We have used conventional and high-resolution transmission electron microscopy to investigate the microstruture of epitaxial, ferroelectric PbTiO3 films grown by pulsed laser ablation on (001) MgO single crystals, and on MgO covered with epitaxial Pt or SrTiO3. Pronounced variations are found in the widths and lengths of a-axis-oriented domains in these films, although the volume fraction of a-axis-oriented material varies only weakly for the different types of samples. In addition, the films deposited onto Pt-coated MgO have a larger grain size than those deposited onto bare MgO or SrTiO3/MgO. Possible reasons for the variations in the distribution of a-axis-oriented material in these samples include differences in the elastic properties and electrical conductivities of the different substrate combinations.

High-purity tungsten was prepared by the self-propagating high-temperature synthesis (SHS) process from a mixture of WO3 and Mg. The MgO in the product was leached with an HCl solution. The complete reduction of WO3 required a 33% excess of magnesium over the stoichiometric molar ratio Mg/WO3 of 3. The product tungsten had a purity of 99.980% which was higher than that of the reactant WO3. This is because the impurities were either volatilized at the high temperatures generated during the rapid exothermic reaction or dissolved into the HCl solution during leaching.

We propose an angular redistribution model to understand the negative ions resputtering effect in sputter depositing YBa2Cu3O7−x (YBCO) films. On the basis of this model, the negative oxygen ions resputtering effect has been greatly minimized by introducing a Cu mask between the substrate and the target to block energetic oxygen particles from directly bombarding the growing film. Thus, YBCO films with almost exact stoichiometric composition and zero resistance critical temperatures as high as 90 K are obtained under oxygen partial pressure as low as 3 mTorr in a temperature regime well beyond that proposed by R.H. Hammond and R. Bormann. Preliminary results of a modified masking and shiclding technique to eliminate the resputtering effect and fabricate large area (>1 in. × 1 in.) YBCO superconducting films with high uniformity are also presented.

Microstructures of a-axis oriented YBa2Cu3O7−x films made by newly developed de 100 MHz hybrid plasma sputtering were investigated using transmission electron microscopy (TEM). The films deposited on (110) NdGaO3 and (100) SrTiO3 substrates were found to grow in a perfect epitaxial fashion and with clear interface. The plan view of the TEM image showed that both films were comprised of two kinds of grains having the c axis aligning along two perpendicular directions in the plane with equal probability. The structures of the grain boundary, however, were found to be very different for the two films from the plan views. The film on NdGaO3 showed a lot of twist boundaries, while the film on SrTiO3 consisted of many symmetrical tilt boundaries and basal-plane-faced tilt boundaries. The type of grain boundary is determined by the anisotropic growth rates of the film between c direction and a-b direction.

YBa2Cu3O7−x (YBCO) and barrier layer films were deposited on single-crystal (Y2O3)0.09(ZrO2)0.91 substrates cut between 3.6 and 35.7°off-axis from the (001) planes. The barrier layers were (Y2O3)0.065(Y-ZrO2)0.935(Y-ZrO2), Y2O3, or multilayered structures of Y-ZrO2 and Y2O3. X-ray diffraction showed that the Y-ZrO2 and Y2O3 barrier layers generally grew epitaxially on the off-axis substrates, with the (001) barrier layer film planes being parallel to those of the substrate, and the (100) directions being parallel. YBCO films deposited on Y2O3 barrier layers also showed epitaxy with the YBCO (001) planes being nearly parallel to the substrate (001) planes, even for miscuts up to 35.7°. In contrast, the (001) planes of YBCO films deposited on Y-ZrO2 barrier layers were almost parallel to the substrate surface, not the (001) substrate planes. However, YBCO films on Y-ZrO2 films maintained particular in-plane epitaxial orientations with respect to the substrate. The YBCO full-width at half-maximum (FWHM) x-ray peaks were slightly narrower (0.8°) on Y2O3 barrier layers than on Y-ZrO2 layers (1.3°). The electrical resistivity versus temperature behavior of the YBCO/Y2O3 films was consistent with increased grain boundary scattering as the degree of substrate miscut increased, whereas YBCO/Y-ZrO2 films' resistivities showed less sensitivity to substrate miscut, consistent with the loss of epitaxy.

The surface of cleaved Bi2Sr2 CaCu2O3 (Bi2212) single crystals has been studied by means of scanning tunneling microscope (STM) and scanning tunneling spectroscopy (STS) at room temperature in ultrahigh vacuum. We obtain atomic images of the BiO surface using logarithmic current mode and conventional mode. It is demonstrated that the Bi atoms in the BiO plane are not missing. Some Bi atoms are depressed down below the BiO surface. STS obtained at different places of the surface shows more or less the same feature, indicating that local electronic density of states does not change much due to the depression or the well-known structural modulation. The possible origins of the variation in the period of the structural modulation in the BiO plane of cleaved Bi2212 single crystals extracted from STM images are also studied.

