Equal amounts of carbon-12 methyl halides and carbon-13 methane, along with hydrogen, have been introduced into a hot-filament diamond CVD chamber. The isotopic ratios of the as-deposited diamond films on tantalum have been measured by Raman spectroscopy. It was found that methyl chloride yielded carbon-12 enriched diamond films, while the other methyl halides resulted in equal amounts of carbon-13 and carbon-12 in the films. Furthermore, the carbon-12 enrichment was more enhanced as the substrate temperature was lowered. Matrix-isolation FTIR analyses of the gas samples collected during the deposition indicated that there was no straightforward agreement between the 12C/13C ratios of the gas phase species, methane and acetylene, and that of the diamond films. The results imply the presence of a new chlorocarbon radical such as CH2Cl, which is postulated as a more effective growth species than the methyl radical.

In recent experiments it has been shown that the yield stress of polycrystalline thin films depends separately on the film thickness and the grain size. It was also shown that the grain size dependence varies as the reciprocal of the grain size. In this paper an analysis is presented which leads to these results and provides a more detailed understanding of the origins of the observed behavior.

Mechanical alloying, a high-energy ball-milling technique, is now widely used for preparing alloy powders with metastable phases (crystalline or amorphous). The technique, however, may contaminate the powder with material eroded from the vial and milling media. We report on the analysis and effects of iron contamination on Al25Ge75 powders that we prepared by mechanically alloying mixtures of aluminum and germanium powders, using different mechanical alloying apparatuses.

Rapid solidification of the Zr3Al liquid alloy allows retention of the high temperature β–Zr solid solution with bcc structure. Mechanical grinding is shown to amorphize this metastable phase very easily. Calculations show that the retained bcc phase has a free energy above that of the amorphous phase. The density of bcc Zr3Al at room temperature is found to be 2% lower than that of its equilibrium L12-ordered fcc structure as determined from their respective lattice parameters. The bcc phase thus represents a 2% volume expansion with respect to the fcc structure.

The microstructure and the composition profile of lead lanthanum zirconate titanate thin film fabricated using the sol-gel method were analyzed using the scanning electron microscope and scanning Auger microscope. The PLZT thin film consists of micron-scale spheroidal perovskite grains and nano-scale pyrochlore grains. The perovskite grain has a higher lead and lower oxygen and zirconium contents than the pyrochlore grain. The Auger spectra of the two phases were similar except for energy shift and extra fine structure of oxygen peaks. The Auger depth profile and SEM observation of the cross-sectional fracture surface showed higher perovskite content near the interface between PLZT and ITO films than the surface of the PLZT film.

The critical current density of melt-textured YBa2Cu3Ox superconductor has been enhanced by mechanical deformation at a high temperature. Hot deformation at 45° to both the slip plane (001) and the slip directions [100]/[010] has resulted in a high density of dislocation loops and stacking faults. The deformed samples are found to exhibit a critical current density (Jc) at Hc-axis as high as that at Ha-b plane at 1.5 T and 77 K. A Jc of 35300 A/cm2 has been achieved at Hc (1.5 T and 77 K) which is twice as high as that observed in undeformed samples. The enhanced Jc in this magnetic field orientation is attributed to pinning by the defects created by mechanical deformation. This pinning mechanism is found to be effective over a wide angle between the magnetic field and the a-b plane and thus results in a marked reduction in the critical current anisotropy.

Experimental correlations of thermoelectric power (TEP), oxygen deficiency (δ), and c-lattice constant in YBa2Cu3O7−δ (YBCO) c-oriented, polycrystalline, thin-film, high-temperature oxide superconductors are presented. The TEP values in the normal state were observed to be positive for samples with oxygen deficiencies between 0.08 ≤ δ ≤ 1.00 and negative for 0.00 ≤ δ ≤ 0.08. Furthermore, the TEP magnitudes were highly sensitive to the amount of oxygen and were found to increase with increasing oxygen deficiency, ranging from values of −2 μ V/K to more than two orders of magnitude higher. In addition, relatively temperature-independent TEP values were observed for hole-conductive samples with low oxygen deficiencies (δ ≤ 0.30). The lattice constants (c) of the same samples were measured by XRD. These were found to increase with oxygen deficiency and to correlate systematically with the TEP values. We conclude that TEP is a reliable indicator of the oxygen content in YBCO materials.

