bluuebunny/crossref_metadata_2025 huggingface dataset:
Methods of Analysis for Protein Dynamics in Living Cells Based on Protein Splicing
Authors: Ozawa Takeaki
Published: May 2005

Protein–protein interactions and protein localization have key roles in many essential biological processes in living cells. We have developed novel reporter proteins with general applicability for detecting the biological processes in living cells and animals. The principle is based on reconstitution of split reporter proteins by protein splicing, which involves a self-catalyzed excision of a protein splicing element, intein, from flanking polypeptide sequences, exteins, leading to ligation of the flanking exteins by a peptide bond. As the exteins, N- and C-terminal halves of rationally-split green fluorescent protein (GFP) or split bioluminescent proteins were used. The N- and C-terminal reporters connected respectively with a pair of interacting proteins worked as indicators for protein–protein interactions in bacteria and mammalian cells. The split GFP reporter provided a genetic method for identifying mitochondrial proteins from large-scale complementary DNA libraries. The split bioluminescent reporter enabled high-throughput sensing and noninvasive imaging of nuclear transport of target proteins in living animals. This basic concept of split reporter reconstitution by protein splicing provides a wide variety of applications not only for fundamental biological studies, but also for assay and screening methods for chemicals that inhibit or facilitate the biological processes in living cells.
Regioselective Preparation of N-Substituted 3,5-Diamino-1,2,4-oxadiazoles
Authors: Suyama Takayuki , Suzuki Noriyuki , Nishimura Masami , Saitoh Yuka , Ohkoshi Hiroyuki , Yamaguchi Jun-ichi
Published: May 2005

Regioselective preparation of 3,5-diamino-1,2,4-oxadiazoles which have a substituent on one or the other amino group has been developed. When 1-substituted 3-cyano-2-ethylisourea (2) was allowed to react with hydroxylamine under basic conditions, 5-amino-3-(substituted amino)-1,2,4-oxadiazole (3) was obtained in good yield. On the other hand, 3-amino-5-(substituted amino)-1,2,4-oxadiazoles (4), a regioisomer of 3, could be synthesized by the reaction of N,O-bis(trimethylsilyl)hydroxylamine (9) with 2 or 1-substituted 3-cyano-2-methylisothiourea (1) and subsequent alcoholysis.
Synthesis of Benzazetine Derivatives by Intramolecular Iodoamination of o-(Acylamino)styrene Derivatives
Authors: Kobayashi Kazuhiro , Miyamoto Kazuna , Morikawa Osamu , Konishi Hisatoshi
Published: May 2005

The iodoamination of o-(acylamino)styrene derivatives using iodine and sodium hydrogencarbonate, producing 7-acyl-8-iodomethylbicyclo[4.2.0]-7-azaoct-1,3,5-triene [1-acyl-2-(iodomethyl)benzazetine] derivatives, is described. Replacement of the iodo moiety by hydrogen or phenylthio group is also reported.
A Preparation of Alkyl or Alkenyl N,N-Dimethylchalcogenocarbamates and Their One-Step Conversion into Symmetrical Dialkyl or Dialkenyl Dichalcogenides
Authors: Shimada Kazuaki , Oikawa Seiji , Nakamura Hidenori , Moro-oka Akiko , Kikuchi Miho , Maruyama Akiko , Suzuki Takahiro , Kogawa Hisashi , Inoue Yukiko , Gong Yaling , Aoyagi Shigenobu , Takikawa Yuji
Published: May 2005

Alkyl or alkenyl N,N-dimethylchalcogenocarbamates were easily prepared by a stepwise treatment of bis(N,N-dimethylcarbamoyl) dichalcogenides with NaH or NaBH4, followed by various alkylating agents or acetylenes bearing electron-withdrawing substituents. The one-step conversion of alkyl or alkenyl N,N-dimethylselenocarbamates or N,N-dimethyltellurocarbamates into the corresponding symmetrical dialkyl or dialkenyl dichalcogenides was also achieved efficiently by treating with SnCl4.
Enantioselective Protonation of a Lithium Enolate Derived from 2-Methyl-1-tetralone Using Chiral Sulfonamides
Authors: Coumbarides Gregory S , Eames Jason , Scheuermann J Erik W , Sibbons Kevin F , Suggate Michael J , Watkinson Michael
Published: May 2005

The synthesis of enantiomerically enriched (R)-2-methyl-1-tetralone (1) with 77% e.e. was achieved through protonation of its lithium enolate (3) using a C2-symmetric tris-sulfonamide (6) as an internal chiral proton source. Access to the complementary (S)-enantiomer 1 with 33% e.e. was achieved using a related C2-symmetric bis-sulfonamide (9) as the chiral proton source.
Rotational Isomerism Involving an Acetylenic Carbon VI. Syntheses, Structures, and Dynamic Stereochemistry of Bis(1-phenyl-9-anthryl)ethynes: Highly Restricted Rotation about Acetylenic Axis in Acyclic Diarylethynes
Authors: Makino Toshiaki , Toyota Shinji
Published: May 2005

Some sterically congested di(9-anthryl)ethynes with substituted phenyl groups (4-Me, 4-iPr, 4-tBu, 3-iPr, 3,5-iPr2) at the 1-positions were synthesized by the Stille coupling of the corresponding triflate and bis(tributylstannyl)ethyne to realize the restricted rotation of the acetylenic axis in diarylethyne derivatives. In the X-ray structure of the 4-Me compound, the two 9-anthryl groups were staggered about the acetylenic axis by ca. 60°. The dynamic NMR study of the iPr substituted compounds afforded the kinetic data of the two independent processes: the faster and slower processes were assigned to the rotation about the acetylenic axis (ΔG≠ 45–51 kJ mol−1) and the rotation of the phenyl groups (ΔG≠ ca. 75 kJ mol−1), respectively, from the details of the lineshape changes. The observed barriers to the rotation about the acetylenic axis are rather high for acyclic diarylethynes, being attributed to the severe steric interactions between the 1-phenyl groups and the rigid di(9-anthryl)ethyne framework in the transition state. The mechanism of the dynamic stereochemistry and the substituent effect on the rotational barrier are discussed on the basis of the kinetic data and the molecular structures.
The Formation of Periodicity within the Pore Walls of Mesoporous Organosilica by Post-Synthesis Treatment
Authors: Goto Yasutomo , Okamoto Kentaro , Inagaki Shinji
Published: May 2005

