bluuebunny/crossref_metadata_2025 huggingface dataset:
New preparation process of Pb(ZrxTi1−x)O3 thin films from PbZrO3 and PbTiO3 multilayers
Authors: He Gang , Iijima Takashi , Funakubo H.
Published: March 2008

This work presents the preliminary experimental results of Pb(ZrxTi1−x)O3 (PZT) thin films preparation to develop a new combinatorial process by chemical solution deposition (CSD) method. PZT thin films were fabricated from the PbZrO3 (PZ) and PbTiO3 (PT) multilayers on a substrate of Si/SiO2/Ti/Pt. The precursor PT and PZ solutions were coated in different sequences, (i) in the PT start sequence and (ii) in the PZ start sequence, and with different PT and PZ concentrations. It was found that the deposition sequence of PT and PZ led to the differences in composition, microstructure, texture, and ferroelectric property of the resultant thin films. The PT start deposition was suitable for preparation of the PZT thin films, while the PZ start deposition caused composition deviation and bad ferroelectric property. The postannealing had little effect for the formation of the PZT thin films from the multi-PT and PZ layers. A single perovskite phase of PZT can be obtained from the deposited multi-PT and PZ layers even without any postannealing when concentrations of the precursor PT and PZ solution are smaller than 0.025 M and the deposition sequence is in the PT start sequence. This method would be a constructive way to develop and study other thin film materials systems.
Fundamental relations used in nanoindentation: Critical examination based on experimental measurements
Authors: Martin M. , Troyon M.
Published: March 2008

The fundamental relations used in the analysis of nanoindentation load–displacement data to determine elastic modulus and hardness are based on Sneddon's solution for indentation of an elastic half-space by rigid axisymmetric indenters. It has been recently emphasized that several features that have important implications for nanoindentation measurements are generally ignored. The first one concerns the measurement of the contact depth, which is actually determined by using a constant value ε = 0.75 for the geometry of a Berkovich indenter and for any kind of material, whereas the reality is that ε is a function of the power law exponent deduced from the analysis of the unloading curve. The second feature concerns the relation between contact stiffness, elastic modulus, and contact area, in which a correction factor γ larger than unity is usually ignored leading to a systematic overestimation of the area function and thus to errors in the measured hardness and modulus. Experimental measurements on fused quartz are presented that show the variation of ε with the geometry of the tip–sample contact; that is to say with the contact depth, as well as the existence of the correction factor γ, as predicted in some recent articles. Effects of both ε and γ on harness and modulus measurements are also shown.
Processing and morphology of permeable polycrystalline silicon thin films
Authors: Dougherty G. G. , Pisano A. A. , Sands T.
Published: March 2008

It is known that thin films of polycrystalline silicon, deposited under the right conditions, can be permeable to HF-based etching solutions. While these films offer unique capabilities for microfabrication, both the poor reproducibility of the permeable film properties and the lack of a detailed physical understanding of the material have limited their application. This work provides a methodical study of the relationship between process, microstructure, and properties of permeable polycrystalline silicon thin films. It is shown that the permeability is a result of small pores, on the order of 10 nm, between the 100–200-nm hemispherical grains characteristic of the permeable film morphology. This morphology occurs only in nearly stress-free films grown in a narrow temperature range corresponding to the transition between tensile and compressive film growth regimes. This result strongly suggests that the monitoring of residual film stress can provide the process control needed to reliably produce permeable films. A simple kinetic model is proposed to explain the evolution of the morphology of the permeable films.
Transmission in irradiated hydroxyethyl methacrylate copolymer at elevated temperatures
Authors: Lu K-P. , Lee Sanboh , Han C. C.
Published: March 2008

Transmission losses were monitored in the ultraviolet-visible spectra of irradiated hydroxyethyl methacrylate (HEMA) copolymer at elevated temperatures. The transmission in irradiated HEMA in the ultraviolet and visible wave length range was almost the same for doses 400 kGy ≤ Φ ≤ 1000 kGy, but was smaller than that of the nonirradiated HEMA copolymer. The reduction in transmission in the irradiated specimens was attributed to the presence of color centers. The concentration of color centers was enhanced by thermal annealing. The transmission data (or absorption data) at 467 nm was found in good agreement with the theoretical model in which the color center production followed a first-order kinetic process. The rate constant satisfies the Arrhenius equation, and the corresponding activation energy is 17.37 kJ/mol and is independent of the dosage. The results were compared with those reported in the literature.
Effect of Si2N2O content on the microstructure, properties, and erosion of silicon nitride–Si2N2O in situ composites
Authors: Park Dong-Soo , Choi Hyun-Ju , Han Byung-Dong , Kim Hai-Doo , Lim Dae-Soon
Published: March 2008

Silicon nitride–Si2N2O in situ composites were prepared by hot pressing powder mixtures of α–Si3N4, 6 wt% Y2O3, 1 wt% Al2O3, and 0–12 wt% SiO2. X-ray diffraction (XRD) analysis indicated that the volume percents of Si2N2O were 0, 13, 31, and 54 for the composites prepared with 0, 4, 8, and 12 wt% SiO2, respectively. XRD results also indicated that both silicon nitride grains and Si2N2O grains were laid down perpendicular to hot pressing direction. As the volume percent of Si2N2O increased, the width and the amount of elongated silicon nitride grains decreased, but the fracture toughness increased. Young's modulus of the in situ composites decreased as the Si2N2O content was increased. The erosion rate decreased as the Si2N2O content was increased, in part, due to both the increased fracture toughness and the reduced grain size. Erosion of the composites occurred primarily due to the grain dislodgment. The sample without Si2N2O experienced micro-chipping due to transgranular fracture.
Orientation imaging studies of Sn-based electronic solder joints
Authors: Telang A. A. , Bieler T. T. , Choi S. , Subramanian K. K.
Published: March 2008

