bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Conductivity of Shock-Compressed Sulphur, Iodine, Bromine and Water
Authors: Yakushev V. V.
Published: April 2011

Experimental investigations of the electrical conductivities of sulphur, iodine, bromine, and water under shock compression are reviewed. The value of sulphur conductivity is approximately 105 Ω−1 m−1 at 30 GPa and increases slowly with pressure up to 110 GPa. The conductivity of iodine is 105 Ω−1 m−1 at approximately 15 GPa and decreases moderately up to 110 GPa. The conductivity of liquid bromine is 12.5 Ω−1 m−1 at 9 GPa and approximately 104 Ω−1 m−1 at 30 GPa. In electrochemical experiments galvanic cells with copper and aluminium electrodes and bromine as an electrolyte were subjected to shock loading and their electrical response was measured. We discovered that the cells produce open circuit voltages of about 0.5 V under shock pressures of 7.4 to 30 GPa. This voltage level clearly shows that the observed electrical signals are electrochemical in nature and connected with an ionic character of bromine conductivity. Analogous experiments were made with water, whose conductivity is ionic at 75 GPa with a value of 2000 Ω−1 m−1.
High-Pressure Synthesis and the Magnetic Properties of Chromium Diantimonide
Authors: Takizawa H. , Uheda K. , Endo T. , Shimada M.
Published: April 2011

A new high-pressure polymorph of CrSb2 was synthesized under high-pressure/ temperature conditions of 7–7.7 GPa and 600–650°C. The crystal structure is body-centered tetragonal with the space group 14/mcm, which is assigned to CuAl2-type structure. The experiments under various pressure conditions revealed that the high-pressure polymorph was formed above 5.5 GPa, and the compound crystallized into the low-pressure marcasite-type structure below 5 GPa. The characteristic of the high-pressure phase is the metallic bond nature including the formation of Cr-Cr-Cr linear chain along the c-axis. The compound shows metallic conductivity and itinerant-electron ferromagnetic behavior with the Curie temperature of ca. 160 K.
The Ruby Scale at Megabar Pressures
Authors: Silvera Isaac F.
Published: April 2011

Diamond anvil cells revolutionized high pressure research because they provided easy to generate extremely high pressures with an optical window on the sample and an easy-to-use pressure gauge based on the shift with pressure of the ruby fluorescence spectrum. The ruby scale provides an accurate method of determining pressure distributions within samples. However, at pressures above 100 GPa measurement of the ruby fluorescence begins to become difficult due to weakening signals, interference from intense diamond fluorescence, and ultimately, strong absorption of the exciting laser by diamond itself. We shall discuss a number of methods which have been devised to extend the ruby pressure optical gauge to 500 GPa, including quasi-direct pumping of the ruby R-lines.
A Multi-Anvil High Pressure System with Synchrotron X-Ray Probe: New Opportunities for In-Situ Materials Research at Simultaneously High Pressure and Temperature
Authors: Wang Y. , Shen G. , Rivers M. , Sutton S.
Published: April 2011

We describe the multi-anvil, large-volume, high-pressure facility that is being constructed at the GeoSoilEnviroCARS (Sector 13) at the Advanced Photon Source, Argonne National Laboratory. Various multi-anvil, high-pressure apparatus will be used to cover pressure and temperature conditions up to 40 GPa and 3000 °C, respectively, with milimeter to centimeter sized samples. This national facility is open to all users, providing excellent opportunities for high pressure, high temperature experiments.
Solid molecular phases of Hydrogen via constant-pressure first-principles Molecular Dynamics
Authors: Kohanoff Jorge , Scandolo Sandro
Published: April 2011

