An ultrahigh vacuum (UHV) diffusion bonding/deposition instrument was designed and constructed, which can produce homophase and heterophase planar interfaces from a wide array of materials. The interfaces are synthesized in situ by diffusion bonding of two substrates with or without various interfacial layers, at temperatures up to about 1500 °C. Substrate surfaces can be heat treated, ion-beam sputter cleaned, and chemically characterized in situ by Auger electron spectroscopy prior to deposition and/or bonding. Bicrystals can be synthesized by bonding two single-crystal substrates at a specified orientation. Interfacial layers can be deposited by electron beam evaporation and/or sputter deposition in any layered or alloyed combination on the substrates before bonding. The instrument can accommodate cylindrical and/or wafer type specimens whose sizes are sufficient for fracture mechanical testing to measure interface bond strength. A variety of planar interfaces of metals, semiconductors, and ceramics were synthesized. Examples of bonded stainless steel/Ti/stainless steel, Si/Si, and sapphire/sapphire interfaces are presented.

For this paper the pulsed laser deposition on single-crystal MgO substrates of Ba4Fe4Ti3O16 target was studied by transmission electron microscopy and x-ray diffraction. The initial stage of the deposition resulted in the formation of the perovskite Ba(Fe, Ti)O3 phase in an epitaxial, cube-on-cube orientation relationship with a substrate. Further growth of the pseudo-cubic phase was interrupted by the formation of oriented grains with a disordered structure. This disordered structure had a mixture of lamellae of the cubic and hexagonal Ba(Fe, Ti)O3 phases. No formation of the Ba4Fe4Ti3O16 (E) phase was observed. Formation of the disordered phase was explained by the higher stability of hexagonal Ba(Fe, Ti)O3 where accommodation of Fe3+ occurred on a twinning plane. The development of the V-shape morphology and a limited number of orientations of the D structure were explained by the faceting and columnar morphology of the perovskite phase.

LiNbO3 thin films were grown on (0001) sapphire substrates by a chemical route, using the polymeric precursor method. The overall process consists of preparing a coating solution from the Pechini process, based on metallic citrate polymerization. The precursor films, deposited by dip coating, are then heat treated to eliminate the organic material and to synthesize the phase. In this work, we studied the influence of the heat treatment on the structural and optical properties of single-layered films. Two routes were also investigated to increase the film thickness: increasing the viscosity of the coating solution and/or increasing the number of successively deposited layers. The x-ray diffraction θ-2θ scans revealed the c-axis orientation of the single- and multilayered films and showed that efficient crystallization can be obtained at temperatures as low as 400 °C. The phi-scan diffraction evidenced the epitaxial growth with two in-plane variants. A microstructural study revealed that the films were crack free, homogeneous, and relatively dense. Finally, the investigation of the optical properties (optical transmittance and refractive index) confirmed the good quality of the films. These results indicate that the polymeric precursor method is a promising process to develop lithium niobate waveguides.

The role of a soft adhesive interlayer in determining critical conditions for fracture in brittle layer structures from indentation with hard spheres is investigated. A model transparent trilayer system consisting of a glass plate overlayer (thickness range 80 μm to 2 mm) joined to a glass plate underlayer (thickness 5.6 mm) by an epoxy adhesive (thickness range 5 μm to 8 mm), loaded at its top surface with a hard tungsten carbide sphere (radius 3.96 mm), facilitates in situ observations of the crack initiation and propagation. Whereas in bulk glass fracture occurs by inner Hertzian cone cracking immediately outside the contact circle, the soft adhesive allows the overlayer glass plate to flex, initiating additional transverse fracture modes within the overlayer: downward-extending outer ring cracks at the top glass surface well outside the contact, and upward-extending radial cracks at the bottom glass surface (i.e., at the glass/adhesive interface) on median planes containing the contact axis. The top and bottom surfaces of the glass overlayers are given selective prebonding abrasion treatments to ensure uniform flaw states, so as to enable accurate comparisons between crack initiation conditions. The adhesive bonding is strong enough to preclude delamination in our layer system. Of the three transverse crack systems, the subsurface radials generates most easily in systems with large adhesive thicknesses (and smaller overlayer thicknesses). Semi-empirical relations are specified for the dependence of the critical loads for radial and ring cracking on adhesive as well as overlayer thickness, based on the assumption that crack initiation occurs when the maximum tensile stresses in the flexing glass plate exceed the bulk strength of the (abraded) glass. Coupled with the traditional “Auerbach's law” for cone crack initiation, these relations afford a basis for the construction of simple design diagrams for brittle layer systems joined by adhesives.