Single shear lap specimens were subjected to creep, isothermal aging, and thermomechanical fatigue (TMF). Scanning electron microscopy micrographs of previously polished specimens revealed changes in surface morphology. Orientation imaging microscopy was carried out on the same specimens to study the microstructural evolution and crystal orientation changes. As-fabricated joints consistently show a preferred crystal orientation with a few minority orientations with highly preferred misorientations. Alloy additions caused an increase in the number of statistically significant crystal orientations and misorientations. The solidification microstructure was unchanged due to room-temperature creep. Aging caused development and motion of well-defined subgrain boundaries and removal of most minority orientations. TMF causes heterogeneous refinement of the microstructure that accounts for the localized grain boundary sliding in regions of high strain concentration. This study implies that the lead-free solder joints are not polycrystals, but multicrystals, so that deformation is very heterogeneous and sensitive to strain and temperature history.
Change of growth orientation in Pt films epitaxially grown on MgO(001) substrates by sputtering
Authors: Ahn Kun Ho , Baik Sunggi , Kim Sang Sub
Published: March 2008

A drastic change of the growth orientation in epitaxial Pt films grown by sputtering on MgO(001) was observed. At higher substrate temperatures, practically pure (001) epitaxial Pt films grow. On the other hand, epitaxial (111) Pt films grow at lower substrate temperatures. Interestingly, the gradual transition from (111) to (001) orientation occurs at lower temperatures when applied at a lower deposition rate. The degree of supersaturation in growth conditions is proposed as a key driver of the orientation change. When homogeneous nucleation occurs under a higher supersaturation, a large number of nuclei grow at the flat (001) terraces possessing (111) tetrahedral orientation. Under a lower supersaturation, a small number of nuclei aligned in (001) orientation to each other form dominantly at surface defects, resulting in a (001) epitaxial film with no grains. Our results suggest that one can selectively prepare either (001) or (111) epitaxial Pt films by properly adjusting substrate temperature and/or deposition rate.
Preparation and tribological investigation of thin silicone films
Authors: Liu Weimin , Zhou Feng , Yu Laigui , Chen Miao , Li Bin , Zhao Guohong
Published: March 2008

Polydimethylsiloxane (PDMS) films were prepared on silicon wafers by spin coating. The tribological properties of the PDMS films sliding against AISI-52100 steel ball were investigated with a dynamic static friction coefficient measurement apparatus in a ball-on-plate configuration. It was found that crosslinking, end grafting, and chemical characteristics of the substrate surfaces combined to play an important role in keeping the films' stability and improving the friction-reduction and wear-resistant properties. It was also noted that crosslinked PDMS films on hydroxylated substrates exhibited the most stable friction coefficient and the longest antiwear life, while a friction coefficient below 0.01 was observed for the crosslinked PDMS films on hydrophobic substrates. The latter might be attributed to the weak interaction at the interface of PDMS layer and the self-assembled monolayer. The friction coefficient appeared to be velocity dependent. At higher sliding velocities, the films showed more stable and smaller friction coefficients; this might be attributed to the shear thinning effect.
Microstructural evolution of Sn–Ag–Cu–Al solder with respect to Al content and heat treatment
Authors: Lin Kwang-Lung , Hsiao Chih-Chun , Chen Kaug-I
Published: March 2008

The Pb-free Sn–Ag–Cu–Al solders were investigated for microstructural evolution with respect to Al% and heat treatment. The Al% varies from 0.1% to 0.45% while the contents of Ag are 3.1%–2.53% and of Cu are 0.41%–0.33%. Differential scanning colorimetry (DSC) was applied to identify the melting behavior. A monotectic temperature of 224 °C and a eutectic temperature of 220 °C are deduced from the DSC results. The microstructure was characterized with x-ray diffraction and scanning electron microscopy-energy dispersive spectroscopy. Ag3Sn and the γ2 phase of Al–Cu system are the intermetallic compounds formed in the as-cast solders. Cu6Sn5 formed upon heat treatment for 1000 h at 150 °C in the 0.45 Al-containing solder, while not found in the other solders or other heat treatment conditions. Sn whiskers were detected in a 0.45 Al-containing specimen after aging for 50 h.
Characteristics of copper films produced via atomic layer deposition
Authors: Huo Jinshan , Solanki Raj , McAndrew James
Published: March 2008

Properties of copper films produced using atomic layer deposition (ALD) were characterized. Composition, morphology, and electrical properties of these films grown on glass, as well as Ta, TiN, and TaN on silicon wafers were examined. The resistivity of films thicker than about 60 nm was near bulk value. Films were deposited using a two-step ALD process in which copper(II)-1,1,1,5,5,5,-hexafluoroacetylacetonate hydrate and water vapor were introduced in the first step and a reducing agent was introduced in a subsequent step. Five reducing agents were evaluated, with the best results obtained using isopropanol or formalin. The optimum deposition temperature with isopropanol was about 260 °C, whereas it was about 300 °C with formalin. These films were also investigated as seed layers for electrodeposition of thicker Cu layers for possible interconnect applications. Excellent fills in high aspect ratio trenches were demonstrated.
Continuous hydrothermal synthesis and crystallization of magnetic oxide nanoparticles
Authors: Cote Linda J. , Teja Amyn S. , Wilkinson Angus P. , Zhang Z. John
Published: March 2008

