“In situ x-ray investigation of hydrogen charging in thin film bimetallic electrodes” [J. Mater. Res. 8, 2091 (1997)]

This paper discusses computational simulations of the evolution of stresses and deformation in unpassivated and SiO2-passivated Al lines on Si substrates. The finite element model accounts for elastic-plastic deformation in the Al lines during etching, passivation, and subsequent thermal cycling, by recourse to a generalized plane strain formulation within the context of a unit cell with appropriately constrained boundary conditions. The effects of different controlled variations in thermal history, and in the width, height, spacing, and yield behavior of the Al lines are analyzed; all these factors are seen to have potentially strong effects on the evolution of stresses within the lines. The predictions of the computations presented in this work are amenable for direct comparisons with experiments of curvature evolution along and perpendicular to the lines upon patterning, passivation, and thermal loading. The predicted stresses in metal interconnects can be directly used for reliability modeling purposes.

Interfacial precipitation in sol-gel derived, titania-doped diphasic mullite gels was investigated using conventional and high resolution transmission electron microscopy. Rutile, anatase, and brookite precipitated on the interface between {110} planes of mullite and glass pockets in the sintered body. The formation of brookite may be attributable to the Si- and Al-rich environment during precipitation. Each polymorph of titania has a unique morphology and orientation relationship with mullite. Brookite exhibits a truncated pill box shape, and anatase displays a vermicular morphology. Quenching experiments suggest that the precipitates grow and undergo phase transformations during cooling.

I-V studies indicate a composition dependent switching behavior (Memory or Threshold) in bulk Al20AsxTe80−x glasses, which is determined by the coordination and composition of aluminum. Investigations on temperature and thickness dependence of switching and structural studies on switched samples suggest thermal and electronic mechanisms of switching for the memory and threshold samples, respectively. The present results also show that these samples have a wider composition range of threshold behavior with lower threshold voltages compared to other threshold samples.

Micro-Raman analysis was used to study the structure of TiO2 powders produced at low (260 °C) and high (600–900 °C) temperatures by vapor hydrolysis of titanium tetraisopropoxide (TTIP). Spatial inhomogeneity was discovered after the amorphous TiO2 powders produced at low temperature were calcined at 700, 800, and 900 °C for 3 h. The TiO2 powders produced at high temperatures (from 600 to 900 °C) were found to be spatially homogeneous and predominately anatase in structure. Small amounts of rutile and brookite are found for powders produced at 700, 800, and 900 °C after calcination at 600 °C for 3 h. The rutile and brookite impurities are believed to be concentrated on the surface of anatase based on a comparison of results of Raman and x-ray diffraction studies.

Thermal stresses in thin Cu films on silicon substrates were examined as a function of film thickness and presence of a silicon nitride passivation layer. At room temperature, tensile stresses increased with decreasing film thickness in qualitative agreement with a dislocation constraint model. However, in order to predict the stress levels, grain-size strengthening, which is shown to follow a Hall–Petch relation, must be superimposed. An alternative explanation is strain-hardening due to the increase in dislocation density, which was measured by x-ray diffraction. At 600 °C, the passivation increases the stress by an order of magnitude; this leads to a substantially different shape of the stress-temperature curves, which now resemble those of aluminum with only a native oxide layer. The effect of passivation is shown to be very sensitive to the deposition and test conditions.

Dilatometer push rods exert uniaxial compressive stresses on powder compacts undergoing sintering. In this study the effect of such stresses on the shrinkage anisotropy behavior of glass powder compacts is considered. A shrinkage anisotropy factor (k), defined by the ratio between axial and radial strain, is used to quantify the anisotropy in cylindrical compacts (k = 1 represents isotropic shrinkage). The available experimental data in the literature indicate that the effect of the applied dilatometer stress is to increase the value of k over that of free sintering conditions. For the small stresses exerted by the dilatometer push rods, it is shown that k is always. 1. The common practice of calculating the sintered density from uniaxial dilatometer data, ignoring the existence of shrinkage anisotropy, is shown to lead to significant errors, even for values of k only slightly different from k = 1.

The kinetics of in situ crystallization of LaNiO3 thin films in sputtering deposition at temperatures ranging from 250 to 450 °C and isothermal crystallization of room-temperature (RT) sputtered LaNiO3 thin films in annealing at 350–500 °C were investigated by the x-ray diffraction method. The crystallization in both cases basically followed the Johnson–Mehl–Avrami (JMA) relation. However, different crystallization kinetics were observed. The transformation index and activation energy of crystallization in high temperature sputtering were about 1.5 and 33 kJ/mole, respectively, while in the annealing of RT-sputtered films, 1.0 and 63 kJ/mole were found. From the determined transformation index, it is suggested that the crystallization rate in high temperature sputtering was determined by a diffusion-controlled process of lateral growth with a decreasing nucleation rate of crystallites in the adsorption layer. However, the annealed films crystallized by an interface-controlled and one-dimensional growth of existing nuclei.