The molecular scale periodicity within the pore walls of amorphous mesoporous phenylene-silicas, derived using triblock copolymers under acidic conditions, was generated by the post-synthesis treatment with alkaline solution. Usually, acid conditions are not favorable for the formation of periodic arrangement of phenylene-silica moieties. The treatment with alkaline solution at 363–373 K facilitated the restructuring of phenylene-silica moieties and resulted in the formation of periodic structure within the pore walls. The treatment also enlarged the pore size of mesoporous phenylene-silica from 5.4 to 12.4 nm. Such a material with large pore size and molecular periodicity should have several advantages in potential applications, particularly in the catalysis for relatively large molecules.
High Rate in situ YBa2Cu3O7 Film Growth Assisted by Liquid Phase
Authors: Ohnishi T. , Huh J-U. , Hammond R.H. , Jo W.
Published: May 2005

High-rate (10 nm/s) in situ YBa2Cu3O7 (YBCO) film growth was demonstrated by molecular beam epitaxy with electron beam co-evaporation at a system pressure of approximately 5 × 10-5 Torr. To explain the phase stability observed, it is suggested that activated oxygen is generated in the process. Growth of very good YBCO, with a Jc of more than 2 MA/cm2, is possible at this very high rate because the growth is in a liquid (Ba–Cu–O), which forms along with the YBCO epitaxy. This liquid seems essential for high Jc-YBCO film growth at very high in situ growth rates and may be essential for all high-rate processes, including postanneal ex situ processes.
Novel Critical Temperature Resistor of Sintered Ni–Fe–O Nanosized Powders
Authors: Suematsu H. , Ishizaka K. , Kinemuchi Y. , Suzuki T. , Jiang W. , Yatsui K.
Published: May 2005

Nanosized powders of Ni–Fe–O were synthesized by a pulsed wire discharge method and sintered at 600 °C for 1 h in air. Abrupt electrical resistivity changes were observed in the temperature dependence of resistivity for the sintered Ni–Fe–O powders above 203 °C. Similar resistivity curves, which had been observed in V–O samples and had been used for the critical temperature resistors, had never been reported in Ni–Fe–O samples. Possible mechanisms to explain the resistivity change in NiFe2O4, including order-disorder transition, semiconductor-metal transition, and surface spin pinning, are discussed.
Mechanical Properties and Fracture Characteristics of Zr-Based Bulk Metallic Glass Composites Containing Carbon Nanotube Addition
Authors: Bian Zan , Zhang Tao , Kato Hidemi , Hasegawa Masashi , Inoue Akihisa
Published: May 2005

Mechanical properties and fracture characteristics of Zr-based bulk metallic glass (BMG) composites containing carbon nanotube (CNT) addition were investigated in detail. The interfacial reaction between the added CNTs and the glass matrix causes the formation of some V-shape nicks on the residual CNTs. These nicks have significant effect on the mechanical properties and fracture modes of the BMG composites. The compressive fracture strength increases with increasing the volume fraction of CNT addition at first, and starts to decrease gradually when the volume fraction of CNT addition is more than 5.0%. The fracture modes of the BMG composites also change from typical shear flow deformation behavior to completely embrittling fracture gradually. The V-shape nicks originating from the interfacial reaction are responsible for the decrease of fracture strength and the variation of fracture modes.
Direct Preparation of Nonagglomerated Indium Tin Oxide Nanoparticles using Various Spray Pyrolysis Methods
Authors: Itoh Yoshifumi , Abdullah Mikrajuddin , Okuyama Kikuo
Published: May 2005

Indium tin oxide particles were prepared using three different spray synthetic techniques: conventional, salt-assisted, and low pressure. Optimum conditions for the preparation of small size, nonagglomerated particles were investigated for these three methods. The use of the conventional spray pyrolysis method resulted in only larger particles (submicrometer order). Salt-assisted spray pyrolysis (SASP) and low-pressure spray pyrolysis (LPSP) produced highly crystalline, dense, homogeneous, and nearly nonagglomerated nanoparticles that were less than 25 nm in size. The size of the particles was in the range 12–24 nm for the SASP method and 8–14 nm for the LPSP method. In addition, the LPSP method led to the production of single nanometer-size multicomponent particles in a single step with less heating time without the need for any post heat treatment and additives.
Transmission Electron Microscopy and High-Resolution Transmission Electron Microscopy Study of Nanostructure and Metastable Phase Evolution in Pulsed-Laser-Ablation–Deposited Ti–Si Thin Film
Authors: Bysakh S. , Mitsuishi K. , Song M. , Furuya K. , Chattopadhyay K.
Published: May 2005