By performing constant pressure ab initio molecular dynamics simulations we analyse the high pressure phases of molecular solid hydrogen. We use a gradient corrected LDA, and a freshly implemented efficient technique for Brillouin zone sampling. An extremely good k-point sampling turns out to be crucial for obtaining the correct ground state. Our constant pressure approach allows us to optimize simultaneously the ori-entational degrees of freedom, the lattice constants, and the space group. This can be done either by a local optimization tehcnique, or by running molecular dynamics (MD) trajectories. The MD allows for the system to undergo structural transformations spontaneously. In the lower pressure, namely for the broken symmetry phase (BSP or phase II), we find a quadrupolar orthorhombic structure, of Pca21 symmetry. By means of an MD investigation, we find, at higher pressures, a slightly distorted orthorhombic structure of Cmc21 symmetry. This structure cannot be straightforwardly identified with the H-A phase (or phase III) because: 1) it is metallic, and 2) the Raman vibron discontinuity would be far too large compared to experiment. In fact, we argue that this phase is the first metallic molecular phase of hydrogen. Metallization would happen then, not via a band-overlap mechanism, but due to a structural transformation. By comparing total enthalpies, we also give suggestions for the structure of phase III.
Magnetism, Electronic Properties and Structure at High Density State of Magnetic Solids
Authors: Gavrejuk A. G. , Stepanov G. N. , Trojan L. A. , Sidorov V. A. , Lyubutin I. S. , Palosz B. , Steumakh S. , Winzenick M.
Published: April 2011

We develop and apply high pressure techniques to study the modification of electronic structure, magnetic properties, and local crystal structure, in magnetic materials under high pressure. The variation in inter-atomic distances and atomic volumes in the high pressure regime provides new information for elucidating electronic processes in solids, and for understanding the connection between electronic structure and magnetic properties of matter.

For our samples we used rare-earth orthoferrites, which are of the perovskite-type structure, and Heusler alloys, with the cubic structure. Those materials are known to be magnetic insulators and magnetic metals, respectively.

We studied the following properties induced by high pressure: electronic structure, spin crossover effects, magnetic to non-magnetic transitions, and insulator-to-metal transitions. The problems of delocalization, distribution of spin, and charge density distribution in dielectric materials, semiconductors, and metals, as well as chemical bonding can be investigated in this way.
Ab-Initio Simulation of Solid State Polymerization of Acetylene Under Pressure
Authors: Bernasconi M. , Parrinello M. , Chiarotti G. L. , Focher P. , Tosatti E.
Published: April 2011

We have recently devised a new method for the ab initio simulation of solid-solid phase transformations under pressure. The method is here applied to the study of the solid-state polymerization of acetylene under pressure and the generation of hydrogenated amorphous carbon from compression of polyacetylene.
Experimental Issues in In-Situ Synchrotron X-Ray Diffraction at High Pressure and Temperature by Using a Laser-Heated Diamond-Anvil Cell
Authors: Yoo C. S. , Cynn H. , Campbell A. , Hu J.-Z.
Published: April 2011

An integrated technique of diamond-anvil cell, laser-heating and synchrotron x-ray diffraction technologies is capable of structural investigation of condensed matter in an extended region of high pressures and temperatures above 100 GPa and 3000 K. The feasibility of this technique to obtain reliable data, however, strongly depends on several experimental issues, including optical and x-ray setups, thermal gradients, pressure homogeneity, preferred orientation, and chemical reaction. In this paper, we discuss about these experimental issues together with future perspectives of this technique for obtaining accurate data.
Growth of Icosahedral Boron-Rich Clusters at High Pressure
Authors: McMillan Paul F. , Hubert Herve , Chizmeshya Andrew
Published: April 2011

The stoichiometry of boron suboxide (B6O1-x) synthesized at high pressure lies closer to the nominal composition (x = 0) than materials obtained at atmospheric pressure. The crystallinity of materials obtained in the presence of molten B2O3 is also higher than for sintered powders. Further, for syntheses at 1700–1800 °C between 4 and approximately 5–6 GPa, the well-crystallized particles are dominated by large (up to ∼40 μm in diameter) icosahedral multiply-twinned particles. This unusual morphology is obtained by Mackay packing; i.e., by assembly of successive shells of icosahedral B12 units around a central icosahedral nucleus. The result is a multiply-twinned particle in which each of the 20 elements has the R 3 m space group of the α-B structure.
Synthesis and Characterization of Nanosized Silicon Carbide
Authors: Klein S. , Winterer M. , Hahn H.
Published: April 2011

