Silica thin films containing organic groups were directly deposited from aqueous solutions of silicon alkoxides. Effects of functional groups of the alkoxides and the deposition conditions on the preparation of the films were investigated in order to clarify the deposition process. Silica films containing methyl and phenyl groups were deposited from aqueous solutions of methyl- and phenyltrialkoxysilanes, respectively, in the pH region lower than 3 or higher than 6. The composition and the property of the deposited films were influenced by pH and the temperature of the solutions and the starting materials. The adhesion of the deposited films on hydrophobic substrates was lower than that on hydrophilic ones, although the films were formed on both surfaces. The refractive index of the methyl-containing films, ca. 1.44, decreased with removal of methyl groups by heating up to 500 °C.

Powders and coatings of zirconia doped with 2.5 mole% yttria have been produced via the sol-gel route. The phase structure and subsequent thermal evolution in heating and cooling cycles have been investigated using mainly perturbed angular correlations spectroscopy. Thermal analyses and XRD as a function of temperature have also been performed to obtain complementary information. Upon heating, the amorphous gels crystallized into the tetragonal structure and showed the same hyperfine pattern and thermal behavior as observed in tetragonal zirconia obtained by the ceramic route: the two configurations of vacancies around zirconium ions denoted as t1 and t2 forms and their mutual t1 → t2 transformation. While the powder sample exhibited an incipient thermal instability above 1000 °C and underwent completely the t2 form to m–ZrO2 transition during subsequent, gradual cooling below 500 °C, the coating retained the tetragonal phase within the whole temperature range investigated. Hyperfine results suggest that the tetragonal phase stabilization is favored by the highly defective nature of the t1 form and consequently hardened by the availability of oxygen. The PAC derived activation energy for the fast diffusion of the oxygen vacancies inherent to the t2 form was determined as 0.54 ± 0.14 eV.

The combined effects of isolation stress, active area size, and SiGe misfit strain on dislocation generation in an advanced SiGe heterojunction bipolar transistor (HBT) process were studied. Eight-inch wafers were patterned with polysilicon-filled deep, and oxide-filled shallow trench isolation similar to that used in IBM's analog SiGe HBT technology. Half of the wafers were subjected to an additional stress-producing oxidation prior to SiGe growth. Si1−xGex films containing 0, 5.5, 9, and 13 at.% Ge were grown epitaxially by ultrahigh vacuum chemical vapor deposition (UHV CVD). The films were of constant thickness with an intrinsic Si cap. Some samples received an additional relaxation anneal following deposition. After the growth and anneal cycles, the dislocation density was determined by transmission electron microscopy (TEM). On nonstressed samples, no dislocations were observed in the device areas, even at Ge concentrations which are not stable to misfit dislocation generation in blanket form. This small area effect has been observed on patterned substrates that do not have functional device isolation. On the stressed-isolation wafers, the compressive stress from the oxidation of the trench sidewalls was found to intensify stress in the SiGe films, and to lower the critical strain at which misfit dislocations appeared. In large active areas on these wafers, two distinct dislocation regions were observed. Defects at the edge resembled those caused by isolation stress, while the defects in the center were more typical of the misfit dislocations associated with lattice-mismatch epitaxial films. It is clear that isolation stress must be minimized when fabricating integrated circuits using SiGe epitaxial films. It is also evident that SiGe films grown on nonstressed isolation exhibit the same increase in critical thickness with decreasing lateral dimension that has been observed on much simpler patterned substrates.

Ceramic-polymer composites with a 1–3 connectivity can be created via a novel process called dielectrophoretic assembly. The process involves an electric field which is applied to a suspension of ceramic particles in an uncured thermoset polymer matrix. Under appropriate conditions, the applied electric field acts to induce a spatial redistribution of the particles into a chained or fibril structure. It was shown previously that the electrorheological response and fibril microstructure are dependent on both the frequency and magnitude of the applied alternating electric field.3 This paper will show that the frequency dependence of the uncured thermoset polymer suspensions results from the complex electrical phenomena specific to each thermoset system. Specifically, it will be shown through low field dielectric measurements and high field current-voltage analysis that the dielectrophoretic effect can be limited by electrode polarization, ionic conductivity, and space charge relaxation. It is the frequency dependence of these limiting phenomena that gives rise to the observed frequency dependence in the dielectrophoretic force of attraction being utilized to drive particulate assembly.

