Polycrystalline samples of HgBa2(Ca0.86Sr0.14)2Cu3O8+δ (denoted as Hg-1223) were prepared by a precursor route, which involves the reaction between HgO and two precursors: Ba2CuO3+x and Ca0.14CuO2. X-ray powder diffraction analysis revealed that the Hg-1223 is isostructural with pristine HgBa2Ca2Cu3O8−δ and TlBa2Ca2Cu3O9−δ. The Hg-1223 has tetragonal symmetry with space group P4/mmm, and lattice parameters a = 3.8648(2) Å and c = 16.0319(2) Å. The as-synthesized Hg-1223 sample has a Tc of about 126 K. After annealing in an oxygen atmosphere at 280 °C for 10 h, the Tc increased to 132 K. Using this precursor pathway, Hg-1223 samples can be reproducibly synthesized.

This communication reports on the microstructure and interdiffusion observed in a new NbSn2/Nb metallization structure on SiO2, previously reported [H. S. Chen et al., Appl. Phys. Lett. 66, 2191 (1995)]. The as-deposited NbSn2 layer was found to be amorphous. After heating, the NbSn2 becomes polycrystalline and heavily diffused with Au from the Au-Sn solder. The Nb layer remains pure and intact after heating. The microstructure, compositions, and phases of the Au-Sn solder layer are also presented.

Crystalline thin films of NdNiO3 have been epitaxially grown on the (100) face of single-crystal LaAlO3 substrates. These films exhibit the characteristic reversible change in electrical conductivity with temperature previously observed in bulk polycrystalline material. The temperature of the electrical transition in the epitaxial thin films was lower than reported for the bulk polycrystalline ceramics. This effect is attributed to lattice strains associated with the film processing and interfacial lattice matching constraints.

This communication describes a technique used to pattern oxide thin layers using microcontact printing (μCP) and sol-gel deposition. The technique involves μCP of self-assembled monolayers (SAM's) of alkylsiloxane on various substrates (SiO2/Si, sapphire, ITO, and glass), followed by deposition of oxide thin layers from sol-gel precursors. Delamination of oxide layers from SAM-derivatized regions allows selective deposition of crystalline dielectric oxide layers on underivatized regions. To demonstrate the viability of this technique for integrated microelectronics and optics applications, patterned (Pb,La)TiO3 (PLT) and LiNbO3 layers were deposited on sapphire, silicon, and indium tin oxide (ITO) substrates. Use of lattice-matched substrates allows lithography-free deposition of patterned heteroepitaxial oxide layers. Strip waveguides of heteroepitaxial LiNbO3 with 4 μm lateral dimensions were fabricated on sapphire. Dielectric measurements for patterned PLT thin layers on ITO are also reported.

A composite microstructure consisting of small α-Al2O3 particles dispersed in a β-NiAl coating matrix was synthesized by chemical vapor deposition (CVD). White the surface of a pure Ni substrate was being reacted with AlCl3 and H2 to form β-NiAl at a temperature of 1050 °C, the partial pressure of CO2 in the reactor was controlled via pulsing to nucleate and disperse 50 to 500 nm α-Al2O3 particles in the β-NiAl matrix. The relative amount of the α-Al2O3 phase increased with coating thickness as the rate of the β-NiAl formation decreased with time. These experimental observations suggest that the synthesis of a graded composite microstructure by the CVD method is feasible.

In the Nd-Ba-Cu-O system, a directional structure produced by a peritectic reaction has been observed. On heating, the sintered Nd1Ba2Cu3O6+δ (Ndl23) precursor formed a rod-like directional structure of Nd4Ba2Cu2O10 (Nd422) phase. These Nd422 rods became thicker from the melting interface to the solidified interface. The [100] direction of Nd422 crystal is parallel to the axis of Nd422 rod and the sample pulling direction. Moreover, Nd422 rod spacing was observed as a function of growth rate and decreased with an increase of growth rate. In addition, with an increase of growth rate, Ndl23 solidified interface morphologies changed from planar, cellular to equiaxed.

