For Y1Ba2Cu3O7, using only reported monocrystal measurements and some analysis–theory, we estimated the complete nine-component orthotropic-symmetry elastic-stiffness matrix, the Voigt Cij matrix. Comparison with very-high-frequency tetragonal-symmetry phonon-dispersion results shows good agreement (9% on average), except for C12.

YBa2Cu3O7−δ superconductor crystals have ferroelastic properties, which makes it possible to interpret their microstructure within the framework of the quasidislocation theory.

The microstructure and microwave properties of YBa2Cu3O7−δ thin films grown on SrTiO3 (100) and MgO (100) substrates by chemical vapor deposition have been studied. Both 100 GHz cavity measurement of surface resistance and ground plane substitution in a 5 GHz microstrip resonator show that films on SrTiO3 have better microwave properties than those on MgO. Although there are some a-axis grains and secondary phases on the surface, a large fraction of each film on SrTiO3 is epitaxial with its c axis normal to the substrate. The 100 GHz surface resistance of these films is less than copper for temperature ⋚ 82 K, and approaches the detection limit at 10–20 K. For the films on MgO, c-axis grains of different in-plane rotation are found together with some a-axis needle-like grains. The grain boundaries are detrimental to the microwave properties, and the resulting surface resistance at 100 GHz and 10–20 K is about 20 mΩ higher than that of films on SrTiO3.

We have examined the atomic structure of growth interfaces in thin films of Y–Ba–Cu–O grown on [001] perovskite or cubic substrates. At substrate heater temperatures in the range of 780–820 °C c-axis oriented growth is observed on these substrates. On SrTiO3, the first layer appears to be either a BaO or a CuO2 plane while on LaAlO3 the first layer appears to be a CuO chain layer. The mismatch on the a-b plane is accommodated by the formation of interface dislocations. Defects on the substrate surface propagate as defects in the film. These defects are primarily translational boundaries and in some cases second phases. At lower substrate heater temperatures, i.e., 650–700 °C, a, b-axis growth dominates. Defects and steps on the substrate surface are more detrimental in the growth of a, b-axis oriented films, since they tend to favor the nucleation of c-axis oriented domains. This is ascribed to the ledge mechanism of c-axis film growth, for which the surface steps are good nucleation sites.

Electrical properties of Y–Ba–Cu–O superconductors, such as the critical current density and the zero-resistance temperature, are systematically improved by changing the compression pressure during the formation process of the specimens. Also, by changing the silver powder content of the superconducting Y–Ba–Cu–O powder, the critical current density and the zero-resistance temperature are remarkably improved. The resistance-drop temperature is insensitive to changes in the compression pressure, silver content, and magnetic field, if the field is applied perpendicular to the specimens. The critical current density of the specimens with and without silver decreases exponentially with the perpendicular magnetic field. The critical current densities of specimens without silver showed much lower sensitivity to perpendicularly applied magnetic fields than those of the specimens having a silver content. Along with the above improvements, the present paper also examines several factors that affect the superconducting characteristics. These factors include impurities in the air and strong magnetic fields.

Bi2.1Sr1.8Cu2O8 fibers having excellent superconducting properties can be grown by a laser-heated float zone process. In order to maintain stable growth conditions and thereby obtain fibers free of diameter fluctuations and voids, dense ceramic starting material containing only the 2212 phase is required. In this study various processing parameters, including calcining and sintering temperatures and times, grain size of the powders used, and pressing pressures were optimized to yield dense, chemically homogeneous starting material. It was found that under most conditions there was no increase in the density on sintering. Retrograde densification was the usual situation except at higher pressures and was found to depend on pressing pressure, calcination history, and sintering temperature. Cold-pressing at higher pressures (100000 psi) yielded denser but chemically inhomogeneous material. Ceramic samples sintered for long times (>48 h) yielded source rods that produced instabilities during fiber growth, presumably due to preferential loss of mass during sintering.

The effect of excess Ca2CuO3 on the superconducting properties in the (Bi, Pb)2Sr2Ca2Cu3Oy, (2223) was investigated through the measurements of ac susceptibility, critical current density, and critical field. All the measurements have been performed on the samples that were identified by x-ray diffraction to consist of the mostly high Tc 2223 phase with varying amounts of excess Ca2CuO3. It was found that when the excess Ca2CuO3 is in the range 0.1 M to 0.3 M the loss peak of ac susceptibility appeared at higher temperature than that for an undoped sample, and the Jc showed a maximum at the excess Ca2CuO3 = 0.2 M, indicating that a proper amount of excess Ca2CuO3 enhanced the flux pinning. The upper critical field, Hc2, determined by using a pulse magnetic field showed a maximum at the excess Ca2CuO3 = 0.1 M, and increased linearly with decreasing temperature within the measurement regime.

