Ge(SiMe3)4 was used as a single-source precursor to deposit thin films of alloys of germanium, silicon, and carbon, Si1−x-yGexCy, by low-pressure chemical vapor deposition on silicon substrates at temperatures 873-973 K. X-ray diffraction studies indicated that the films grown above 898 K were cubic phase (a = 0.441–0.442 nm). Infrared spectra of the films showed a major absorption near 783 cm−1. X-ray photoelectron spectra of a typical thin film showed binding energies of Ge3d, Si2p, and C1s electrons at 30.0, 100.6, and 283.2 eV, respectively. As determined by wavelength dispersive spectroscopy, x was 0.07–0.15 and y was 0.43–0.50, indicating that the films contained 7–15% Ge, 38–43% Si, and 43–50% C. At 973 K, the C/(Si + Ge) ratio was 1. Based on these data, the films deposited above 898 K have a structure of β-SiC with Ge atoms replacing some Si atoms in the lattice.

The analytic solution to the time-dependent nucleation problem by Shi-Seinfeld-Okuyama (SSO) [Phys. Rev. A 41, 2101 (1990)] is reviewed. The singular perturbation solution employed by SSO is extended to examine the effect of initial quench position on the incubation time. Two cases are discussed. The first investigates the role of excess vacancies from the high temperature quench on the transient kinetics. The second case examines the change in the incubation time due to the effects of a preexisting subcritical cluster size distribution which forms during the high temperature anneal.

Undoped and Cr doped rodlike Al-Al3Ni eutectics have been studied as initial alloys of Raney nickel catalysts. The aim was to localize the dopant at different stages of the catalyst life: in the initial alloy, after Al leaching out, and after hydrogenation reaction. We have followed this dopant by STEM analysis and high resolution Auger spectroscopy. The outcome is that during Al leaching out, the dopant is also extracted from its initial phase and then forms a deposit on the Ni crystallites of the catalyst. Moreover, during the hydrogenation, the quantity of Cr remains roughly constant.

This paper deals with the growth by molecular beam epitaxy of semimetallic (rare-earth group V element) compounds on III-V semiconductors. Results are presented, first on the Er-Ga-As and Er-Ga-Sb ternary phase diagrams, second on the lattice-mismatched ErAs/GaAs (δa ≈ +1.6%), YbAs/GaAs (δa/a = +0.8%), and ErSb/GaSb (δa/a ≈ +0.2%) heterostructures, and third on the lattice-matched Sc0.3Er0.7As/GaAs and Sc0.2Yb0.8As/GaAs systems (δa/a < 0.05%). Finally the growth of YbSb2 on GaSb(001) is reported. The studies made in situ by reflection high-energy electron diffraction (RHEED) and x-ray photoelectron diffraction and ex situ by x-ray diffraction, transmission electron microscopy, He+ Rutherford backscattering, and photoelectron spectroscopy are presented. We discuss the atomic registry of the epitaxial layers with respect to the substrates, the appearance of a mosaic effect in lattice-mismatched structures, and the optical and electrical properties of the semimetallic films. The problems encountered for III-V overgrowth on these compounds (lack of wetting and symmetry-related defects) are commented on, and we underline the interest of compounds as YbSb2 which avoid the appearance of inversion defects in the GaSb overlayers.

Palladium-supported alumina aerogels were prepared by two different supercritical drying methods. In one method, an alumina wet gel was dried under supercritical conditions of ethanol in an autoclave. In the other, the aerogel was supercritically dried by extracting ethanol using carbon dioxide in an extractor. The Pd-supported alumina aerogel prepared in the autoclave exhibited a high specific surface area of 112.8 m2/g after firing at 1200 °C for 5 h, while the other had a specific surface area of only 5.2 m2/g due to α-alumina transformation. Their catalytic properties for methane combustion were measured. The Pd-supported alumina aerogel prepared in the autoclave combusts methane perfectly at 50–60 °C lower temperature than the other. Palladium particles on the alumina aerogel prepared in the autoclave contained palladium oxide, while those prepared in the CO2 extractor contained only palladium metal.