Nanosized silicon carbide powders are synthesized by the Chemical Vapor Synthesis (CVS). Grain and particle sizes are measured by XRD and BET. Agglomeration, crystallinity and the chemical composition of the SiC samples are investigated as a function of storage conditions and the CVS process parameters: precursor material, synthesis temperature and reactor length. Grain and particle sizes below 10 nm are observed in all samples.
Novel method for synthesis of engineered particulates with thin coatings
Authors: Fitz-Gerald J. , Singh R. K.
Published: April 2011

Particulate coatings have wide ranging applications in several new technologies such as flatpanel displays, sintering of advanced ceramics, rechargeable batteries, etc. In this paper, we show the feasibility of the pulsed laser ablation technique to make very thin, uniformly distributed and discrete coatings in particulate systems so that the properties of the core particles can be suitably modified. Presently, laser ablation techniques have been primarily applied to deposit thin films on flat substrate materials. To deposit discontinuous particulate coatings, the laser induced plume from the target comes in contact with an agitated bed of core particles (size 1–800μm). The pressure and nature of the background gas (inert or active) controls the cluster size of the particles in the laser plume. Experiments were conducted for laser deposition of silver particles on alumina core particles by excimer laser (wavelength = 248 nm and pulse duration = 25 nanosecond) irradiation of silver targets. The surface coverage and the coating of the film wasf found to depend on the laser parameters (energy density and number of laser pulses) as well as the residence time of the core particles in the plume regime. The films were characterized by wavelength and energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy techniques.
Characterization of Diamond like Carbon film Fabricated by ECR Plasma CVD at room Temperature
Authors: Kuramoto K. , Domoto Y. , Hirano H. , Tarui H. , Kiyama S.
Published: April 2011

Low temperature (about 50°C) fabrication of diamond like carbon (DLC) films with a high hardness (>3000Hv) and a high electrical resistivity (>1011 Ωm) has been achieved.

In order to obtain such a result, the effect of ion impingement on the growth and structural change of DLC films in an electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (CVD) method was investigated. It was confirmed that ion impingement was fundamentally required in the growth of DLC films. Furthermore, impingement with ions energized by bias voltages between 50V and 150V had a major influence on the sp 2/sp 3 configuration in DLC films. This configuration is found to be rather sensitive to optoelectronic properties but not so sensitive to film hardness.

Additionally, this method could fabricate ultrathin DLC films that exhibited excellent wear resistance for protective applications.
Synthesis of Hard Nitride Coatings by ion Beam Assisted Deposition
Authors: Demaree J. D. , Fountzoulas C. G. , Hirvonen J. K. , Monserrat M. E. , Halada G. P. , Clayton C. R.
Published: April 2011

Ion beam assisted deposition (IBAD) has been used to deposit chromium nitride coatings using 1200 eV nitrogen ions from an RF-type ion source and thermally evaporated chromium. The ion/atom arrival ratio R was varied from 0 to 8 to modify the coating composition, microstructure, growth rate and stress state in order to optimize the properties of the material for use as a possible substitute for electroplated chromium in a number of anti-corrosion and tribological applications. The coatings were examined using Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy, and contained up to 44 at % nitrogen in a mixture of bcc Cr-N, Cr2N, and CrN. The microstructure of the coatings was examined by scanning electron microscopy, and the tribological behavior of the coatings was examined using an automated scratch testing and nanoindentation. XPS examination of the coatings indicates that nitrogen near the surface was bound to the metal as CrN and Cr2N in most of the coatings studied by XPS, which is expected to significantly affect their corrosion behavior. The high R values needed to form large amounts of the CrN phase in the bulk of the coating causes significant sputtering during deposition. This study indicates that it is not possible to form a coating consisting solely of cubic CrN by IBAD under these experimental conditions (room temperature substrate and partial pressure of nitrogen of 1.8 × 10−2 Pa). Nevertheless, the IBAD coatings produced were hard, in a compressive stress state, and highly adherent, all properties that make them candidates for use in selected Army applications.
Properties of C and CN Films Prepared by Mass-Separated Hyper-Thermal Carbon and Nitrogen Ions
Authors: Tsubouchi N. , Horino Y. , Enders B. , Chayahara A. , Kinomura A. , Fujii K.
Published: April 2011