Thin films with a nominal composition close to Ti62.5Si37.5 were deposited on NaCl substrate at room temperature by pulsed laser ablation to study the evolution of the intermetallic compound Ti5Si3 using a combination of high-resolution and in situ transmission electron microscopy. The as-deposited amorphous films contain Ti-rich clusters, which influence the phase evolution and the decomposition behavior of the amorphous film. These clusters influence the nucleation of a metastable fcc Ti solid solution (ao = 0.433 nm) with composition richer in Ti than Ti62.5Si37.5 as the first phase to crystallize at 773 K. The Ti5Si3 nanocrystals form later, and even at 1073 K they coexist with fine fcc Ti-rich nanocrystals. Subsequent Ar+ ion-milling of the crystallized film results in a loss of silicon. The composition change leads to the dissolution of the Ti5Si3 nanocrystals and evolution of a new metastable Ti-rich fcc phase (ao= 0.408 nm).
Polymeric Composites Tailored by Electric Field
Authors: Kim GeunHyung , Shkel Yuri M.
Published: May 2005

A solid composite of desirable microstructure can be produced by curing a liquid polymeric suspension in an electric field. Redistribution effect of the field-induced forces exceeds that of centrifugation, which is frequently employed to manufacture functionally graded materials. Moreover, unlike centrifugational sedimentation, the current approach can electrically rearrange the inclusions in targeted areas. The electric field can be employed to produce a composite having uniformly oriented structure or only modify the material in selected regions. Field-aided technology enables polymeric composites to be locally micro-tailored for a given application. Moreover, materials of literally any composition can be manipulated. In this article we present testing results for compositions of graphite and ceramic particles as well as glass fibers in epoxy. Electrical and rheological interactions of inclusions in a liquid epoxy are discussed. Measurements of tensile modulus and ultimate strength of epoxy composites having different microstructure of 10 vol% graphite, ceramic particles and glass fiber are presented.
Molecular-Dynamics Analysis of Interfacial Diffusion Between High-Permittivity Gate Dielectrics And Silicon Substrates
Authors: Iwasaki T.
Published: May 2005

Interfacial oxygen diffusion from high-permittivity gate dielectrics (ZrO2 and HfO2) into Si substrates in ultra-large-scale integrated circuits must be suppressed to prevent the formation of interfacial layers between the gate dielectrics and the Si substrates. Oxygen diffusion was analyzed by using a molecular dynamics technique that includes many-body interactions and charge transfer between different elements. The analysis results showed that the addition of Ti is effective in suppressing interfacial oxygen diffusion. The results also showed that the diffusion at the ZrO2/Si(111) and HfO2/Si(111) interfaces is much more suppressed than the diffusion at the ZrO2/Si(001) and HfO2/Si(001) interfaces.
Study of Crystal Yb3+:Ca3Y2(BO3)4
Authors: Wang Yan , Tu Chaoyang , Huang Changcang , You Zhenyu
Published: May 2005

Yb3+-doped single-crystal Ca3Y2(BO3)4 with dimension φ20 × 55 mm was grown by the Czochralski method. The structure of it was determined by x-ray diffraction. It belongs to the orthorhombic system, space group Pnma, with the following parameters: a= 7.1690(4), b = 15.4758(8), c = 8.5587(6) Å, V = 949.55(10)Å3, Mr = 537.51, Z = 2, Dc = 3.8 g/cm3, (MoKa) = 0.71073 Å, F(000) = 508, μ = 6.927 mm-1, final R = 0.0670, and wR = 0.1542 for 2975 independent reflections. The structure of Yb:Ca3Y2(BO3)4 is made up of three set of M-oxygen distorted polyhedrons, and three set of BO3 planar triangles. Ca2+ and Y3+ ions occupy three M sites statistically. Yb3+ ions substitute Y3+ ions to enter these three lattices. The adsorption and emission spectra were measured. It exhibits a broad absorption band ranging from 850 to 1000 nm in the absorption spectrum, which is well matched with the emission wavelength of a laser diode. A broad emission spectrum ranging from 927.95 to 1102.7 nm was observed under the excitation of 895 nm.
Hydrophilic Co–Pt Alloy Nanoparticles: Synthesis, Characterization, and Perspectives
Authors: Bourlinos Athanasios B. , Panagiotopoulos Ioannis , Niarchos Dimitrios , Petridis Dimitrios
Published: May 2005

Hydrophilic Co–Pt alloy nanoparticles nearing the equiatomic ratio and dispersedin water-soluble sodium carboxymethyl cellulose were synthesized by the aqueous reduction of CoCl2⋅6H2O and [Pt(NH3)4]Cl2⋅H2O with NaBH4 in presence of the cellulosic derivative. The as-received Co–Pt nanoparticles in the cellulosic matrix possess a disordered fcc structure that, upon calcination under an Ar atmosphereand carbonization of the cellulosic mantle of the particles, transformed to an ordered fcc phase. Both as-synthesized and calcined samples are magnetically soft at room temperature and exhibit a strong magnetic response when a magnetic field is applied. On account of the chemical composition of the carboxymethyl cellulose, the coated Co–Pt nanoparticles are easily soluble in water in high concentrations and exhibit interesting ion-exchange properties.
Analysis of Phase Transformation Kinetics by Intrinsic Stress Evolutions During the Isothermal Aging of Amorphous Ni(P) and Sn/Ni(P) Films
Authors: Song J.Y. , Yu Jin , Lee T.Y.
Published: May 2005

The kinetics for the crystallization of amorphous Ni(P) films and the formation of intermetallic compounds in Sn/Ni(P) films during isothermal aging treatment were studied with in situ intrinsic stress measurements. The intrinsic stress changes from crystallization were about 200 and 150 MPa for Ni(14P) and Ni(11.7P) films, respectively, and according to Johnson–Mehl–Avrami analysis, the Avrami exponents were about 3.6 ± 0.46 and 4.2 ± 0.39, and the activation energies were 242 and240 kJ/mol, respectively, for the crystallization of Ni(14P) and Ni(11.7P) films. The stress due to the formation of intermetallic compounds such as Ni3Sn4 and Ni3P in Sn/Ni(11.7P) films was about 320 MPa. Application of in situ stress measurementsto the empirical growth model during isothermal phase transformation of Sn/Ni(P) showed that the intermetallic compounds growth was interface reaction-controlled (n = 0.91 ± 0.08) in the early stage and then became diffusion-controlled (n =0.38 ± 0.01), and the activation energy was about 35.9 kJ/mol.
Oxygen Permeability of Ferroelectric Thin Film Top Electrodes and Its Effect on Detectable Fatigue Cycling-Induced Oxygen Isotope Motion
Authors: Schloss Lawrence F. , Kim Hyoungsub , McIntyre Paul C.
Published: May 2005