Niobium-doped lead zirconate stannate titanate thin films have been prepared by a modified sol-gel spin on technique, utilizing the hydrolysis-resistant precursor lead acetylacetonate. Films of compositions in the antiferroelectric tetragonal and antiferroelectric orthorhombic phases were prepared and phase-switched with the application of appropriate electric fields. A distinctly “square” hysteresis response was observed in a low titanium, low tin, orthorhombic composition, with a maximum polarization, Pmax, of 40 μC/cm2 and switching field values of Ef = 175 kV/cm and Ea = 75 kV/cm, while varying degrees of squareness, along with lower polarizations and switching fields, were observed in the higher tin, tetragonal compositions. Electric field-induced strains of up to 0.33% have been measured in the orthorhombic composition, with tunable electromechanical coefficients. Film properties showed only slight variation with electrode size over a range of diameters from 0.8 mm to 6.35 mm; large area electrodes are vital for practical actuator and sensor devices. With a capacitance density of 30–35 μF/cm2, films of the orthorhombic composition are promising as power plane decoupling capacitors in multichip modules.

The influence of single solute atoms and solute clusters on an extended edge dislocation dipole in Al was studied by atomistic simulation. Single Cu and Ag solute/dislocation interaction energy calculations showed that Cu interacts strongly with an Al extended dislocation and prefers sites in the compressive region, in agreement with elasticity theory predictions. Single Ag atoms, however, are strongly repelled by an Al extended dislocation, in contrast with elasticity theory predictions. Monte Carlo simulations of Al: 1% Cu, Al: 2% Cu, Al: 1% Ag, Al: 0.5% Cu, 0.5% Ag, and Al: 0.75% Cu, 0.25% Ag were carried out in the presence of an extended dislocation dipole at 600 K allowing for solute segregation. Cu atoms in the binary alloys were observed to segregate to the compressive regions of the extended dislocation dipole, forming widespread “atmospheres” over the width of both extended dislocations which did not affect the partial dislocation spacing. Ag in the binary alloy formed small Ag zones which also had little influence on the spacing between the partials. The ternary systems, however, exhibited highly localized solute clusters that had a large impact on the extended dislocation dipole structure, increasing the separation between the partial dislocations. The resulting cluster structures are discussed along with their influence on the apparent stacking fault energy of the alloy systems.

A transmission electron microscopy study of the microstructural development for (111)Si wafers implanted with Ti ions and annealed subsequently at 950 °C is presented. The as-implanted wafers have a Ti-rich amorphous layer at the surface with embedded silicides, which correspond to a crystalline form of TiSi2 that has not been reported previously. Below this lies a Ti-lean crystalline layer with extensive radiation damage. The annealed layers have large incoherent islands of C54 TiSi2, with a layered microstructure in the Si between them consisting of twins, then topotaxial silicides, then dislocation loops. It is proposed that this microstructure arises from silicide growth prior to epitaxial regrowth, whereas for the continuous epitaxial films observed previously at lower annealing temperatures, epitaxial regrowth precedes silicide development.

The measurements of the desorption pressure-composition-temperature (P-C-T) of the TixZr1−xNiyV2−y (0 ≤ x ≤ 1,0 ≤ y ≤ 2) alloy have been investigated by means of a 32 factorial design method. The response surface function of hydrogen desorption between 0.01 and 10 atm was calculated by Yates' algorithm. Alloy with x = 0.35, y = 0.60 (i.e., Ti0.35Zr0.65Ni0.6V1.4) was found to possess maximum hydrogen desorption capacity. When examined by EDAX and SEM, this alloy shows three distinguishable phases and exhibits C14 structure. The effect of substitution of Mn and Ni for V was also studied. Alloy such as Ti0.35Zr0.65Ni1.2V0.4Mn0.4 has nearly a pure C14 structure with 89% hydrogen desorption ability. This alloy has 255 mAh/g, 231 mAh/g, and 210 mAh/g capacities at 25 mA/g, 50 mA/g, and 100 mA/g discharge rates, respectively. This indicates that the substitution of Mn and Ni for V not only can improve its hydrogen desorption ability, but also make the alloy structure more uniform and more suitable to be an electrode material.