Amorphous carbon films and CN films were prepared by ion beam deposition using isotopically mass-separated, hyper-thermal (50–400eV) ion species such as 12C2−, 12C14N− or simultaneous 12C2− and 14N+ under high vacuum condition. Film properties such as structures, bonding states, compositions, etc. were investigated. The optical band gaps of amorphous carbon films deposited by using 12C2−ions or CN films deposited by using 12C14N− ions were estimated from optical constants. The gaps were about 2.3eV for the amorphous carbon films and about 0.8 eV for the CN films. Energy dependence of optical constants of CN films formed by simultaneous deposition of C2− and N+ was investigated. The refractive index (n) and extinction coefficient (k) at λ = 675nm increased 1.5 to 2.4 and 0.3 to 1.3, respectively, with increasing N+ kinetic energy. The relations between bonding states and kinetic energy of hyper-thermal ions are discussed.
Vanadium Oxide Precipitates in Sapphire Formed by Ion Implantation
Authors: Abe Hiroaki , Naramoto Hiroshi , Yamamoto Shunya
Published: April 2011

Some vanadium oxides undergo phase transformations which give rise to attributable for large variations in optical and electronic properties. Since one can expect dynamic rearrangement of implanted species and a distorted lattice due to implantation, we investigated the precipitation process under ion implantation at high temperature. Sapphire samples were implanted with 300-keV V+ ions at temperatures from 470 to 1070 K in a transmission electron microscope interfaced with ion accelerators. Evolution of vanadium oxide precipitates was observed simultaneously. Damage evolution such as dislocation loops and voids were observed at fluences of the order of 1018-1019 and 1020 ions/m2, respectively. At implantation fluence of the order of 1021 ions/m2, dot and plate contrast was observed in addition to radiation damage. Electron diffraction analysis reveals that hexagonal and monoclinic V2O3, tetragonal and monoclinic VO2, and V7O13 precipitates were formed in the substrate depending on the surface normal of the substrate. Some of precipitates were thermally unstable phases. Crystallographic relationship between matrix and the precipitates was investigated as well as the swelling effect both in the substrate and in the precipitates. Temperature dependence reveals precipitation starts at temperature higher than 670 K.
Simulation of Interstitial Cluster Mobility and Cluster Mediated Surface Topologies
Authors: Wirth B. D. , Odette G. R. , Maroudas D. , Lucas G. E.
Published: April 2011

Molecular statics and molecular dynamics (MD) simulations based on the embedded atom method (EAM) are used to model the energetics and mobility of tightly bound clusters of selfinterstitial atoms (SIA) in bcc iron. Single and clusters of SIA are directly produced in displacement cascades generated in neutron and high energy charged particle beam irradiations. The clusters are composed of <111> split dumbbells and crowdions with binding energies in excess of 1 eV. Clusters containing specified ‘magic’ numbers of SIA can be described as perfect prismatic dislocation loops with Burgers vector b=a/2<111>; however, the core region is extended compared to an isolated edge dislocation and the loops are intrinsically kinked. As the loops grow, SIA occupy successive edge rows, with minimum energy cusps found at the magic numbers corresponding to filled hexagonal shells. The SIA clusters are highly mobile, undergoing rapid one-dimensional diffusion on their glide prism. The activation energy for glide diffusion is less than 0.3 eV and the corresponding mechanism is related to easy motion of the intrinsic kinks. The kinks, which are preferentially observed on the hexagonal corners, propagate around the loop periphery, resulting in stochastic increments of glide. Image drift forces bias cluster motion near free surfaces and the consequential annihilation of clusters at the surface produces islands bounded by hexagonal ledges. The potential effect of islands modifying surface topology is also discussed. While these simulations are specific to iron, similar behavior is expected for other cubic alloys.
Arc Suppression and Defect Reduction in Semiconductor Metallization
Authors: Li Xiangbing , Loo David , Stimson Brad , Seamons Scott , Narasimhan Murali
Published: April 2011