We investigated the discrepancy between the significant 18O isotope motion observed after bipolar voltage cycling used to induce ferroelectric fatigue in unannealed Pt/Pb(Zr,Ti)O3/Ir (PZT) capacitors and the lack of any observable oxygen tracer motion in annealed capacitors. We found that while unannealed Pt electrodes are permeable to oxygen, annealed Pt electrodes are oxygen impermeable. Further, when the initial oxygen tracer profile does not vary strongly with depth, the ability to detect oxygen motion during fatigue voltage cycling depends critically on the oxygen permeability of the capacitor’s top electrode. Our results indicate that oxygen exchange between the PZT film and external oxygen sources and sinks during voltage cycling is not necessary for ferroelectric fatigue to be manifest. In addition, studies of the dependence of ferroelectric materials properties on ambient gases should be accompanied by analysis of the permeability of exposed surfaces to the gases of interest.
Elimination of Au-embrittlement in solder joints on Au/Ni metallization
Authors: Alam M.O. , Chan Y.C. , Tu K.N.
Published: May 2005

Systematic experimental work was carried out to understand the mechanism of Au diffusion to the solder interface, and a novel method was proposed to eliminate Au embrittlement by circumventing the continuous layer of (Au,Ni)Sn4 at the solder interface. Contrary to the usual expectation, it was determined that utilization of a very thin Ni metallization in the Au/Ni/Cu under bump metallization (UBM) was an effective means of maintaining mechanical integrity of the solder joint. It was found that the out-diffusion of Cu during the aging period changes the chemistry and morphology of the intermetallic compounds at the interface.
Distortion of the oxygen sublattice in pure cubic-ZrO2
Authors: Wang C.M. , Azad S. , Thevuthasan S. , Shutthanandan V. , McCready D.E. , Peden C.H.F.
Published: May 2005

Multilayer films of pure ZrO2 and CeO2 were grown using molecular beam epitaxy on a yttria-stabilized zirconia (YSZ) substrate. Distinctive forbidden diffraction spots of (odd, odd, even) type were observed on the selected-area electron-diffraction patterns of the film. Dark-field imaging clearly revealed that these forbidden diffraction spots were solely due to the ZrO2 layers. Comparison of the electron diffraction pattern with that simulated by dynamical calculations suggest that the pure ZrO2 layers possess a cubic structure of space with the group P4 3m oxygen sublattice being displaced diagonally, rather than along the c axis as suggested for YSZ. Our results further suggest that the displacement of the oxygen from the ideal (¼, ¼, ¼) position might have been introduced during the film growth process.
Electron microscopy characterization of Ba(Cd1/3Ta2/3)O3 microwave dielectrics with boron additive
Authors: Sun J. , Liu Shaojun , Newman N. , McCartney M.R. , Smith David. J.
Published: May 2005

The microstructure of Ba(Cd1/3Ta2/3)O3 ceramics with boron additive was investigated by high-resolution and analytical electron microscopy. Superlattice reflections were present at positions of (h ± 1/3, k ± 1/3, l ± 1/3) away from the fundamental reflections in the [110] zone diffraction pattern for the pseudocubic perovskite unit cell. Lattice images showed a well-ordered structure with hexagonal symmetry. No boron segregation and amorphous phase was observed along grain boundaries. An amorphous phase rich in boron-oxide was observed to form pockets partially penetrating along multiple grain junctions.
Hardness, elasticity, and fracture toughness of polycrystalline spinel germanium nitride and tin nitride
Authors: Shemkunas M.P. , Petuskey W.T. , Chizmeshya A.V.G. , Leinenweber K. , Wolf G.H.
Published: May 2005

The hardness, elastic moduli, and fracture toughness of the spinel phases, γ–Ge3N4and γ–Sn3N4, were determined using indentation data and theoretical calculations. Measurements were performed on polycrystalline specimens using the technique of nanoindentation to determine the reduced moduli and hardnesses from the unloading portion of the indent curves. Reduced moduli of γ–Ge3N4and γ–Sn3N4were found to be 295 and 167 GPa, respectively. The nanohardnesses of γ–Ge3N4and γ–Sn3N4were found to be 31 and 13 GPa, respectively. The shear moduliG0and Poisson’s ratios ν0were derived using theoretical bulk moduliB0obtained from density-functional theory calculations. The calculated values wereB0= 260 GPa,G0= 146 GPa, ν0= 0.26 for γ–Ge3N4, andB0= 186 GPa,G0= 64 GPa, ν0= 0.34 for γ–Sn3N4. Fracture toughness was estimated by direct measurement of radial cracks emanating from Vickers microindents. It was determined that for γ–Ge3N4,KIC= 2.3 MPa(m)1/2, while for γ–Sn3N4,KIC= 1.4 MPa(m).1/2
High-temperature properties of a silicon nitride/boron nitride nanocomposite
Authors: Kusunose Takafumi , Sung Rak-Joo , Sekino Tohru , Sakaguchi Shuji , Niihara Koichi
Published: May 2005

