bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Potential Printed Wiring Board Materials: Thermoplastic Polyimide + Polymer Liquid Crystal Blends
Authors: Brostow Witold , D'Souza Nandika Anne , Gopalanarayanan Bhaskar , Jacobs Elizabeth G. 
Published: April 2011

ABSTRACTPolymer liquid crystals (PLCs) have potential applications as printed wiring board materials and in other aspects of plastic packaging. They have a number of desirable properties such as low moisture absorption, thermoplastic behavior, and low thermal expansivity. However, PLCs can have significant anisotropy in expansivity with negative expansivities in the drawing or molding direction and relatively low positive expansivities in the transverse directions. By incorporating PLCs into an engineering polymer (EP) matrix, in our case a thermoplastic polyimide (TPI), we expected to be able to control the expansivity of the resulting blend – thereby aiding in long-term service performance and reliability. Properties such as low moisture absorption, dimensional stability at elevated temperatures, good adhesion properties, and reworkability were also sought. In this paper, we report on our work to process a TPI/PLC blend and characterize the thermal properties of the blends.An amorphous TPI was chosen over a semicrystalline one because of a thermo-irreversible cold crystallization in the latter, causing undesirable changes in the morphology and poor adhesion to metals. Our evaluations of TPIs through thermally stimulated depolarization (TSD) and temperature-modulated differential scanning calorimetry (TMDSC) reveal sub-glass transition relaxations. We have investigated the selected semicrystalline TPI + PLC pair in the entire composition range, and concluded that the narrower range, up to 30 wt. % of the PLC, is sufficient for the achievement of our objectives. The glass transition temperature Tg = 240°C of the TPI determined by DSC is unaffected by variations of the PLC concentration. The cold crystallization temperature of the semicrystalline TPI decreases with increasing PLC concentration but upon formation of the LC-rich islands this effect becomes smaller. All the blends exhibit degradation onset temperature over 520°C. The thermal conductivity of the amorphous TPI + PLC blends varies as a function of the PLC concentration. The blends show very good film formability. The addition of the PLC improves the processability of the TPI. Thermomechanical analysis (TMA) reveals that the desired control of the expansivity of the blends is also achieved by varying the PLC concentration.
Optical Probes and Electrical Resistivity Measurements of Conductive Die Attach Adhesives
Authors: Miragliotta Joseph , Benson Richard C. , Phillips Terry E. , Emerson John A. 
Published: April 2011

ABSTRACTAn important phenomenon in silver (Ag) particle-filled adhesives is the development of electrical conductivity as the polymer composite is cured. We report the results of optical and electrical measurements performed on a commercially available Ag particle/polymer composite as a function of sample temperature. Surface enhanced Raman scattering (SERS) was used to probe the chemical nature of the Ag interface while a four-point contact probe monitored the onset of DC electrical conductivity. Complementary to the die attach adhesives studies, SERS experiments were also performed on commercially available neat Ag flake with controlled adsorbate coverages. For both the neat flake and filled adhesive, a carboxylate layer was attached to an oxygen-covered Ag flake surface via the carboxylic acid end of the molecule. The SERS results observed a partial decomposition of the carboxylate species into an amorphous carbon layer upon an increase in the temperature of both the flake and filled adhesive samples. However, the temperature threshold for the chemical conversion was lower for the Ag-filled adhesive relative to the neat flake. In the composite samples, the formation of the amorphous carbon layer occurred well below the curing temperature and coincided with a corresponding decrease in the electrical resistivity of the adhesive. Thus, an initial step in developing electrical conductivity appears to be the partial conversion of the lubricant adsorbate to an amorphous carbon layer.
Under Bump Metallization Development for Eutectic Pb-Sn Solders
Authors: Hong S. J. , Korhonen T. M. , Korhonen M. A. , LI C.-Y. 
Published: April 2011

ABSTRACTDue to its advantage in number of I/Os over other interconnection method, flip chip interconnection technology plays a key role in today's electronics packaging. Good understanding of interfacial reactions between the solder balls and under bump metallizations (UBM) is crucial in producing sound and reliable solder joints. In the present paper, several new under bump metallization (UBM) schemes using Ni or CuNi alloys as solderable layer are investigated. Cr or Ti is used as the adhesion layer. Test joint are made by reflowing eutectic Pb-Sn solder balls on UBMs and through the use of scanning electron microscopy (SEM) and micromechanical shear testing, the reliability of the UBM scheme is determined. Experimental result shows that some of the new schemes, featuring CuNi wettable layer with Cr or Ti adhesion layer produce reliable joints.
Magnetic Force Microscopy Analysis of Thermal Stability in Longitudinal Media
Authors: Abarra E. N. , Okamoto I. , Suzuki T. 
Published: April 2011