Ultrafine MnFe2O4 powder with its crystallites less than 100 nm was prepared using a combustion process. The coprecipitates containing the stoichiometric amount of Mn2+ and Fe3+ to form MnFe2O4 were prepared by dissolving the required metallic nitrates in de-ionized water and adding NH4OH to adjust the pH of the solutions to 9. The collected dried precipitates were then heated up to predetermined temperatures and then quickly contacted with the acetone spray. Upon contacting with the heated precipitates, the acetone spray was ignited. The combustion of acetone caused the precipitates to form crystalline MnFe2O4 without chemical segregation. The crystallinity of MnFe2O4 powder so obtained depended on the ignition temperature of acetone spray. MnFe2O4 powder obtained at acetone ignition temperature of 773 K had higher crystallinity than that obtained at acetone ignition temperature of 523 K. The presence of a small amount of Mg2+ or Zn2+ in the composition of the coprecipitates promoted the mobility of constituent ions of the combusted powder and resulted in bigger MnFe2O4 crystallites at a lower acetone ignition temperature.

The effects of plasticity in thin copper layers on the interface fracture resistance in thin-film interconnect structures were explored using experiments and multiscale simulations. Particular attention was given to the relationship between the intrinsic work of adhesion, Go, and the measured macroscopic fracture energy, Gc. Specifically, the TaN/SiO2 interface fracture energy was measured in thin-film Cu/TaN/SiO2 structures in which the Cu layer was varied over a wide range of thickness. A continuum/FEM model with cohesive surface elements was employed to calculate the macroscopic fracture energy of the layered structure. Published yield properties together with a plastic flow model for the metal layers were used to predict the plasticity contribution to interface fracture resistance where the film thickness (0.25–2.5 μm) dominated deformation behavior. For thicker metal layers, a transition region was identified in which the plastic deformation and associated plastic energy contributions to Gc were no longer dominated by the film thickness. The effects of other salient interface parameters including peak cohesive stress and Go are explored.

The local environment of titanium in glasses of the system TiO2–BaO–ZnO–B2O3 was studied by x-ray absorption spectroscopy. In all glasses, for TiO2 content varying from 35 to 49 mol%, the titanium atoms are mainly fourfold coordinated network formers. For the glass with the highest titanium content, about 20% of the titanium enters into a sixfold environment, indicating the presence of precrystalline nuclei. These nuclei are responsible for the decrease of the optical performance of the glass above threshold titanium content, prior to any observable crystallization.

Al2O3–TiB2 composites were synthesized by the combustion reaction 3TiO2 + 3B2O3 – (10 + x)Al, with x ranging from 0 to 4.71. The products consisted of corundum, TiB2, and a trace of Ti2O3 for the reactions with x = 0 and x = 1.4. However, the products of the reaction with x = 2.96 contained corundum and TiB2 only. For products of samples with x = 0, 1.4, and 2.96, similar room-temperature absorption spectra were observed in the ultraviolet and visible range at wavelengths of 265, 706, and 844 nm. Room-temperature photoluminescence spectra of the composites showed one visible band at about 720 nm. Room-temperature cathodoluminescence (CL) spectra of the composites synthesized by reactions with x = 0 and 1.4 exhibited two visible bands centered at 400 and 710 nm, respectively. From samples synthesized with x = 2.96, another visible band centered at 570 nm was observed in the CL spectrum. Comparing secondary electron images to panchromatic and monochromatic CL images of the composites, it was found that the light-emitting phase is TiB2-containing corundum. The 710-nm band is attributed to the transition between 1T1 (et) and 3T2 (et) excited states, and the 570- and 400-nm bands to the transitions between 3T1 (et) or 3A2 (e2) and 1T1 (et) excited states and 3T1 (t2) ground state of Ti2+ in corundum, respectively.

A novel approach to determine the molecular orientation of dimethyl terephthalate molecules with respect to the direction of the crystal axis is reported. This determination was achieved by changing the crystal orientation with respect to the incident laser light of a micro-Raman spectrometer. Raman spectra were obtained at different incidence angles of the laser beam with respect to the crystal symmetry axis. The intensities of some specific bands were analyzed as a function of the tilting angle. With this information the molecular orientation with respect to the crystal axis was determined making use of a simple mechanical model.

