Al2O3 and the Au interconnect. These results are validated by data from thermal cycling experiments. Average shear strength after thermal cycle, thermal shock, and thermal aging (MIL-STD-883C, Condition C) was 64 grams/bump. Electrical characterization (from 45 MHz to 8.1 GHz) using a coplanar waveguide flip chip test structure showed no thermal stress-induced microwave energy losses.
Diode Laser-Assisted Deposition of Gold and Copper from Thin Organometallic Films
Authors: Evoy Stephane , Bernier Marie-Hélène , Izquierdo Ricardo , Pieri Fabrice , Meunier Michel , Sacher Edward 
Published: March 2011

AbstractWe have developed a simple, compact and economical diode laser-assisted process for the direct writing of gold and copper on polyimide. Gold precursor films were deposited by spin-coating a commercially available organometallic compound onto the substrate. The local pyrolysis of these films was induced by the focused beam of an AlGaAs diode laser array ( Pmax = 1 W, λ = 796 nm). Direct writing was achieved in open air while moving the substrate at speeds up to 15 mm/s. Gold lines 13–17 μm wide, ∼0.1 μm thick, and having a resistivity of 30 μΩ·cm, were obtained on polyimide with good reproducibility using writing speeds > 10 mm/s. Following a simple annealing process, these gold lines successfully activated the electroless plating of copper. After 45 min of plating, 2 μm thick Cu/Au conductors, having a resistivity of 8 μΩ·cm, were deposited. A commercially available copper precursor was also studied for the direct deposition of copper.