An autostoichiometric vapor deposition method is implemented to achieve deposition of stoichiometric LiTaO3 using LiTa(OButn)6 precursor. Precisely stoichiometric LiTaO3 can be grown by this method. A simple low pressure reactor is used to facilitate the autostoichiometric vapor deposition through hydrolysis polycondensation of double alkoxides in the vapor phase. Typical deposition and annealing conditions are described. X-ray diffraction, SEM, and compositional analyses are performed on the films grown on fused silica, Pt, (100) sapphire, and LiNbO3(001). Rocking curve measurements indicated excellent epitaxial growth of LiTaO3 on (100) sapphire. Compositional analysis by measurement of lattice parameters confirmed that the present method can produce high quality stoichiometric LiTaO3. The nonstoichiometry factor for LiTa(OButn)6 is negligible. Mass spectrometric study of the precursor compound LiTa(OButn)6 suggests that the volatile species is Li2Ta2(OButn)12.

The crystallization kinetics of the pyrochlore to perovskite phase transformation in lead zirconate titanate (PZT) thin films have been analyzed using rapid thermal processing (RTP). Sol-gel PZT thin films, fabricated on platinum electrodes, were annealed at 550 °C to 650 °C with hold times ranging from 1 s to 5 min. Glancing angle x-ray diffraction (XRD) was used for depth profiling to identify the location of phases in the films. Transmission electron microscopy (TEM) provided information on grain structure, nucleation, and growth. The phase information was correlated to the ferroelectric and dielectric properties. The perovskite phase nucleated in the pyrochlore phase throughout the film thickness, and at 650 °C the transformation was complete in 15 s. Fast growing (100) PZT nucleated at the platinum and consumed a small-grained matrix until a columnar structure was obtained. A ramp rate of 100 °C/s was sufficiently fast to prevent transformation during heating and allowed the direct application of an Avrami model for transformation kinetics. An activation energy of 610 kJ/mol was determined.

Using facing target sputtering, crystalline magnetoplumbite-type barium ferrite (BaFe12O19 or BaM) thin films have been prepared in situ at a substrate temperature of 640 °C without postdeposition annealing. Using our facing target sputtering system, BaM thin films grow randomly if they are directly deposited onto Si or thermally oxidized Si substrates. However, deposited onto a sputtered ZnO layer (∼230 Å) on Si substrates, BaM thin films show excellent c-axis out-of-plane texture with a 0.2°c-axis dispersion angle, as indicated by x-ray diffraction (XRD). Cross-section transmission electron microscopy (XTEM) reveals that the textured films epitaxially grow on a transition layer, which is formed between BaM and ZnO. No direct epitaxial relation between BaM and ZnO was observed. This transition layer is identified by TEM and XRD as ZnFe2O4, which, from a structure point of view, reduces the lattice mismatch between BaM and ZnO, and also enhances the c-axis out-of-plane epitaxial growth. ZnFe2O4 is a reaction product of BaM and ZnO, as indicated by both TEM and XRD. After ex situ annealing the film in air at 800 °C, the ZnFe2O4 layer becomes thicker at the expense of BaM and ZnO. The lattice parameters of both BaM and ZnO decreased as annealing time increased.

We examine the use of chemisorptive emission (electron emission accompanying the adsorption of a reactive gas on a metal surface) and atomic force microscopy as measures of plastic deformation during fracture along a metallic Mg/glass interface. Localized ductile deformation in the metallic phase enhances the fracture energy, exposes metallic Mg to the reactive O2 atmosphere, and produces intense emissions. The number of electrons emitted following fracture in low-pressure oxygen atmospheres is strongly correlated with the total energy expended during failure (peel energy). The presence of localized ductile deformation is verified by atomic force microscopy (AFM): voids are observed on surfaces yielding significant cmissions and enhanced fracture energies. These voids are not observed on samples yielding the lowest peel energies and emission intensities, i.e., where the contribution of deformation to the peel energy is negligible. Quantitative use of roughness data derived from the AFM images is, however, problematic. The potential for chemisorptive electron emission as a probe of deformation along interfaces involving Mg, Ti, Zr, and Al is promising.

In the context of studying the feasibility of photocatalytically self-cleaning windows and windshields, clear, abrasion resistant, photocatalytic films of TiO2 were formed on soda lime glass and on fused quartz by a sol-gel process. The rate of photooxidation of contaminant deposits was estimated by measuring the rate of decrease in the integrated IR absorbance associated with the C-H stretching vibrations of a thin solution-cast film of stearic acid under 365 nm (2.4 mW/cm2) or 254 nm (0.8 mW/cm2) irradiation. Approximately 3 × 10−4 stearic acid molecules were stripped per 365 nm photon in either front- or back-illuminated soda lime glass, and 6 × 10−4 molecules when the films were coated on fused quartz. For thin TiO2 films on fused quartz, the rate of photooxidation, normalized by the number of photons absorbed per unit area, was independent of the wavelength. In contrast, for films on soda lime glass, the rate of photooxidation, when similarly normalized, was higher for the less penetrating wavelength. The reduced photoactivity on glass at the deeply penetrating wavelength (365 nm), as well as the greater photoefficiency on quartz than on glass, are attributed to diffusion of sodium oxide from the glass into the inner glass-contacting zone of the TiO2 layer.