This paper reports a study of the microstructural evolution of Ag-containing 1223 Tl-Ca-Ba-Cu oxide superconductors in spray-deposited films. The films were formed by spray depositing nitrates of Ca, Ba, Cu, and Ag onto a polycrystalline yttria-stabilized zirconia substrate. These deposits were then converted to a mixture of oxides (calcia, calcium-copper oxide, and barium cuprate) and metallic silver by heating in oxygen. When thallium oxide vapor was passed over the film, the thallium was incorporated into the film and the 1223 phase was formed. The evidence strongly suggests that the development of the 1223 superconductor involves the formation of a liquid phase. Our analysis suggests that the initial phase to form a liquid is CaO which contains thallium, barium, copper, and silver. Once this initial liquid is formed, it incorporates more thallium which, in turn, allows it to dissolve other types of oxides present in the film. In this way the liquid spreads across the surface. The equilibrium 1223 phase precipitates from it.

GaAs layers grown by close-spaced vapor transport on (100) Ge substrates have been investigated as a function of the experimental growth conditions. The effects on the microstructure of the surface preparation, substrate misorientation, and annealing were studied using optical microscopy and transmission electron microscopy. Microtwins and threading dislocations are suppressed by oxide desorption before deposition. Single domain GaAs layers have been obtained using a 50 nm thick double domain buffer layer on an annealed Ge substrate misoriented 3°toward [011]. The mismatch strain is mainly accommodated by dissociated 60°dislocations. These misfit dislocations extend along the interface by the glide of the threading dislocations inherited from the substrate, but strong interaction with antiphase boundaries (APB's) prevents them from reaching the interface. These results are discussed and compared with previous reports of GaAs growth on Ge(100).

The hardness of thick, high-purity, epitaxially grown silver on sodium chloride is found to be dependent on the size of the indentation for sizes below ≃10 μm. The measurement of the size effect has been made in two ways. In one, the hardness has been calculated from the load-displacement curve obtained from an instrumented microhardness testing machine and assuming a geometric self-similarity in the indenter shape. In the other measurement, the hardness was obtained from the load exerted by the microhardness tester divided by the indentation impression area as measured by atomic force microscopy. The observed variation in microhardness with indentation size is consistent with a simplified strain gradient plasticity model in which the densities of the geometrically necessary and statistically stored dislocations are fitting parameters. An equally good fit can also be made with a simple geometric scaling relationship. Transmission electron microscopy observations of a thin (≃50 nm) epitaxial gold film embedded in the silver layers revealed that the deformation was primarily restricted to the sharp edges of the indentation. In addition, deformation twinning within the indentation impression was observed on the {1H} planes.

The progress of high temperature deformation in samples of two commercial titanium alloys with superplastic (SP) structure, non-SP structure, and with an SP layer sandwiched between the non-SP regions has been studied on the scale of the entire deformed volume and on the scale of grain groups. The results of mechanical behavior showed that samples with SP layer exhibit higher stress level than those with completely SP structure and higher strain rate sensitivity than those with completely non-SP structure. Samples with SP layer demonstrate a more pronounced deccrease in strain rate sensitivity with the increase of strain than samples with completely SP structure. Deformation in the SP layer proceeds as grain shear in a layer-by-layer manner. The deformation of SP layer through the operation of cooperative grain boundary sliding, i.e., sliding of grain groups as an entity along certain grain boundary surfaces, provides the main contribution to the total strain.

A process was developed to prepare nanocrystalline and quantum-confined particles of manganese-doped zinc sulfide. By the reaction of diethylzinc with solubilized hydrogen sulfide, particle sizes of 30–36 Å were achieved by control of reactant concentration, and size appeared to vary with the thermodynamic considerations indicative of homogeneous precipitation. Managanese doping required the development of an in situ chemical reaction compatible with the homogeneous precipitation reaction. To that end, ethylmagnesium chloride was reacted with manganese chloride to form the metastable diethylmanganese which acted as the dopant source. Quantum confinement of the particles was accomplished by using methacrylic acid and poly(methyl methacrylate) polymer of low molecular weights. These surfactants were transparent to the ultraviolet wavclcngths of light which allowed luminescent excitation of the material and provided surface passivation which enhanced phosphor brightness. The surfactant adsorption and effect of ultraviolet curing of the surfactant on the luminescent efficiency of the doped nanocrystals was investigated by infrared spectroscopy. These results indicate that the chemisorption of the surfactants to the nanoparticle surface and oxidation followed by crosslinking during curing are responsible for the improvement in luminescent efficiency.