Bismuth was implanted at room temperature in (100)-Si wafers with controlled energy and doses to result in a plateau-like implantation profile. The van der Pauw Si : Bi samples were characterized by the Hall effect and resistivity measurements from room temperature down to 13 K. The electron concentration of the prepared samples at 290 K varied from 3.0 × 1017 to 1.4 × 1020 cm−3. The resistivity of the Si : Bi samples presents a larger enhancement, compared to other dopants, when decreasing the Bi concentration. The metal-nonmetal transition was determined to be around 2 × 1019 cm−3. The calculated values obtained from the Generalized Drude Approach and an equation derived from Kubo formalism agree very well with the experimental data. The results confirm also the behavior ρc (Bi) < ρc(As) < ρc(P) < ρc(Sb) at 290 K.

As-synthesized, low iron content, ferrisilicates of ZSM-5-type contain well-separated Fe(III) ions in a tetrahedral environment and display paramagnetic behavior. After hydrothermal treatment, the iron ions are partially extracted from the framework, generating nanosize iron oxide or oxyhydroxide ferrimagnetic particles. This process has been studied by transmission electron microscopy (TEM), Mössbauer spectroscopy, magnetic ac susceptibility (χac), and field dependent magnetization, on samples containing up to 6.7 wt.% Fe. The experiments evidence the growth of nonaggregated particles, with a typical size around 3 nm, presumably located at the surface of the ferrisilicate crystallites. From a thorough granulometric analysis involving TEM and χac data, it is concluded that, in the range from 1.5 to 4.6 wt.% Fe, the particle size distributions are significantly independent of the iron content.

High quality single-crystal CoSi2 layers have been successfully formed on Si(100) using low energy high dose Co ion implantation followed by subsequent annealing method as a buffer layer for the deposition of YBa2Cu3O7−x (YBCO) thin films. Rutherford backscattering spectrometry with channeling (RBS-C) measurements showed that CoSi2 layers after annealing at temperatures between 850 and 950 °C had a minimum yield Xmin of about 3%. X-ray diffraction (XRD) spectra revealed that CoSi2 layers had the same orientation as the Si(100) substrates. Phi scan XRD spectra proved that CoSi2 layers epitaxially grew in the cube-on-cube epitaxial growth mode with respect to the Si(100) substrates. YBCO films and CeO2/YSZ buffer layers were deposited on CoSi2/Si(100) substrates via laser ablation and electron beam evaporation, respectively. θ-2θ, ω, and φ scan XRD spectra illustrated that YBCO films and CeO2/YSZ buffer layers had the epitaxial structure both in a-b plane and along the c-axis. YBCO films grown on this multilayered structure demonstrated excellent superconducting properties with the zero resistance transition temperature Tc0 of 87–90 K. The transition width (ΔTc) was about 1 K. Orientation and epitaxial crystalline quality of YBCO films and CeO2/YSZ buffer layers were confirmed by XRD and RBS-C characterization. All films consisted of c-axis oriented grains. RBS-C spectra indicated a high degree of crystalline perfection with a channeling minimum yield for Ba as low as 8%, and interdiffusion between the YBCO film and buffer layers or between the YBCO film and the substrate was limited. This multilayer system shows the possibility for the application of YBa2Cu3O7−x thin films on technical Si substrates in the field of hybrid superconductor-semiconductor technology.