The activation energies, Ea's, for Pt2Si and PtSi formation were determined using in situ resistance measurements with ramp rates ranging from 0.4 °C/m to 100 °C/s. Measurements were performed using both conventional furnace and rapid thermal annealing (RTA). Pt films were evaporated on undoped polycrystalline Si and single-crystal Si on sapphire substrates. The Ea's determined from Kissinger plots were 1.63 ± 0.05 and 1.61 ± 0.06 eV for Pt2Si formation and 1.83 ± 0.06 and 1.83 ± 0.07 eV for PtSi formation with polycrystalline Si and silicon on sapphire substrates, respectively. These are the first reported measurements of Ea's for Pt2Si and PtSi formation over such a wide range of heating rates (greater than four orders of magnitude) and at such high heating rates. The phase formation sequence remained the same for the range of heating rates examined.

A model for estimating the temperature rise in a laser-irradiated oxide target is developed and applied to laser-firing of sol-gel films on oxide substrates. The model incorporates a continuous-wave (CW) Gaussian laser beam translated across a sol-gel film on a semi-infinite substrate. Heat effects due to phase changes are assumed to be absent. In addition, the laser energy is assumed to be absorbed primarily in the substrate material (since many sol-gel films are much thinner than the absorption depth of typical laser wavelengths). The model also takes into account the temperature dependence of the thermal properties of the substrate. The predictions from the model are compared to experimental data from various laser firing experiments. The temperatures predicted by the model are shown to agree well with experimental results.

Bremsstrahlung-excited Auger electron spectroscopy (AES) was used to study the oxidation kinetics of an aluminum nitride powder oxidized in air at 750, 800, 850, and 900 °C. An equation was derived to calculate the average surface oxide film thickness from the aluminum AES spectra. The oxidation of this powder was found to follow a parabolic rate law within this temperature range. The measured activation energy was 230 ± 17 kJ/mol (55 ± 4 kcal/mol). Analysis with x-ray photoelectron spectroscopy (XPS) showed that in addition to the nitride N 1s peak, there was a second N 1s peak. This peak has been observed in previous studies and can be attributed to N-O bonding either within the growing oxide film or at the Al2O3/AlN interface.

The recent announcement of the synthesis of C3N4 has increased interest in this unique material. Carbon nitride may have several useful applications as wear and corrosion resistant coatings, electrical insulators, and optical coatings. We have produced amorphous carbon nitride coatings containing up to 40% nitrogen using planar magnetron RF sputtering with and without an ion beam in a nitrogen atmosphere. Both wavelength dispersive x-ray spectrometry (WDX) and x-ray photoelectron spectroscopy (XPS) indicate this composition. Coatings up to 2 μm thick were produced on alumina, silicon, SiO2, and glass substrates using a graphite target. Films with transparency greater than 95% in the visible wavelengths and harder than silicon have been produced. The properties of these films are correlated with composition, fabrication, conditions, and subsequent heat treatments. A scanning tunneling microscope (STM) and transmission electron microscopy (TEM) were used to characterize the morphology of the films. XPS studies confirm the stability of a carbon nitrogen phase up to 600 °C. Compositional variations were determined with secondary ion mass spectrometry (SIMS) depth profiling, and the Raman spectra are compared with those of carbon and carbon nitride films prepared by other methods.

Combustion synthesis of NbAl3 and Nb2Al was studied using the volume combustion mode. The effects of heating rate and green density were examined for NbAl3 synthesis. The effect of green density was also investigated for Nb2Al. Greater reaction completion was achieved at higher heating rates and green densities. In both NbAl3 and Nb2Al samples, the reaction was initiated above the melting point of Al. Quenching (Nb+3Al) samples pressed at relatively high and low densities below the ignition temperature, and results of a particle-foil experiment, identified the spreading characteristic of molten Al over Nb, providing mechanistic details about niobium aluminide product formation.

A directionally solidified alloy based on the NiAl-(Cr, Mo) eutectic was examined by transmission and scanning electron microscopy to characterize the microstructure and room temperature deformation and fracture behavior. The microstructure consisted of a lamellar morphology with a 〈111〉 growth direction for both the NiAl and (Cr,Mo) phases. The interphase boundary between the eutectic phases was semicoherent and composed of a well-defined dislocation network. In addition, a fine array of coherent NiAl precipitates was dispersed throughout the (Cr, Mo) phase. The eutectic morphology was stable at 1300 K with only coarsening of the NiAl precipitates occurring after heat treatment for 1.8 ks (500 h). Fracture of the aligned eutectic is characterized primarily by a crack bridging/renucleation mechanism and is controlled by the strength of the semicoherent interface between the two phases. However, contributions to the toughness of the eutectic may arise from plastic deformation of the NiAl phase and the geometry associated with the fracture process.