AbstractThe thermal stability of written bits in high density longitudinal recording media is investigated using magnetic force microscopy (MFM). The time dependence of the MFM signal is examined for different linear densities on CoCrPt-based media of various thickness. At ambient temperature, lesser decay is observed using the MFM compared to spin stand measurements on the same CoCrPtTaNb media on Al which emphasizes the dependence of bit stability with writing conditions. Moderate anneals at 373 K reveal a rapid initial ∼ 10% signal decay followed by stable behavior not observed in the magnetization time dependence measurements. 200 kfci tracks on a 20-nim thick CoCrPtTa medium on Si with a coercivity of 3 kOe displayed stable (∼ 2%) behavior against a 105-hour anneal at 373 K in air. These results are correlated with media properties to obtain parameters that are good indicators of thermal stability performance.
Large Magnetic Anisotropy in Co3Pt Ordered Phase Thin Films
Authors: Yamada Yoshiyasu , Suzuki Takao 
Published: April 2011

AbstractThe very large perpendicular magnetic anisotropy of the order of 2 x 107 erg/cm3 at room temperature was found in CoJ-x Ptx(0<x<0.5) alloy thin films made by e-beam evaporation. The large magnetic anisotropy is likely related to the anisotropic Co-Co bonding distribution, which is similar to the cases of Co/Pt multilayers and FePt alloy thin films. The activation energy estimated for the ordering is approximately 0.3 eV, which is preferably compared to 0.2 eV for FePt. A model is proposed, for which both a short range and long range ordering are present, depending on substrate deposition temperature.
Thickness Dependent Perpendicular Magnetic Domain Patterns in Sputtered Epitaxial FePt (001) L10 Films
Authors: Thiele J.-U. , Folks L. , Toney M. F. , Weller D. K. 
Published: April 2011

AbstractThe present paper discusses the magnetic anisotropy and magnetic domain structure of highly ordered epitaxial FePt(001) films grown on Pt seeded MgO(001) substrates. These films were grown by dc-magnetron sputtering from a Fe50Pt50 alloy target at a substrate temperature of 550°C during deposition. Thicknesses were varied between 15 and 170 nm. The presence of the highly anisotropic face centered tetragonal L10 crystal structure with a maximum long range chemical ordering of 95% and a low degree of misorientations was confirmed by specular and grazing incidence X-ray diffraction measurements. For film thicknesses ≥ 50 nm in-plane and out-of-plane hysteresis measurements indicate large perpendicular magnetic anisotropy and at the same time low remanent magnetisation. Magnetic force microscopy reveals highly interconnected perpendicular stripe domain patterns. From their characteristic width, which is strongly dependent on the film thickness, a value of the dipolar length, D0, of 50 ±5 nm is derived. Assuming an exchange constant of 10-6 erg/cm, this value is consistent with an anisotropy constant Ku ∼ 1.108 erg/cc.
Compensation Temperature of a Mixed Ising Ferrimagnetic Model in the Presence of External Magnetic Fields
Authors: Buendia G. M. , Machado E. , Novotny M. A. 
Published: April 2011

AbstractThe behavior of the compensation temperature of a mixed Ising ferrimagnetic system on a square lattice in which the two interpenetrating square sublattices have spins σ (±1/2) and spins S (±1,0) has been studied with Monte Carlo methods. Our model includes nearest and next-nearest neighbor interactions, a crystal field and an external magnetic field. This model is relevant for understanding bimetallic molecular ferrimagnetic materials. We found that there is a narrow range of parameters of the Hamiltonian for which the model has compensation temperatures and that the compensation point exists only for small values of the external field.
Study of Hard Disk and Slider Surfaces Using X-Ray Photoemission Electron Microscopy and Near Edge X-Ray Absorption Fine Structure Spectroscopy
Authors: Anders Simone , Stammler Thomas , Singh Bhatia C. , Stöhr Joachim , Fong Walton , Chen Chao-Yuan , Bogyi David B. 
Published: April 2011