High transition temperature superconducting YBa2Cu3O7−x (YBCO) thin films have been epitaxially grown on YZ-cut LiNbO3 (LNO) substrates by the pulsed laser deposition technique. The interface between YBCO and LNO has been systematically investigated by scanning electron microscopy, atomic force microscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy. Off-stoichiometry LiNbOx phases are found to segregate on the substrate surface because of lithium and oxygen vacancies formed during the high temperature YBCO growth. These submicrometer particles are observed along the Z-axis on the X-Z plane of LNO with height of ∼30 nm above the LNO surface. This rough growth surface results in YBa2Cu3O7−x thin films grown on the LNO surface that have reduced Jc and Tc, possibly limiting the use of YBCO/LNO heterostructures for surface acoustic wave (SAW) devices.

The preparation of thick films of the LaBa2Cu3Oy (La-123) phase by using the partial melting technique (PMT) of powders deposited on MgO substrates by drying alcoholic suspensions is reported. The effects of the starting composition, processing time (t), and temperature (T) on the superconducting properties of the La1+xBa2Cu3Oy (−0.25 ⋚ x ⋚ 0.5) system were investigated. The presence of the La4Ba2Cu2O10 (La 422) phase was detected in the samples quenched in liquid N2 after heating up to 1200 °C. The crucial step of the processing is the cooling rate down to the crystallization temperature, Tp, determined by DTA analysis, in order to favor the formation of the La-123 phase from the reaction between the La-422 solid phase and the liquid. The superconducting properties, tested by magnetization measurements, showed a diamagnetic onset temperature (Tc,diam) as high as 89 K.

Kikuchi electron diffraction patterns are used extensively to determine crystal orientations via transmission electron microscopy (TEM) or in the electron backscattering pattern (EBSP) mode of scanning electron microscopy (SEM). A new method is presented that is capable of finding crystal orientations, the camera length, and the projection center from only one pattern per grain using a least-squares technique. This method eliminates the need to perform an alignment with a reference crystal in the backscattering mode. Application to a Σ = 13a silicon bicrystal is presented for TEM patterns and EBSP's. A complete analysis of the propagation of random measurement errors into the disorientation axis/angle pair is carried out. The root mean square deviation from the nominal disorientation angle is found to be 0.3°in the case of TEM and 0.5°in the case of EBSP. The root mean square inclination between the nominal and measured disorientation axis is found to be 1°in the case of TEM and 0.5°in the case of EBSP.

Morphology of twinned diamond particles grown by chemical vapor deposition was characterized by atomic force microscopy in both contact and tapping modes. Quantitative angle measurements using a surface normal algorithm were performed on untwinned crystals, penetration twins, re-entrant corners, and fivefold dimples. Tip-sample interaction is discussed. The morphology of the penetration twins and some of the re-entrant corners can be explained by low order Σ3 twins and flat crystallographic surfaces. Abnormally shallow re-entrants with large vicinal faces are attributed to rapid nucleation of new layers at a point along the re-entrant intersection.

Diamond was deposited on Si(100) substrates by the microwave plasma-assisted chemical vapor deposition method in three steps: carburization, biasing, and growth. High-resolution transmission electron microscopy in cross-sectional view has been used to observe the evolution of microstructures around the interfacial region between diamond and Si in each processing step. The chemistry near the interface was characterized with elemental mapping using an energy-filtered imaging technique with electron energy loss spectroscopy. An amorphous carbon layer, β-SiC and diamond particles, and graphite plates have been observed in the carburization stage. β-SiC can form in epitaxial orientation with Si in the following stage of biasing. Graphite and amorphous carbon were not observed after the bias was applied. Diamond grains were aligned in a strongly textured condition in the growth stage. It has been found that diamond, SiC, and Si all have (111) planes in parallel. The relation of the evolution of microstructure with the processing conditions is also discussed.