The dielectric temperature characteristics and microstructures of BaTiO3-based ceramics sintered with additives such as Sm2O3, CeO2, and Bi2O3:Nb2O5 were investigated using TEM, XRD, and EDS. For a Sm2O3-modified BaTiO3 ceramic whose additives were uniformly distributed in grains, the ferroelectric transition temperature (Tc) was shifted to a lower temperature, while the transition temperatures (T1 and T2) were shifted to a higher temperature. The additions of CeO2 and Bi2O3: PbO to BaTiO3 formed the chemical inhomogeneity which was composed of grain core, grain shell, and concentration gradient region. The dielectric curve versus temperature of CeO2-modified BaTiO3 has the shape of one strong peak, whereas BaTiO3 ceramics sintered with Bi2O3:Nb2O5 exhibit the broad dielectric constant at the low temperature region and 130 °C ferroelectric transition peak. The dielectric temperature characteristics of additives modified BaTiO3 were determined in terms of the chemical inhomogeneity and stress induced by the difference of the unit cell volume between grain core and grain shell.

The thermodynamic parameters that drive the atomic migration in B2 alloys are studied using Monte-Carlo simulations. The model is based on a vacancy jump mechanism between nearest neighbor sites, with a constant vacancy concentration. The ordering energy is described through an Ising Hamiltonian with interaction potentials between first and second nearest neighbors. Different migration barriers are introduced fur A and B atoms. The results of the simulations compare very well with those of experiments. The ordering kinetics are well described by exponential-like behaviors with two relaxation times whose temperature dependences are Arrhenius laws yielding effective migration energies. The ordering energy contributes significantly to the total migration energy.

The effects of high current density electropulsing on the hyperfine structure of amorphous alloys Fe73Si9.5B17.5, Fe75Si10B15, and Fe79Si7B14 were investigated by Mössbauer spectroscopy. Electropulsing influenced the microstructure at a temperature well below the bulk crystallization temperature. In the alloy having least boron (or highest concentration of Fe), α-Fe particles ≃3 nm in size precipitated from the amorphous matrix, giving a change in internal magnetic field.

Silicon carbide fiber-reinforced alumina bodies have been produced by ram extrusion. The Al2O3 powder and SiC fiber were milled together to give a dry dispersion of up to 30 vol % fiber which was subsequently mixed to a paste by high shear kneading using hydroxypropylmethylcellulose solutions as the binder phase. Extruded bodies with green densities ranging between 56 and 63% full theoretical density were achieved. The paste flow behavior was characterized using physically based equations which show that for any given moisture content the pressure drop and the constituent paste parameters are all systematically reduced as the fiber loading is increased. This observation can be explained almost completely by combining packing theory with the paste rheology data. Fiber interactions within the paste and the die system appear not to greatly influence the rheological character of the material. It is shown statistically that the fibers are homogeneously dispersed throughout the paste mass after extrusion. Image analysis has been used to aid in macrodefect analysis, and it is shown that the optimum concentration of fiber was 20 vol % with a quantity of binder sufficient to give an initial yield stress of 2 MPa.

The stress/strain behavior of bulk material is usually investigated in uniaxial tension or compression; however, these methods are not generally available for very small volumes of material. Submicrometer indentation using a spherical indenter has the potential for filling this gap with, possibly, access to hardness and elastic modulus profiles, representative stress/strain curves, and the strain hardening index. The proposed techniques are based on principles well established in hardness testing using spherical indenters, but not previously applied to depth-sensing instruments capable of measurements on a submicrometer scale. These approaches are now adapted to the analysis of data obtained by stepwise indentation with partial unloading, a technique that facilitates separation of the elastic and plastic components of indentation at each step and is able to take account of the usually ignored phenomena of “piling up” and “sinking in”.