AbstractX-ray Photo Emission Electron Microscopy (X-PEEM) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy were applied to study the properties of amorphous hard carbon overcoats on disks and sliders, and the properties of the lubricant. The modification of lubricants after performing thermal desorption studies was measured by NEXAFS, and the results are compared to thermal desorption data. The study of lubricant degradation in wear tracks is described. Sliders were investigated before and after wear test, and the modification of the slider coating as well as the transfer of lubricant to the slider was studied. The studies show that the lubricant is altered chemically during the wear. Fluorine is removed and carboxyl groups are formed.
Optimized Nonreciprocal Rib Waveguides for Integrated Magneto-Optic Isolators
Authors: Wallenhorst M. , Backherms V. , Josef A. , Bahlmann N. , Lohmeyer M. , Dötsch H. , Hertel P. 
Published: April 2011

AbstractGarnet films of composition (Lu,Bi)3(Fe,Ga,Al)5O12 and (Tm,Bi)3(Fe,Ga)5O12 are grown by liquid-phase epitaxy on [111]-oriented substrates of gadolinium gallium garnet. Ferrimagnetic films with positive or negative Faraday-rotation as well as paramagnetic films with negligible Faraday-rotation are produced by variations of the rare earth ion substitutions. The temperature dependence of Faraday-rotation is fitted with a molecular field model. Optical rib waveguides in single and double layer garnet films with different Faraday-rotations are realized. The nonreciprocal phase shift of the TM0-Mode is studied both theoretically and experimentally at a wavelength of 1.3 μm. Results show that the maximum nonreciprocal effect at room temperature of double layer films with opposite Faraday-rotation is 1.6 times as large as that of comparable single layer waveguides. But, because of the large temperature dependence of the Faraday-rotation of the positive rotating films, these waveguides show a large temperature dependence of the nonreciprocal phase shift. This problem can be avoided if the positive rotating layer is replaced by a paramagnetic layer. Agreement between calculations and measurements is excellent.
Magneto-Optical Properties of Co Doped Bi3Fe5O12 Garnet Film
Authors: Okuda T. , Mima T. , Ando K. , Ohmori N. , Adachi N. , Ohsato H. 
Published: April 2011

AbstractCo-doped Bi3Fe5O12 garnet (BIG) films were prepared on Gd3(ScGa)5O12(GSGG) substrates using two types of ion-beam-sputtering (IBS) technique. In the films deposited by sputtering the Co and the BIG source targets alternately with short periodicity, the interface exchange coupling of BIG and Co-spinel ferrite was characteristically observed in the Faraday hysteresis loop. The magnetic and the Faraday hysteresis loops were found to have different coercivity. In the films deposited by conventional IBS method using the BIG target doubly substituted by Co and Ge, Co2+ ions were highly replaced up to 0.7 atoms/formula unit for Fe3+ in BIG. The specific Faraday rotation angle (θ F) at a wavelength of 1.5 μ m was 1.1 deg/μm/Co atom. The magnetic easy direction was normal to the film plane.
Synthesis of Coated Nanoparticulate Ceramic Powders
Authors: Vollath D. , Szabó D. V. 
Published: April 2011

ABSTRACTThe microwave plasma process is capable to produce larger quantities of nanoparticulate powders with mean particle sizes in the range from 5 to 20 nm. The products may be oxides, nitrides, sulphides, selenides, or even metals. Additional, it is possible to coat these particles with a layer of a second ceramic, a polymer or carbon. Sintered ZrO2-Al2O3 nanocomposites and super-paramagnetic cores of γ-Fe2O3-polymer composites are given as examples.
Synthesis and Characterization of AL2O3/ZRO2, AL2O3/TIO2, and AL2O3/ZRO2/TIO2 Fine Particles Prepared by Ultrasonic Spray Pyrolysis
Authors: Ri Chang-Seop , Shim In-Su , Kim Chang-Hyun , Lee Byung-Kyo , Lee Kyung-Hee 
Published: April 2011

ABSTRACTThe fine ceramic particles of zirconia toughened alumina (ZTA), titania toughened alumina (TTA), and zirconia-titania toughened alumina(ZTTA) were synthesized through ultrasonic spray pyrolysis at various temperatures and compositions. The starting solution was prepared to have the concentration of 0.05 ∼ 0.1 M adjusting with water as a solvent. The temperature regulated for particle synthesis was 400 ∼ 550 °C as a drying zone, 850 ∼ 1400 °C as a pyrolysis zone. The produced particles were collected by a wet process and were analyzed to give characteristic properties after being dried. Various properties such as thermal behavior, phase, particle size and size distribution, shape, diffraction pattern, content of elements, etc, of particles synthesized with different experimental conditions were determined and studied by XRD, TG/DTA, PSA, ICP, and SEM, and the optimum experimental conditions for the particle synthesis were proposed.
Compaction Stress in Fine Powders
Authors: Scott J.E. , Kenkre V.M. , Pease E.A. , Hurd A. J. 
Published: April 2011