Thin films of ZrO2-Al2O3 were grown on cubic-Zr(Y)O2 substrates by a liquid precursor route. Phase formation and epitaxy of these films was studied as a function of heat-treatment temperature and time. The following sequence of phases was observed in these thin films: Precursor → t-(Zr,Al)O2 → t-(Zr,Al)O2 + γ-(Al,Zr)2O3 → m-ZrO2 + α-Al2O3 Observations strongly suggest that the epitaxial process initiated before the metastable, single phase t-(Zr, Al)O2 partitioned to t-(Zr, Al)O2 + γ-(Al, Zr)2O3. Observations at 1400 °C show that, after the γ to α transformation, α-Al2O3, grains develop an elongated, prismatic morphology and an epitaxial relation with the underlying and surrounding m-ZrO2. The phase that is chemically and structurally similar to the substrate, in this case t-(Zr,Al)O2, or m-ZrO2, forms an epitaxial layer between the substrate and isolated, prismatic grains of heteroepitaxial α-Al2O3.

Epitaxial thin films (4–1000 Å) of Ti contacts have been deposited via UHV electron beam evaporation at room temperature on monocrystalline, n-type, alpha (6H)-SiC(0001). The interfacial chemistry and microstructure, and the electrical properties, were investigated at room temperature and after annealing at 700 °C up to 60 min. High resolution TEM analyses revealed the formation during annealing of reaction zones consisting of Ti5Si3 and TiC. The corresponding electrical properties exhibited considerable stability except after an initial 20 min anneal. Current-voltage (I-V) measurements showed that the Ti contacts were rectifying with low ideality factors (n < 1.09) and typical leakage currents of 5 × 10−7 A/cm2 at −10 V. The Schottky barrier heights calculated from x-ray photoelectron spectroscopy and I-V and V-V measurements were between 0.79 and 0.88 eV for the as-deposited contacts and between 0.86 and 1.04 eV for the annealed contacts.

Ion-irradiation induces amorphization in many intermetallics and ceramics, but spinel (MgAl2O4) is considered a “radiation resistant” ceramic. Spinel was irradiated with 1.5 MeV Kr+ at 20 K and observed in situ by transmission electron microscopy (TEM). The spinel remained crystalline to a high dose of 1 × 1016 ions/cm2, without any evidence of amorphization. Another spinel was preimplanted with Ne (400 keV and 50 keV). The microstructure revealed a still crystalline material with 8 nm interstitial loops. After irradiation with 1.5 MeV Kr+ (20 K), amorphization, a result of cation disordering, initiated at a dose of 1.7 × 1015 ions/cm2. At a dose of 1 × 1016 ions/cm2, the spinel was partially amorphous and the remaining crystalline domains disordered. These results show that spinel can be disordered and that amorphization can be triggered by the introduction of stable defects, followed by ion irradiation at low temperature.

A mixed alkoxide liquid precursor was used to form epitaxial PbTiO3 thin films by spin-coating on cubic (001) SrTiO3 substrates. The films were heat-treated at temperatures between 380 °C/1 h and 800 °C/1 h. X-ray diffraction, atomic force microscopy, scanning and transmission electron microscopy were used to characterize the microstructure of the films and to evaluate the epitaxial phenomena. At ∼400 °C/1 h, a polycrystalline, metastable Pb-Ti fluorite crystallizes from the pyrolyzed amorphous precursor. At slightly higher temperatures (∼420 °C/1 h), the thermodynamically stable phase with the perovskite structure epitaxially nucleates at the film/substrate interface. A small number of epitaxial grains grow through the film toward the surface and consume the nanocrystalline fluorite grains. Coarsening of the perovskite grains leads to a reduction in mosaic spread during further heating. Pores, which concurrently coarsen with grain growth, produce a pitted surface as they disappear from within the film. At 800 °C/1 ha dense epitaxial PbTiO3 film with a smooth surface is observed. Parameters governing the formation of a- and c-domains are discussed as well as the small tilts of the domain axes away from the substrate normal.