For both Co and Ni, a series of electrodeposited films of varying thickness (2–10 nm) was grown under otherwise identical conditions using potentiostatic control. The substrates were pieces of Si wafer onto which a Cu basal layer had been thermally evaporated. Contact mode atomic force microscopy was used to measure both the root-mean-square peak height (nm) and the areal peak density (μm−2) of each film. Root-mean-square (rms) peak heights for Co initially increase with film thickness and then plateau at a layer thickness of 3 nm. For Ni, the rms peak heights increase almost linearly for layer thicknesses less than 11 nm, reaching a value of 6 nm. Peak density shows the opposite trend, decreasing with layer thickness before reaching an approximately constant value for both metals at a film thickness of 4 nm. The atomic force microscopy data indicate that Ni and Co have different deposition mechanisms. A Co film initially nucleates rapidly; then the nucleation phase is followed by multinuclear, multilayer growth. Ni deposits also have initial rapid nucleation, but the dominant growth mode is primarily vertical, with increasing peak heights but no change in peak density. Increased peak density is linearly correlated with decreased peak height for the thinnest films in both systems.

Carbon nanotubes, typically of 0.5-μm length and 20-nm diameter, were prepared with good selectivity by disproportionation of CO in He over a Pd/La2O3 catalyst. The catalyst was formed in situ by reduction of a La4PdO7 precursor. The obtained nanotubes had the so-called fishbone structure with the graphitic planes inclined at an angle to the long axis of the nanotube. The effect of CO concentration was studied at 673 °C, and it was found that, among the concentrations studied, 20 vol% CO in the gas was suitable for nanotube growth. The obtained nanotube/La2O3/Pd composite contained typically only 3 wt% nanotubes after 8 h of CO treatment. A process for selective dissolution of La2O3 and Pd was applied, and a product containing 85 wt% nanotubes was obtained. The nanotubes were characterized by high-resolution, transmission, and scanning electron microscope studies, combined with element analyses using energy dispersive spectrometers, x-ray powder diffraction studies, and thermogravimetric analysis.

Alumina/alumina and alumina/kovar/alumina joints were produced via two joining techniques: (i) a moly-manganese process and (ii) active metal brazing. These joints were heat treated at 400 °C for 100 h to evaluate their fracture strength, fracture behavior, and high-temperature reliability. Depending on the joining methods employed, the optimum microstructure of ceramics for joining is different. It was found in most cases, that the active metal brazing resulted in superior joint strength and reliability over the moly-manganese process. The fracture strength and reliability of alumina/kovar/alumina joints were lower than those of alumina/alumina joints and showed different fracture behaviors. After heat treatment, fracture strength and reliability decreased due to the formation of brittle phases at the joint interface. The fraction of brittle debonding at the interface increased with heat treatment, while that of fracture within the alumina decreased.

Nanoscale composites have been a technological dream for many years. Recently, increased interest has arisen in using carbon nanotubes as a filler for polymer composites, owing to their very small diameters on the order of 1 nm, very high aspect ratios of 1000 or more, and exceptional strength with Young's modulus of approximately 1 TPa. A key issue for realizing these composites is obtaining good interfacial adhesion between the phases. In this work, we used force-field based molecular mechanics calculations to determine binding energies and sliding frictional stresses between pristine carbon nanotubes and a range of polymer substrates, in an effort to understand the factors governing interfacial adhesion. The particular polymers studied were chosen to correspond to reported composites in the literature. We also examined polymer morphologies by performing energy-minimizations in a vacuum. Hydrogen bond interactions with the ∏-bond network of pristine carbon nanotubes were found to bond most strongly to the surface, in the absence of chemically altered nanotubes. Surprisingly, we found that binding energies and frictional forces play only a minor role in determining the strength of the interface, but that helical polymer conformations are essential.

Spherical alumina particles were prepared following the sol-emulsion-gel method by systematic variation of (i) the concentration of the surfactant Span 80 above or below the critical micelle concentration (CMC) in different organic solvents and (ii) hydrophilic–lipophilic balance (HLB) of different surfactants in cyclohexane. The experimentally determined CMC of Span 80 was found to increase with increasing dielectric constant of the organic solvent, influencing the sol droplet and alumina particle size. With an increase in the HLB value of the surfactants, the tendency of monodispersed sphere formation among the particles increased with a decrease in the size distribution and average particle size (d50).