ABSTRACTA vexing feature in granular materials compaction is density extrema interior to a compacted shape. Such inhomogeneities can lead to weaknesses and loss of dimensional control in ceramic parts, unpredictable dissolution of pharmaceuticals, and undesirable stress concentration in load-bearing soil. As an example, the centerline density in a cylindrical compact often does not decrease monotonically from the pressure source but exhibits local maxima and minima. Two lines of thought in the literature predict, respectively, diffusive and wavelike propagation of stress. Here, a general memory function approach has been formulated that unifies these previous treatments as special cases; by analyzing a convenient intermediate case, the telegrapher's equation, one sees that local density maxima arise via semidiffusive stress “waves” reflecting from the die walls and adding constructively at the centerline.
Structural Investigation of a Surfactant-Templated Silica Aerogel by Small-angle Scattering
Authors: Riekerlt Thomas P. , Anderson Mark T. , Sawyer Patricia S. , Rane Shrish , Beaucage Gregory 
Published: April 2011

ABSTRACTThe structure of a surfactant-templated silica aerogel is studied by small-angle x-ray and light scattering. By combining the two techniques, we obtain structural information on length scales from Ångstroms to 0.1 millimeters. For this sample, we find five structural features, including the morphology of large scale aggregates.
Porous Al Alloys by Local Melting and Diffusion of Metal Powders
Authors: Wang N. , Starke E. A. , Wadley H. N.G. 
Published: April 2011

ABSTRACTA novel method exploiting local melt and diffusion induced porosity is described for producing porous Al alloys. Aluminum powder and zinc powder were blended and cold-compacted to a near net shape. A porous AI-Zn alloy component was then formed by annealing the material above the melting point of zinc but below the solidus temperature of the alloy. Pores were generated by the diffusion of molten Zn into the solid Al grains. The pore structure is shown to be determined by the volume fraction, distribution, and size of the Zn powders in the powder mixture, and by time and temperature of the annealing heat treatment. The pores can be further expanded by incorporating small amounts of titanium hydride into the powder blend and conducting the annealing treatment above the decomposition temperature of the titanium hydride (T>447°C). Porosity levels of 45 vol.% have been achieved to date. This processing approach appears amenable to the production of sandwich panels with a gradient porosity core and fully dense face sheets, and is applicable to other solid solution systems.
Calibration of Wafer Temperature to Nist Traceable Standards Using an Isothermal Cavity
Authors: Vandenabeele Peter , Renken Wayne 
Published: April 2011

ABSTRACTThe offset between Si temperature and indicated TC temperature when a thermocouple instrumented wafer is placed in a double side heated RTP system was measured by means of an isothermal cavity, formed by 2 parallel Si wafers mounted in the system. The lamp powers were controlled to get an equal wafer temperature, making the cavity isothermal. Inside the cavity, an R-type TC with a NIST traceable calibration was mounted. Outside the cavity, a standard type K 1530 SensArray thermocouple [1] was exposed to the typical conditions in an RTP system. The offset was measured as the difference between the indicated temperature of the standard 1530 TC and the temperature of the NIST traceable type R TC. The 3 sources of the offset are discussed and a typical correction factor is proposed.
An Atomic Force Microscopy and Ellipsometry Study of The Nucleation and Growth Mechanism of Polycrystalline Silicon Films on Silicon Dioxide
Authors: Basa C. , Tinani M. , Irene E. A. 
Published: April 2011

ABSTRACTA study was performed using a combination of in-situ real time ellipsometry and atomic force microscopy (AFM) to follow the RTCVD process in real time and measure key nucleation parameters in an effort to elucidate the mechanism of Si nucleation on SiO2. Real time ellipsometry data, in terms of delta versus time, showed significant changes as the deposition evolves from critical nuclei through coalescence to continuous film growth thereby allowing. process monitoring and control. From the AFM images, nuclei parameters such as nuclei height, radius, and density were collected and compared across processing temperatures. It was found that kinetic factors control the growth process resulting in a transition temperature (660°C) where the size, shape, and density of the nuclei abruptly changes from small numerous nuclei to large, sparse disk-like nuclei.
Facet Free Selective Silicon Epitaxy by Rapid Thermal Chemical Vapor Deposition
Authors: Violette Katherine E. , Wise Rick , Chao Chih-Ping , Unnikrishnan Sreenath 
Published: April 2011