The continuous hydrothermal synthesis of nanoparticles of two metal oxides (α–Fe2O3 and Co3O4) is described. Two variations of the technique were investigated, involving the precipitation reaction between a metal salt solution and a hydroxide solution at ambient conditions and at elevated temperatures. Elevated temperatures resulted in more uniform particles of α–Fe2O3 and Co3O4, although the actual sizes of the particles were apparently unaffected by the temperature. This behavior was attributed to the species present in solution and the solubilities of the cation(s), both of which were calculated via a thermodynamic model for the systems under study.
Development of conductivity in low conversion temperature silver pastes via addition of nanoparticles
Authors: Bell Nelson B. , DiAntonio Chris B. , Dimos Duane B.
Published: March 2008

Silver nanoparticles were incorporated in a dispersion of micron-sized silver spheres for testing as a low-temperature reactive component to form conductive particle networks. The development of conductivity depended on the arrangement of the micron-sized particle network, the amount of material reacted to form necks at the points of contact of micron-sized particles, and sintering of the particle network. Nanoparticles reacted to bond the micron-sized particles, but the stress issues involved in nanoparticle sintering can cause macroscopic cracking. Critical processing variables include the state of particle dispersion, the heating rate, and the fraction of nano-sized material.
Mechanically induced solid-state reaction for synthesizing glassy Co75Ti25 soft magnet alloy powders with a wide supercooled liquid region
Authors: El-Eskandarany M. Sherif , Zhang Wei , Inoue A.
Published: March 2008

A single phase of glassy Co75Ti25 alloy powders was synthesized by high-energy ball milling the elemental powders at room temperature, using the mechanical alloying method. The final product of the glassy alloy, which is obtained after ball milling for 86 ks, exhibits soft magnetic properties with polarization and coercivity values of 0.67 T and 2.98 kA/m, respectively. This binary glassy alloy, in which its glass transition temperature (Tg) lies at a rather high temperature (833 K), transforms into face-centered-cubic Co3Ti (ordered phase) at 889 K through a single sharp exothermic reaction with an enthalpy change of crystallization (ΔHx) of −2.35 kJ/mol. The supercooled liquid region before crystallization ΔTx of the synthesized glassy powders shows an extraordinary high value (56 K) for a metallic binary system. The reduced glass transition temperature [ratio between Tg and liquidus temperatures, Tl (Tg/Tl)] was 0.56. We also demonstrated postannealing experiments of the mechanically deformed Co/Ti multilayered composite powders. The results show that annealing of the powders at 710 K leads to the formation of a glassy phase (thermally enhanced glass formation reaction). Its heat formation was measured directly and found to be −0.56 kJ/mol. The similarity in the crystallization and magnetization behaviors between the two classes of as-annealed and as-mechanically alloyed glassy powders implies the formation of the same glassy phase.
Raman measurement and thermal properties of SmCa4O(BO3)3 crystals
Authors: Xia H. H. , Lu G. G. , Zhang S. S. , Cheng Z. Z.
Published: March 2008

SmCa4O(BO3)3 (SCOB) crystallizes in the noncentrosymmetric monoclinic space group Cm with cell parameters a = 0.8129(5), b = 1.6076(1), c = 0.3584(1) nm, β = 101.36(2)°, and Z = 2. Raman results showed that the characteristic spectra of SCOB are mainly contributed by the B–O triangles and partly by the Ca(1)–O octahedra. The structural rigidity of SCOB is mainly ascribed to the B–O bond stretching and bending modes and partly by the Ca(1)–O bonds. The rigid structure of the B–O triangles and the quasi-rigid structure of the Ca(1)–O octahedra are necessary to the SCOB crystal as a laser host. The large distortions of the Sm–O and Ca(2)–O octahedra intensify the polar forces and anisotropic lattice forces, which generally imply the best nonlinear properties possible for SCOB as a nonlinear optical material and piezocrystal. Thermal measurements show a larger value of the specific heat and three small expansion coefficients, which show that SCOB can allow a large temperature gradient, especially in the Y direction. Displacement parameters indicated that the thermal ellipsoids of the Sm and Ca(2) atoms had significantly large components along the b direction. Synthetical study indicated that the SCOB crystal should be outstanding as an efficient self-frequency doubled material.
Epitaxial growth of ZnO films on Si(111)
Authors: Tiwari Ashutosh , Park M. , Jin C. , Wang H. , Kumar D. , Narayan J.
Published: March 2008

In this paper, we report the growth of ZnO films on silicon substrates using a pulsed laser deposition technique. These films were deposited on Si(111) directly as well as by using thin buffer layers of AlN and GaN. All the films were found to have c-axis-preferred orientation aligned with normal to the substrate. Films with AlN and GaN buffer layers were epitaxial with preferred in-plane orientation, while those directly grown on Si(111) were found to have random in-plane orientation. A decrease in the frequency of the Raman mode and a red shift of the band-edge photoluminescence peak due to the presence of tensile strain in the film, was observed. Various possible sources for the observed biaxial strain are discussed.
High-temperature oxidation of CoGa: Influence of the crystallographic orientation on the oxidation rate
Authors: Koops U. , Hesse D. , Martin M.
Published: March 2008