Hollow polyimide shells, to be used in inertial confinement fusion experiments, were fabricated by codepositing monomer precursors onto spherical mandrels. Polyimide shells with 700 to 950 μm diameters and 4 to 13 μm wall thicknesses were produced. The shell wall shrunk 20–30% due to imidization. Burst and buckle pressure tests on these shells yielded estimated mechanical strength properties: ∼ 15 GPa elastic modulus and ∼ 300 MPa tensile strength. The permeability of D2 through polyamic acid at 298 K was 7.4 × 10−17 mol · m/m2 · Pa · s and increased to 6.4 × 10−16 mol · m/m2 · Pa · s upon curing the shell to 150 °C. The permeability of D2 at 298 K through vapor-deposited polyimide flat films was 240 times greater than through polyamic acid.

(Pb1−xBax) (Zr0.75Ti0.25)O3 ceramics were modified with Y3+ and Nb5+, and their dielectric and electrostrictive properties were investigated as a function of x (0.23 ≤x ≤ 0.33). With increasing Ba2+ content, the axial length (a) was increased and distortion of rhombohedral angle (90°-α) approached to zero, resulting in the increased symmetry of the (Pb1−xBax)0.96Y0.02(Zr0.75Ti0.25)0.98Nb0.02O3 structure. As the Ba2+ content increased, the maximum dielectric constant decreased and the curve of field-induced strain became a parabolic one with lower hysteresis of strain. When 25−27 mol% of Ba2+ was substituted on the Pb2+ sites, the specimens showed excellent electrostrictive properties which were 1.04−1.17 × 10−3 of longitudinal strain and 12–18% of hysteresis of strain at 10 kV/cm.

Iridium dioxide (IrO2) thin films, deposited on Si substrates by reactive rf sputtering method under various conditions, were characterized by atomic force microscopy (AFM), x-ray diffraction (XRD), electrical-conductivity, spectrophotometry, ellipsometry and Raman scattering measurements. The average grain sizes of the films were estimated by AFM. A grain boundary scattering model was used to fit the relation between the average grain size and electrical resistivity. The optical and dielectric constants were determined by the ellipsometry measurements. The results of the electrical and optical studies show a metallic character of the films deposited at higher temperatures. The results of XRD and Raman scattering indicate that the IrO2 films deposited at temperatures higher than 300 °C show the presence of (200) texture.

The self-propagating high temperature synthesis (SHS) of Al–Zr–N system composite ceramics was investigated in this paper. The melting point of Al was low (Tm = 660 °C), while that of Zr was high (Tm =1855 °C). Therefore, Al will melt and coalesce during reaction, which inhibit diffusion of nitrogen from outside the metal compact to interior due to collapse of the pore openings, while Zr will not melt under the combustion temperature which is lower than its melting point. It will not affect the permeation of nitrogen under the conditions. Accordingly, the ratio of Al and Zr in the initial mixed powders will affect the permeation of nitrogen from outside the sample to the interior, which results in different phase formation of the products. In this study, the relationship between the combustion parameters and the phase formation of the products will be experimentally determined through XRD analysis, and then thermodynamically analyzed.

The half-thickness and mass absorption coefficient of 13.0 keV x-rays, 46.5 keV γ-rays, and 1.16 MeV βƟ particles have been measured for pristine, bromine intercalated, and iodine monobromide intercalated pitch-based graphite fiber composites. Since these materials have been proposed to replace aluminum structures in spacecraft, the results were compared to aluminum. Pristine graphite epoxy composites were found to have about 4.0 times the half-thickness, and 40% of the mass absorption of aluminum for ionizing radiation. Bromine intercalation improved performance to 90% of the half-thickness, and 1.7 times the mass absorption coefficient of aluminum. Iodine monobromide extended the performance to 70% of the half-thickness and 3.0 times the mass absorption of aluminum. Thus, intercalation not only makes up the deficiency conventional composites have in shielding components from ionizing radiation, but actually confers advantages in mass and thickness over aluminum. The βƟ particle shielding of all the materials tested was found to be very effective. The shielding of all of the materials was found to have nearly the same mass absorption coefficient of 17.8 ± 0.9 cm2/g. Inelastic scattering processes were found to be important in βƟ particle shielding; however, the extent of inelastic scattering and thus the distribution of energies of the transmitted electrons did not vary with material.

The effects of dimethylformamide (DMF) on morphology and texture of hematite particles produced from a forced hydrolysis reaction of FeCl3 –HCl solution were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), thermogravimetry and differential thermal analysis (TG-DTA), N2 and H2O adsorption, and zeta potential measurements. The morphology of synthetic hematite particles was concentration dependent; they changed from large sphere with a diameter of ca. 600 nm to diamond-like shape with increasing DMF concentration in the aging solution accompanying a reduction of their size to 80 nm without incorporation of DMF in the particles. This fact was explained by an acceleration of phase transformation from β–FeOOH to hematite with an elevation of the solution pH owing to dimethylamine produced from a hydrolysis of DMF at an elevated temperature. TEM and XRD suggested that the diamond-like hematite particles formed above 6–10 vol% DMF possess a single-crystal nature. Gas adsorption technique revealed that the particles produced above 10 vol% DMF possess a high thermal stability. TG and FTIR indicated that the hematite particles produced with DMF contained small amounts of OH_ ions in the lattice though they provided a single-crystal nature.