Hexagonal graphitic BN (h-BN) is interesting as a second phase for high-temperature structural ceramics because it has the same crystal structure as graphite, for which fracture strength and Young’s modulus increase with increased temperature. In this study, high-temperature mechanical properties of Si3N4/BN nanocomposite were evaluated to clarify the effect of fine h-BN particles at elevated temperatures. As a result, we found that high-temperature strength and hardness of the nanocomposite were maintained up to high temperatures; also, its Young’s modulus increased gradually, concomitant with elevated temperatures up to 1400 °C. Finally, these properties were compared with those of monolithic Si3N4and Si3N4/BN microcomposite.
Microstructural, mechanical, and electrical characteristics of alumina-reinforced ytterbia-stabilized cubic zirconia-based composites
Authors: Wada Masashi , Sekino Tohru , Kusunose Takafumi , Nakayama Tadachika , Niihara Koichi
Published: May 2005

Al2O3-dispersed Yb2O3-stabilized cubic-ZrO2 (YbSZ) composites are fabricated by pressureless sintering of composite powders to obtain fine and homogeneous microstructures by the solution chemistry route. Al2O3 particles are deposited on ZrO2 powders by the precipitation of aluminum nitrate followed by calcination in air. The sinterability of the composites was affected by the calcination temperature. Microstructures of the sintered bodies are dependent on the Al2O3 content. For the5 vol% Al2O3-dispersed composite, fine Al2O3 particles were mainly located insidethe grains of zirconia, whereas relatively large Al2O3 particles almost dispersed at the grain boundaries when the Al2O3 content was increased. The grain growth of YbSZ was suppressed by the Al2O3 addition, and the refinement of the matrix grain improved the fracture strength of YbSZ. The YbSZ and YbSZ/Al2O3 composites exhibited almost similar ionic conductivity at high temperatures of around 1000 °C.
Preparation of (Pb,Ba)TiO3 powders and highly oriented thin films by a sol-gel process
Authors: Boland Stacey W. , Pillai Suresh C. , Yang Wein-Duo , Haile Sossina M.
Published: May 2005

Solid solution Pb1-xBaxTiO3, with particular emphasis on Pb0.5Ba0.5TiO3, was prepared using a sol-gel process incorporating lead acetate trihydrate, barium acetate, and titanium isopropoxide as precursors, acetylacetone (2,4 pentanedione) as a chelating agent, and ethylene glycol as a solvent. The synthesis procedure was optimized by systematically varying acetylacetone: Ti and H2O:Ti molar ratios and calcination temperature. The resulting effects on sol and powder properties were studied using thermogravimetric analysis/differential scanning calorimetry, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and x-ray diffraction (XRD). Crystallization of the perovskite structure occurred at a temperature as low as 450 °C. Thin films were prepared by spin coating on (100) MgO. Pyrolysis temperature and heating rate were varied, and the resultant film properties investigated using field-emission scanning electron microscopy, atomic force microscopy, and XRD. Under optimized conditions, highly oriented films were obtained at a crystallization temperature of 600 °C.
Quantitative relationships between boehmite and γ-alumina crystallite sizes
Authors: Sánchez-Valente J. , Hernández-Beltrán F. , Guzman-Castillo M.L. , Fripiat J.J. , Bokhimi X.
Published: May 2005

Nanocrystalline boehmite obtained by limited hydrolysis of aluminum tri-sec-butoxide or aluminum chloride was aged under different conditions before being calcined above the dehydroxylation temperature. When aging was carried out under hydrothermal conditions, the condensation of the structural units obeyed a first-order kinetic law with apparent activation energy of 12.2 kcal/mol. Under dehydroxylation conditions, the boehmite fragmentation is accounted for by a simple power law that links its volume to that of the resulting γ-alumina. The main variable is the volatile compounds content (water for instance) in the fresh sample. In terms of texture, a better organization of the initial nanoparticles in the boehmite means a lower surface area and larger pore diameter in the corresponding γ-alumina.
Synthesis, characterization, and phase stability of ultrafine TiO2 nanoparticles by pulsed laser ablation in liquid media
Authors: Liang Changhao , Shimizu Yoshiki , Sasaki Takeshi , Koshizaki Naoto
Published: May 2005

We synthesized ultrafine TiO2 nanoparticles by pulsed laser ablation of a titanium target immersed in an aqueous solution of surfactant sodium dodecyl sulfate (SDS) or deionized water. The surfactant concentration dependence of TiO2 nanocrystal formation was systematically investigated by various characterization techniques. The maximum amount of ultrafine anatase nanocrystalline particles (with mean size of 3 nm in diameter) was obtained in an aqueous solution of 0.01 M SDS. A probable formation process was proposed based on the laser-induced reactive quenching and surfactant-mediated growth. The phase transformation and particle growth of as-prepared products were also investigated by heat treatment up to 500 °C. Single-phase anatase nanoparticles with a mean size of 8 nm were obtained by heat treatment of samples prepared in water or in a 0.01 M SDS solution. Particle size did not substantially increase through annealing, probably due to the relatively homogeneous size distribution and crystallinity of as-prepared titania nanoparticles.
Ignition mechanism of mechanically activated Me–Si(Me = Ti, Nb, Mo) mixtures
Authors: Anselmi-Tamburini U. , Maglia F. , Doppiu S. , Monagheddu M. , Cocco G. , Munir Z.A.
Published: May 2005

The influence of mechanical activation on the characteristics and mechanism of ignition of self-propagating high-temperature synthesis processes of different silicides in the systems Me–Si (Me =Ti, Nb, Mo) was investigated. The results show that mechanical activation does not alter the mechanism involved but influences significantly the ignition characteristics. The influence, however, strongly depends on the stoichiometry of the mixtures. The composition Ti:Si = 1:2 shows the largest influence, with the ignition temperatures decreasing from 1400 °C for unmilled powders to about 600 °C for powders milled for several hours. The compositionsTi:Si = 5:3, Nb:Si = 1:2 show less pronounced decreases, while the compositionMo:Si = 1:2 shows no decrease. These differences are discussed in terms of the role of microstructure in the reaction mechanism and the different response of the systems to contamination, particularly from oxygen. The results suggest that for these systems self-ignition processes during milling cannot be explained only on the basis of the decrease in the ignition temperature.
Thermodynamic modeling of the Ni–Al–Ga–N system
Authors: Hull B.A. , Mohney S.E. , Liu Z-K.
Published: May 2005

