Large-scale twin structures in single crystal Bi2Ca1Sr2Cu2O8 (2122) are reported for the first time. Symmetrical 90° (i.e., a-b) twins with a [110] type twin boundary were observed. A characteristic layer-growth morphology and jagged twin walls suggest that twin formation occurred layer by layer during crystal growth; i.e., the twins were growth twins. Hot-stage optical microscopy, x-ray diffraction, and electron microscopy results are discussed with reference to twin morphology.

Using a computer-controlled inverted torsion pendulum at frequencies near 1 Hz, we determined the mechanical losses in a uniaxially fiber-reinforced composite. The composite comprised glass fibers in an epoxy-resin matrix. We studied three fiber contents: 0,41, and 49 vol.%. Three mechanical-loss peaks appeared: above 300 K, near 200 K, and near 130 K. They correspond closely to α, β, and γ peaks found previously in many polymers. We failed to see a mechanical-loss peak for either the glass or the glass-resin interface. Between 300 and 4 K, the torsion modulus increased in the resin by a factor of 3.30 and in the 0.49 glass-epoxy by a factor of 2.37.

Ferroelectric thin film of strontium-barium niobate was successfully fabricated by the sol-gel technique. The films were made on several types of substrate, including quartz, single crystal silicon wafer, and glass slides. The processing temperature was as low as 700 °C. The film obtained with thickness of 3000 Å was dense, transparent, and showed excellent ferroelectricity.

Regular networks of localized grain boundary dislocations (GBDs) have been imaged by means of transmission electron microscopy in three different types of high-angle grain boundaries in YBa2Cu3O7-δ, implying that these boundaries possess ordered structures upon which a significant periodic strain field is superimposed. The occurrence of these GBD networks is shown to be consistent with the GBD/Structural Unit and Coincidence Site Lattice (CSL)/Near CSL descriptions for grain boundary structure. Thus, these dislocations appear to be intrinsic features of the boundary structure. The spacing of the observed GBDs ranged from ∼10 nm to ∼100 nm. These GBDs make the grain boundaries heterogeneous on a scale that approaches the coherence length and may contribute to their weak-link character by producing the “superconducting micro-bridge” microstructure which has been suggested on the basis of detailed electromagnetic measurements on similar samples.

In order to obtain essential information on the formation process of the high-Tc phase in the Bi, Pb-Sr-Ca-Cu-O system, phase equilibria in the system PbO-CaO-CuO have been studied, mainly by x-ray diffraction analysis and thermal analysis. Temperature versus composition diagrams were established for the systems PbO-CuO(Cu2O) and PbO(PbO2)–CaO in air. Three invariant points were detected in these systems: a eutectic reaction (PbO + Ca2PbO4 = L) at 847 ± 6°C, a peritectic reaction (Ca2PbO4 = L + CaO) at 980 ± 2°C, and a eutectic reaction (PbO + CuO = L) at 789 ± 3°C. For the system PbO(PbO2)-CaO-CuO, subsolidus phase equilibrium in air was established. The liquidus was also examined at 780, 800, and 820°C, and a ternary (PbO-Ca2PbO4-CuO) eutectic point was detected at 772 ± 6°C.

NiTi was irradiated with Ni ions at various temperatures in order to study the temperature dependence of the irradiation-induced crystalline-to-amorphous transition. The irradiations were conducted above the Af temperature, and thus the specimens contained only the ordered B2 (CsC1) phase. The irradiations to similar doses at 150, 200, and 250°C showed that the amorphization kinetics slow down appreciably as the temperature is increased in this range. No amorphization was detected at irradiation temperatures of 350°C or higher, even after doses of 4 dpa. The small volume fraction of amorphous material observed after irradiation to 0.67 dpa at 250°C indicates that the cutoff temperature for amorphization is in the vicinity of this temperature. The amorphous regions of partly amorphous samples are distributed in a nonuniform manner and exhibit a morphology similar to the martensitic microstructure that existed in the specimens before heating to the irradiation temperature. Large amorphous regions in these samples exhibit some very fine crystalline debris which tends to disappear with increasing irradiation dose. Post-irradiation annealing experiments indicated that no thermally activated crystallization occurred during irradiation at temperatures up to 250°C.