Suppression of arcing between the target and plasma during PVD is a key issue for defect reduction, yield improvement and high quality metallization in microelectronics manufacturing. An integrated mini sparcle product has been designed for Endura HP PVD™ sputtering sources. Characteristics of arcing and mechanisms for suppression are discussed here. Process characterization with Ti, TiN and Al sputtering proves that the arc suppression unit has little adverse impact on film properties. The uniformity of reactive sputtered TiN is improved with arc suppression. Marathon evaluation indicates significant reduction in TiN defect and Interconnect metal stack defect. The study of the application for a wide variety of materials (Al, Ti, TiN, SiW, Si) establishes a correlation between deposition rate loss and sputtering power and this relation is found to be almost independent of the materials sputtered. The impact on throughput for typical metal stack is also presented in this paper.
Growth and Luminescence Properties of III-N:Er Materials Doped During Chemical Beam Epitaxy
Authors: Mackenzie J. D. , Abernathy C. R. , Pearton S. J. , Hömmerich U. , Seo J. T. , Ren F. , Wilson R. G. , Chen Paul , Zavada J. M.
Published: April 2011

The incorporation and optical activation of Er in III-N optically-pumped and electroluminescent structures has been studied. For the first time, strong Er3+-related photoluminescence (PL) was measured at 300K for GaN:Er doped during growth on c-plane Al2O3 and Si. Also, room temperature electroluminescence was observed for simple GaN:Er structures on Si. Experiments to evaluate the effects C and 0 on the optical activity of Er indicated that these impurities enhance Er PL and EL in GaN. GaN films doped with Er to a concentration of 3 ×1018 cm−3 with [0] ∼ 1020 cm−3 and [C] ∼1021 cm−3 luminesce at 1.54 pim with an intensity ∼2 orders of magnitude greater than films with oxygen and carbon backgrounds of less than 1019 cm−3. Implantation and activation annealing was also shown to increase Er3+ signal in p(Mg)-i(Er)-n(Si) structures where C and 0 implant profiles were made to coincide with the Er-doped layers. The thermal PL quenching behavior was also markedly different for samples of varying 0 and C content. Er3+ photoluminescence from Gan:Er/Al2O3 samples with high O and C concentrations quenched by only 10% between 15 K and 300 K while the integrated PL signal from samples with lower [O] and [C] quenched ∼85% over the same temperature range.
Comparison of Oxygen and Hydrogen Gettering at High-Temperature Post-Implantation Annealing of Hydrogen and Helium Implanted Czochralski Silicon
Authors: Job R. , Fahrner W. R. , Ivanov A. I. , Palmetshofer L. , Ulyashin A. G
Published: April 2011

P-type Czochralski (Cz) Si was implanted with H (180 keV, 2.7.1016 cm−2) or He (300 keV, 1.1016 cm−2) ions. The gettering of O and H atoms by the buried implantation damage layers during annealing up to 4 hours (1000°C in H2 or N2 ambient) was studied by secondary ion mass spectroscopy (SIMS) and spreading resistance probe (SRP) measurements. Buried defect layers act as good getter centers for O and H atoms at appropriate heat treatments. The enhanced gettering of O atoms in H implanted Cz Si (as compared to the gettering of O in He implanted samples) as well as the enhanced gettering of O during annealing in H2 flow (as compared to N2 ambient) can be explained by a hydrogen enhanced O diffusion towards the defect layers. According to a strong accumulation of O at the buried damage layers and near the surface some anomalies of the SRP profiles can be observed after post-implantation annealing.
Interface Defects and Rectification Properties of Heterojunctions Between Solid C60 and GaAs
Authors: Chen K.M. , Zhang Y.X. , Jin S.X. , Wu K. , Liu H.F.
Published: April 2011