Isothermal sections in the Ni–Al–Ga–N quaternary phase diagram were calculated to provide a greater understanding of interfacial reactions between Ni contacts and AlxGa1−xN. The calculations were performed employing a thermodynamic database of the Ni–Al–Ga–N system that was constructed by combining the six binary systems of the four component system. The model of the Ga–N binary system was created in this work. The models of the Ni–Ga and Ni–Al systems, both of which were taken from the literature, were modified to be compatible with one another. Thermodynamic data and phase boundaries for other binary systems were taken from the literature, as was information on portions of the Al–Ga–N and Ni–Al–Ga phase diagrams. The calculated sections reveal that during reaction between Ni and AlxGa1−xN, Ni is favored to react with the GaN component of the semiconductor alloy, leaving an Al-enriched AlxGa1−xN. These predictions are consistent with a recent analysis of the Ni, Al, and Ga elemental distributions across the interface between a Ni thin film and an Al0.47Ga0.53N epitaxial layer following annealing at 850 °C. Consideration of the thermodynamic driving forces suggests that this may be a general phenomenon existing in other metal–Al–Ga–N systems.
Growth and characterization of gallium nitride nanowires produced on different sol-gel derived catalyst dispersed in titania and polyvinyl alcohol matrix
Authors: Chatterjee A. , Chattopadhyay S. , Hsu C.W. , Shen C.H. , Chen L.C. , Chen C.C. , Chen K.H. , Lee H.Y.
Published: May 2005

Sol-gel derived catalyst systems of cobalt, nickel, and iron were used in the growth of gallium nitride (GaN) nanowires by thermal chemical vapor deposition. A diffusion barrier matrix of titania (TiO2) has been used in which the catalysts were dispersed to have control of the catalyst particle sizes and hence on the size and morphology of the GaN nanowires. This single-step and cost-effective processing of the catalyst bed produced good-quality GaN naowires with comparable structural and optical properties with those previously reported. In a particular case, a stress-induced cubic admixture to the otherwise hexagonal structural symmetry was observed. The samples were characterized by high-resolution scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and cathodo-luminescence studies.
Enthalpy of formation of cubic yttria-stabilized hafnia
Authors: Lee Theresa A. , Navrotsky Alexandra
Published: May 2005

The enthalpy of formation of cubic yttria-stabilized hafnia from monoclinic hafnia and C-type yttria was measured by oxide melt solution calorimetry. The enthalpies of formation fit a function independent of temperature and quadratic in composition. The enthalpies of transition from m-HfO2 and C-type YO1.5, to the cubic fluorite phase are 32.5 ± 1.7 kJ/mol and 38.0 ± 13.4 kJ/mol, respectively. The interaction parameter in the fluorite phase is strongly negative, -155.2 ± 10.2 kJ/mol, suggesting even stronger short range order than in ZrO2–YO1.5. Regular solution theory or any other model assuming random mixing on the cation and /or anion sublattice is not physically reasonable. A more complex solution model should be developed to be consistent with the new calorimetric data and observed phase relations.
Tensile fracture behaviors of solid-state-annealed eutectic SnPb and lead-free solder flip chip bumps
Authors: Jang Jin-Wook , De Silva Ananda P. , Lin Jong-Kai , Frear Darrel R.
Published: May 2005

The tensile fracture behavior for solid-state-annealed eutectic SnPb and lead-free solder flip chip bumps was examined. The annealing temperatures were in the range of 125–170 °C for 500 h. Prior to solid state annealing, the eutectic Sn–37Pb (SnPb) and Sn–0.7Cu (SnCu) solders showed fracture through the bulk solder. Brittle interfacial fracture occurred in the Sn–3.5Ag (SnAg) solder. After solid-state annealing, the fracture behavior changed dramatically. For eutectic SnPb solder, the fracture modes gradually changed from cohesive solder failure to interfacial fracture with increasing annealing temperature. The fracture mode of the SnCu solder showed greater change than the SnPb and SnCu solders. After annealing at 125 °C, the SnAg solder had a ductile taffy pull fracture, but an increase in temperature resulted in brittle interfacial fracture again. The SnCu solder maintained the same ductile taffy pull mode up to170 °C annealing, independent of the under bump metallization (UBM) type. Microstructure analysis showed that the interfacial fracture of the SnPb and SnAg solder bumps was ascribed to Pb-rich layer formation and Ag embrittlement at the interface, respectively. The bulk solder fracture of SnAg annealed at 125 °C appeared to be a transient phenomenon due to the abrupt breakdown of the hard lamella structure. The eutectic SnCu solder bumps had no significant change in the interfacial structure, except for interfacial intermetallic growth.
Structure, bonding, and growth at a metal–organic interface in the weak chemisorption regime: Perylene–Ag(111)
Authors: Eremtchenko M. , Bauer D. , Schaefer J.A. , Tautz F.S.
Published: May 2005

