Absorption spectra of added Co(II) ions and EPR spectra of both Co(II) and ubiquitous Fe(III) ions in an alkali-borosilicate glass of vycor-type composition are studied both before and after thermal phase separation of the glass as well as in a silica glass derived from the phase-separated glass through vycorization. The results show that although almost all Co(II) ions migrate to the separated alkali-borate phase at the time of phase separation, only the interstitial ions in the case of Fe(III) take part in similar migration. The Fe(III) ions in the substitutional silicon sites, however, remain unaffected. It is also revealed that as a consequence of the process of phase separation a small fraction of the interstitial Fe(III) ions gets converted into substitutional ions leading to a net increase in the concentration of substitutional Fe(III) ions in the glass. Analysis of both absorption and EPR spectra of the Co(II) ions suggests that a change of host of the ion due its migration does not bring about any significant change in its coordination structure, which is typically a distorted tetrahedron both in the parent glass as well as in the phase-separated borate glass.

Carbon ions were implanted with energies between 50 and 150 keV into thin iron layers at temperatures of –10 °C and –70 °C. Formation of iron carbide phases was studied as a function of fluence, which was varied from 1.2 × 1017 C+-ions/cm2 up to 1.4 × 1018 C+-ions/cm2. The sequence of phase transformation during subsequent annealing to temperatures of up to 450 °C was also investigated. Detailed analysis of structure and morphology was done by cross-sectional transmission electron microscopy and electron diffraction experiments. The existence of metastable iron carbide phases, θ-Fe3C, Χ-Fe5C2, η-Fe2C, and also the amorphous phase Fe(C), after high-fluence carbon ion implantation and the transformation of the formed metastable phases by subsequent annealing into the θ-Fe3C phase are demonstrated.

Molybdenum and niobium carbides (β−Mo2C, NbC), as well as mixed carbides of molybdenum and niobium, were synthesized by the temperature-programmed carburization method (TPC) using a 20 vol% CH4/H2 gas mixture. The starting materials were MoO3, B-Nb2O5, and physical mixtures of B-Nb2O5/MoO3 with Nb/(Nb + Mo) atomic ratios varying from 0.2 to 0.8, respectively. Results from catalytic and temperatureprogrammed oxidation (TPO) measurements indicate that during the carburization of the Nb2O5/MoO3 physical mixture with Nby(Nb + Mo) = 0.8 there is, besides β−Mo2C and NbC formation, the appearance of a carbidic phase not detectable by x-ray diffraction (XRD). This phase appears to be highly active and selective for the dibenzothiophene hydrodesulfurization (HDS) reaction.

We report here on the preparation of La2/3Sr1/3MnO3 magnetoresistive thick films on polycrystalline Al2O3 substates by using the screen printing technique. It is shown that films can be obtained using high temperature sintering. While there is a reacted layer, this improves adhesion and is not too troublesome if the films are made thick enough. It is shown that PbO–B2O3 –SiO2 glass additives allow sintering at lower temperatures and can be used to improve the mechanical stress of the films. However, it is found that glass concentrations large enough to significantly improve the film adherence result in a weak low field magnetoresistance probably because grains are coated with high resistivity material. Strategies to overcome these difficulties are discussed.

The effects of Al and Nb doping on the leakage current behaviors were studied for the Ba0.5Sr0.5TiO3 (BST) thin films deposited on Pt/Ti/SiO2/Si(100) substrate by rf magnetron sputtering. Al and Nb were selected as acceptor and donor dopants, respectively, because they have been known to replace Ti-sites of the BST perovskite. The BST thin films prepared in situ at elevated temperatures showed relatively high leakage current density and low breakdown voltage. However, the BST thin films deposited at room temperature and annealed subsequently in air showed improved electrical properties. In particular, the leakage current density of the Al-doped BST thin film was measured to be around 10−8 A/cm2 at 125 kV/cm, which is much lower than those of the undoped or Nb-doped thin films. The results suggest that the Schottky barriers at grain boundaries in the film interior could determine the leakage behavior in the BST thin films.