The crystallographic orientation plays an important role in high-temperature oxidation of the intermetallic compound CoGa. When CoGa is exposed to air at elevated temperatures, the oxide β–Ga2O3is formed, and different scale growth rates are observed, depending on the crystallographic orientation of the CoGa grains. This dependence is a consequence of the anisotropy of the gallium diffusion rate through the β–Ga2O3scale and of a topotaxial orientation relationship occurring between β–Ga2O3and CoGa. The combination ofex situtechniques, such as transmission electron microscopy and electron backscatter diffraction with optical microscopy, appliedin situresulted in a thorough understanding of these relations and of the oxidation process in general.
Thermal spray coating of aluminum nitride utilizing the detonation spray technique
Authors: Krishna L. Rama , Sen D. , Rao Y. Srinivasa , Rao G. V. Narasimha , Sundararajan G.
Published: March 2008

The main objective of this work is to examine the feasibility of depositing aluminum nitride (AlN) powders, synthesized using self-propagating high-temperature synthesis, on a mild steel substrate using the detonation spray coating technique. Thick coatings produced by utilizing the AlN powder were obtained at four different oxygen–acetylene ratios and analyzed for microstructure, microhardness, porosity, indentation fracture toughness, and phase distribution. The AlN powder particles were found to be undergoing oxidation during the deposition process. The interrelationship between the spray parameters and the extent of oxidation of AlN during the coating process was investigated. Tribological performance of the coatings was evaluated using a dry sand abrasion test and a pin-on-disc sliding wear test. The mechanical and tribological properties of the above four coatings were compared with pure alumina (Al2O3) coatings. The correlation between the structure of the coatings and their tribological performance was also established.
Luminescence in europium-doped titania: Part II. High concentration range of Eu3+
Authors: Ovenstone James , Titler Philip J. , Withnall Robert , Silver Jack
Published: March 2008

In continuation of our previous work [J. Ovenstone, P.J. Titler, R. Withnall and J. Silver, J. Phys. Chem. B, 105, 7170 (2001)] we report the following results. Amorphous europium-doped titania phosphors (Ti1−3xEu4xO2) were prepared with europium concentrations from x = 0.000397 to x = 0.143. From investigations using photoluminescence (PL), it was deduced that the luminescence was due to a europium/titanium compound rather than from a europium-containing precipitate dispersed within a titania precipitate. PL brightness was shown to increase linearly to a concentration of x = 0.0159 before quenching began, and the rate of increase of brightness dropped. Brightness then continued to rise (almost linearly) from x = 0.0238 to x = 0.143. Under electron beam excitation these phosphors showed weak cathodoluminescence; for the amorphous materials no quenching was observed. For the crystalline materials (prepared by annealing the amorphous materials at high temperature) no red luminescence was observed above a concentration of x = 0.00318; however, some faint red luminescence was observed below this concentration. In addition, some faint blue emission was observed in crystalline samples that had no red luminescence, indicating the presence of small amounts of Eu2+ ions. This was attributed to reduction of the Eu3+ ions in the electron beam. Europium doping was shown to increase the size of the band gap in the amorphous materials, but had little effect on the band gap of the crystalline powders.
Chemical solution deposited GaN films from oxygen- and nitrogen-based precursors
Authors: Kisailus David , Choi Joon Hwan , Lange F. F.
Published: March 2008

GaN films were produced by the chemical solution deposition method (CSD) using two different precursors—gallium dimethyl amide (GDA; containing gallium–nitrogen bonds) and gallium isopropoxide (GIP; containing gallium–oxygen bonds). Pyrolysis of the GDA film at 600 °C produced a continuous layer of GaN grains with a single orientational relation with the substrate [GaN (0001) ∥ Al2O3 (0001) and GaN (1010) ∥ Al2O3 (1120)], and an overlying polycrystalline film. At temperatures greater than 600 °C, the oriented grains consumed the polycrystalline layer via an evaporation–condensation mass transport. Pyrolysis of the GIP films at 600 °C produced a continuous layer of gallium oxynitride having the corundum structure [i.e., α–Ga2O(3−x)N2/3x] with an epitaxial relation to the substrate (α–Ga2O(3−x)N2/3x[0001] ∥ Al2O3 [0001] and α–Ga2O(3−x)N2/3x [1010] ∥ Al2O3 [1120]), and an overlaying polycrystalline gallium oxynitride film with a spinel structure. Increasing temperature caused growth of oriented grains in contact with the substrate and conversion of the oxynitride to wurtzite GaN at 800 °C. Room-temperature (300 K) and low-temperature(77 K) photoluminescence measurements behaved similarly to metal-organic chemical vapor deposition based GaN with additional photoluminescence most likely due to nitrogen vacancy impurities.
Plasma deposition and characterization of acrylic acid thin film on ZnO nanoparticles
Authors: Shi Donglu , He Peng , Lian Jie , Wang Lumin , van Ooij Wim J.
Published: March 2008

Acrylic acid polymer thin films were deposited on the surfaces of nanoparticles of ZnO using a plasma polymerization treatment. The average size of nanoparticles was on the order of 50 nm in irregular shapes. High-resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin film of the acrylic acid layer (15 nm) was uniformly deposited on the surfaces of the nanoparticles. The HRTEM results were confirmed by time-of-flight secondary ion mass spectroscopy. The effect of plasma power on the polyacrylic thin film was studied by Fourier transform infrared experiments. The deposition mechanisms and the effects of plasma treatment parameters are discussed.
Electron field emission from Ar+ ion-treated thick-film carbon paste
Authors: Reynolds Gillian A. M. , Cheng Lap-Tak , Bouchard Robert , Moffett Paul , Jones Howard , Robinson Linda F. , Shah S. Ismat , Amey Daniel I.
Published: March 2008