The effect of the γ′ phase on the deformation behavior fracture resistance of melt-spun ribbons and consolidated bulk specimens of a series of NiAl-based alloys with Co and Hf additions has been examined. The morphology, location, and volume fraction of the γ′ phase are significant factors in enhancing the fracture resistance of the normally brittle NiAl-based alloys. In particular, the results indicate that a continuous grain boundary film of γ′ can impart limited room temperature ductility regardless of whether B2 or L10 NiAl is present. Guidelines for microstructure control in multi-phase NiAl-based alloys are also presented.

The susceptibility of a hot isostatically pressed Ni3AI, Cr, Zr alloy to hydrogen embrittlement has been studied. The base alloy and a second alloy containing 5 vol. % Y2O3 particles were tested by cathodically charging with hydrogen prior to or simultaneously with tensile testing. Embrittlement of both alloys was noted under both charging conditions, but was much more severe for simultaneous charging. Intergranular fracture due to hydrogen was noted in the base alloy, while the dispersoid-containing alloy failed along prior particle boundaries. The results are explained by a dislocation transport mechanism in which hydrogen is delivered to interior fracture sites by mobile dislocations. Much greater penetration of hydrogen is achieved under simultaneous charging conditions.

A series of simulations has been performed on grain boundaries in Ni and Ni3Al with and without boron doping using embedded atom-style potentials. A new procedure of obtaining “reference” data for boron related properties from electronic band structure calculations has been employed. Good agreement with existing experimental structural and energetic determinations was obtained. Boron is found to segregate more strongly to grain boundaries than to free surfaces. Adding boron to grain boundaries in Ni and Ni3Al increases their cohesive strength and the work required to pull apart the boundary. This effect is much more dramatic for Ni-rich boundaries than for stoichiometric or Al-rich boundaries. In some Ni-rich cases, adding boron increases the cohesive strength of the boundary to such an extent that the boundaries become stronger than the bulk. Bulk Ni3Al samples that are Ni-rich produce Ni-rich grain boundaries. The best cohesive properties of Ni3Al grain boundaries are obtained when the boundary is Ni saturated and also with boron present. Boron and nickel are found to cosegregate to the grain boundaries.

The electronic mechanism behind the brittle fracture of trialuminide alloys is investigated using the full-potential linearized augmented plane-wave (FLAPW) total-energy method within the local density functional approach. To this end, the bulk phase stability, the elastic constants, the anti-phase boundary (APB) energy, the superlattice intrinsic stacking fault (SISF) energy, and the cleavage energy on different crystallographic planes have been determined. A small energy difference (=0.10 eV/unit formula) is found between the DO22 and L12 structures of Al3Ti. In general, the trialuminide alloys have large elastic modulus, small Poisson's ratio, and small shear modulus to bulk modulus ratio. An extremely high APB energy (=670 mJ/m2) on the (111) plane is found for Al3Sc, indicating that the separation between ½(110) partials of a (110)(111) superdislocation is small. Since the total superdislocation has to be nucleated essentially at the same time, a high critical stress factor for dislocation emission at the crack tip is suggested. The high APB energy on the (111) plane is attributed to the directional bonding of Sc(d-electron)-Al(p-electron). The same type of directional bonds is also found for Al3Ti. In addition, moderately high values of SISF energy (=265 mJ/m2) on the (111) plane and APB energy (=450 mJ/m2) on the (100) plane are found for Al3Sc. The brittle fracture of trialuminide alloys is attributed to the higher stacking fault energies and a lower cleavage strength compared to those of a ductile alloy (e.g., Ni3Al). While the (110) surface has the highest surface energy, the cleavage strength (=19 GPa) of Al3Sc is found to be essentially independent of the crystallographic planes. The directional Sc—Al bond becomes even stronger on the (110) surface, which may explain the preferred (110) type cleavage observed by experiment.

