This study seeks to provide a mechanistic rationale for the substrate confinement effect on the strength and plasticity of thin metal films. Atomistic simulations of tensile loading of the freestanding and substrate-bonded films were carried out. Particular attention was devoted to correlating the overall mechanical response and the defect mechanisms on the atomic scale. The existence of an interface with the underlying substrate was observed to constrain significantly the dislocation motion in the film. The extent of film strengthening due to the substrate was dictated by the capability of atoms to slide along the interface.

In the current work, a device was proposed for the first time to deposit the particles in situ on a transmission electron micrography grid within furnace aerosol reactors. The device was successfully tested on iron particles produced by thermal decomposition of Fe(CO)5 at 600 °C in a quartz tube heated by an electric heater. The particle depositions were made at four different spatial locations in the axial direction and investigated by transmission electron microscopy. At the reactor inlet, chain agglomerates of 2–3-nm particles were observed. At 19 cm from the inlet, the particles within the agglomerate structures fully coalesced by sintering, and at 32 cm (reactor outlet), polyhedral particles of about 100 nm in diameter emerged from the sintered body.

We report a new Mg-based bulk metallic glass-forming alloy: Mg65Cu7.5Ni7.5Zn5 Ag5Y10. The alloy exhibits a glass-forming ability significantly stronger than all previously discovered Mg-based glass formers. Fully glassy rods 9 mm in diameter can be obtained by using copper mold casting. The critical cooling rate for glass formation was estimated to be <50 Ks−1. The reduced glass-transition temperature (Trg) of the glass was determined to be 0.59.

Ultralow dielectric constant values were measured on Ni–Zn ferrites prepared using Fe2O3 as a starting material and sintered in a microwave field. Significant differences in microstructure, magnetic, and dielectric properties were observed between microwave-sintered Ni–Zn ferrites prepared using Fe3O4 (T34) and those starting with Fe2O3 (T23) ingredients. Higher magnetization values observed in T23 ferrite are attributed to large grain size, possibly containing abundant domain walls and the presence of fewer Fe2+ ions. The ultralow dielectric constant values observed on T23 ferrites show that this procedure is highly suitable to prepare Ni–Zn ferrites for high-frequency switching applications.

Nanoporous tungsten oxide (WO3), with pores of 50 to 100 nm in diameter, has been obtained by galvanostatic (constant-current) anodization of tungsten in a 0.25 M oxalic acid electrolyte. At room temperature, the optimum current density for nanoporous formation is approximately 6.5 to 8 mA/cm2. Monitoring of the anodization voltage during the fabrication process reveals a close match with the theoretical model of Parkhutik et al. [V.P. Parkhutik and V.I. Shershulsky, J. Phys. D 25, 1258 (1992)] for growth of nanoporous Al2O3. The as-anodized films are amorphous and crystallize upon annealing at 350 °C in an oxygen atmosphere.

Ab initio calculation was performed to predict the structures, lattice constants, and cohesive energies of metastable Cu75Cr25 and Cu50Cr50 phases. An n-body Cu–Cr potential was derived through fitting to some ab initio calculated results and was capable of reproducing some intrinsic properties of the Cu–Cr system. Based on the derived potential, molecular dynamics simulations predicted that for a Cu100−xCrx alloy, the face-centered-cubic structure is more stable than the body-centered-cubic (bcc) one when 0 ≤ x ≤ 25, while the bcc structure becomes energetically favored when 25 < x ≤ 100. Interestingly, the predictions match well with the experimental observations.

A novel experimental configuration was devised to measure the evolution of the deformation field and the corresponding toughness in solder joints for microelectronic packaging. The utilized material system comprised a ductile layer of tin-based solder encapsulated within relatively hard copper shoulders. The experimental configuration provided pure shear state within the constrained solder layer. Different Pb/Sn compositions were tested with grain size approaching the film thickness. The in-plane strain distribution within the joint thickness was measured by a microscopic digital image correlation system. The toughness evolution within such highly gradient deformation field was monitored qualitatively through a two-dimensional surface scan with a nanoindentor. The measurements showed a highly inhomogeneous deformation field within the film with discreet shear bands of concentrated strain. The localized shear bands showed long-range correlations of the order 2–3 grain diameters. A size-dependent macroscopic response on the layer thickness was observed. However, the corresponding film thickness was approximately 100–1000 times larger than those predicted by nonlocal continuum theories and discreet dislocation.