This work attempts to determine an appropriate passivation structure in the real integrated circuit (IC) pattern to improve stress-related reliability problems after the plastic packaging. Several different types of amorphous passivation materials were first tested to learn how effectively they protect underlying Al interconnection lines during thermal displacement-induced fatigue at temperature ranges from −65 °C to 150 °C. It was also studied how effectively the occurrence of cracking in a passivation layer can be suppressed by the improvement of its topological feature or increase in its thickness. According to the experimental results, an increase in passivation thickness up to 21,000 Å (7000 Å for oxide and 14,000 Å for SiN, respectively) was found to be a highly effective way to suppress stress-induced passivation damage on the inside of the chip in plastic IC packages. However, at the edges of the chip, smoothing of the passivation layer by a sloping metal sidewall was more important for the improvement of thermal cycling performance than thickening of the passivation layer.

Subsolidus phase relations in the BaTiO3–La2TiO5–TiO2 part of the ternary BaO–La2O3–TiO2 system at 1300 °C in air were determined. The phases were characterized by x-ray diffraction, scanning electron microscopy, and electron probe wavelength dispersive spectroscopic microanalysis. A combination of techniques was employed because of insensitivity in detecting secondary phases by x-ray diffraction. The location and extent of Ba6−xLa8+2x/3Ti18O54 ternary solid solution 0.2(1) ⩽ x ⩽ 2.3(1) and Ba1−yLayTi1−y/4 (VTi)y/4O3 binary solid solution 0 ⩽ y ⩽ 0.3 at 1300 °C was established. Tie lines between various barium polytitanates with a sequence of Ba6−xLa8+2x/3Ti18O54 solid solution regions were determined.

A system of (1 − x)Pb(Yb1/2Nb1/2)O3 (PYN)–xPb(Mg1/3Nb2/3)O3 (PMN) (0 ≤ x ≤ 1) has been investigated with regard to its phase transition, densification, and dielectric and electrostrictive properties. According to the XRD study, a crystal structure transformed from orthorhombic to pseudocubic at approximately x = 0.22. The superlattice peaks were gradually weakened with increasing x, and disappeared above x = 0.22. Increasing x led to an increase in the maximum dielectric constant and a decrease in transition temperature over the entire composition range. As a result of P-E hysteresis loops, successive phase transitions of ferroelectric-antiferroelectric-paraelectric were observed to occur in the range of 0.18 ≤ x ≤ 0.25 with increasing temperature, while the direct transition into the paraelectric region was found to take place for x ≥ 0.3. From the field-induced strain measurement, high electrostrictive coefficients, 7.3–8.2 × 10−2 (m4/C2), were determined in the PYN-rich range (x ≤ 0.1). Based on the results, a phase diagram of the system was constructed with variations in x and temperature.

The structure of MoS2 films grown by ion beam assisted deposition is investigated using transmission electron microscopy. Films consist of stacks of S–Mo–S planes with a [001] texture; however, three-dimensional crystal symmetry is disrupted by a high density of planar defects. Selected area electron diffraction patterns show (hk0) and (00l) reflections, features similar to a random layer structure, as well as diffuse (103) reflections. It is suggested that these films do not have a true random layer structure, but rather a two-dimensional structure formed by nonrandom in-plane translations.

Results are presented on the influence of the size of diamond powders and the laser power on the main Raman line. These results show conclusively that there is a consistent and systematic, reversible, downshift with both decrease of powder size, and increase of power. The shift can be explained by local heating of about 500 °C in the extreme case. Its significance applies to interpretation of the alleged “downshifting” of the 1332 cm−1 line in all diamond research. In the future, the grain size, the thermal contact, and the beam power must be carefully monitored in reporting and interpreting any frequency shifts.

Transmission electron microscopy and high-resolution electron microscopy have been used to study microstructural properties of conductive SrRuO3 films grown by pulsed laser deposition on (001) LaAlO3 and (001) SrTiO3 substrates. It was found that the SrRuO3 films deposited on both substrates consist of mixed domains of [001] and [110] orientations, with orientation relationships that can be described as (i) (001)f ‖ (001)s and [110]f ‖ [100]s and (ii) (110)f ‖ (001)s and [001]f ‖ [100]s, respectively. The SrRuO3 films deposited on SrTiO3, in particular, were found to have a layered domain structure, with the [110] domain grown initially on the substate, followed by growth of the [001] oriented domain with increasing thickness. The films on SrTiO3 are strained and have a coherent interface with the substrate. The SrRuO3 films deposited on LaAlO3, on the other hand, contain a high density of structural defects such as stacking faults and microtwins on the (022) planes. Microtwins as large as 50 nm in thickness are observed in the films deposited on LaAlO3. Possible causes for the observed structural defects in the films are discussed.