Asymmetric growth of amorphous layer in a Ni/Zr bilayer, in which a thin disordered interlayer is preset, upon annealing at medium temperatures is observed by molecular-dynamics simulation with an n-body potential. It is shown that the amorphous layer is extended from the interlayer with different speeds toward two opposite directions and that the growth kinetics follows time dependence of t1/2, indicating amorphization upon annealing in the Ni/Zr bilayer is indeed through a diffusion-limited reaction. Besides, two low temperature limits allowing the growth of amorphous layer toward Ni and Zr layers are also obtained.

The thermal decomposition of a heteronuclear complex, La[Fe(CN)6] · 5H2O, leads to the preparation of nanosized single-phase perovskite-type LaFeO3 powders. The microstructural evolution of LaFeO3 with the temperature has been studied by x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The product of the decomposition at 500 °C consists of nanoporous grains which have the morphology of the complex, but diffracting as a monocrystal of LaFeO3. At the higher temperatures, the nanosized particles start to separate from each other, still keeping the shape of the complex grains and forming soft agglomerates. The formation of LaFeO3 from the complex at low temperatures is facilitated by the formation of an orthorhombic transition phase.

The growth kinetics of SiO2 thin films obtained by low-pressure chemical vapor deposition (CVD) from SiH4/O2/N2 gas mixtures has been determined at different temperatures and flow rates. The results show that the film growth is originated by some intermediate species (e.g., SiOxHy) produced in the gas phase. At low temperatures the deposition rate is limited by some homogeneous reaction with an apparent activation energy of 1.42 eV. Furthermore, the observation of critical limits when total pressure, oxygen/silane flow ratio, and temperature are decreased gives support to a branching-chain mechanism of deposition. Finally, we have observed that the deposition rate shows a hysteresis behavior when varying the temperature within the 300–400 °C range, which has been attributed to the inhibition of silane oxidation by the Si–OH surface groups of the films grown on the reactor walls.

Ion beam deposition provides an additional control of ion beam energy over the chemical vapor deposition methods. We have used a low energy ion beam of hydrogen and carbon to deposit carbon films on Si(100) wafers. We found that graphitic films, amorphous carbon films, and oriented diamond microcrystallites could be obtained separatedly at different ion beam energies. The mechanism of the formation of the oriented diamond microcrystallites was suggested to include three components: strain release after ion bombardment, hydrogen passivation of sp3 carbon, and hydrogen etching. Such a process can be extended to the heteroepitaxial growth of diamond films.

Tungsten bronze ferroelectrics with a morphotropic phase boundary (MPB) have become increasingly important for a variety of applications because of their enhanced and unique properties near the MPB. Lead barium niobate (Pb1−xBaxNb2O6) crystals, which have a morphotropic phase boundary between the orthorhombic (1 − x > ∼0.63) and tetragonal (1 − x, <, 0.63) phases, were grown in sealed Pt crucibles by the vertical Bridgman method for tetragonal compositions near the MPB, and their ferroelectric properties were investigated. The ferroelectric domain structures in as-grown crystals were revealed either by etching in hydrofluoric acid or by polishing with colloidal silica, the latter providing clearer features. Domain size on the surface perpendicular to the polar axis was 10–50 μm. Crystals could be poled by slowly cooling from above the Curie temperatures (300–400 °C) under a dc field of 5 V/mm. The spontaneous polarization Ps of tetragonal Pb1−xBaxNb2O6 was found to be in the range of 0.40–0.70 μC/mm2 at room temperature depending on composition and increased as the composition approached morphotropic phase boundary (1 − x = ∼0.63), as expected.