Biaxially oriented Ba1−xSrxTiO3 (BST) thin films were fabricated under a highly reducing atmosphere (oxygen partial pressure ∼10−18 atm) on base metal substrates (〈100〉 Ni) using a fluorinated chemical solution deposition method. The degree of film orientation was investigated with respect to film annealing temperature and composition (x = 0, 0.33, 0.5, 0.67, 1). The solution synthesis route included fluorinated solvents, donor-dopants, and chelating agents for control of orientation, defect chemistry, and morphology. Free-energy and phase diagrams guided solution development using halide addition to avoid intermediate BaCO3 formation and instead produce direct crystallization of BaTiO3-type materials from BaF2. The degree of (200) orientation of BST films deposited on 〈100〉 Ni substrates displayed a compositional dependence for 0 < x < 1, with a maximum orientation Lotgering factor approaching unity. Low-temperature (500 °C) crystallization of highly oriented films was demonstrated for solution-derived BST on Ni, which may have enabling materials integration implications for capacitors and other applications.

This article describes both electrochemical deposition and electrophoretic deposition of high-density tellurium (Te) nanowire arrays with wire diameters of 60 nm and lengths of 15–20 μm in the nanochannels of anodic aluminum oxide (AAO) templates. The Te nanowires synthesized via electrochemical deposition (ECD) are generally single crystalline in nature with the wire longitudinal axis along the [001] direction, whereas those synthesized via electrophoretic deposition (EPD) show polycrystalline structures with numerous tiny Te crystallites packed randomly in the wires. The single-crystalline Te nanowires produced by the ECD route are believed to form under a near chemical equilibrium condition; however, the imposed transport and the rapid packing of Te nanocrystallites in the nanochannels of AAO template in external fields lead to polycrystalline Te nanowires in the EPD process. This comparative study of the Te nanowire formation in the nanochannels of AAO template will facilitate the tailoring of the growth of other inorganic nanowires of high quality.

Thermal oxide covered silicon wafers were polished with slurries containing (i) only nano-sized particles of ceria, monodispersed colloidal spherical silica, or hematite of different shapes, (ii) a binary mixture of the same nano-sized and uniform colloidal particles, and (iii) the same colloids coated with nano-sized ceria. The procedures for the preparation of the coated particles are described in this article. The polish rates and surface qualities were in all cases higher with mixed slurries, and even more so with coated particles. The performance of composite systems also depended on the shape of the particles, cubic ones being the most and spheres least efficient. Experimental results indicated that ceria in mixtures was responsible for the enhanced polish process, while core materials enhanced a closer contact of nano-sized particles with the wafer. In general, the polish rates were higher with the larger contact area between the abrasives and the wafer. This mechanism was further verified by polishing oxide wafers on 3-M fixed abrasive pads, which have cylindrical structures with flat surfaces.

The parameters of the mechanically activated field-activated pressure-assisted synthesis (MAFAPAS) process, which were recently developed and patented for producing dense nanostructured materials, were studied in the case of the B2-FeAl intermetallic. Based on x-ray diffraction (XRD) experiments, residual stresses XRD analysis, relative density measurement, and secondary-electron microscopic observations, the optimal synthesis conditions (time, current intensity, and pressure) were studied. Fe + Al powders were comilled in a specially designed planetary mill to obtain a mixture of reactants at the nanoscale without the formation of any product. The milled mixtures were then subjected to a high density of alternating current (60 Hz ac, total current 1250 or 1500 A), a uniaxial pressure (70 or 106 MPa), and different times (from 2 to 5 min). This work confirms the reproducibility of the MAFAPAS process, showing the essential role of the mechanical activation step to produce a pure nanostructured material. In addition, the composition and the microstructure of MAFAPAS end-products depended on the processing parameters (time, current density, mechanical pressure). In particular, it was observed that the process of simultaneous synthesis and consolidation of the product introduced a high level of residual stresses.

The formation of barium monomolybdate (BaMoO4) in inequimolar powder mixtures of BaCO3 and MoO3 was examined under isothermal and nonisothermal conditions upon heating in air at 25–1200 °C, using thermogravimetry. Concurrence of the observed mass loss (due to the release of CO2) to the occurrence of the formation reaction was evident. Accordingly, the extent of reaction (x) was determined as a function of time (t) or temperature (T). The x-t and x-T data thus obtained were processed using a well-established mathematical apparatus and methods to characterize the nature of the reaction rate-determining step and derive isothermal and nonisothermal kinetic parameters (rate constant, frequency factor, reaction order, and activation energy). Moreover, the reaction mixture quenched at various temperatures (450–575 °C) in the reaction course was analyzed by various spectroscopic (x-ray diffractometry, infrared spectroscopy, and laser Raman spectroscopy) and microscopic (scanning electron microscopy and x-ray energy dispersive spectroscopy) techniques for material characterization. The results obtained indicated that the reaction rate may be controlled by unidirectional diffusion of MoO3 species through the product layer (BaMoO4), which was implied to form on the barium carbonate particles. The nonisothermally determined activation energy (156 kJ/mol) was found to be close to the isothermally determined one (164–166 kJ/mol)