Organic semiconductors on single-crystalline metal surfaces are model systems for injection contacts in organic field-effect transistors (OFET) and light-emitting diodes. They allow us to classify possible metal–organic interaction scenarios and to elucidate general tendencies, which most likely will also be found at metal–organic interfaces in real devices. In this contribution, we report a comprehensive investigation of the interface of perylene, a promising material for OFETs, with the close-packed noble metal surface Ag(111), using high-resolution electron energy loss spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy as surface analytical techniques. The most important findings are: In the monolayer, molecules are oriented flat and form an incommensurate, most probably fluid overlayer. The molecules interact electronically with the substrate and become weakly metallic. Scanning tunneling microscopy reveals a propensity of perylene molecules toward a specific adsorption site on Ag(111), if the influence of intermolecular interactions is inhibited. Film growth at room temperature is similar to Stranski–Krastanov type. Finally, co-planar adsorption of perylene on Ag(111) is metastable, and annealing the monolayer at 420 K leads to a structural transformation of the film. The perylene–Ag(111) interface can therefore be classified as weakly interacting.
Morphology and electrical transport in pentacene films on silylated oxide surfaces
Authors: Shankar Karthik , Jackson Thomas N.
Published: May 2005

A study comparing the morphology and electrical transport properties of pentacene films on underlayers of different self-assembled monolayers (SAMs) is presented. The SAMs studied as underlayers were phenyltrichlorosilane, n-octadecyltrichlorosilane, and t-butyldiphenylchlorosilane. Pentacene thin films were grown by vacuum sublimation on SiO2 surfaces treated with self-assembled monolayers. During deposition, substrates were held at a temperature of 70 °C. The morphologies of the films at different stages of deposition were studied by atomic force microscopy, and the transport properties of the films were characterized by I-V measurements in a simple field-effect transistor (FET) structure. The SAM underlayers strongly influence the film morphology in the first few molecular layers and hence significantly impact the electrical transport in the resulting FETs.
Characterization of white electroluminescent devices fabricated using conjugated polymer blends
Authors: Hwang Do-Hoon , Park Moo-Jin , Kim Suk-Kyung , Lee Nam-Heon , Lee Changhee , Kim Yong-Bae , Shim Hong-Ku
Published: May 2005

We report the characterization of white light emitting devices fabricated using conjugated polymer blends. Blue emissive poly[9,9-bis(4′-n-octyloxyphenyl)fluorene-2,7-diyl-co-10-(2′-ethylhexyl)phenothiazine-3,7-diyl] [poly(BOPF-co-PTZ)] and red emissive poly(2-(2′-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene) (MEH-PPV) were used in the blends. The inefficient energy transfer between these blue and red light emitting polymers (previously deduced from the photoluminscence (PL) spectra of the blend films) enables the production of white light emission through control of the blend ratio. The PL and electroluminescence (EL) emission spectra of the blend systems were found to vary with the blend ratio. The EL devices were fabricated in the indium tin oxide [poly(3,4-ethylenedioxy-thiophene)-poly(styrenesulfonate)] (ITO/PEDOT-PSS)blend/LiF/Al configuration, and white light emission was obtained for one of the tested blend ratios.
Determination of the anisotropic optical properties for perfluorinated vanadyl phthalocyanine thin films
Authors: Gordan O.D. , Friedrich M. , Michaelis W. , Kröger R. , Kampen T. , Schlettwein D. , Zahn D.R.T.
Published: May 2005

Thin films of perfluorinated vanadyl phthalocyanine F16PcVO were prepared by physical vapor deposition in high vacuum on KBr and fused silica substrates. The absorption spectra in the visible region show that the films on different substrates have different structure. The optical constants for F16PcVO films were obtained in the spectral range of 0.7–4.5 eV from the simulation of ellipsometry spectra with an anisotropic uniaxial model. From the difference between the in-plane and out-of-plane components of the extinction coefficient the average tilt angle of the F16PcVO molecular planes with respect to the substrate plane was found to be 56° for fused silica substrates and between 0° and 3° for KBr substrates.
Organic thin film transistors: From theory to real devices
Authors: Horowitz Gilles
Published: May 2005

The organic thin-film transistor (OTFT) is now a mature device that has developed tremendously during the last twenty years. The aim of this paper is to update previous reviews on that matter that have been published in the past. The operating mode of OTFTs is analyzed in view of recent model development. This mainly concerns the distribution of charges in the conducting channel and problems connected with contact resistance. We also delineate what differentiatesn- andp-type semiconductors, and show how this concept differs from what it covers in conventional semiconductors. In the chapter devoted to fabrication techniques, emphasis is placed on solution-based techniques and particularly printing processes. Similarly, soluble materials are given a prominent place in the section dedicated to the performance of devices. Finally, special attention is given to devices at the nanoscale level, which demonstrate a new route toward molecular electronics.
Manufacturing and commercialization issues in organic electronics
Authors: Sheats James R.
Published: May 2005

Techniques for manufacturing organic electronic devices [organic light-emitting diodes (OLEDs), photovoltaic cells, transistors, and solid-state memory] are reviewed and analyzed with respect to cost and market fitness in comparison to competitive approaches based on silicon electronics. The conclusions are (i) OLED displays will be successful using infrastructure largely borrowed from liquid crystal displays, because they provide fundamental customer value not dependent on lower cost; (ii) OLEDs for general lighting and organic–inorganic hybrid photovoltaic cells currently confront substantial barriers in cost and efficiency, but solutions appear feasible and would lead to very large volume businesses; (iii) organic crossbar memories are promising, but require innovations in driver architecture and interconnection; and (iv) organic transistors have not yet found a viable major market, but have great promise for highly customized, small-volume product runs using digital patterning techniques.
High Curie temperature perovskite BiInO3–PbTiO3 ceramics
Authors: Duan Runrun , Speyer Robert F. , Alberta Edward , Shrout Thomas R.
Published: May 2005

