Integrating porous low-permittivity dielectrics into Cu metallization is one of the strategies to reduce power consumption, signal propagation delays, and crosstalk between interconnects for the next generation of integrated circuits. The porosity and pore structure of these low-k dielectric materials, however, also affect other important material properties in addition to the dielectric constant. In this paper, we investigate the impact of porogen loading on the stiffness and cohesive fracture energy of a series of porous organosilicate glass (OSG) thin films using nanoindentation and the double-cantilever beam (DCB) technique. The OSG films were deposited by plasma-enhanced chemical vapor deposition (PECVD) and had a porosity in the range of 7−45%. We show that the degree of porogen loading during the deposition process changes both the network structure and the porosity of the dielectric, and we resolve the contributions of both effects to the stiffness and fracture energy of the films. The experimental results for stiffness are compared with micromechanical models and finite element calculations. It is demonstrated that the stiffness of the OSG films depends sensitively on their porosity and that considerable improvements in stiffness may be obtained through further optimization of the pore microstructure. The cohesive fracture energy of the films decreases linearly with increasing porosity, consistent with a simple planar through-pore fracture mechanism.

A simple and convenient method for preparing visible light response photocatalyst polypyrrole/TiO2 (PPy/TiO2) nanocomposite was developed. The products were characterized by x-ray diffraction, transmission electron microscopy, atomic force microscopy, ultraviolet-visible, and Fourier transform infrared techniques. The results indicated that the nanohybrid was composed of anatase TiO2 and PPy and exhibited an enhanced visible light-capturing ability. Average diameters of TiO2 and PPy/TiO2 were 18 and 35 nm, respectively. The photocatalytic activity of the nanocomposite was evaluated by the degradation of methyl orange under visible light irradiation. In the presence of PPy/TiO2 nanocomposite, the degradation efficiency of methyl orange of 95.54% could be obtained under visible light irradiation within 120 min. The apparent rate constant was 2.19 × 10−2, which was better than that Degussa P25 nano-TiO2. The sensitization mechanism of PPy/TiO2 photocatalyst was discussed briefly.

Nanostructural characterizations of liquid metal–organic precursors-derived cobalt-doped amorphous silica (Si–Co–O) membranes supported on a mesoporous anodic alumina capillary (MAAC) tube were performed to study their unique high-temperature hydrogen gas permeation properties. Cross-sectional scanning transmission electron microscopy images and selected-area electron diffraction patterns indicated that the metal cobalt and the different oxidation states of cobalt oxides (CoO and Co3O4) nanocrystallites having a size range of 5–20 nm were in situ formed in the mesopore channels of the MAAC tube. In addition, high-resolution transmission electron microscopy micrographs and electron energy loss spectroscopy elemental mapping images indicated that the highly dense Co-doped amorphous Si–O formed within the mesopore channels of the MAAC tube. These nanostructural features could contribute to the hydrogen-selective permeation properties observed for the membranes.

In literature related to forced hydrolysis of zirconia, heterocoagulation between large particulates and primary crystallites is generally accepted as the principal route of growth. Our dynamic light scattering (DLS) results revealed an S-shaped growth curve with the growth rate (slope) varying notably from one stage to the other, implying that other coagulation mechanisms may be present. Time-sequenced side-by-side electron microscopy and DLS analyses were conducted along the curves alongside with field emission scanning electron microscopy of full-grown particles. We find that particles growth follows a two-stage heterocoagulation process with primary crystallites and small particles produced from the first-stage serving as building blocks for the first and second stages, respectively. It interesting to note that growth during the second stage occurs by self-assembly and a hypothesis is proposed. Convection-induced coagulation leads to enhanced particle growth for a low precursor concentration but minimal growth for a higher one, both of which conform to the predictions of Melis et al. [AIChE J. 45, 1383 (1999)].

An analytical solution for the Kissinger equation relating the activation energy, E, with the peak temperature of the reaction rate, Tm, has been found. It is accurate (relative error below 2%) for a large range of E/RTm values (from 15 to above 60) that cover most experimental situations. The possibilities opened by this solution are outlined by applying it to the analysis of some particular problems encountered in structural relaxation of amorphous materials and in kinetic analysis.

