Initial growth features of Yba2Cu3Oy (YBCO) crystal on an MgO substrate by a liquid-phase epitaxy (LPE) process were investigated and compared with homoepitaxial growth on a YBCO substrate. The partial dissolution of the seed grains in the initial stage of the LPE growth was influenced by the crystallinity of in-plane alignment of the seed grains, which could be explained by the preferential dissolution and growth mechanism. Concurrently, the slope angle of the growth grain varied with growth time. The opposite tendency of the slope angle change between the hetero- and the homoepitaxial growth was observed and could be explained by considering the difference in the step-advancing rates on each interface. It could be understood that the formation of entrapped liquid inclusions was the combination phenomena of both the small step-advancing rate of YBCO crystal on the MgO surface and the roughening of the MgO surface due to the partial dissolution of MgO to the solution.

Power applications of high-temperature superconducting (HTS) coated conductors will require stabilization against thermal runaway. We have developed conductive buffer layers to electrically couple the HTS layer to the underlying metal substrate. The structure comprises the layer sequence of SrRuO3 (SRO) on LaNiO3 (LNO) on biaxially textured Ni substrates. We report baseline investigations of compatibility of SRO/LNO multilayer structure with processing of Yba2Cu3O7−δ (YBCO) and demonstrate biaxially textured YBCO films on conductively buffered Ni tapes. These YBCO coatings exhibit self-field Jc values as high as 1.3 × 106 A/cm2 at 77 K, and the entire structure (HTS + conductive buffers + metal substrate) shows good electrical connectivity. These results demonstrate that SRO/LNO buffer layers may provide a basis for stabilized coated conductors.

The optical constants of Si/ZnO composite films grown on quartz glass substrates were determined in the spectral range 1.5–5.0 eV by spectroscopic ellipsometry using a rotating-analyzer ellipsometer. The structure of the samples was modeled by a two-phase (substrate–film) model, and the optical functions of the film were parameterized through different effective medium approximations. The results allowed us to estimate the microstructural film parameters, such as film thickness, the volume fractions of each of the constituents, and optical constants.

Cristobalite is formed when initially amorphous Pyrex borosilicate glass (Corning 7740) is fired at temperatures ranging from 700 to 1000 °C. The sigmoidal devitrification kinetics of cristobalite obeys Avrami-like three-dimensional diffusion-controlled kinetics. Activation energy analysis indicates that the diffusion of Na+ in the glass is the rate-limiting step during phase transformation. The above conclusion is further confirmed by calculated and measured results of linear growth rates.

In a metastable solution the particle growth rate of silicon dioxide increased with an increase in the initial supersaturation of the metastable solution and agitation speed in the ranges of 2.5 × 10−4 to 2.0 × 10−3 M and 300–1500 rpm, respectively. Based on a power law expression, the particle growth rate order was estimated as 2.0 independent of the initial supersaturation and agitation speed. Meanwhile, the particle growth rate coefficient was enhanced from 2.0 × 10−3 to 1.4 × 10−2 with increase in the agitation speed from 300 to 1500 rpm. From the experimental data, it would appear that the enhanced particle growth rate resulted from the promotion of molecular transport due to the agitation and driving force of the supersaturation in the particle growth process. A slight addition of sodium chloride into the metastable solution caused a marked reduction of the particle growth rate due to the inhibition of growth process by sodium chloride adsorbed on the particle. This effect of sodium chloride on the particle growth appeared in a significant drop of the particle growth rate coefficient from 4.5 × 10−3 to 8.0×10−4 with increase in the sodium chloride concentration from zero to 5.0×10−3 M, but not in the particle growth rate order. The influence of sodium chloride on the particle growth process of silicon dioxide predicted with a Langmuir isotherm matched with the experimental data.