The evolution of structure and chemical distribution in sol-gel derived Pb(Zr0.53T10.47)O3 thin layers was monitored by x-ray diffraction, analytical electron microscopy, and diffuse reflectance Fourier transform infrared spectroscopy. Electron microscopy confirmed the as-deposited coatings were amorphous with short-range order. Medium-range order developed on heat treatment, and chemical heterogeneity was observed at the nanoscale. The extent of compositional heterogeneity decreased with increasing temperature. Above 500 °C, the coatings crystallized into an intermediate phase which converted to the perovskite phase above 600 °C.

The composition and chemistry of the near-surface region of BaTiO3 have been studied using x-ray photoelectron spectroscopy (XPS). It is found that the Ba3d photoclectron peak shows two chemical states, one of which is attributed to the bulk perovskite and the other to a special surface state unrelated to contamination. The bulk component is reduced and the surface component increases when the material is annealed at high temperatures (either in reducing or oxidizing atmosphere). Both the components are unaltered if the sample is exposed to air, solvents, or water: processes that lead to adsorption of impurities. The surface peak, therefore, attributed to a relaxation related and not contamination-related state, has been compared with those in other Ba-containing oxides. The oxygen photoelectron peak consists of a normal perovskite peak typical of most titanates and a higher energy component clearly related to surface contamination. Annealing in reducing atmosphere results in drastically different optical and electrical properties, and in chemical reduction of some Ti4+ ions to Ti3+. The overall stoichiometry, however, does not change with annealing atmosphere. These results have been discussed in light of our current understanding of this and other related oxides.

The effects of Si1−xGex alloy composition on the Ti-Si1−xGex solid phase reaction have been examined. Specifically, effects on the titanium gcrmanosilicide phase formation sequence. C54 Ti(Si1−yGey)2 nucleation temperature, and C54 Ti(Si1−yGey)2 morphology were examined. It was determined that the Ti-Si1−xGex reaction follows a “Ti-Si-like” reaction path for Si-rich Si1−xGex alloys and follows a “Ti-Ge-like” reaction path for Ge-rich Si1−xGex alloys. The coexistence of multiple titanium germanosilicide phases was observed during Ti-Si1−xGex reactions for Si1−xGex alloys in an intermediate composition range. The morphology and stability of the resulting C54 germanosilicides were directly correlated to the Ti-Si1−xGex reaction path. Smooth continuous C54 titanium germanosilicide was formed for samples with Si1−xGex compositions in the “Ti-Si-like” regime. Discontinuous islanded C54 germanosilicides were formed for samples with Si1−xGex compositions in the mixed phase and “Ti-Ge-like” regimes. Using rapid thermal annealing techniques, it was found that the C54 titanium germanosilicides were stable to higher temperatures. This indicated that the morphological degradation occurs after C54 phase formation. The C54 Ti(Si1−xGex)2 formation temperature was examined as a function of alloy composition and was found to decrease by ≍ 70 °C as the composition approached x ≍ 0.5. An optimum Si1−xGex alloy composition range of 0 ⋚ x ⋚ 0.36 was determined for the formation of stable-continuous-low-resistivity-C54 titanium germanosilicide films from the solid phase reaction of Ti and Si1−xGex alloy. The results were described in terms of the relevant nucleation processes.

We have studied effects of hydrogen on texture in diamond films grown by hot filament assisted chemical vapor deposition by utilizing x-ray diffraction (XRD). We present results for the relative intensities of the XRD peaks originating from the (111). (220), and (400) crystallographic planes as functions of CH4/H2 makeup during growth and post-growth H2 treatment of the films. The texture of the films can be controlled by varying composition of the CH4/H2 mixture during growth and also by subjecting films to hydrogen treatment. The complementary characterization of these films by XRD, Raman spectroscopy, and positron annihilation techniques exemplifies a correlation among film texture, diamond contcnt, and dcnsity of the microvoids in the films.

The current-voltage (I-V) characteristics and time-dependence photoconductivity of the undoped and B-doped diamond films (DF's) before and after annealing were investigated. The boron and hydrogen concentration in diamond films were measured by means of nuclear reaction analysis (NRA) and the elastic-recoil detection (ERD) technique, respectively. The results show that induced boron atoms and hydrogen atoms affect the electrical and photocoaductive properties of diamond films. During the annealing process, B concentration kept even, but H content decreased. For undoped diamond films, the escaping of H atoms has great effects on the electrical characteristics, but for B-doped samples, this effect decreases with the increase of B concentration.