Texture evolution in Si/SiC multilayers deposited by atmospheric pressure chemical vapor deposition on carbonized Si(001) substrates was investigated using x-ray diffraction and transmission electron microscopy. SiC layers were epitaxial and (001)-oriented. Si layers deposited on the SiC exhibited a columnar structure with predominantly (110) orientation which could be related to the nucleation. Orientational relationships were Si[111] ║ SiC[110] and Si[112] ║ SiC[110]. Also, a low density of (112)-oriented columns was present. Extensive twinning on the vertical {111} planes within the Si columns led to domains of hexagonal stacking up to 10 nm in size with the presence of 2H-Si and 4H-Si. Subsequent SiC layer growth on the (110)-oriented Si layer resulted in a (110)-oriented SiC layer if the Si layer was carbonized prior to growth.

Surface morphologies and microstructures of epitaxial (Pb1−xLax)TiO3 (PLT, x = 0.00, 0.08, 0.16, and 0.24) thin films grown on (001) MgO have been investigated using SEM, AFM, and TEM. Surface roughness of PLT films varies severely with La concentration. For 0.08La-PLT film, very smooth surface has been achieved with 9.3 Å of RMS roughness. 0.00La- and 0.08La-PLT films show 90° domain structure, and periodic dimension of the domain is reduced by La substitution. 0.16La- and 0.24La-PLT films show the presence of triangular grains, causing rough surface and poor crystal quality. However, they are distributed uniformly in 0.16La-PLT film while agglomerated in 0.24La-PLT film. Optical propagation losses of PLT films measured by prism coupling technique were 22.3, 6.0, 11.4, and 20.7 dB/cm for x = 0.00, 0.08, 0.16, and 0.24, respectively. Such a variation in optical losses seemed to be due to the surface morphology and abundance of domain boundaries that change continuously as a function of La concentration in epitaxial PLT thin films.

Metastable face-centered cubic (fcc) solid solutions of Ni1–xAlx and Ni1–xZrx have been prepared in thin-film form using dc planar magnetron sputtering in a UHV system. In both these alloy systems, extended solubilities in the fcc phase and a pronounced (111) texture are observed after sputter deposition. An amorphous phase is found to form in Ni1–xAlx for x ≥ 0.30 and in Ni1–xZrx for x ≥ 0.05. Lattice constants, thermal expansion coefficients, and Debye temperatures were derived from x-ray diffraction measurements. These parameters were also calculated by using ab initio methods in the framework of the local-spin density and coherent potential approximations for the electronic subsystem and the Debye–Grüneisen model for the vibrational properties of the nuclei subsystem. Experiment and theory are compared and discussed.

Measurements of Faraday and Mössbauer effects have been performed at room temperature for alkali silicate glasses containing a large amount of Eu2+ ions to examine the relation between local structure and magnitude of Verdet constant. The Mössbauer spectra indicate that about 80% of europium ions are present as a divalent state. The effective transition wavelength and effective transition probability for the 4f7 → 4f65d transition of Eu2+, which causes the Faraday effect, are derived from the wavelength dependence of Verdet constant. Both effective transition wavelength and effective transition probability are large compared with borate glasses, leading to the large magnitude of Verdet constant of the alkali silicate glasses. The variation of effective transition wavelength with glass composition is connected with the change of 6s-electron density of Eu2+ evaluated from the Mössbauer spectroscopy.

High surface area tungsten oxynitride has been prepared by the temperature programmed reaction (TPR) of WO3 with NH3. All samples were characterized by x-ray diffraction (XRD), nitrogen physisorption, CO chemisorption, and elemental analysis. Samples were prepared at different heating rates (β), and a Redhead analysis yielded an activation energy for nitridation of 109 kJ mol−1. A heating rate of 0.016 K s−1 gave optimal synthesis conditions. Solid state intermediates were studied by interrupting the temperature program at various stages. No distinct suboxide phases were found using XRD. The nitridation step was determined to be a continuous transformation from oxide to oxynitride. Surface area, CO uptake, and nitrogen weight % were all found to increase as the reaction progressed. Reactivity experiments showed reasonable hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) activity, but little hydrogenation (HYD) or hydrodesulfurization (HDS) activity.