A fiber-reinforced in situ metal matrix composite (MMC) consisting of copper (Cu) and 20 mass% niobium (Nb) was produced by large strain cold rolling. The rolled MMC revealed a very high strength combined with good electrical conductivity. The microstructure of single Nb filaments was investigated employing transmission electron microscopy (TFM). In heavily rolled specimens (∊max = 99.4%) randomly arranged dislocations as well as dislocation cells were observed. Furthermore, structurally less-ordered areas were discovered, the size of which frequently extended over the entire filament width. The shrinkage of these zones during heating was directly observed in the TEM. The impact of such structurally less-ordered areas on the strength was assessed. The discovery of the degradation of structural regularity in the Nb filaments of heavily cold-worked Cu-20 wt. % Nb shows that the underlying microstructural mechanisms responsible for the high strengths observed are far from being understood and that the strain-hardening models for Cu-based in situ composites currently discussed do not yet account for all relevant microstructural features.

Iron/alumina multilayers have been deposited on sapphire wafers using RF magnetron sputtering. To study the interdiffusion, the multilayers were annealed in a tubular furnace under a 10−7 mbar vacuum, and the samples examined by using a combination of classical diffractometry (θ/2θ) and Grazing Incidence Scattering (GIS) for the phase determination, and Small Angle X-ray Scattering (SAXS) for the superstructure of the multilayers. In all cases, in the as-deposited state the alumina is amorphous and the iron is crystalline in the bcc phase. Thermal anneals at temperatures between 573 and 873 K give evidence for segregation to the interfaces. At higher temperatures, interdiffusion occurs, leading to the formation of different phases. The Fe-Al2O3 interdiffusion coefficient has been evaluated in the temperature range from 873 to 1273 K.

Novel thin films of ultrafine titanium dioxide particles dispersed in a matrix of hydroxypropylcellulose (HPC) polymer have been made on quartz and silicon substrates. The titanium dioxide particles were made by the hydrolysis and condensation of titanium tetraethoxide (TEOT) in solutions of HPC in a mixture of ethanol and water. HPC controlled the particle size by adsorbing at the particle surface during the growth process and generating repulsive steric forces. The TiO2/HPC composite films were transparent in the visible region and completely blocked ultraviolet radiation at 300 nm. These films were crack-free and uniform in composition and thickness. Transparent films of amorphous TiO2 were made by burning out the HPC at 500 °C. These films were highly uniform and had no macroscopic cracks. X-ray diffraction revealed a transition to the anatase form upon sintering at 600 °C. A film sintered at 700 °C had a porosity of 38%. The crystalline films remained transparent until they densified at 800 °C.

The recent announcement of the synthesis of C3N4 has increased interest in this unique material. Carbon nitride may have several useful applications as wear and corrosion resistant coatings, electrical insulators, and optical coatings. We have produced amorphous carbon nitride coatings containing up to 40% nitrogen using planar magnetron RF sputtering with and without an ion beam in a nitrogen atmosphere. Both wavelength dispersive x-ray spectrometry (WDX) and x-ray photoelectron spectroscopy (XPS) indicate this composition. Coatings up to 2 μm thick were produced on alumina, silicon, SiO2, and glass substrates using a graphite target. Films with transparency greater than 95% in the visible wavelengths and harder than silicon have been produced. The properties of these films are correlated with composition, fabrication, conditions, and subsequent heat treatments. A scanning tunneling microscope (STM) and transmission electron microscopy (TEM) were used to characterize the morphology of the films. XPS studies confirm the stability of a carbon nitrogen phase up to 600 °C. Compositional variations were determined with secondary ion mass spectrometry (SIMS) depth profiling, and the Raman spectra are compared with those of carbon and carbon nitride films prepared by other methods.