Heat-treatment temperature/time and ambient effects on the properties of YBa2Cu3O7−x superconducting films derived from carboxylate precursors were investigated. The thin films were processed under O2, N2, or N2/O2 mixed atmosphere. The use of N2 or N2-rich atmosphere facilitated the 123 phase formation, grain growth, and orientation due to liquid phase assist sintering. Thin films with Tc(zero) = 87.8 and Jc > 105 A/cm2 at 77 K were prepared under such atmosphere at T ≤ 920 °C. Higher temperatures were required for thin films processed under O2 atmosphere and inferior transport properties were obtained. Processing above the melting temperature resulted in highly oriented films with dense microstructures and large grains, but significant post annealing was needed to obtain good film properties.

High Tc superconductors need to be fabricated into desirable configurations such as wires for practical applications. Toward this objective, the plastic extrusion process was applied to the fabrication of wires and rods of YBa2Cu3O7−x. The ceramic oxide powder is combined with several organic additives to form a slurry which is extruded by forcing it through a small aperture. This is subjected to a sequence of heat treatments for drying, binder burn-out, and sintering. The critical current density of these wires ranges from 800 A/cm2 to 1500 A/cm2 depending upon the diameter and the current-carrying capacity is uniform over long lengths of up to 140 cm. This process was also applied to fabrication of larger cross-sectional area rods and hollow cylinders, capable of carrying up to 245 A. The mechanical properties of these wires were also investigated.

The mechanisms of reaction in sputter-deposited Al–Zr thin film couples have been investigated using extensive transmission electron microscopy (TEM) observations of cross-sectional specimens prepared by the novel use of an ultramicrotome. The TEM observations greatly facilitated understanding of composition-depth profiles obtained by Rutherford backscattering spectroscopy (RBS). The reaction between Al and Zr in thin films, and the influence of Cu on this reaction, was shown by the TEM to be much more complex than previously reported in studies that largely used RBS. Reaction of Al and Zr in sputter-deposited films occurs in two stages. Initially reaction occurs by growth of an amorphous layer at the Zr interface and is promoted by intermixing of Al and Zr during deposition. Growth of an amorphous layer in an Al-transition metal thin film couple has not been reported previously. Subsequently, the amorphous layer is consumed by growth of microcrystalline Al3Zr from the Zr/reaction layer interface. The transition from growth of amorphous to microcrystalline Al3Zr results in thickening of the reaction layer with an overall growth rate exponent of 1/3. The Al3Zr grows with the metastable L12 cubic structure, except in the presence of Cu, when it grows with the tetragonal DO23 structure. The fine initial Al and Zr grain sizes limit the influence of Cu on the morphology of the reaction; in all cases, a continuous and uniform reaction layer thickness is observed by TEM.

The electron diffraction contrast of two types of rectangular dislocation networks in an Al70Co15Ni15 decagonal quasicrystal has been analyzed. One type of dislocation network consists of two dislocation sets whose Burgers vectors are parallel to the tenfold axis A10 and a twofold axis A2D. The other type of dislocation network consists of two dislocation sets whose Burgers vectors are parallel to the A10 and the other twofold axis of A2P. The characteristics of the diffraction contrast of the dislocation networks in the Al–Co–Ni decagonal phase are similar to those in conventional crystals.

Titanium hydrides having two different crystal structures were observed in α–Ti thin films grown epitaxially on sapphire substrates by e-beam physical vapor deposition. One of the hydrides (γ-hydride) had a face-centered tetragonal structure (c/a > 1) with an ordered arrangement of hydrogen atoms. The second hydride formed was the fcc δ-hydride. The γ-hydride grew as platelets in the α–Ti lattice with {10$\overline 1$0}Ti habit planes, whereas the γ-hydrides formed directly on the sapphire substrate parallel to the (0001)Ti. These hydrides are one of the principal causes of film decohesion.

A simple model is described with which the entire force versus penetration behavior of indentation with a sphere, during loading and unloading, may be simulated from knowledge of the four test material parameters, Young's modulus, Poisson's ratio, flow stress at the onset of full plastic flow and strain hardening index, and the elastic properties of the indenter. The underlying mechanisms are discussed and the predictions of the model are compared with data produced by an ultra low load, penetration measuring instrument.

An intermetallic compound c–NiZr and a mixture of elemental powders of nickel and zirconium [Ni50Zr50 (at. %)] have been mechanically ground (MG) and mechanically alloyed (MA), respectively, using a high-energy ball mill in various atmospheres. The products were characterized by x-ray diffraction, transmission electron microscopy, differential scanning calorimetry, and chemical analysis as a function of milling time. An amorphous a–NiZr alloy was prepared by both MG and MA in an argon atmosphere. By MG of NiZr, an amorphous nitride a–NiZrN0.15 was synthesized in a nitrogen atmosphere, while a crystalline hydride c–NiZrH3 was formed in a hydrogen atmosphere. On the other hand, ZrN and ZrH2 were formed by MA in a nitrogen and a hydrogen atmosphere, respectively. The amorphization reaction was observed between ZrH2 and Ni by further MA in a hydrogen atmosphere, and a mixture of a–NiZrxHy (x < 1) and ZrH2 was obtained. However, no amorphization was observed by MA between ZrN and Ni in a nitrogen atmosphere. The effects of the milling atmosphere on the phase formations during MG and MA are discussed based on the gas absorption rate.