We studied the constrained-film sintering of a gold circuit paste used in microelectronic packaging applications. Optical techniques were developed to determine the shrinkage profiles of constrained and free films and stresses generated during sintering in the constrained films. Constrained films approximately 60 μm thick were made by multiple screen-printing of the gold paste on rigid alumina substrates, while the free films were obtained by peeling off portions of the gold films from the substrate after binder burnout. Constrained films for stress measurement were made by multiple screen-printing on an oxidized 25 μm thick silicon substrate. Sintering runs were done in a hot stage at temperatures between 650 °C and 900 °C. The densification rates were much lower in the constrained films than those in the free films. The in-plane tensile stresses in the constrained films, determined by wafer curvature measurement, rose rapidly to a maximum level of 510 kPa during the initial stage of sintering and then gradually decreased. The reduction in the sintering potential due to the hydrostatic stress is not large enough to completely account for the retarded densification in constrained films. SEM micrographs of the film microstructures after sintering showed no-significant difference in grain growth kinetics between the constrained and free films. However, the activation energy for densification was found to be very different between the two types of films, 90.1 ± 4.3 kJ/mole for the free film and 188.8 ± 6.7 kJ/mole for the constrained film. We suggest that the retarded densification kinetics in the constrained gold films is due to (i) the reduction in the sintering potential by the hydrostatic stress and (ii) a change in the dominant sintering mechanism from grain-boundary diffusion in the free films to lattice diffusion in the constrained films.

Powder metallurgy and casting have been used to produce aluminum with 1.3, 4, and 8 vol. % fullerene additions. Fullerene extract was mixed with Al and heat-treated to obtain various levels of dispersion of the fullerenes. Intergranular dispersion of stable fullerenes was accomplished by both powder metallurgy and casting; however, x-ray diffraction indicated the formation of some Al4C3. Homogeneous dispersion did not occur because of limited diffusion in the solid state or limited solubility of fullerene in Al in the liquid state. Enhancements in hardness over that for Al were observed yet were not comparable to precipitation hardened Al alloys since a less homogeneous dispersion was achieved. Interest in Al having fullerene additions is for development of fullerene strengthened materials where fullerenes act as nanosize dispersoids for dispersion strengthening of metals or as a lightweight reinforcement in metal-matrix composites.

Composed of packed nanophase nodules in which the carbon atoms are linked with the tetrahedral bonding of diamond, laser plasma films are deposited in vacuum onto almost any substrate by condensing carbon ions carrying keV energies. These multiply charged ions are obtained from the laser ablation of graphite at intensities in excess of 1011 W cm−2. The high energy of condensation provides both for the chemical bonding of such films to a wide variety of substrates and for low values of residual compressive stress. Coatings of 2–5 μm thicknesses have extended lifetimes of important optical materials against the erosive wear from high-speed particles and droplets by factors of tens to thousands. In this work, the optical properties of these films at infrared (IR) wavelengths were studied. Transmission spectra of several freestanding films on silicon frames were measured. Using a model considering rough surface scattering and free carrier absorption, satisfactory fits to these transmission spectra were obtained and from them the optical parameters were extracted. The characterization studies performed in this work indicated a great potential for the laser-deposited nanophase diamond films in optical applications.

The behavior of screw dislocations dynamically emitted from the tip of a surface crack during loading and unloading has been investigated using a discrete dislocation model. The critical stress intensity factor at the crack tip for dislocation emission is a function of friction stress, core radius of dislocation, and dislocations near the crack tip. During motion, the velocity of dislocation is assumed to be proportional to the effective shear stress to the third power. The effect of crack length and friction stress on dislocation distributions, plastic zone, and dislocation-free zone during loading and unloading was examined.

A finite-difference model was used to simulate the temperature and composition distributions produced inside a specimen heated with microwave energy during a process involving a change in composition. The dielectric properties of the specimen change with composition, resulting in nonuniform microwave power absorption and steady-state temperature gradients. When the specimen becomes less lossy as it reacts, or if the changes in the microwave heating properties are gradual, the reaction proceeds relatively uniformly and the volumetric microwave heating creates an inside-out reaction profile leading to increased conversions for processes such as reaction bonding and chemical vapor infiltration (CVI). If the specimen becomes more lossy as it reacts, then the reaction proceeds nonuniformly with rapid reaction rates in the hottest parts of the specimen and little or no reaction in the cooler areas. The process may then occur as a reaction front which moves along the specimen, as with combustion synthesis. This type of processing has potential advantages and disadvantages depending on the system.

Nanosized TiO2 is synthesized in a nanosized alumina matrix by a sol-gel procedure. The results of the study of the blueshift of the TiO2 UV band edge are compared to the information obtained from transmission electron microscopy (TEM). As long as the atomic ratio Ti/Al remains smaller than 17.5%, no individualized TiO2 particles are detected by TEM, in spite of the fact that no modification of the alumina structure occurs, as revealed by 27Al MAS NMR. The shift of the UV band edge suggests the growth of homogeneous TiO2 domains in the alumina matrix. Above a critical radius, on the order of 1.2 nm, individual and crystalline TiO2 particles become visible in the TEM picture, and the porosity of the material decreases markedly.