ABSTRACTA facet-free, selective epitaxy process has been identified using the SiH2CI2 /HCI/H2 chemistry in a commercially available, single-wafer epitaxy reactor. The pre-epitaxy bake required a minimum of 900°C in order to obtain a clean silicon surface with reasonable throughput while preserving the integrity of the shallow trench isolation structures. The epitaxy growth rate ranged from as low as 130Å/rnin at 825°C, 10 torr to as high as 1500 Å/min at 875°C and 70 torr while the deposition rate of polysilicon on polysilicon differed significantly: at 10 torr, the epitaxy growth rate is greater by as much as 50%, and at 70 torr the polysilicon deposition rate is greater by as much as 40%. The facet suppression depended heavily on two things: the undercut beneath the polysilicon gate sidewall insulator and the process pressure. The undercut is believed to be responsible for suppressing the initial stage of facet formation, most probably by completely eliminating lateral overgrowth of the crystal. The process conditions then enable continued facet suppression perhaps by restricting the silicon surface mobility. The sidewall structure and process conditions combine to make a reliably facet-free selective epitaxy process
Beyond Thermal Budget: Using D · t In Kinetic Optimization Of RTP
Authors: Ditchfield R. , Seebauer E. G. 
Published: April 2011

ABSTRACTRapid thermal processing (RTP) has found continually increasing use for oxidation, silicidation, CVD, and other steps in microelectronic fabrication. Kinetic effects in rapid thermal processing (RTP) are often assessed using the concept of thermal budget, with the idea that low thermal budgets should minimize dopant diffusion and interface degradation. Some definitions of budget employ the product of temperature and time (T-t). In previous work, we have shown that this definition for budget often leads to qualitatively incorrect conclusions regarding heating program design. However, other definitions of budget employ the product of diffusivity and time (D-t), where the diffusivity describes unwanted diffusion or interface degradation. Here we show that minimization of D-t by itself is insufficient to kinetically optimize a heating program; account must be taken of the relative rates of the desired and undesired phenomena. We present a straightforward but rigorous method for doing so.
Structure and Surface Morphology of Epitaxial Ni Films on MgO(111) and (001) Substrates: Growth of High Quality Single Domain Films
Authors: Sandström Per , Svedberg Erik B. , Birch Jens , Sundgren Jan-Eric 
Published: April 2011

AbstractNi films were deposited by ultra high vacuum magnetron sputtering onto MgO(111) and (001) substrates kept at temperatures Ts between 20°C and 600°C. The structure and the morphology of the 100 nm thick films were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM). On MgO(111), all Ni films have a strong [111] oriented texture with high out-of-plane as well as high in-plane orientations with an increased crystalline quality with temperature. At 300°C the Ni 111 peak width is ∼0.25° in the ω direction, showing a high crystal quality for a heteroepitaxial metal film. Pole-figure analysis shows that the films are built up of two domains for temperatures ≤200°C and at 600°C, while at 300°C and 400°C only one domain is formed. The RMS roughness, as measured with AFM, of the film increases with temperature with a local maximum between 150° to 200°C and a local minimum at 300°C which corresponds to the transition from two domains to one. On MgO(001), Ni shows three completely different textures depending on the deposition temperature. At ambient temperature a mixed (1 −4 1) and (022) texture with traces of (002) is formed. Between 100°C and 200°C Ni grows with a single domain (001) texture. At higher temperatures a highly oriented 8-fold (75-1) texture is formed. The highest crystalline quality is obtained at 100°C where the FWHM of the Ni 002 peak at 100°C is 0.24° in the ω−2θ direction and 0.18 in the ω direction which shows the good crystalline quality also in this case. Both the RMS surface rougness and the surface feature size increases with the deposition temperature but with local miminas at 100°C corresponding to the film with highest crystalline quality.The weak Ni-O interaction together with a strong metal-metal bonding between the Ni atoms results in an in plane supercell matching between the Ni film and the MgO substrates at 300-400°C for the MgO(111) substrate and 100-200°C for the MgO(001) substrate.The (7 5 −1) texture formed by Ni on MgO(001) substrates at deposition temperatures ≥300°C, places each interfacial Ni atom in the preferred position on top of an O atom on the MgO surface, and in addition, also better accommodates the mismatch between the two crystal lattices.