Solid C60/GaAs contacts were fabricated by growing solid C60 films on both n-type and p-type GaAs(100) substrates through vacuum deposition. The electronic states at C60/GaAs interfaces were studied. Both C60/n-GaAs and C60/p-GaAs contacts were found to be strong rectification junctions with a rectifying ratio higher than 106 at a bias of ± 1.OV. Two distinct traps were also observed at the C60/GaAs interfaces with deep level transient spectroscopy (DLTS); one is the electron trap at 0.35 eV below the GaAs conduction band and the other is a hole trap at 0.45 eV above the GaAs valence band.
Donor Neutralization by Fluorine Containing Plasmas in Si -Doped N -Type GaAs Crystals
Authors: Wada J. , Matsukura Y. , Ogihara T. , Furukawa Y. , Tanaka H.
Published: April 2011

CF4, SF6 and CF 4/O2 plasma-induced damage in silicon-doped n-type GaAs crystals have been investigated by using Hall measurements, and SIMS analysis. We observed that the carrier density degraded with post annealing after plasma exposure. The degree of deactivation of carrier density with post annealing was strongly dependent on the plasma chemistries and the self-bias Vdc of the plasmas. From SIMS analysis, fluorine contamination was observed in the surface region of GaAs crystals after CF4 plasma exposure. The internal diffusion of fluorine atoms and the localization of fluorine atoms in n-type GaAs layers were observed after post annealing at 400°C. From these results, we proposed a mechanism of plasma induced damage in which internally diffused fluorine atoms neutralize the donor silicon by forminq a Si-F bond. We determined the effective diffusion coefficient of fluorine in GaAs as 1.5 × 10−11 cm2/s (at 400°C).
Injection-Level Spectroscopy of Metal Impurities in Silicon
Authors: Ahrenkiel R.K. , Johnston S.
Published: April 2011

Using a modified photoconductive eddy-current technique, excess carrier decay can be measured and used to identify the specific defect dominating recombination. As the dynamic range of the measurement system is linear over about three orders of magnitude, the injection-level spectroscopy technique can be performed in a single measurement for rapid defect identification.
Picosecond time-resolved studies of defect-related recombination in high resistivity CdTe, CdZnTe
Authors: Ghislotti G. , Ielmini D. , Riedo E. , Martinelli M.
Published: April 2011

High resistivity CdTe:In and CdZnTe samples were studied by means of continuos and picosecond time-resolved photoluminescence (PL). Detected PL signal is affected by non-radiative trapping into defects, while radiative recombination has an excitonic character. Time-resolved PL can be described by two lifetimes: the first (30-60 ps) takes into account fast non radiative recombination, the second in the range 200-300 ps can be related to exciton decay.
A Molecular Dynamics Study of Step Motions on Vicinal Silicon Surfaces
Authors: Mazzone A.M.
Published: April 2011

A Molecular Dynamics simulation method has been applied to the motion of steps on a surface vicinal to {100}in Si. Undulation of the steps and ‘kissing sites’ are observed to arise from thermal fluctuations at 300°K. The dependence of the characteristic energy of these configurations on the terrace width complies with a free fermion picture which also includes dipolar and nearest neighbours interactions.
On the Shear Strength and Mixed-mode Fracture Toughness of a Lead-Tin and a Tin-Silver Solder
Authors: Manoharan M. , SIOW K. S. , WEISER M. W.
Published: April 2011

The increasing demands on solder joints have made it imperative that they perform not only their traditional role of electrical connection but also possess good mechanical integrity. One such key mechanical property is the shear strength of the solder. A number of specimen geometries can be used to evaluate the shear strength of solders, each with its advantages and limitations. This study uses a modified double lap shear geometry to measure the shear strength of the solders as a function of strain rate. It is ahown that the shear strength measured this way is truly reflective of the complex composite formed by the copper, solder and intermetallics and may be more representative of actual conditions of use rather than measurements of the shear strengths of the bulk solder. The study also uses a modified compact tension specimen to measure the fracture of the solder under combined tensile-shear loading conditions. It is shown that the solder fracture under these conditions follows the general principles of a mixed-mode fracture mechanism map.
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

Polymer 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

An 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

Due 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

The 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

The 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

The 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

The 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

X-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

Garnet 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

Co-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

The 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

The 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

A 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

The 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

A 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

The 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

A 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

A 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

Rapid 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.