Ion bombardment was used to produce electron-emitting microscale features on surfaces of thick films printed with carbon pastes. This technology can potentially enable the development of large-area field emission displays. Systematic investigations using microscopy and electron field emission experiments have demonstrated a close link among paste formulation, ion processing parameters, and the development of surface microstructures. These investigations were also useful in understanding the fundamentals of microstructure formation under ion bombardment and the field emission characteristics of the carbon-based emitters. Several device concepts aimed toward achieving a low-voltage switchable triode were also tested with varying degrees of success. In this paper, we discuss various technological issues related to the materials, processes, and devices.
Characterization of superconducting SmBa2Cu3O7 films grown by pulsed laser deposition
Authors: Jia Q. X. , Foltyn S. R. , Coulter J. Y. , Smith J. F. , Maley M. P.
Published: March 2008

We have investigated epitaxial superconducting SmBa2Cu3O7 (Sm123) films grown by pulsed-laser deposition on single-crystal SrTiO3 substrates. The deposition temperature plays an important role in determining the superconducting properties of Sm123 films. The superconducting transition temperature increases with the deposition temperature whereas the transition width decreases at deposition temperatures in the range of 700–875 °C. A Sm123 film deposited at 850 °C exhibits a transition temperature above 93 K with a transition width less than 0.5 K. Even though Sm123 films exhibit a higher transition temperature than Yba2Cu3O7 (Y123), the Sm123 shows lower critical current density at liquid-nitrogen temperature. The nominal critical current density of Sm123 film is less than 1 MA/cm2 at 75.4 K. Nevertheless, the Sm123 films have less anisotropy and stronger pinning characteristics compared to Y123. They are also much smoother with fewer particulates, as revealed by scanning electron microscopy.
Viscoelastic effects during unloading in depth-sensing indentation
Authors: Ngan A. H. W. , Tang B.
Published: March 2008

With polypropylene as a prototype viscoelastic material at room temperature, it was found that a “nose” may appear in the unloading segment of the load–displacement curve during nanoindentation when the holding time at peak load is short and/or the unloading rate is small, and when the peak load is high enough. The load at which the nose appears was also found to decrease linearly with decreasing unloading rate. A linear viscoelasticity analysis was performed to interpret this effect. The analysis predicts a linear variation between the nose load and the unloading rate, and the slope of such a linear variation is also shown to be proportional to the viscosity parameter of the material. Thus, by measuring the slope of the nose-load versus unloading rate plot at a given temperature, the viscosity parameter of the specimen can be found. This is a new way of measuring the viscosity parameter of a material in addition to the existing method of force modulation and noting the frequency response of the displacement.
High-energy electron irradiation study of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 and Pb1−xLax[Mg(1+x)/3Nb(2−x)/3]O3 by transmission electron microscopy
Authors: Miao Shu , Zhu Jing , Zhang X. W. , Chen X. H.
Published: March 2008

The electron irradiation sensitivities of Pb(Mg1/3Nb2/3)O3 (PMN) and Pb1−xLax[Mg(1+x)/3Nb(2−x)/3]O3 (PLMN) ceramics were investigated by transmission electron microscopy. Nanoscale Pb particles formed in these materials under electron beam radiation. It was found that these fine Pb particles generally had a preferred crystallographic orientation relationship with the PMN/PLMN host and always existed at positions slightly rich in Mg2+. A preliminary mechanism involving defect chemistry reactions is proposed to interpret this unusual Pb precipitation. Possible limitations to the practical applications of these materials are discussed.
Perovskite crystallization of sol-gel processed (Pb,La0.06,Gd0.02)(Zr0.65,Ti0.35)O3 thin films: Dielectric, ferroelectric and optical properties
Authors: Thomas Reji , Mochizuki Shoichi , Mihara Toshiyuki , Ishida Tadashi
Published: March 2008

Ferroelectric lead lanthanum gadolinium zirconium titanate (PLGZT) thin films were prepared by the sol-gel spin coating technique. Three-step preannealing heat treatment was employed to prepare crack-free films. Various types of substrates, and the effects of the seed layer and annealing temperature on the perovskite crystallization were studied. Phase-pure perovskite crystallization was obtained by annealing the films on PbTiO3/Pt/Ti/Si substrates at 700 °C for 30 min. The Auger electron spectroscopy depth profile showed uniform elemental distribution along the thickness except the surface and interface regions. Dielectric constant and loss tangent at 10 kHz were 1000 and 0.06, respectively. Remanent polarization (Pr) and coercive field (Ec) were 11.8 μC/cm2 and 71 kV/cm, respectively. The direct band gap energy was 3.55 eV for the amorphous films. The refractive index and extinction coefficient at 610 nm for amorphous PLGZT films were 2.14 and 0.0028, respectively. The dispersion of the refractive index was interpreted in terms of a single electronic oscillator at 6.06 eV.
Preparation and characterization of zinc-doped gallophosphate molecular sieve
Authors: Yoshino Masatoshi , Matsuda Motohide , Miyake Michihiro
Published: March 2008