Oxygen-containing precursor systems for the synthesis of mixed aluminum–gallium nitride (AlxGa1−xN with x = 0.1 to 0.5) through ammonolysis (heat treatment under ammonia) were evaluated. Three different precursor systems were studied: (i) aluminum isopropoxide (aluminum sec-butoxide)/gallium isopropoxide hydrolyzed with excess water and cross-linked with 1,6-hexanediol, (ii) aluminum–gallium hydroxide coprecipitated from aluminum–gallium nitrate solution, and (iii) spray-dried aluminum–gallium nitrate solutions. The specimens were heat-treated between 700 °C and 1100 °C and were characterized mainly by x-ray diffraction, nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM). NMR was used to follow the conversion of oxygen to nitrogen bonds. TEM in combination with energy-dispersive x-ray spectroscopy was used to determine the solid-solution composition for separated particles. It is possible to synthesize a mixed hexagonal (Al,Ga)N with crystallite sizes in the range of ∼10 nm from all three precursor systems, but all products contained larger GaN crystals ranging from 20 nm (alkoxide-derived) to 200 nm (hydroxide-derived) and a fraction of untransformed Al–O bonds; e.g., (amorphous or γ-phase) Al2O3.

Nanoscale hollow spheres of amorphous phosphorus nitride (P3N5) were synthesized by reacting PCl3 with NaN3 at 150–250 °C. Transmission electron microscope images show that the hollow spheres have a diameter of 150–350 nm, and the thickness of the shell is 20 nm. A very small amount of curly films were also found in the sample prepared at 150 °C. The infrared spectrum indicates a high degree of purity. X-ray photoelectron spectroscopy indicates the presence of P and N, with a molar ratio of 1:1.62 for P:N. Ultraviolet-visible absorption spectroscopy shows an absorption band at 265–315 nm. Under photoluminescent excitation at 230 nm, the P3N5 emits ultraviolet light at 305 nm. With a band gap of 4.28 eV, the products may be a wide gap semiconductor. A possible mechanism and the influence of temperature on the formation of the hollow spheres are also discussed.

A thin film of mixed manganese and vanadium oxides was formed on a platinum electrode by electro-oxidation of Mn2+ precursors in aqueous solution with VO3−. X-ray analysis revealed that the film consists of an amorphous phase including trivalent and tetravalent Mn ions. The infrared spectrum exhibited the bands attributable to V2O5, suggesting that protonation and dehydration of VO3− occur to form the polymeric structure. The mixed oxide film showed no electron spin resonance signal in an as-deposited state. After the film-coated electrode was immersed into water and then dehydrated, however, a characteristic signal (g = 2.022) of Mn2+ in the solid phase appeared, accompanying a decrease in the vanadium content. This suggests that Mn3+ ions not in the oxide network, but pairing with unreacted VO3−, are disproportionated to MnO and MnO2 by the reaction with water, while the VO3− is diffused to keep the charge valance of the film.

Using Ar-induced promotion of microcrystallization to the Si:H network, P-doped μc-Si:H films were prepared at a deposition rate of 50 Å/min. However, a large fraction of an amorphous component was identified, and a definite structural inhomogeneity was evident in the Si:H matrix. Efficient defect elimination, structural reorientation, and grain growth were performed, and an improved microcrystalline network with enhanced dopability was attained by introducing H2 to the Ar-assisted SiH4 plasma and by using their individual advantages to facilitate the microcrystallization process. A high conductivity of approximately 2 × 101 S cm−1 and a homogeneous distribution of micrograins of average diameter approximately 80 Å, contributing to a crystalline volume fraction of 67% in the matrix, were obtained. A significant achievement was to maintain microcrystallinity at a very low thickness of the bulk layer. The n-type μc-Si:H film of dark conductivity approximately 100 S cm−1 was realized at a thickness of approximately 350 Å with a deposition rate of 24 Å/min. Using this material at the tunnel junction as well as at the bottom layer of a double-junction a-Si solar cell, a conversion efficiency of 11.7% was attained without compromising the other parameters.