Sn whisker formation was studied in a “bimetal ledge specimen” that consisted of a uniform layer of Sn that was covered by Cu on only half the sample. Whiskers are observed to grow in the Cu-free region of the sample, which is attributed to stress generated by the diffusion of Sn atoms along the network of columnar grain boundaries. The Sn diffusion is driven by the intermetallic growth, but the whisker density extends out much further than any measurable Cu concentration. Whiskers were also observed to grow in the Cu-coated region by punching through the overlayer, leaving a Cu-grain on the tip of the Sn whisker.

Bulk hybrid polymethyl methacrylate (PMMA)/SiO2 glass with Sb2S3 nanocrystals was prepared by the sol-gel process. We tried to minimize the quantity of water as much as possible in tetraethyl orthosilicate (TEOS) hydrolyzing, prepolymerized the organic monomers, mixed inorganic precursors, and prepolymerized organic monomers under a noncosolvent condition to reduce possible volume shrinkage. A silane coupling agent, which hydrolyzed simultaneously with TEOS, was introduced into the system to improve the miscibility of the organic and inorganic materials. The maximum dopant of Sb2S3 was 9 wt% in our experiments. The second-harmonic generation was observed in the hybrid PMMA/SiO2 glasses with electron-beam poling. Second-harmonic intensity increased with increase of accelerating voltage, current, and the content of Sb2S3 nanocrystals. The maximum χ2 in our study, as large as 1.64 p.m./V, was obtained under the optimized poling condition conducted at 25 kV, 20 nA, and 10 min. It was indicated from the thermally stimulated depolarization current measurements that the nonlinear layer was located in the thin 10-μm irradiated surface of the glass.

Synchrotron x-ray tomography was performed on titanium foams with aligned, elongated pores, initially created by sintering directionally freeze-cast preforms using two different powder sizes. Three-dimensional reconstructions of the pore structures were analyzed morphologically using interface shape and interface normal distributions. A smaller powder size leads to more completely sintered titanium walls separating the dendritic pores, which in turn created a more compact distribution of pore shapes as well as stronger pore directionality parallel to the ice growth direction. The distribution of pore shapes is comparable to trabecular bone reported in the literature, indicating the foam's potential as a bone replacement material.

Photoluminescence (PL) properties of SiOx thin films deposited by pulsed laser ablation of Si in a reactive oxygen ambient and annealed in a nitrogen atmosphere were studied at room temperature. Raman spectroscopy, Fourier transform infrared spectroscopy, and optical transmission measurements were used to characterize the deposited films before and after annealing and complement the PL studies. Strong PL due to quantum confinement was observed at room temperature from Si nanocrystals with an average diameter of approximately 5 nm at 325-nm light excitation. An apparent dependence of PL on the oxygen pressure for film deposition was observed. A detailed analysis of the effects of the annealing temperature revealed a significant PL evolution in luminescence intensity, spectrum profile, peak position, and spectrum range with the annealing temperature ranging from 300 to 1200 °C. Structural variations induced by thermal annealing of the films deposited at different oxygen pressures were also discussed on the basis of their correlation with the PL evolution.

A thermodynamic study was carried out to resolve discrepancies in the enthalpy of formation and related parameters for lanthanum zirconate pyrochlore. The homogeneity field for single phase pyrochlore formation was determined to be ∼33–35 mol% La2O3 at 1500 °C. High-temperature oxide melt drop solution calorimetry was performed in sodium molybdate and lead borate solvents on three compositions ranging from La1.98Zr2.01O7 to La2.07Zr1.95O7. The enthalpy of formation from oxides at 25 °C, ΔH0f,ox, for stoichiometric lanthanum zirconate pyrochlore is −107.3 ± 5.1 kJ/mol, and the standard enthalpy of formation from elements, ΔH0f,el, is −4102.2 ± 6.0 kJ/mol. La2Zr2O7 pyrochlore was found by differential thermal analysis to be stable up to its melting point. The melting point and the fusion enthalpy of La2Zr2O7 pyrochlore were measured as 2295 ± 10 °C and ∼350 kJ/mol, respectively.