The structure of pulsed laser irradiated graphite surfaces has been elucidated. The pulse fluences range up to 4 J cm−2 with durations no longer than 30 ns. The region exterior to the irradiated spot is littered with ∼0.1 μm diameter carbon spheroids. The boundary region is characterized by both spheroids and torn layers 1–5 μm. in lateral extent. The central region displays carbon spheroids and surface upheavals. The carbon spheroids are attributed to hydrodynamic sputtering of carbon. The surface upheavals and torn carbon layers are attributed to constrained thermal expansion and contraction of the irradiated region. It is estimated that a nearly instantaneous 1000°C temperature change is necessary to cause the observed surface deformation. Pulse fluences in excess of 0.8 J cm−2 cause a thin layer of carbon to melt. This is proven by the fact that the irradiated layer in the solid phase has a turbostratic structure. Electron diffraction experiments and dark-field imaging experiments show that the basal plane grain size of the resolidified material varies from ∼20 Å at the melt threshold to ∼100 Å for samples irradiated with 4.0 J cm−2.

The epitaxial growth of Cu on Si(111) substrate at room temperature was achieved using the Partially Ionized Beam (PIB) deposition technique in a conventional (10−4 Pa) vacuum without prior in situ cleaning of the substrate or post-annealing of the film. The beam contained ≍2% of Cu self-ions, and a bias of 0 to 4.2 kV was applied to the substrate during deposition. X-ray diffraction studies showed the existence of a twin structure in the epitaxial Cu layer deposited at 1 kV. A mechanism of epitaxial growth of Cu(111) on Si(111) substrate via an η″—Cu3Si intermediate phase is proposed. Based on the crystal structure of η″—Cu3Si, it is demonstrated that the geometrical lattice matching concept provides a simple picture of lattice continuity at the interface in this epitaxial system.

Under circumstances in Zone-Melt-Recrystallization (ZMR) of Si-on-Insulator (SOI) structures where radiative heat loss is significant, the ∼50% decrease in emissivity when Si melts destabilizes the Si molten zone. We have demonstrated this both experimentally using a slowly scanned e-beam line source and numerically with a finite-element computational simulation. The resulting instability narrows the process window and tightens requirements on beam control and background heating uniformity, both for e-beam ZMR systems and optically-coupled systems such as a graphite strip heater.

An amorphous-to-fine-grain-polycrystalline phase transformation has been observed during annealing of Sn-implanted Si when the peak Sn concentration exceeds about 2 at.%. At lower Sn concentrations, epitaxial growth is retarded in (100) Si but proceeds to completion with a large fraction of Sn residing on substitutional lattice sites. As the Sn concentration is increased, epitaxy is pre-empted by the sudden transformation of the near-surface Sn-doped region into polycrystalline Si. The time required to initiate the transformation is temperature dependent and is characterized by an activation energy of ∼1.7 eV. Rapid redistribution of Sn has been observed to accompany the transformation. Our observations are shown to be consistent with a melt-mediated crystallization process which is rate limited by Sn diffusion and precipitation in amorphous Si.

The internal gettering of nickel in (100) silicon wafers implanted with 2.5 ⊠ 1015 argon-ions/cm2 at 280 keV has been studied by electron microscopy. Nickel deposited on the back surface is gettered by forming a discontinuous layer of nickel silicide, NiSi2, in the argon-implanted region near the front surface. Electron microdiffraction and high-resolution electron microscopy indicate that the layers of nickel silicide probably grow epitaxially on the undamaged silicon surrounding the silicide.