The sol-gel synthesis and structural characterization of SiO2–TiO2 powders are reported. Samples with titania concentrations in the range of 0 to 30 mol%, calcined at temperatures between 120 and 1300 °C, were characterized by 29Si magic-angle-spinning nuclear-magnetic-resonance (MAS NMR) and cross polarization MAS NMR, Raman and Fourier transform infrared spectroscopies, and powder x-ray diffraction. Tetrahedrally coordinated Ti (IV) ions were found in the titanosilicate matrix. When the titania content increases beyond approximately 10 mol% and upon calcination at temperatures over approximately 700 °C, the segregation of an amorphous silica-rich phase occurs, together with the precipitation of anatase nanocrystallites with average sizes between 3 and 17 nm, depending on the temperature. An increase in the heat treatment temperature, or the titania content, leads to an increase in the degree of homocondensation (Si–O–Si and Ti–O–Ti bonds) and a simultaneous reduction in the degree of heterocondensation (Si–O–Ti bonds).

A study of the mechanisms of CsLiB6O10 (CLBO) crystal performance degradation during harmonic generation in the ultraviolet (UV) region was performed. The degradation rate of transmissivity during irradiation with the fourth harmonic light of an Nd3+ doped YLiF4 laser (4.7 eV) was linearly proportional to the concentration of hydroxyl (OH) groups in the CLBO crystal. In this study, the formation of OH groups was recognized by infrared absorption spectroscopy, and a method for determination of OH groups was proposed. The concentration of OH groups in the CLBO was linearly proportional to water vapor pressure and the CLBO containing OH groups absorbed UV light. We propose that one of the main mechanisms of surface degradation is the generation and growth of the mutants and that these mutants are generated by a UV photon-assisted reaction via OH group formation associated with absorbing water molecules into CLBO crystal.

The wetting of mullite (3Al2O3 · 2SiO2) by a Y2O3–Al2O3–SiO2 (YAS) glass and by a B2O3–SiO2 (borosilicate) glass was investigated in air as a function of temperature through a sessile drop technique. The wetting behavior was found to be strongly dependent on the glass composition and on the temperature. For the YAS glass, the contact angle showed a rapid decrease from 100° to 20° in the temperature range of 1400 to 1450 °C followed by a more gradual decrease to a value of 10–15° at approximately 1600 °C. In the case of the borosilicate glass, the change in the contact angle with temperature was more uniform, with the value decreasing from 100° to 45° between 1300 and 1600 °C. Microstructural observations of the interfacial region between the solidified sessile drop and the mullite substrate revealed significant corrosion of the interface and penetration into the mullite grain boundaries by the YAS glass. In the case of the borosilicate glass, corrosion was limited and the interface was clearly defined. The consequences of the data for the design of in situ toughened mullite are discussed.

Single-phase filled skutterudite compounds, CeyFexCo4−xSb12 (x = 0 to 3.0, y = 0 to 0.74), were synthesized by a melting method. The effects of Fe content and Ce filling fraction on the thermoelectric properties of CeyFexCo4−xSb12 were investigated. The lattice thermal conductivity of Ce-saturated CeyFexCo4−xSb12, y being at the maximum corresponding to x, decreased with increasing Fe content (x) and reached its minimum at about x = 1.5. When x was 1.5, lattice thermal conductivity decreased with increasing Ce filling fraction till y = 0.3 and then began to increase after reaching the minimum at y = 0.3. Hole concentration and electrical conductivity of Cey Fe1.5Co2.5Sb12 decreased with increasing Ce filling fraction. The Seebeck coefficient increased with increasing Ce filling fraction. The greatest dimensionless thermoelectric figure of merit T value of 1.1 was obtained at 750 K for the composition of Ce0.28Fe1.52Co2.48Sb12.

Nanomechanical properties, nanohardness and elastic modulus, of an Antarctic sponge Rosella racovitzea were determined by using a vertical indentation system attached to an atomic force microscope. The Rosella spicules, known to have optical waveguide properties, are 10–20 cm long with a circular cross section of diameter 200–600 μm. The spicules are composed of 2–10-μm-thick layers of siliceous material that has no detectable crystallinity. Measurements through the thickness of the spicules indicated uniform properties regardless of layering. Both the elastic modulus and nanohardness values of the spicules are about half of that of either fused silica or commercial glass optical fibers. The fracture strength and fracture energy of the spicules, determined by 3-point bend tests, are several times those of silica rods of similar diameter. These sponge spicules are highly flexible and tough possibly because of their layered structure and hydrated nature of the silica. The spicules offer bioinspired lessons for potential biomimetic design of optical fibers with long-term durability that could potentially be fabricated at room temperature in aqueous solutions.