The effect of Zn doping on crystallization of gallophosphate molecular sieve, cloverite, synthesized hydrothermally at 170 °C, using starting gels with ZnO, was investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), and molecular dynamics (MD) simulation, etc. The SEM observations and crystallinities estimated from XRD data revealed that Zn-doped cloverite with very good crystallinity was successfully prepared, and the addition of ZnO to the starting gel was effective in promoting the crystallization process in a short reaction time. The results of chemical analyses, estimated unit cell dimensions, and MD simulations suggested the substitution of Zn atoms for Ga atoms in the framework of Zn-doped cloverite.
Growth of electromigration-induced hillocks in Al interconnects
Authors: Nucci J. A. , Straub A. , Bischoff E. , Arzt E. , Volkert C. A.
Published: March 2008

Electromigration-induced hillock growth in polycrystalline Al segments was extensively investigated. Hillocks composed of columnar grains grew near the anode by epitaxial Al addition at the interface between the Al and underlying TiN layer, which pushed up the original Al film. The hillocks rotated away from their initial (111) out-of-plane orientation in a manner consistent with the physical rotation of the hillock surface. Wedgelike and rounded hillocks were observed, and their formation is explained by the interaction between grain extrusion and grain growth. Trends elucidated by review of both thermal- and electromigration-induced hillock studies can be explained by the mechanisms identified in this work.
Rapid method to measure diffusion of paramagnetic species: Mn2+ in poly(ethylene-co-methacrylic acid) ionomers
Authors: Tierney Neena K. , Register Richard A.
Published: March 2008

We present a facile method to measure Fickian diffusion coefficients of paramagnetic species in materials, using electron spin resonance (ESR) spectroscopy. The method requires no postannealing sample preparation, is adaptable to in situ measurement, and requires only that the spectrum of the paramagnetic species change monotonically with its local concentration. We illustrated this method with poly(ethylene-co-methacrylic acid) ionomers, using laminates prepared from the same copolymer neutralized with either paramagnetic Mn2+ or diamagnetic Zn2+. For Mn2+, the exchange interaction between neighboring Mn2+ caused the six-line hyperfine pattern to transform to a single broad signal, providing the measurement of local concentration. Diffusion coefficients of Mn2+ in this ionomer pair measured by ESR were compared with those for Zn2+ measured by conventional electron probe microanalysis and found to be in satisfactory agreement.
Influence of substrate metallization on diffusion and reaction at the under-bump metallization/solder interface in flip-chip packages
Authors: Zhang F. , Li M. , Chum C. C. , Tu K. N.
Published: March 2008

In flip-chip packages, the effect of Ni metallization on the substrate side on interfacial reactions between solders and an Al/Ni(V)/Cu under-bump metallization (UBM) on the chip side was investigated during the reflow process. The Ni substrate metallization greatly accelerated interfacial reactions on the chip side and quickly degraded the thermal stability of the UBM due to a fast consumption of the Ni(V) layer. This phenomenon can be explained in terms of rapid Ni or Sn diffusion in the ternary (Cu,Ni)6Sn5 phase, which was formed in the solder adjacent to the Ni(V) layer and the enhanced dissolution of (Cu,Ni)6Sn5 into the molten solder. Without the Ni metallization on the substrate side, the Al/Ni(V)/Cu UBM remained very stable with both eutectic SnPb and Pb-free solders.
Boron nitride nanotubes filled with zirconium oxide nanorods
Authors: Shen Z. Q. , He L. L. , Wu E. D. , Fan Y. Y. , He J. F. , Cheng H. M. , Li D. X. , Ye H. Q.
Published: March 2008

Boron nitride nanotubes (BNNTs) filled with zirconium oxide (ZrO2) nanorods were synthesized by the improved solid-gas multiphase reaction method. The structure of ZrO2 nanorods was monoclinic single crystal or multi-twin crystal. The diameters of ZrO2 nanorods varied from 20 to 40 nm. The inner diameters of BNNTs were similar to those of corresponding ZrO2 nanorods. The BNNTs exhibited open end, closed end, or an end connected with a short tube grown from the tip of the ZrO2 nanorod. No preferred orientation was observed for the growth of ZrO2 nanorods.
Crystallization behavior of polymer-derived Si–B–C–N ceramics in a high-pressure nitrogen environment
Authors: Cai Y. , Zimmermann A. , Prinz S. , Aldinger F.
Published: March 2008

This communication presents the effects of nitrogen pressure on the crystallization behavior of Si3.0B1.1C5.3N3.0 ceramics annealed at 1800 °C for 3 h. Transmission electron microscopy observation reveals that increasing nitrogen pressure results in the retardation of the crystallization process. Besides SiC and Si3N4 nanocrystals, individual large crystallites were also detected. These crystals were composed only of Si and N, and they possessed hexagonal structure with lattice parameters a = 0.737 nm and c = 0.536 nm. Crystallites of this novel phase were more frequently found with increased nitrogen pressure.
Synthesis of Y-branching multiwalled carbon nanotubes with a bamboolike structure
Authors: Gu P. , Zhao J. H. , Li G. H.
Published: March 2008

Y-branching multiwalled carbon nanotubes with a bamboolike structure were grown by chemical vapor deposition from a C–H–N gas system when B2O3 and Ti was supplied. Transmission electron microscopy images reveal that these novel junctions contain a tube branched into two tubes with nearly the same diameter. In addition, the tube walls show perpendicularly stacked graphite planes, which take on a bamboolike structure. The influence of preparation conditions on the structure of these carbon nanotubes is discussed. This novel structure may offer promising application for nanotube-based composites.
Single-step deposition of Eu-doped Y2O3 phosphor coatings through a precursor plasma spraying technique
Authors: Devi P. Sujatha , Margolis Joshua , Parise John B. , Grey Clare P. , Sampath Sanjay , Herman Herbert , Gafney Harry D.
Published: March 2008