The migration of a (100) θ = 43.6°(Σ29) twist grain boundary is observed during the course of a molecular-dynamics simulation. The atomic-level details of the migration are investigated by determining the time dependence of the planar structure factor, a function of the planar interparticle bond angles, and the location of the center of a mass of planes near the grain boundary. It is found that a migration step consists of local bond rearrangements which, when the simulation cell is made large enough, produce domain-like structures in the migrating plane. Although no overall sliding is observed during migration, a local sliding of the planes near the migrating grain boundary accompanies the migration process. It is suggested that a three-dimensional cloud of thermally produced Frenkel-like point defects near the boundary accompanies, and facilitates, its migration.

Small angle neutron scattering (SANS) was applied to achieve insight into the magnetic correlations in nanostructured Fe. The results confirm the expected microstructure involving ferromagnetic grains and a nonmagnetic or weakly magnetic interface region, the interfaces occupying about half the specimen volume. The SANS measurements further reveal that in nanostructured Fe the magnetic correlations are not confined to single grains, but are extended across the interfaces and result in the alignment of the magnetization over several hundreds of grains. An external field of 1.5 kOe is not sufficient for complete magnetic alignment of the entire specimen. However, the long-range magnetic correlations are considerably disturbed by this field. Reducing the external magnetic field to zero causes the magnetic correlations to resume microstructural characteristics similar to what they had in the original state.

The fracture toughness for first matrix cracking of a uniaxially reinforced C-fiber/C-matrix composite is investigated using a modified controlled surface flaw method. The theoretical models for first matrix cracking of brittle matrix composites including the stress intensity and the potential energy approaches are reviewed in the light of the experimental results. The sharing of the applied load between the reinforcing fibers and the brittle matrix along with extensive crack front debonding enhance the fracture toughness for first matrix cracking.

We have studied selective epitaxial growth of silicon in the SiCl2H2/HCl/H2 system. Our results on growth rate and selectivity are reported here. We found that the growth rate and selectivity are strong functions of the partial pressures of HCl, SiCl2H2, H2, exposed Si area, and wafer position. We propose that growth and selectivity are controlled by surface reactions between SiCl2H2 and HCl and the SiO2 and Si surfaces. Higher HCl flow rates decrease the adsorption coefficients and/or incorporation rates of the reactive SiCl2H2(g) species on both SiO2 and Si. When either is zero for SiO2 and both are greater than zero on Si, selective depositions occur. Finally, we present data on the effect various SiO2 surface treatments have on the density and distribution of Si nuclei on this surface.

Thin poly-Si layers deposited at 625 °C by LPCVD that are used in silicon technology for microelectronics exhibit a pronounced additional x-ray diffraction peak at about 0.334 nm. High-resolution electron microscopy (HREM) reveals that this peak stems from {010} reflections of a diamond hexagonal (dh) Si phase, which occurs as small inclusions with the orientation relationship (01) ‖ (0001), [011] ‖ [20] to the diamond cubic (dc) Si matrix. Due to the high density of planar faults on {111}, the dh-Si phase also exists in the form of the 2H silicon polytype with the orientation relationship (1) ‖ (0001), [011] ‖ [20]. In the first case the formation of the dh-Si phase may be understood by a multiple twinning transformation process, and in the second case by glide of Shockley partial dislocations on {111} planes. Various other hexagonal polytypes occur, which have all the {010} reflections in common and make a major contribution to the 0.334 nm peak. The medium temperature of 625 °C for layer deposition leads to a 〈011〉 preferential orientation and a high density of twins as well as to high compressive stress in the poly-Si layer itself. This seems to promote the formation of dh-Si. The strong twinning behavior produces a typical tilt grain boundary between adjacent dh-Si grains: [20], (016), Θ = 35°with a translation vector t = 1/2[031] parallel to it. The dh-Si phase vanishes in this poly-Si film after annealing at temperatures above 1000 °C due to grain growth by recrystallization.

A systematic theory is presented that models the effects of interstitial oxygen on the deformation behavior of silicon. The theory is based on calculation of the dependence of the dislocation velocity on the applied stress in the crystal and determination of the locking and unlocking stresses for dislocation motion. Internal stresses in the oxygen-hardened crystals are modeled by the superposition of the unlocking stress, a back stress due to the interaction between mobile dislocations, and an internal stress that arises from the interaction between a dislocation and the oxygen cloud around other dislocations. The initiation of dislocation multiplication is modeled as a two-step thermally activated process; the first step is the unlocking of the dislocation and the second step is the formation of jogs along the dislocation line. The coupled model for oxygen transport and dislocation motion is used to simulate crystal deformation in dynamic experiments and to reproduce stress-strain curves. The predictions of the initial stage of deformation are in good agreement with the experimental data of Yonenaga et al. [J. Applied Phys. 56, 2346 (1984)].