Highly ordered TiO2 nanowire arrays were prepared in anodic alumina membranes by a sol-gel method. The nanowires are single-crystalline anatase phase with uniform diameters around 50 nm. At room temperature, photoluminescence (PL) measurements of these TiO2 nanowire arrays showed a visible broad band with three peaks, which were located at about 425, 460, and 530 nm that are attributed to self-trapped excitons, F, and F+ centers, respectively. A model is also presented to explain the PL intensity drop-down of the TiO2 nanowire arrays embedded in the alumina membrane: the blue PL band of the anodic alumina membranes arises from the F+ centers on the pore walls, and the TiO2 nanowires first form in the center area of the pores and then extend to the pore walls.

The thermal activation energies for conduction of Nb-doped SrTiO3 grains and grain boundaries have been investigated by impedance spectroscopy. First, to observe the effect of electrode/SrTiO3 bulk interface, the varied impedances of SrTiO3 single crystal were measured with temperatures. The activation energy of an electrode/bulk interface was determined to be 1.3 eV, whereas that of bulk was 0.8 eV. When the impedances of Nb-doped SrTiO3 ceramics were measured, it was suggested that the more precise impedance values of a single grain and a single grain to grain junction be obtained using a microelectrode method. The activation energies for a grain, a grain boundary, and an electrode/bulk interface were determined to be about 0.8, 1.3, and 1.5 eV, respectively. From these measured results, it was suggested that the activation energy, 0.8 eV, measured in grain was originated from oxygen vacancies and the activation energy, 1.3 eV, in grain boundary was from strontium vacancies.

Nanophase precipitates of CdS formed in amorphous SiO2 by ion implantation and thermal processing have recently been found to exhibit a “hollow-particle” or “shell-like” microstructure. The present investigations show that this hollow-particle microstructure can be reproduced for a variety of materials other than CdS, and these results provide new insight into the mechanisms responsible for the formation of hollow precipitates embedded in solid hosts. Various elemental metal nanocrystals were formed in (100)-oriented crystalline Si hosts by ion implantation coupled with thermal treatments in which the annealing parameters were varied to investigate the “hollow-particle” formation conditions. The results indicate that depending on the melting points and vapor pressure of the precipitates or on the initial state of the host material, several processes acting either independently or in concert can lead to hollow precipitate formation. First, the implantation of materials having a high vapor pressure, either at the implant temperature or when heated during annealing, can lead to the formation of cavities in the crystalline host. Hollow precipitates can then form by a partial filling and coating of the cavity walls by the implanted species in a diffusion-based gettering/ripening process. Internal void formation can also occur or be enhanced by volume contraction during cooling if the particle solidifies from a liquid phase.

Striation defects in spin-coated thin films are a result of unfavorable capillary forces that develop due to the physical processes commonly involved in the spin-coating technique. Solvent evaporation during spinning causes depletion at the surface of the more volatile solution components while simultaneous viscous out-flow occurs providing the main source of solution thickness reduction during any typical spinning run. The composition changes in the surface layer can either stabilize or destabilize the surface with respect to convective motions within the coating solution. Destabilization (and therefore possible striation formation) happens when the surface composition changes so that a larger surface tension will develop. Thus, a careful cross-referencing of solvent volatility with surface tension effects can help establish solution conditions that will prevent this instability from arising. A plot of solvent vapor pressure (Pv) versus solvent surface tension (σ) is introduced and utilized to help discuss the impact of solvent choice when making coatings via spin coating. One important result is that when desiring to deposit a coating having a surface tension of σsolid, then it is favorable to use a fully miscible solvent that has a higher surface tension (i.e., σliquid > σsolid). More complicated solution mixtures were also examined, including dual-solvent systems and water-containing systems.