Diamond films were deposited on Si substrates by Electron-Assisted Chemical Vapor Deposition (EACVD) using various methane concentrations below 8.1%. It was found that the deposited films were strongly (110)-oriented. This seemed to arise from a high nucleation density of diamond caused by the initial deposition of an amorphous carbon film. A comparison of the graphite etching rate between EACVD and Microwave Plasma CVD (MPCVD) under the standard growth conditions showed that EACVD was able to etch graphite about five times faster than MPCVD. Hence, it was concluded that the differences in the growth rate and morphology between EACVD and MPCVD arise from the different graphite etching rates as well as different chemical species in the reaction gas.

The growth of BaO and SrO on SrTiO3(100) substrates using mass-separated low-energy (50 eV) O+ beams has been studied using x-ray diffraction, reflection high-energy electron diffraction, and high-resolution transmission electron microscopy. It was found that the BaO and SrO films have been epitaxially grown with new structures different from those of corresponding bulk crystals: The BaO films have a cubic structure with a lattice constant of 4.0 Å, and the SrO films have a tetragonal structure with a lattice constant of a = 3.7 Å parallel to the substrate and with c = 4.0 Å normal to the substrate.

A number of the samples with general formula Sr2Cu1−xLixMO6−δ, where M = W, x ≤ 0.5 and M = Mo, x ≤ 1.0 was synthesized by means of solid state reactions at 800–950 °C in flowing oxygen atmosphere. The powder x-ray diffraction data show that most of the samples have a cubic structure. The results of magnetic measurements indicate a near Curie behavior for Sr2Cu0.5Li0.5WO6-δ. The effective number of Bohr magnetrons per copper atom for tungsten-containing samples decreases from 1.62 (x = 0) to 1.39 (x = 0.5) with increasing lithium content. The samples show electrical insulator behavior.

Thin copper films are deposited onto glass and irradiated, in air, by means of a scanned Ar+ laser beam. The kinetics of oxidation are measured by an interferometric method. The laser-synthesized oxide films are characterized by optical microscopy, scanning tunneling microscopy, and optical spectroscopy. It is shown that the oxidation kinetics, as well as the structural and optical properties of the oxide, depend on the laser beam power and on the initial thickness of the copper film. It is argued that these facts are related to the thermal history of the samples under laser irradiation.

Several sol-gel syntheses make use of “additives” in the sol-preparation step. These additives can react with metal alkoxides causing important structural changes. In order to demonstrate the nature of the reactions involved in the molecular modification process, a model system based on Ta(OC2H5)5, acetic acid and acetylacetone (as modifiers), was studied using FTIR spectroscopy. At room temperature, both modifiers react with the ethoxide to cause formation of new organotantalum precursors. The acetic acid modification was observed from the characteristic symmetric and asymmetric vibrations of the COO groups. The average difference in wave numbers (δv = vasymm – vsymm) between the two of 140 cm−1, observed for different ratios of ac/Ta, signifies a bridging nature of the acetate group. For ac/Ta ≥ 1, formation of ethyl acetate, probably as a result of the reaction between ethanol and excess acetic acid, was also observed using FTIR. Results of the acetylacetone modification showed the enol form of acetylacetone which has its v(C–O) and v(C–C) vibrations centered around 1625 cm−1, split into two bands at 1581 and 1518 cm−1, respectively, indicative of chelation of the acetylacetanate ligand to Ta. In the case of acetylacetone modification, the formation of ethanol was confirmed by FTIR analysis of the liquid fraction distilled at ∼80 °C.

A two-step seeding process has been developed to lower the transformation temperature and modify the grain structure of ferroelectric lead zirconate titanate (PZT) thin films with high Zr/Ti ratio. Previous study has shown that nucleation is the rate-limiting step for the perovskite formation. Therefore, any process that enhances the kinetics of nucleation is likely to decrease the transformation temperature. In this process, a very thin (45 nm) seeding layer of PbTiO3, which has a low effective activation energy for perovskite formation, was used to provide nucleation sites needed for the low temperature perovskite formation. In this study, we have shown that the pyrochlore-to-perovskite phase transformation temperature of PbZrxTi1−xO3 films of high Zr/Ti ratio (e.g., x = 53/47) can be lowered by as much as 100 °C. The grain size of these films can also be substantially modified by this two-step approach.