We report on the exact shape of a propagating crack in a plate with a high width/thickness ratio and subjected to bending deformation. Fracture tests were carried out with brittle solids—single crystal, polycrystalline, and amorphous. The shape of the propagating crack was determined from direct temporal crack length measurements and from the surface perturbations generated during rapid crack propagation. The shape of the crack profile was shown to be quarter-elliptical with a straight, long tail; the governing parameter of the ellipse axes is the specimen's thickness at most length of crack propagation. Universality of the crack front shape is demonstrated. The continuum mechanics approach applicable to two-dimensional problems was used in this three-dimensional problem to calculate the quasistatic strain energy release rate of the propagating crack using the formulations of the dynamic energy release rate along the crack loci. Knowledge of the crack front shape in the current geometry and loading configuration is important for practical and scientific aspects.

In this paper a novel buffer layer architecture consisting of LaMnO3/MgO/TiN is proposed as a suitable structural and chemical template for the epitaxial growth of high-transition temperature (Tc) superconductors on Cu metal surfaces. Using techniques such as high-energy electron diffraction and scanning transmission electron microscopy, we present in situ and ex situ analyses of the buffer-layer and superconductor growth with focus on structural properties of the interfaces formed. While MgO is a good barrier to oxygen diffusion, we find that MgO alone is not a suitable buffer layer due to rapid Cu diffusion. Further, growth of MgO with a single epitaxy can be hindered by the presence of impurities such as S, which form strongly bonded superstructures on the metal surface. With the addition of a TiN layer as a barrier to Cu diffusion, oxide formation is suppressed, interfaces are clean, and a single cube-on-cube epitaxy is observed. While the Cu/TiN and TiN/MgO interfaces are rough, the MgO and LaMnO3 layers planarize the material, leading to growth of smooth YBa2Cu3O7−δ (YBCO). Residual strain in the YBCO film is 0.25% or less and does not lead to apparent cracking. The superconducting properties of the samples were investigated by electrical transport and magnetization measurements. For the first time, high critical current density (Jc) values are reported for YBCO films grown on (001) single-crystal and 100‹100›?textured Cu surfaces without intervening metal coatings. Jc on single crystal-like substrates is as high as 3.5 MA/cm2. Reduced Jc of approximately 1 MA/cm2 on rolled Cu tapes is limited by damage to the tape surface during the rolling process.

Er3+-doped Al2O3 powders were prepared by the sol-gel method, using aluminum isopropoxide [Al(OC3H7)3]-derived Al2O3 sols. The phase content diagram for the Er-doped Al–O system with the doping concentration up to 20 mol% is presented for sintering temperature from 550 to 1250 °C. The different crystalline types of (Al,Er)2O3 phases—γ, θ, α—and two Er-Al-O phases—ErAlO3 and Al10Er6O24—were detected. The Er3+ doping in the Al2O3 phases has a significant effect on phase transformations for γ → θ and θ → α, indicating the enhancement for stability of the γ and θ phases. Compared with the γ–Al2O3 phase, the γ–(Al,Er)2O3 phase can be obtained at high temperatures up to about 1100 °C. The θ–(Al,Er)2O3 phase, together with the α–(Al,Er)2O3 phase, was still observed at 1200 °C under the high Er3+ doping concentration. The Er3+ doping suppressed the crystallization of the γ and θ phases. At a low Er3+ doping concentration from about 2 to 5 mol%, the ErAlO3 phase precipitated out around 1100 °C. The Al10Er6O24 phase was observed at all sintering temperatures; the precipitation was carried out to all Er3+ doping concentrations with increasing sintering temperatures up to about 1200 °C.

The structural, transport, and magnetic properties of La0.65Ca0.35MnO3 films grown on MgO substrates by pulsed-laser deposition under different substrate arrangements in the laser plume were studied. In addition to the standard substrate arrangement in the main stream of particles, substrate arrangements in the periphery area of the laser plume and in an area shielded from the plume were used. In the latter case, the deposition occurs from the flux that is reflected from a side screen. It was found that the substrate arrangement influences considerably the surface topography, structure, chemical composition, magnetic, transport, and magnetoresistance properties of the films. It was found that the substrate arrangements in the periphery area of the laser plume and in the shielded area of the plume eliminate deposition of large particulates. The latter arrangement is the most effective in elimination of particulate deposition. In this case, the film has the smoothest surface with root mean square roughness of about 2 nm. The data obtained revealed interesting correlations between the structural and transport properties as well. In particular, films deposited in the periphery and shielded areas of the laser plume have increased nonstoichiometry (La deficiency), higher resistivity, and broader magnetic transitions. The polycrystalline nature of the films studied is taken into account in the discussion of their transport properties.