Europium-doped yttrium oxide (Y2O3:Eu3+) luminescent coatings were produced in a single step directly from a solution precursor using a radio frequency induction plasma spray technique. Crystalline and luminescent coatings were grown on Si(100) and steel substrates by this process. X-ray diffraction analyses on these coatings confirmed that polycrystalline cubic Y2O3 phase formed in situ with no impurity phases. The observed photoluminescence from these coatings is in all probability due to the highly crystalline nature of the coating combined with submicron spherical morphology of the grains.
Ag3Sn plate formation in the solidification of near ternary eutectic Sn–Ag–Cu alloys
Authors: Henderson Donald W. , Gosselin Timothy , Sarkhel Amit , Kang Sung K. , Choi Won-Kyoung , Shih Da-Yuan , Goldsmith Charles , Puttlitz Karl J.
Published: March 2008

Near-ternary eutectic Sn–Ag–Cu alloys are leading candidates for Pb-free solders. These alloys have three solid phases: β–Sn, Ag3Sn, and Cu6Sn5. Starting from the fully liquid state in solidifying near-eutectic Sn–Ag–Cu alloys, the equilibrium eutectic transformation is kinetically inhibited. The Ag3Sn phase nucleates with minimal undercooling, but the β–Sn phase requires a typical undercooling of 15 to 30 °C for nucleation. Because of this disparity in the required undercooling for nucleation, large, platelike Ag3Sn structures can grow rapidly within the liquid phase, before the final solidification of the solder joints. At lower cooling rates, the large Ag3Sn plates can subtend the entire cross section of solder joints and can significantly influence the mechanical deformation behavior of the solder joints under thermomechanical fatigue conditions. In this paper, it is demonstrated that the Ag3Sn plate formation can be inhibited, an important factor in assuring the reliability of solder joints composed of these alloys.
Solid-state recycling from machined scraps to a cellular solid
Authors: Chino Yasumasa , Shimojima Koji , Hosokawa Hiroyuki , Yamada Yasuo , Wen Cui'e , Mabuchi Mamoru
Published: March 2008

Cellular solids were processed from machined scraps of a medium carbon steel by sintering. Mechanical properties of the cellular solids were investigated by compressive tests from the viewpoint of effects of high dislocation density in the machined scraps on the solid-state bonding. The flow stress in the plateau region for the cellular solid made of the as-machined scraps was higher than that of the one made of the annealed scraps. Clearly, the bonding strength between scraps was increased by the high dislocation density in the as-machined scraps.
Crystalline structure and dielectric behavior of (Ce,Ba)TiO3 ceramics
Authors: Jing Zhi , Yu Zhi , Ang Chen
Published: March 2008

In this work, (Ba1−xCex)Ti1−x/4(VTi)x/4O3 ceramics with x = 0.02, 0.04, 0.06, and 0.08 (VTi denotes titanium vacancies) were synthesized by the mixed-oxide method. The results of x-ray diffraction analysis and scanning electron microscopy show that all the samples are monophasic. The crystalline structure can be indexed as tetragonal for the samples with x ≤ 0.06, but as cubic for x = 0.08. Three phase transitions were observed in the temperature dependence of the dielectric permittivity, similar to those observed in pure BaTiO3, and the three phase transition temperatures (Tc, T1, and T2) shifted to lower temperatures with the rates of −18, −12, and −7 K per molar percentage of Ce3+, respectively. This is quite different from that observed in BaTiO3 with Ce substitution at the Ti-site, in which Tc shifted to a lower temperature, and T1 and T2 to higher temperatures. The permittivity maximum increased with increasing Ce content, which is mainly attributed to an increase in the grain size.
Preparation and enhanced off-resonance optical nonlinearities of CdS-capped gold nanoparticles embedded in BaTiO3 thin films
Authors: Yang Yong , Shi Jianlin , Chen Hangrong , Dai Shugang , Huang Weiming , Liu Ye
Published: March 2008

A simple approach has been developed for the synthesis of Au@CdS core-shell nanoparticles by a direct self-assembling process. Stable Au@CdS composite colloids were prepared by thiourea, as a double-functional reagent that acted as the linkage agent between Cd2+ ions and gold nanoparticles. The CdS-capped gold composite nanoparticles were successfully integrated into BaTiO3 films. A significant enhancement of third-order nonlinear optical susceptibility in the Au@CdS nanoparticles with core-shell structure is reported. To compare the effect of enhanced nonlinear response, single gold or CdS nanoparticles embedded in BaTiO3 films were also prepared.
Microstructure evolution during sintering of self-propagating high-temperature synthesis produced ZrB2 powder
Authors: Mishra S. K. , Das S. , Ramchandrarao P.
Published: March 2008

A transmission electron microscopy investigation on the microstructure evolution of the sintered compact of zirconium diboride was carried out. Grain boundary phases, structure, and morphology of the grains and defect structures were studied to understand the sintering behavior of these borides. The impurities, such as Fe, were found to stay at the triple junction point as (Fe, Zr)2B. Different types of defect structures, such as dislocations, twins, and faceted growth, were observed. No diffusion of Fe into ZrB2 could be observed, but the Zr diffusion into Fe was established.
Microwave sintering of high-density, high thermal conductivity AlN
Authors: Xu Geng-fu , Olorunyolemi Tayo , Wilson Otto C. , Lloyd Isabel K. , Carmel Yuval
Published: March 2008