A nanocomposite of a chemically synthesized nanostructured aluminum nitride (AlN) and a polyimide has been studied. Using a nonaqueous polar solvent, N-methylpyrrolidinone (NMP), as the suspension media, the degree of particle agglomeration of AlN was reduced dramatically from micron to nanoscale size. Upon the addition of poly(amic acid) to the AlN/NMP suspension, a further deagglomeration of the particles was observed. The surface physicochemical interactions have been investigated by characteristic model reactions using FTIR spectroscopy. A mechanistic interpretation for the deagglomeration and stabilization behavior is discussed. The formation of the AlN/PI nanocomposite was achieved by the rapid solidification of the precursor suspension followed by compression molding. Such an approach for nanocomposites exhibits better homogeneity with ultrafine fillers and allows a tailorable composition and property at the nanoscale level. Finally, AlN/PI nanocomposites with an increased ceramic loading, up to 65% by volume, were attained and their thermal and mechanical properties, along with the compositional effects, have been investigated.

Silicon suboxides thin films obtained by sol-gel and dip-coating methods, starting from a sol containing different percentages of TEOS (tetraethoxysilane) and MTEOS (methyltriethoxysilane), were grown onto silicon substrates. The samples were annealed at 100, 300, and 500 °C, and the electronic and compositional properties of the surface were studied by x-ray photoelectron spectroscopy (XPS) detecting the Si “Auger parameter” and the valence band. The effects produced by an ion-sputtering treatment of the samples were also studied.

A chemical approach to the formation of columnar defects involving the growth and incorporation of MgO nanorods into high temperature superconductors (HTS's) has been developed. MgO nanorods were incorporated into Bi2Sr2CaCu2Oz, Bi2Sr2Ca2Cu3Oz, and Tl2Ba2Ca2Cu3Oz superconductors at areal densities up to 2 × 1010/cm2. Microstructural analyses of the composites demonstrate that the MgO nanorods create a columnar defect structure in the HTS matrices, form a compositionally sharp interface with the matrix, and self-organize into orientations perpendicular and parallel to the copper oxide planes. Measurements of the critical current density demonstrate significant enhancements in the MgO nanorod/HTS composites at elevated temperatures and magnetic fields compared with reference samples.

Ion-irradiation was observed to transform MgAl2O4 spinel first to a metastable crystalline phase and then to an amorphous phase at cryogenic temperatures. Elastic stiffening of 15% occurred upon formation of the metastable crystalline phase. A second transformation from the metastable crystalline spinel to an amorphous state was accompanied by elastic softening of 25% relative to unirradiated spinel. This phase transformation behavior in spinel appears to be different from that in intermetallic compounds where only elastic softening associated with radiation damage accumulation is observed. A two-stage radiation damage model is proposed to explain the observed phase transformations.

The influence of the starting materials on the crystalline phases observed after hydrothermal synthesis of nickel and manganese-zinc ferrites was investigated. The combination of sulfates and sodium hydroxide showed the best results for the conditions studied. The morphological parameters of MnZn ferrites produced at different hydrothermal conditions (110–190 °C, 4–30 h) were analyzed. Changes in lattice parameter, particle size, density, size and total volume of pores, and in the surface area of the particles were analyzed as a function of temperature and processing time. The sintering process was employed in order to verify the reactivity of the hydrothermal powders at controlled atmosphere. High density and surface homogeneous ceramic bodies were obtained, without zinc volatilization. Lattice parameter variations were associated with changes in the cations distribution of the spinel during sintering.

The effect of ultraviolet irradiation on the xerographic sensitometry of organic photoreceptors was studied. Absorbed ultraviolet light decreased both the dark decay and the photoinduced discharge rates, and an increased buildup of the residual potential was observed. Above a threshold dose of ultraviolet irradiation, the residual potential was seen to decrease, and at the same time a slight increase of the hardness of the photoreceptor surface was detected. These behaviors originate from a decrease in the density of charge transport sites which is caused by the photochemical changes in the charge transport layer system.