The growth of SrTiO3 (STO) thin films is examined using classical molecular dynamics simulations. First, a beam of alternating SrO and TiO2 molecules is deposited on the (001) surface of STO with incident kinetic energies of 0.1, 0.5, or 1.0 eV/atom. Second, deposition of alternating SrO and TiO2 monolayers, where both have incident energies of 1.0 eV/atom, is examined. The resulting thin film morphologies predicted by the simulations are compared to available experimental data. The simulations indicate the way in which the incident energy, surface termination, and beam composition influence the morphology of the thin films. On the whole, some layer-by-layer growth is predicted to occur on both SrO- and TiO2-terminated STO for both types of deposition processes, with the alternating monolayer approach yielding thin films with compositions that are much closer to that of bulk STO.

The objective of the present study is to investigate the dynamic indentation behavior of steel plate material when impacted by ogive-shaped projectiles and in particular under indentation conditions involving large depths of penetration (i.e., depth of penetration greater than projectile radius). Toward the above purpose, dynamic indentation of steel plates of thickness 20, 40, and 80 mm have been carried out using projectiles of diameter 6.2 and 20 mm, and over a range of impact velocities so as to attain depths of penetration in the range 1.4 to 3.6 times the projectile radius. The results indicate that the dynamic hardness, the plastic zone size, specific energy consumed in plastic deformation within the plastic zone, and the average plastic strain within the plastic zone increases continuously with increasing values of depth of penetration normalized by projectile radius. Certain subtle differences regarding the nature of plastic deformation between indentation at large and shallow depths of penetration are presented. However, on a macroscopic scale, the indentation mechanisms and processes are broadly similar and show continuity in terms of behavior across the whole penetration depth range.

Effect of H2O2 on synthesis and powder properties such as surface area and agglomerate size of nanocrystalline Ce0.8M0.2O1.90 (M: Sm, Gd) was explored by treating cerium nitrate and rare-earth nitrate with NaOH in the presence/absence of H2O2. The resultant products were characterized by x-ray diffraction, Raman spectroscopy, thermo-gravimetry–differential thermal analysis, dynamic light scattering, surface area analysis, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. The presence of H2O2 was found to have a profound effect on powder properties such as surface area and particle size of these doped ceria samples and results in smaller crystallite size, softer agglomerates, and larger surface area. A mechanism is proposed to explain the observed better powder properties of the samples. It was also shown that the samples prepared in the presence of H2O2 can lower the conversion temperature of CO to CO2, proving these to be better catalysts. Interestingly, temperature-programmed reduction studies on Sm3+-doped samples showed that the doping in conjunction with the use of H2O2 leads to enhanced reduction properties of the samples over multiple cycles.

Plasticity in amorphous alloys is associated with strain softening, induced by the creation of additional free volume during deformation. In this paper, the role of free volume, which was a priori in the material, on work softening was investigated. For this, an as-cast Zr-based bulk metallic glass (BMG) was systematically annealed below its glass transition temperature, so as to reduce the free volume content. The bonded-interface indentation technique is used to generate extensively deformed and well defined plastic zones. Nanoindentation was utilized to estimate the hardness of the deformed as well as undeformed regions. The results show that the structural relaxation annealing enhances the hardness and that both the subsurface shear band number density and the plastic zone size decrease with annealing time. The serrations in the nanoindentation load-displacement curves become smoother with structural relaxation. Regardless of the annealing condition, the nanohardness of the deformed regions is ∼12–15% lower, implying that the prior free volume only changes the yield stress (or hardness) but not the relative flow stress (or the extent of strain softening). Statistical distributions of the nanohardness obtained from deformed and undeformed regions have no overlap, suggesting that shear band number density has no influence on the plastic characteristics of the deformed region.