Microwave energy was used to sinter high thermal conductivity AlN ceramics (160–225 W/mK). The effects of sintering time, temperature, and amount of additive on phase composition, phase distribution, densification behavior, grain growth, and thermal conductivity were studied. The thermal conductivity of AlN was greatly improved by the addition of Y2O3, extended sintering time, and higher sintering temperatures. Thermal conductivity development in Y2O3-doped AlN showed two distinctive time regimes: (i) densification, where full densification, secondary phase formation, concentration and segregation, and rapid purification of AlN grains occur, accompanied by a large increase in thermal conductivity; (ii) postdensification, where grain growth and secondary phase sublimation/evaporation occur, yielding a further increase in thermal conductivity. Our results indicate that microwave sintering is a promising approach for synthesis of high thermal conductivity AlN ceramics.
Microstructure and orientation of iron crystals by thermal chemical vapor deposition with imposition of magnetic field
Authors: Yoshikawa Noboru , Endo Takanori , Taniguchi Shoji , Awaji Satoshi , Watanabe Kazuo , Aoyagi Eiji
Published: March 2008

Iron crystals were deposited by thermally activated chemical vapor deposition with imposition of magnetic field. In this study, the deposition was conducted by imposing a magnetic field up to 3.5 T in a temperature range between 0.48 and 0.51 of TmFe (melting point of iron), which is below the Curie point of iron (0.58 TmFe). The microstructures and crystal orientations of the deposits were investigated. In the deposition process, island-shaped crystals were formed on a scale of several microns; then a film was grown by their coalescence. As the magnetic field magnitude increased, population of the island-shaped crystals having a cubic shape increased. Simultaneously, their ω-scanned (200) profile became sharper. Their degree of (100) preferred orientation was dependent on the magnetic field up to 3.5 T, which is usually high enough for the saturated magnetization of iron crystals. However, when the substrate was placed parallel to the magnetic field, (100) preferred orientation was not observed for the island-shaped crystals. A large and bimodal ω-scanned (110) profile having sharp peaks was obtained when the substrate was inclined 45° to the field. Preferred (100) orientation was not obtained from the iron films, for which two reasons were pointed out. The first is the secondary grown crystals on the island-shaped crystals having different orientations, and the second is the observed zone III grain structure of the films, where grain boundary migration occurred.
Morphology and thermal characteristics of nano-sized Pb–Sn inclusions in Al
Authors: Bhattacharya P. , Bhattacharya V. , Chattopadhyay K.
Published: March 2008

Nanoembedded aluminum alloys with bimetallic dispersoids of Sn and Pb of compositions Sn82–Pb18, Sn64–Pb36, and Sn54–Pb46were synthesized by rapid solidification. The two phases, face-centered-cubic Pb and tetragonal Sn solid-solution, coexist in all the particles. The crystallographic relation between the two phases and the matrix depends upon the solidification pathways adopted by the particles. For Al–(Sn82–Pb18), we report a new orientation relation given by [011]Al//[010]Sn and (o11)A1//(101)Sn. Pb exhibits a cube-on-cube orientation with Al in few particles, while in others no orientation relationship could be observed. In contrast, Pb in Sn64–Pb36and Sn54–Pb46particles always exhibits cube-on-cube orientation with the matrix. Sn does not show any orientation relationship with Al or Pb in these cases. Differential scanning calorimetry studies revealed melting at eutectic temperature for all compositions, although solidification pathways are different. Attempts were made to correlate these with the melting and heterogeneous nucleation characteristics.
Preparation of epitaxial Pb(Mg1/3Ta2/3)O3 thin film by chemical solution deposition
Authors: Jeong D. S. , Moon J-H. , Lee B-T. , Kim J. H.
Published: March 2008

Pb(Mg1/3Ta2/3)O3 (PMT) powders and heteroepitaxial thin films on (001) SrTiO3 (STO) substrates were prepared by the chemical solution deposition method. The phase development in PMT powders and thin films was investigated by x-ray diffraction, and the microstructure of PMT thin films was studied by transmission electron microscopy. Phase transformation from pyrochlore to perovskite in the PMT powder samples occurred in the temperature range of 700–800 °C, and perovskite phase was mainly observed in samples annealed above 800 °C. However, perovskite phase in PMT thin films on STO substrates was formed mainly in samples annealed as low as 750 °C/1 h, and it shows an epitaxial orientation relationship of [100](001)PMT∥[100](001)STO.
Growth behavior of evaporated porous thin films
Authors: Vick D. , Smy T. , Brett M. J.
Published: March 2008

Recent experimental work by a number of researchers has demonstrated that unusual high porosity thin films may be obtained in physical deposition systems by combining glancing angle deposition with in situ substrate motion control. The microstructure of these films consists of isolated columns engineered into shapes such as helices, posts, or chevrons. Due to the isolated nature of the columns, the films present a unique opportunity to study fundamental thin film growth behavior and, in particular, the influence of the self-shadowing mechanism in three dimensions. Apart from this academic motivation, there is the need to characterize the physical constraints imposed on the engineering of these films. In particular, this study will have implications for the realization of isolated, periodically arranged nanostructures envisioned for certain applications such as photonic band gap crystals. Results from an ongoing study of growth dynamics, morphology, porosity, and scaling behavior, and the dependence of these features on deposition parameters are presented.