In this study, trifluoroiodomethane (CF3I), a non-global-warming gas, has been investigated as a substitute for typical PFC's currently used in wafer patterning and CVD chamber cleaning processes. Dielectric films consisting of plasma enhanced chemically vapor deposited silicon dioxide and silicon nitride were comparatively etched in CF3I and C2F6/O2 plasma environments. The etch rate of these films was ascertained as a function of applied rf power, etchant gas flow rate, reaction chamber pressure, and CF3I: O2 ratio. Destruction efficiencies of CF3I at different processing parameters were evaluated. Depending on the flow rate, rf power, and chamber pressure, utilization efficiency of CF3I varied from as low as 10% to as high as 68%. CF4, C2F6, COF2, and CO2 were the predominant by-products found in the exhaust stream; however, their concentrations were very low compared to the traditional process employing C2F6/O2 mixtures.

Ultrafine preceramic Si/C/N composite powders have been prepared from hexamethyldisilazane (HMDS) by laser-induced gas phase reaction, using a new kind of tworeaction-zone reactor which could efficiently increase laser efficiency and production yield compared with a one-reaction-zone reactor. The as-formed products were nanosized (50–80 nm), amorphous powders containing Si–C and Si–N bonds homogeneously mixed with some excess carbon. The production yield was in the range of 88–120 g/h. Changes of chemical composition and crystallization of the powders during heat treatment at 1350 and 1550 °C under nitrogen for 1 h were studied.

A microwave plasma generator, which functions under high pressure, has been developed and used in the fabrication of fine carbon particles. The plasma generator is a two-stage-type resonator, which consists of rectangular and semi-cylindrical-type resonators which are coupled in series for torching plasma and keeping it stable under high pressure. The plasma can be torched in helium gas at 3 × 106 Pa by tuning the dimensions of apparatus elements. Fine carbon particles of ~50 nm are obtained using a mixture of helium and methane gas. The particles are found to be crystalline from the results of transparent electron microscopy and diffraction analysis.

We have modified the microscratch test to create a near plane strain loading condition. In the Microwedge Scratch Test (MWST), a wedge-shaped diamond indenter tip is drawn along a fine line (i.e., narrow strip of film), while simultaneously being driven into the line. We compare microwedge scratching of zone 1 (voided grain boundaries) and zone T (metallurgical grain boundaries) thin film specimens of sputtered tungsten on thermally grown SiO2. Symptomatic of its weak grain boundaries, the zone 1 film displays three separate crack systems. Because of its superior grain boundary strength, the zone T film displayed only one of these—an interfacial crack system. By correlating fracture phenomena to signature events in the load-displacement curve, we develop governing equations for propagating interfacial cracks, including expressions for strain energy release rate, bending strain, and mode mixity. Grain boundary fracture causes zone 1 films to spall before a stable crack is formed. Zone T films survive the bending strains, and hence adhesions may be inferred from stable crack growth mechanics. We conclude by contrasting and comparing experimental results for plane strain indentation versus plane strain scratching.

Crystallization behavior of various compositions of MgAl2O4 –SiO2 glasses was investigated. Glasses with chemical compositions from MgAl2O4/SiO2 = 1/1 to 1/8, spanning the range of cordierite composition (1:2.5) were prepared by a rapid quenching method using an arc image furnace and twin roller. During thermal treatment, all the glasses first crystallized to form high-quartz solid solution (HQss), then transformed to high-cordierite at higher temperature. Transformation from high-cordierite to low-cordierite required prolonged firing times even at high temperature. The crystallization temperature of HQss and the transformation temperature from HQss to high-cordierite changed only slightly in the glasses with MgAl2O4/SiO2 ratios greater than cordierite composition, whereas large increases were found for glasses with MgAl2O4/SiO2 ratios lower than cordierite. The HQss phase appeared in the samples spanning a wide MgAl2O4/SiO2 range and showed superlattice reflections which doubled the fundamental lattice parameters. The cause for HQss formation prior to the appearance of cordierite in these glass samples is discussed from a structural viewpoint involving ordering-disordering of SiO4 and AlO4 tetrahedra deduced from 29Si and 27Al MAS-NMR spectra.