The codiffusion of B and Sb implanted in Si with a dose of 2 × 1016 cm−2, corresponding to concentration far above the solid solubility, is investigated at 900 and 1000 °C on the basis of SIMS and carrier profile measurements and TEM observations. The comparison of the codiffusion data with the corresponding ones obtained by the diffusion of each element alone revealed several anomalous effects due to dopant interaction. In particular, our experimental results support the hypothesis of the formation of mobile donor-acceptor pairs and of the increase of the Sb solubility in the region where a high concentration of acceptors is present. On the basis of this feature, a diffusion model that takes pairing and precipitation into account is presented. A simulation program including this model allows us to foresee most of the anomalous phenomena occurring in the high concentration codiffusion experiments and shows in general a satisfactory agreement with experimental profiles.

Electrical characteristics of trench capacitors using RTO (Rapid Thermal Oxidation) oxides, nitroxides, and reoxidized nitroxides as the gate insulators are discussed. High temperature RTO is effective in preventing oxide thinning at the trench corner, and so the dielectric strength of trench capacitors is improved drastically. The mean time to failure (MTTF) of trench capacitors using RTO is more than ten times longer than that of trench capacitors using conventional furnaces. Using reoxidized nitroxides as the gate insulator, superior charge to breakdown (QBD) is obtained. RTP (Rapid Thermal Processing) is superior to the process using the conventional furnace for the gate insulators of trench capacitors. Improvements in temperature uniformity, repeatability, and lessening of slip line formation are essential for RTP equipment to be practical.

It is shown how the bond valence method can be used to estimate expected interatomic distances in coherent interfaces. The method is illustrated by application to the Si/NiSi2 (111) interface with results generally in accord with experimental data.

An amorphous SiO2 substrate was co-implanted with 175 keV Mo+ and 74 keV S+ ions at doses of 4.97 × 1016 and 1.02 × 1017 cm−2, respectively. Energies of the Mo+ and S+ ions were chosen to obtain nearly overlapping depth profiles. Transmission electron microscopy and Rutherford backscattering techniques were used to characterize the ion-implanted materials. The formation of a MoS2 phase was observed in the as-implanted condition. Annealing of the as-implanted material was performed in an oxygen-free atmosphere as well as in air. The MoS2 phase remained stable at 700 °C for 8 h in an oxygen-free atmosphere whereas it starts oxidizing in air at 600 °C for 2 h. Results are discussed in terms of the available data on the oxidation of MoS2 coatings.

A thermochemical analysis is performed in the system Cu–In–S at 298 K. Free energies of the compounds In6S7, In2.8S4, CuInS2, CuIn5S8, and of the recently discovered CuIn2 have been estimated, the numerical values (kJ/mol) of which are −1043 ± 21, −556 ± 8.8, −315 ± 54, −1238 ± 113, and −51 ± 26. A consistent set of data is used for the calculation of the Gibbs triangle as well as of the predominance area diagram. The results are in nearly complete agreement with the measurements published recently, in particular with those using the nuclear method of perturbed angular correlations (PAC). The compound CuInS2, one of the possible base materials for thin film solar cells, is shown to equilibrate with nearly all of the compounds of the system. A nonvariant four-phase equilibrium CuIn2−InS–In–CuInS2 is found at about 298 K. It is noted where more precise data are needed.

A two-step process has been developed to form highly oriented thin films in material systems with dissimilar crystal structures and interatomic spacings. This processing method utilizes current polycrystalline thin film deposition techniques. In this method, a polycrystalline thin film is first deposited and heat treated to promote its breakup into isolated grains. The breakup process favors those grains that have a low substrate interfacial energy and so produces a film of highly oriented but isolated grains. In the second process step, another polycrystalline thin film is deposited. The remnant grains act as seeds for the growth of a highly oriented thin film. The process is demonstrated through the growth of highly (100) oriented thin films of cubic ZrO2 (25 mol % Y2O3) on (0001) Al2O3 single crystal substrates, a material system in which film and substrate have dissimilar structures and interatomic spacings. Implications for the growth of epitaxial films using this method are discussed.

Chemical vapor deposition (CVD) of boron nitride (BN) is most readily performed using BCl3 and NH3, which are brought into the deposition zone through two separate tubes. This causes some problems: inadequate mixing leading to a nonuniform deposit, formation of solid intermediates, etc. To avoid these problems, the process was performed by mixing BCl3 and NH3 at elevated temperatures (120–220 °C) prior to entering the deposition zone. The reaction between them took place by the forming of volatile stoichiometric B–N compounds (trichloroborazine and iminochloroborane), which were then transported through a single tube into a deposition zone. The resulting deposit was found to be hexagonal boron nitride.