A process for the fabrication of textured Ba2CuO3 material with a microstructure similar to that of melt-processed YBa2Cu3Oy (Y123) superconductor is discussed. The Ba2CuO3 samples were melt processed with the intent to use them as textured precursors for processing of HgBa2CuOy superconductor. The microstructure formation of the Ba2CuO3 phase was studied by observing the samples being quenched from intermediate stages of a melt growth schedule. The microstructure of melt-processed Ba2CuO3 reveals randomly oriented large-sized grains, similar to that of melt textured Y123. Other important microstructural features observed were finely distributed properitectic BaO particles, the absence of the platelet gaps within the domains, and the presence of a different kind of twin structure. The conversion of melt textured Ba2CuO3 into superconducting HgBa2CuOy phase by a two-step process is discussed.

The influence that trace concentrations of SiO2 have on improving grain-boundary conduction via precursor scavenging using additional heat treatment at 1200 °C for 40 h before sintering was investigated. At a SiO2-impurity level (SIL) ≤160 ppm by weight, the grain-boundary resistivity (ρgb) decreased to 20% of its value, while no improvement in grain-boundary conduction was found at a SIL ≥ 310 ppm. The correlation between the resistance per unit grain-boundary area, rgb, and average grain size indicated that the inhomogeneous distribution of the siliceous phase in the sample with a SIL ≥ 310 ppm hampered the scavenging reaction.

Room-temperature scanning probe microscopy was used to generate out-of-plane deformation maps around Cu vias and polyimide mesas in single-level Cu–polyimide damascene interconnect structures subjected to a room-temperature to 350 °C thermal cycle. The deformation maps are obtained by taking the difference between the images obtained before and after thermal processing. The deformation of the Cu is shown to be highly heterogeneous on the submicrometer scale. Direct evidence of Cu–Ta interfacial sliding, Cu–Cu grain boundary sliding, and diffusion creep is presented. The direction of Cu–Ta sliding is shown to depend on polyimide mesa size. A hot-stage atomic force microscope was used to show that hillock/extrusion growth occurs at temperatures between 130 and 180 °C. We propose that this hillock/extrusion growth is correlated with dips in stress–temperature plots for blanket, uncapped Cu films in the same temperature range and that the absence of dips for nitride-capped Cu films is due to suppression of the hillock/extrusion growth.

Atomic force microscopy (AFM) has been used to study the cracks developed on thin-film coatings on a polymer substrate subjected to external tension. To conduct in situ tensile tests in AFM, a special stage has been built. A new technique to image the same control area at different strains was developed and used to study the propagation of a crack with increasing strain in magnetic tapes. Metal particulate tapes developed numerous cracks of shorter length, perpendicular to the loading direction. In contrast, metal-evaporated tapes developed cracks that extend edge to edge. The variation of the crack width and the spacing with strain were measured and explained with the help of models based on elasticity.

We developed a diamond surface that does not mist near the room temperature under a saturated humidity atmosphere, by sheet electron beam irradiation (SEBI) treatment. SEBI treatment decreased the time to clear vision of the diamond surface. Following SEBI treatment for 1.91 s (= 0.72 MGy) to a diamond surface, the time to clear vision was less than 2 s. The effective duration time was a few hours. Based on the results of the size distribution of the drops on the misting-free diamond surface following blowing for 3 s, we proposed an explanation for the short time to clear vision of the diamond surface treated by SEBI.

Solid-phase epitaxy was examined in deep amorphous volumes formed in silicon wafers by multi-energy self-implantation through a mask. Crystallization was effected at elevated temperatures with the amorphous volume being transformed at both lateral and vertical interfaces. Sample topology was mapped using an atomic force microscope. Details of the process were clarified with both plan-view and cross-sectional transmission electron microscopy analyses. Crystallization of the amorphous volumes resulted in the incorporation of a surprisingly large number of dislocations. These arose from a variety of sources. Some of the secondary structures were identified to occur uniquely from the crystallization of volumes in this particular geometry.