Epitaxial La0.7Ca0.3MnO3 thin film and [Y0.7Ca0.3MnO3/La0.7Ca0.3MnO3]10 multilayers of about 140 nm in thickness were grown by pulsed laser deposition on (001)LaAlO3. Their microstructures were investigated by transmission electron microscopy and associated techniques. It was found that both the film and the multilayers contain an almost defect-free layer near the substrate, followed by columnar grain grown. The columns were separated by strained regions in the top layer. No interfacial dislocations were observed at either of the La0.7Ca0.3MnO3/LaAlO3 or the Y0.7Ca0.3MnO3/La0.7Ca0.3MnO3 interfaces. Interestingly, both the epitaxial film and the multilayers exhibited layered crystallographic domains. The formation mechanisms of the layered domain structures observed are discussed.

The crystallization kinetics and film microstructure of poly-SiGe layers obtained by solid-phase crystallization of unimplanted and C- and F-implanted 100-nm-thick amorphous SiGe films deposited by low-pressure chemical vapor deposition on thermally oxidized Si wafers were studied. After crystallization, the F- and C-implanted SiGe films showed larger grain sizes, both in-plane and perpendicular to the surface of the sample, than the unimplanted SiGe films. Also, the (111) texture was strongly enhanced when compared to the unimplanted SiGe or Si films. The crystallized F-implanted SiGe samples showed the dendrite-shaped grains characteristic of solid-phase crystallized pure Si. The structure of the unimplanted SiGe and C-implanted SiGe samples consisted of a mixture of grains with well-defined contour and a small number of quasi-dendritic grains. These samples also showed a very low grain-size dispersion.

Nickel thin films were deposited with Ni(C5H5)2 \NiCp2, bis(cyclopentadienyl)nickel, nickelocene]/H2 at various temperatures and H2/Ar ratios. The deposition rate, resistivity, purity, crystal structure, and surface morphology of the nickel film were investigated. Also, thermal analysis was done to find out the dissociation characteristics of NiCp2, and Fourier transform infrared spectroscopy diagnostics were carried out to study the gas phase reaction kinetics of NiCp2. Nickel films deposited at higher temperatures (>225 °C) had high carbon content and high resistivity. At higher temperatures, thermal decomposition of NiCp2 and subsequent decomposition of Cp induced a large amount of carbon incorporation into the film. At lower temperatures (<190 °C), the slow dissociation of NiCp led to some extent of carbon incorporation in the film. Nickel films deposited at around 200 °C showed carbon content lower than 5% and lower resistivity because of the effective dissociation of Ni–Cp and desorption of Cp from the surface. Nickel films deposited with hydrogen addition showed higher purity, crystallinity, and lower resistivity due to the removal of the carbon on the surface.

Indium tin oxide powder with an In to Sn mole ratio of 95:5 was successfully prepared from a coprecipitated In–Sn hydroxide gel by hydrothermal processing followed by calcination at relatively low temperatures (∼500 °C). Hydrothermal treatment of the In–Sn coprecipitated gel at 300 °C for 24 h led to the formation of a single phase of tin-doped indium oxyhydroxide (InOOH:Sn). Under hydrothermal conditions the oxyhydroxide phase appeared well crystallized with particles ∼80 nm in size. Calcination of the oxyhydroxide phase above 450 °C in air yielded a substitutional-vacancy-type solid solution of In2Sn1−xO5−y.

Transmission electron microscopy and electron diffraction were used to study hardness indentations made at room temperature in ⟨001⟩-oriented single crystals of MoSi2. Two families of slip systems, {110}⟨001⟩ and {101}⟨010⟩, were identified. The first system formed ⟨001⟩ dislocation loops by prismatic punching beneath the indenter, while the second system led to large rotations of the crystal lattice beneath the indenter. The lattice rotations were used to estimate the density of dislocations stored in this volume. The results demonstrate that the hardness response of MoSi2 can be explained by the expanding cavity model with most of the plastic accommodation occurring immediately beneath the indenter.

Spherical particles of α–Fe2O3 80 to 100 nm in size were prepared with the polyol method. Scanning electron microscopy, x-ray powder diffraction, and measurements of the diffuse reflection were used to characterize the powder material. The characteristic red color of hematite was adjusted after brief heating (250 °C, 15 min) which did not lead to further particle growth. The polyol method turned out to be suited for the preparation of quite concentrated (up to 20 wt%) and very stable suspensions of submicron Fe2O3 particles. Based on such suspensions, the red emitting phosphor Y2O2S:Eu was coated as a model substrate. As a result, very homogeneous coatings of α-Fe2O3 on the phosphor material were realized. Individual iron oxide particles on the phosphor surface confirm the presence of nonagglomerated Fe2O3 particles in the polyol medium.