A LaAlO3 precursor solution was prepared via an all alkoxide sol-gel route. The solution of lanthanum methoxyethoxide and aluminum methoxyethoxide in 2-methoxyethanol was prepared via ligand exchange starting from lanthanum isopropoxide and aluminum sec-butoxide and was used to make both LaAlO3 powders and films. Complete hydrolysis of the solution formed a gel that yielded well-crystallized LaAlO3 powders when fired in air at 800 °C. A partially hydrolyzed solution was spun-cast on SrTiO3 (100) single crystal substrates. Epitaxial films of LaAlO3 were subsequently formed during pyrolysis in O2 at 800 °C in a rapid thermal annealing furnace for a total of 8 min. The films were strongly c-axis oriented, verified by x-ray rocking curve results from the (003) plane with full-width at half-maximum (FWHM) = 0.87°, and had good in-plane texture shown by a φ scan of the (202) plane with FWHM = 1.07°.

Stress driven nucleation of voids in passivated aluminum interconnect lines is analyzed within the context of classical nucleation theory. A discussion of sources of tensile stress in such lines leads to an upper limit of 2 GPa. Calculations suggest that even at this high stress, nucleation rates are far too low to account for observed rates of voiding. Void formation at a circular defect at the line/passivation interface is then considered. In this case, a flaw on the order of nanometers in size may develop into a void under the imposed stress. These results strongly suggest that void nucleation in aluminum interconnect lines can be controlled by eliminating defects in the line/passivation interface.

We studied amorphous lead titanium alkoxide-derived heterometallic complexes, prepared from lead acetate and titanium n-propoxide or n-butoxide in parent alcohol medium. According to gas-liquid chromatography (GLC) and thermogravimetric analysis with mass spectrometry of evolved species (TGA/EGA) analyses, the type of alkoxide group influences oxo or acetate bridging, as well as the amounts of hydroxyl and organic groups bound to the metal network. From XANES and EXAFS analysis, local environments of lead and titanium atoms were determined within the analyzed range of 3.4 Å. Local environments depend weakly on the type of alkoxide used. Titanium atoms are pentacoordinated. A Pb–Ti correlation is established with lead atoms bound to titanium atoms by oxygen linkages.

Scanning tunneling microscopy images are reported for the wurtzite GaN(0001) surface. Terraces are observed, with three kinds of defect structures that are assigned to ordered N-vacancies: (i) striations perpendicular to the step edges, (ii) row defects spaced about 16 Å that intersect the steps at an angle of 30°, and (iii) “oval” defects that result from intersections of lines of vacancies (oriented at 60° with respect to step edges) with the row defects.

A method for the preparation of nanosized zirconium (hydrous) oxide particles of narrow size distribution is described. The procedure yields stable dispersions at low temperatures and short reaction times in the absence of surfactants, using inorganic zirconium salts. Crystal structure, particle size distribution, electrokinetic properties, stability, and thermal behavior of the prepared particles were investigated. Colloidal dispersions were treated with ultrasound to study their effect on the crystal structure of the calcined samples.

The rate at which Ag-clad (Bi, Pb)2Sr2Ca2Cu3Ox tapes are cooled from their final reaction heat treatment influences both the intergranular connectivity and intragranular flux pinning strength of the polycrystalline filaments. As the cooling rate from 825 °C to 730 °C in 7.5% O2 was decreased over a range of 5 °C/min to 0.005 °C/min, Jc (77 K, 0 T) increased from ∼8 to ∼24 kA/cm2, and the irreversibility field increased from, ∼120 to, ∼200 mT. The Jc (4.2 K, 0 T) increased in a similar fashion. Cooling slowly also sharpened the critical temperature transition and increased the critical onset temperature from 107 K to 109 K. These improvements in the superconducting properties occurred despite partial decomposition of the (Bi, Pb)2Sr2Ca2Cu3Ox phase into non-superconducting impurity phases during the slow cooling. A microstructural basis for these multiple effects is described.

The response of ferroelastic crystals on an applied stress is considered, and a distinction is seen between the reorganization of the domain structure within a grain at low stress and the reorientation of whole grains at high stress. The procedures are modeled in the framework of defect theory, i.e., by twinning dislocations and deformation twinning. The reorganization is controlled by the motion of pre-existing twinning dislocations. Since the Peierls stress of the twinning dislocations is very small, domain reorganization occurs under a very small load. The process of grain reorientation involves the nucleation of dislocations and, therefore, it requires a much higher stress. This concept is confirmed by comparison with experiments.