The extent of BiInO3 substitution in the perovskite system xBiInO3–(1 - x)PbTiO3 and the corresponding raise in the Curie temperature were investigated using thermal analysis, dielectric measurements, x-ray diffraction, and electron microscopy. Maximum tetragonal perovskite distortion (c/a = 1.082) was obtained for x = 0.20, with a corresponding Curie temperature of 582 °C. Phase-pure tetragonal perovskite was obtained for x ⩽ 0.25. Compound formation after calcining mixed oxide powders resulted in agglomerated cube-shaped tetragonal perovskite particles, which could be fired to 94.7% of theoretical density (TD). Sol-gel fabrication resulted in nano-sized tetragonal or pseudo-cubic perovskite particles, which after two-step firing, resulted in a tetragonal perovskite microstructure at as high as (x = 0.20) 98.1% of TD.
Nickel–tungsten bimetallic sulfide nanostructures of fullerene type
Authors: Olivas A. , Camacho A. , Yacamán M.J. , Fuentes S.
Published: May 2005

Bimetallic NiW sulfide nanostructures of the inorganic fullerene-like (IF-like) type were prepared by a chemical method employing ammonium thiotungstate and nickel nitrate as metal-sulfide precursors followed by sulfidation in H2S/H2 at 400 °C. The nanostructures were grown with a Ni excess, at an atomic ratio R = 0.85 (R = Ni/Ni + W). The x-ray diffraction patterns showed poorly crystalline WS2, WO2, NiS, and Ni9S8 phases. High-resolution electron microscopy micrographs revealed the formation of two fullerene-like nanostructures, nickel sulfide nanoparticles and long nanotubes filled with tungsten suboxide, both coated by several WS2 layers. The surface area of 18 m2/g measured by nitrogen adsorption (BET surface-area) revealed that these materials contained micropororosity.
Stress-induced migration model based on atomic migration
Authors: Aoyagi Minoru
Published: May 2005

Stress-induced migration is one of the problems related to the reliability of metal interconnections in semiconductor devices. This phenomenon generates voids and disconnections in the metal interconnections. The purposes of this work are to establish the stress-induced model based on atomic migration and theoretically clarify the temperature characteristics of void formation and disconnection using the presented model. First, the stress-induced migration model based on atomic migration in which the driving force is the gradient of elastic potential is presented. Next, to clarify the temperature characteristics of stress-induced migration, the presented model is applied to the formation of voids and disconnections and the results of theoretical analyses are compared with experimental results. It was found that the temperature characteristics of the void formation show various patterns depending on the void interval, and the temperature characteristics of the disconnection show various patterns depending on the void interval and void radius. These theoretical results are in agreement with the experimental results.
Photoluminescence properties of yttria-stabilized zirconia single crystal
Authors: Nakajima Hiromitsu , Mori Toshiyuki , Itoh Shinji
Published: May 2005

The photoluminescence (PL) and PL excitation spectra of the single-crystal samples of yttria-stabilized zirconia (YSZ) were measured. We found that the PL spectra of two samples for the 280-nm excitation significantly differ from one another in intensity, although the two samples have the same macrostructure and the same chemical composition. These results indicate that PL spectroscopy is a useful method for studying the microstructure of YSZ. The result of the trace-impurity analysis suggests that the large difference in PL intensity between the two samples can be explained by considering the influence of Nb in the YSZ sample. It seems that Nb in YSZ caused an yttria-associated defect. The broad emission band around 550 nm would be attributed to this defect. These results suggest that information can be obtained from its PL measurement not only on the yttria-associated defect, but also on the trace impurity in the YSZ.
Defect chemistry and transport properties of BaxCe0.85M0.15O3-δ
Authors: Wu J. , Li L.P. , Espinosa W.T.P. , Haile S.M.
Published: May 2005

The site-incorporation mechanism of M3+ dopants into A2+B4+O3 perovskites controls the overall defect chemistry and thus their transport properties. For charge-balance reasons, incorporation onto the A2+-site would require the creation of negatively charged point defects (such as cation vacancies), whereas incorporation onto the B4+-site is accompanied by the generation of positively charged defects, typically oxygen vacancies. Oxygen-vacancy content, in turn, is relevant to proton-conducting oxides in which protons are introduced via the dissolution of hydroxyl ions at vacant oxygen sites. We propose here, on the basis of x-ray powder diffraction studies, electron microscopy, chemical analysis, thermal gravimetric analysis, and alternating current impedance spectroscopy, that nominally B-site doped barium cerate can exhibit dopant partitioning as a consequence of barium evaporation at elevated temperatures. Such partitioning and the presence of significant dopant concentrations on the A-site negatively impact proton conductivity. Specific materials examined are BaxCe0.85M0.15O3-δ (x = 0.85 - 1.20; M = Nd, Gd, Yb). The compositional limits for the maximum A-site incorporation are experimentally determined to be: (Ba0.919Nd0.081)(Ce0.919Nd0.081)O3, (Ba0.974Gd0.026)(Ce0.872Gd0.128)O2.875, and Ba(Ce0.85Yb0.15)O2.925. As a consequence of the greater ability of larger cations to exist on the Ba site, the H2O adsorption and proton conductivities of large-cation doped barium cerates are lower than those of small-cation doped analogs.
Transmission electron microscopy investigation of fullerene nanowhiskers and needle-like precipitates formed by using C60 and (η2-C60)Pt(PPh3)2
Authors: Miyazawa Kun'ichi , Suga Tadatomo
Published: May 2005

Nanowhiskers and needle-like precipitates obtained by the liquid-liquid interfacial precipitation method for the systems of isopropyl alcohol and toluene solutions of C60 and (η2-C60)Pt(PPh3)2 were examined by transmission electron microscopy. Morphology of the C60 precipitates was remarkably changed by the addition of (η2-C60)Pt(PPh3)2 in the C60 toluene solution, and capsular needle-like crystals of C60 were formed. C60 cages were found to be directly contacted along the growth axis of (η2-C60)Pt(PPh3)2 needle-like crystals.