Zone-melting recrystallization (ZMR) is a lateral epitaxy technique used to recrystallize polycrystalline thin films on substrates. Large-area multilayer structures of thin films processed with ZMR are usable in microelectronics applications. During the processing, slight variations in thermal gradients can lead to different crystalline qualities. Thus, processing uniformity over the wafer is strongly affected by the sensitivity of both the melt width and the solid/liquid interface to changes in the thermal environment. Processing control must either be set initially in a stable operating range or adjusted dynamically to variations in processing. Numerical simulations of the ZMR process were conducted to evaluate the sensitivity of the process over a wide range of temperatures and materials. Results indicate that material with melting points below 900 °C are very sensitive to temperature disturbances. This is due to the increased influence of conductive heating and decreased influence of radiative heating. The increased reflectivity during phase change curbs the amount of absorbed radiation. As the absorbed radiation becomes less influential, the sensitivity of the slush width decreases. Conductive effects should be considered when processing materials with melting points at or below 900 °C.

Optical properties of semi-insulating polycrystalline silicon (SIPOS) thin films containing 30 at. % oxygen atoms are investigated in the near ultraviolet, visible and infrared region to improve knowledge on the structure and chemical bonding of these mixtures. An effective medium approximation model is used for a microscopic investigation of the oxide species involved as a function of the annealing temperature (600–1200 °C). The results are compared with other optical spectroscopies (infrared and Raman) and with transmission electron microscopy to give a selected picture of the pure and oxide components.

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 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.

The SiL2.3 emission spectra of amorphous W/Si multilayers were measured. For the as-deposited samples the SiL2,3 emission spectra have been found to be very close to that of amorphous Si. The formation of WSi2 phase during annealing of W/Si multilayers at a temperature ≥50 °C was detected. From the SiL2,3 emission spectra of as-deposited and annealed samples, the amount of W/Si2 phase was estimated. It is shown that this technique can be used for quantitative estimation of the ratio of amorphous Si and WSi2 phases in W/Si multilayers.

A comparative dynamic x-ray diffraction (DXRD) and differential thermal analysis (DTA) study was performed in the investigation of mullite and spinel formation from slowly hydrolyzed single phase gels with Al/Si ratios ranging from 1/1 to 14/1. Both metastable tetragonal mullite and spinel were observed to form at temperatures <1000 °C in the gels with Al/Si ratios <8/1 and mullite transformed to the orthorhombic structure at ∼1250 °C. However, at higher Al/Si ratios, spinel was the only crystalline phase detected at <1000 °C and orthorhombic mullite formed directly at temperatures >1250 °C. As the Al/Si ratio increases, both the tetragonal mullite and spinel formation temperatures decrease while the orthorhombic mullite formation temperature increases. Based on the Al/Si composition where the formation extents of tetragonal mullite and spinel were maximum, their compositions are estimated to be 2Al2O3 · SiO2 and 6A12O3 · SiO2, respectively.

Barium-substituted lanthanum manganite (La1−xBaxMnO3) powders have been synthesized by a novel autoignition technique, and the effect of barium content on the autoignition characteristics, stability of the compound, and the powder characteristics have been investigated. X-ray examinations show that the material exists as a single phase having perovskite structure up to 40 at. % substitution of Ba for La, beyond which mixed phases of LaMnO3 and BaMnO3 are formed at least up to the highest limit of substitution (50 at. %) and calcination temperature (1350 °C) investigated. Electrical conductivity and thermal expansion behavior of the material have been studied for plausible use as cathode material in solid oxide fuel cells.

The electromechanical properties of (Pb1−xLax)(ZryTi1−y)O3 [PLZT x/y/(1 - y)] have been investigated in the compositional range 0 < x < 0.10 for y = 0.65 (rhombohedral PLZT) and 0 < x < 0.18 for y = 0.40 (tetragonal PLZT). Both field-induced strains (∊-E) associated with polarization switching and piezoelectric responses (d33) were studied. Transmission electron microscopy (TEM) and dielectric investigations were also performed. Room temperature TEM investigations revealed common trends in the domain structure with increasing La content for both PLZT x/65/35 and x/40/60, including a micron-sized domain structure, a subdomain tweed-like structure, and a nanopolar domain state. Changes in the field-induced strains and piezoelectric properties were then related to these microstructural trends. The dominant electromechanical coupling mechanism in the micron-sized domain state was found to be piezoelectricity. However, an electrostrictive coupling became apparent with the appearance of the subdomain tweed-like structures, and became stronger in the nanopolar domain state. It is believed that polarization switching can-occur through 70°or 110°domains, the subdomain tweed-like structure, or nanopolar domains depending on La content.

The dielectric and electrostrictive properties of (1 - x) PMN−xPMW (x ⋚ 0.2) using chloride salts were investigated as a function of x. When the PMN-PMW powders were calcined at 700 °C for 1 h, the perovskite phase formed was 92%–97% at any given PMW composition (x ⋚ 0.2). With the increase of PMW content up to 0.2, the relative density of the specimens increased slightly, and the electrostrictive coefficient Q11 of the 0.8 PMN−0.2 PMW specimen increased about 6 × 10−2 m4/C2. However, the dielectric constant and electrostrictive strain of the specimens decreased despite the improved sinterability.