The simultaneous gettering of iron and nickel in a float-zone silicon wafer in the (100) orientation and implanted with 2.5 ⊠ 1015 argon ions/cm2 at 280 keV has been investigated. Iron was deposited on one half of the back surface of the wafer and nickel was deposited on the other half. Chemical analyses by secondary ion mass spectroscopy, energy dispersive x-ray spectroscopy, and high-resolution imaging by high-resolution electron microscopy revealed the gettering rate of iron was orders of magnitude lower than that of nickel. The results also suggested that gettering is a metal-diffusion-controlled process. The simultaneous gettering of iron and nickel results in a complex distribution of the two metals in the silicon wafer.

In this paper we report on the growth of pseudomorphically strained Si1−xGex alloys on 〈001〉 Si by solid phase epitaxy. One set of amorphous alloys was formed by high dose ion implantation 74Gc implanted at an energy of 200 kcV to a fluence of 9.6 ⊠ 1020/m2). Our TEM observations show that regrowth of these Si1−xGex(xmax = 0.14) films at ≍590°C results in a high density of planar defects and that these defects are associated with faceting of the amorphous/crystalline interface during annealing. These results were compared with the solid phase regrowth of MBE-grown Si0.7Ge0.3 amorphized with 170 keV 28Si ions which exhibited identical defects and faceting during regrowth. Attendant with this faceting was a decrease in the regrowth velocity, a result of a change from a planar {001} growth morphology to a multi-faceted growth surface containing many <50 nm deep pyramidal impressions. The regrowth rate was quantified, at a particular temperature, by the use of Si homoepitaxy for calibration of in situ TEM experiments. It was shown that the regrowth rate at 594°C in pure Si was 51 nm/min, whereas in the Si0.7Ge0.3 the regrowth rate decreased, as a result of {111} faceting, to 21 nm/min. RBS was used to characterize Ge concentrations and lattice resolution TEM was used to study the development of the faceted interface and associated planar defects during regrowth.

We have studied the structural and electrical properties of ultrathin cobalt silicide films deposited on Si(211) and (311) and annealed at a variety of temperatures. Transmission electron microscopy reveals two regimes of silicide growth. If more than 10 Å of Co is deposited, textured CoSi forms at low temperatures, which transforms to two epitaxial orientations of CoSi2 at about 500°C. If less than 10 Å of Co is deposited, only one epitaxial CoSi2 orientation is observed, which occurs in discontinuous islands or lines. The resistivities of the thinnest films reflect the degree of continuity of the silicide layers. In thicker films, where disorder is the major factor, the resistivity for intermediate annealing temperatures (∼500°C) depends dramatically on the orientation of the Si substrate, being an order of magnitude lower for Si(311) and (211) than for (111). The differences between these observations and those made on films grown under the same conditions on Si(111) can be understood by noting both the greater tendency of the film to form intermediate phases which are epitaxial on the high symmetry Si(111) surface and the faceting of the CoSi2-Si(311) and (211) interfaces.

Shallow n-p GaAs solar cells have been made by implantation of Si into Zn-doped (p-type) GaAs substrates followed by rapid thermal annealing. The structure of the GaAs crystal has been determined by the DSL photoetching method (Diluted Sirtl-like etchants used with Light). It was found that implantation-induced-damage (revealed by DSL as microroughness and craters) was not removed after annealing for energies exceeding 60 keV. This leads to substrates that contain many precipitates, which appears to be disastrous for the fabrication of good solar cells. In addition, good cell performance is hampered by compensation effects in the n-p transition region and in the n-type layer itself.

The anisotropic powder metallurgy of n-type Bi2Te2.85Se0.15 doped with bromines was studied by both x-ray diffraction and thermoelectric measurements. The statistical orientation of platelet-like grains in the samples was characterized using the orientation factor estimated by the Lotgering formula from (0,0,1) x-ray diffraction intensities. It is demonstrated that the orientation factor which is strongly influenced by the hot-pressing conditions and the particle size of the starting material has a strong effect on the thermoelectric properties of the samples in this system. This implies that the powder metallurgy has the additional freedom of controlling the thermoelectric properties in addition to the doping level in the grains.