In a previous paper, we have demonstrated that a microcrystalline copper film well bonded to a polymer substrate can be stretched beyond 50% without cracking. The film eventually fails through the coevolution of necking and debonding from the substrate. Here we report much lower strains to failure (approximately 10%) for polymer-supported nanocrystalline metal films, the microstructure of which is revealed to be unstable under mechanical loading. We find that strain localization and deformation-associated grain growth facilitate each other, resulting in an unstable deformation process. Film/substrate delamination can be found wherever strain localization occurs. Therefore, we propose that three concomitant mechanisms are responsible for the failure of a plastically deformable but microstructurally unstable thin metal film: strain localization at large grains, deformation-induced grain growth, and film debonding from the substrate.

The orientation relationships among TiB (B27), B2, and Ti3Al phases have been investigated by transmission electron microscopy. By using the composite selected-area electron diffraction technique, the orientation relationship between TiB (B27) and B2 was determined to be [100]TiB[001]B2, (001)TiB(010)B2; and that between TiB (B27) and Ti3Al was . These orientation relationships have been predicted precisely by the method of coincidence of reciprocal lattice points.

This article describes the synthesis and the characterization of a polyamide-12 filled with a nanostructured organic/inorganic titanoniobate hybrid material. The pristine oxide KTiNbO5 has been successfully organomodified by N-alkyl amines via an acido-basic reaction after a cationic exchange step as shown by x-ray diffraction. Transmission electron microscope study and scanning transmission electron microscope observations have been used to describe the change of morphology of the nanofillers before and after processing; the micronic aggregates were changed into single sheets and dispersed in the polymer. Thermomechanical properties of the composites have been determined, and their analyses with structure-properties models are consistent with the exfoliation of the organomodified titanoniobates.

Various α-GaOOH nanorods were synthesized through a microwave-assisted method at 80 °C. In the synthesis, Ga(NO3)3 was used as the gallium source, and urea, L-cysteine, and EDTA disodium salt were used as the additives. The thermal decomposition of the as-prepared α-GaOOH nanorods could selectively produce α-, β-, and ε-Ga2O3 nanorods. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and cathodoluminescence were used to characterize the resulting samples. On the basis of characterization results, the possible growth mechanisms of these various GaOOH nanorods were proposed. This study provides a controllable method to prepare various gallium oxyhydroxide and gallium oxide nanorods.

Fundamental knowledge on the oxidation behavior of pure indium, commonly used as a low-temperature, fluxless soldering material in micro-electro-mechanical system (MEMS) devices, is of importance as it influences the solder joint reliability. A thermodynamic model of the oxidation and reduction behavior of indium is developed by constructing an Ellingham diagram, and by using H2(g) reactions. Partial pressure (p) of H2O was shown to be the critical parameter in creating a reducing environment in the applicable solder reflow temperature range. Verification of the thermodynamic models was then carried out through heating and melting of indium in controlled glove box environments by adjusting p(H2)/p(H2O). The nanometer scale thickness of the oxide layer grown on indium was measured by a spectroscopic ellipsometer. The growth mechanism for oxidation in air below 220 °C follows Uhlig's logarithmic law where electron transport is the rate-controlling mechanism, implying that there is an incubation period for the onset of initial oxidation. Its activation energy was found to be 0.65 eV.

A uniaxial synchro-compression test of a cylindrical bulk metallic glass (BMG) specimen along with a crystalline metallic ring having an inner diameter much larger than the specimen’s diameter and thereby without radial confinement on the BMG specimen was performed. The plastic deformation behavior of a conventional Zr65Cu17.5Ni10Al7.5 BMG under synchro-compression with a cupper ring was investigated. It was found that remarkably plastic deformation in the inherently brittle BMG could occur under the uniaxial stress state as the loading area of the cupper ring was sufficiently large, and multiplication of the shear band on the synergistically deformed BMG specimen could be accomplished. The synergistic effect of the crystalline metal on the plastic deformation behavior of the BMG was attributed to the reduced thermal softening extent inside the shear bands that resulted from the restraining effect of the copper ring on the spring-back action of the testing machine.