The decomposition mechanism of hillebrandite (Ca2SiO4 · H2O) to larnite (β-Ca2SiO4) was studied by conventional and in situ hot-stage TEM methods. The hillebrandite structure is suggested to be a composition of parawollastonite (CaSiO3) and portlandite [Ca(OH)2] adjoining on {001} planes. The larnite fibers showed occasional bending and kinking as well as internal defects such as dislocations and domains. No transformation-related microstructures such as twinning were observed. The preferred orientations in the larnite fibers were not distinct. The decomposition mechanism of hillebrandite in air and in a vacuum may be different. In air, the CaO from the decomposed portlandite layer directly participates in the process of SiO4 chain breaking to form larnite. In the TEM this CaO is removed and apparently reprecipitated, so that hillebrandite converts directly to parawollastonite, A possible lattice correspondence between hillebrandite (C2SH) and larnite (β-C2S), based on crystallographic considerations, is proposed to be bC2SH ¶bβ-c2s, αC2SH ¶ ≍[102]β-C2S, and CC2SH ¶ ≍ [401]β-C2S.

Cobalt oxide system Co3O4-CoO has been studied on the ZrO2 matrix surfaces with FTIR and XPS. The tetragonal and monoclinic ZrO2 matrix materials have been synthesized from the Zr-n-propoxide-acetylacetone-water-isopropanol system. The study shows that the ZrO2 matrix is able to retain the relative Co3O4:CoO population at elevated temperatures. The thermodynamically stable oxide population (Co3O4:CoO) at room temperature for ZrO2-supported Co3O4-CoO is about 50:50 (Co2+ :Co3+ = 2:1), which is markedly different from the 100:0 case (Co2+ :Co3+ = 1:2) for an unsupported Co3O4-CoO surface oxide system. The relative Co3O4 :CoO ratio in the surface region of the ZrO2 is temperature dependent but matrix-polymorph independent. The composition of an oxide solid solution formed by the Co3O4-CoO and matrices of ZrO2 is determined to have a cobalt molar percentage of 4.5%. Diffusion thermodynamic quantities are investigated, and the measured diffusion activation energy for a cobalt ion in the ZrO2 matrices is 0.21 eV. The mechanism of the ZrO2 memory effect on surface Co3O4-CoO transition will also be addressed.

A new method for the preparation of well-defined colloidal barium titanate (BaTiO3) crystals by the controlled double-jet precipitation (CDJP) technique is described. The process is extremely fast and requires a low temperature (<100 °C). The reactants, barium and titanium salts, can be used in high concentrations and the yield is quantitative. The stoichiometry of the BaTiO3 particles can be controlled precisely and reproducibly. The effects of the composition of the reactant solutions, flow rates, reaction time, and the addition of polymers on the precipitation process were investigated. The BaTiO3 powders, produced by the CDJP technique, sinter to high density at a temperature as low as 1200 °C and exhibit a relative dielectric constant of 5000 at 20 °C, which is the highest value reported in the literature. The grain sizes of the sintered samples are small and uniform, ranging between 1 and 2 μm.

A novel method was proposed for measuring the epitaxial growth rate of diamond by microwave plasma-assisted chemical vapor deposition (MPCVD). Cubo-octahedral crystals were formed on an Si(100) wafer and were used as the substrate in the homoepitaxial growth. Growth rates of the {100} and {111} were simultaneously measured from the change in the top view size of crystals. Thus, the relative growth rate of {100} to {111} was obtained without any limitation of its value. The homoepitaxial growth rate was strongly affected by the type of diamond faces, CH4 concentration in the gas phase, and deposition temperature. The growth rate of {100} was more dependent on CH4 concentration than that of {111}, while the activation energy for the [100] growth was about half that for the [111] growth. These tendencies were in accord with growth mechanisms proposed for each diamond plane. Reaction conditions were optimized based on the relative growth rate of (100) to (111) planes, and a highly oriented (100) diamond film with a quite smooth surface was formed on an Si(100) wafer.

The simultaneous determination of light element contamination levels and accurate nitrogen-to-metal ratios in nitride thin films deposited on silicon substrates is demonstrated by using α-particle beam energies in the range 3–4 MeV. In this energy range, significant light element sensitivity enhancements are observed, while the heavy elements show classical Rutherford behavior. The use of resonance scattering at different resonance energies is shown to be the method of choice for analyzing BN films on silicon. Also, a technique is suggested for analyzing very thin films in which an aluminum foil substrate and buffer layer are used to enhance sensitivities.