New structural planar defects in Ba-deficient Y1Ba2Cu3O7−δ (YBCO) (1:1.6:3) thin films grown on NdGaO3 and SrTiO3 substrates by metalorganic chemical vapor deposition have been observed by means of high-resolution electron microscopy. The defects are associated with perturbations of the YBCO “1:2:3” stacking sequences along the c direction, which give rise to structural variants with locally “2:5:7,” “3:4:7,” or “4:6:10” cationic stoichiometries. The defects can be consistently interpreted as CuO–YO–CuO/CuO conversions or YO/BaO (BaO/YO) interconversions in the (a,b) planes and extending over a few nanometers along the c axis. Structural models based on image matching with simulations are proposed for two particular cases. It is thought that these structural imperfections can be effective sites of flux pinning.

Nanocrystalline diamond has been synthesized on a mirror-polished Si(001) substrate by means of direct ion beam deposition. Low-energy (80–200 eV) hydrocarbon and hydrogen ions, generated in a Kaufman ion source, were used to bombard the substrates. The bombarded samples were characterized by high-resolution transmission electron microscopy and Raman spectroscopy. Nanocrystalline diamond particles of random orientation were observed in a matrix of amorphous carbon film on the Si(001) substrate. The size of the nanocrystalline diamond particles varied in the range of 50–300 Å. The mechanism of ion-induced formation of nanocrystalline diamond is discussed.

The nucleation and growth of NdBa2Cu3O7–δ (Nd123)–Nd4Ba2Cu2O10 (Nd422) single-grain composites in a controlled 1% O2 in N2 atmosphere were investigated in detail as a function of solidification temperature and Nd422 phase content using a top-seeded melt growth technique. A schematic process phase diagram in the peritectic solidification region of Nd–Ba–Cu–O (NdBCO) was constructed primarily from constant isothermal growth experiments at various temperatures for several compositions and used to fabricate large single-grain material by both isothermal and continuous slow cooling over a limited temperature range. The nucleation at the seed surface and subsequent growth of uniform grains was observed to depend critically on the controlled rate of grain growth and the temperature range over which solidification occurred.

A novel one-step solvothermal decomposition process (SDP) was successfully developed for fabrication of Bi2S3 nanowires via a reaction between BiCl3 and thiourea in polar solvents at 140 °C for 6–12 h. The influence of solvents, reaction temperature, and reaction time on the formation of Bi2S3 nanowires was investigated. The yield was as high as 98%. The particle sizes of Bi2S3 nanowires are controlled by the choice of solvents. The possible formation mechanism of Bi2S3 nanowires via the so-called SDP method is proposed. The present technique is expected to synthesize other nanostructural metal chalcogenides under mild conditions.

Plasma treatment was applied on glasslike carbon spheres to modify their gas adsorption behavior. After the oxygen plasma treatment, a selective adsorption of CO2 gas was obtained, almost no nitrogen adsorption being detected, at low temperatures. Surface morphology observed by using field-emission scanning electron microscopy, atomic force microscopy, and scanning tunneling microscopy was found to be changed after the oxygen plasma treatment.

The microstructures and the solidification behavior in unidirectionally solidified Y–Ba–Cu–O/Ag (YBCO/Ag) superconducting current leads were investigated. The solidification model of this system was discussed by the Y2Ba1Cu1O5–Ba3Cu5Ox–Ag quasiternary phase diagrams constructed by analysis of the solute compositions in the melt. The diffusion fields and the spacing between silver particles in the YBCO/Ag system were discussed. The relationship between the shapes of entrapped silver particulates, the miscibility gap in the phase diagram, and the wetting behavior at the growth interface in two-dimensional monotectic reactions were also discussed.

Thin films with microstructures controlled on a nanometer scale have been fabricated using a recently developed process called glancing angle deposition (GLAD) which combines oblique angle evaporation with controlled substrate motion. Critical to the production of GLAD thin films is the requirement for a narrow angular flux distribution centered at an oblique incidence angle. We report here recent work with low-pressure, long-throw sputter deposition with which we have succeeded in fabricating porous titanium thin films possessing “zig-zag,” helical, and “pillar” microstructures, demonstrating microstructural control on a level consistent with evaporated GLAD. The use of sputtering for GLAD simplifies process control and should enable deposition of a broader range of thin film materials.

The crystal growth of InSb thin films on mica substrates was investigated by conventional three temperature vacuum evaporation with varied Sb/In flux ratios and temperature programming for the substrate. The Sb/In flux ratio was varied from higher than 1.0 (about 2.0 is optimum), to less than 1.0 (about 0.7 is optimum), to again much higher than 1.0 during the stages of evaporation. The electromagnetic characteristics were investigated and x-ray analysis of the films at various stages was undertaken. The films obtained contained no excess In and they were (111) highly oriented in x-ray analysis, showing high electron mobility. These films were used to prepare high performance Hall elements.

Variation of hardness with penetration in nanoindentation of a rough surface is a compound effect of variation in asperity geometry with penetration, designated geometric effect, and genuine property gradients with depth as may exist in a near-surface zone. We simulate indentation of a rough surface numerically to elucidate the geometric effects and validate it by some model “macro” experiments. Finally, we formulate a general framework to deconvolute genuine property variation by normalizing the measured hardness with the geometric effect.

The creep behavior of single-crystal Zn-doped CdTe was examined in the small strain regime. Specimens from two different sources, with tensile axes [110] and [112], were deformed at 1073 and 1173 K. Strain rates were of order 10−6 to 10−7 s−1. A laser interferometer was constructed to measure the small sample displacement. Cadmium overpressure was used to inhibit sublimation of test specimens at elevated temperatures. Some tests showed a transition from secondary to tertiary creep at low levels of strain. An activation energy for steady-state creep was calculated as QC = 1.46 eV, and the creep exponent was found to be approximately n = 4.2. These results, coupled with reported activation energies for self-diffusion of Cd in Cd(Zn)Te, indicate a dislocation creep mechanism. Etch pit density was measured before and after deformation and approached a common level regardless of initial etch pit density.

Microstructures in the reaction interface between molten Al and dense mullite have been studied by transmission electron microscopy to provide insight into mechanisms for forming ceramic–metal composites by reactive metal penetration. The reactions, which have the overall stoichiometry 3Al6Si2O13 + (8 + x)Al → 13Al2O3 + xAl + 6Si, were carried out at temperatures of 900, 1100, and 1200 °C for 5 and 60 min and 1400 °C for 15 min. Observed phases generally were those given in the above reaction; their proportions and interfacial microstructures, however, were strongly dependent on the reaction temperature. Using previously measured reaction kinetics data, the observed temperature dependence of the interfacial microstructure has been modeled as three sequential steps, each of which is rate limiting in a different temperature range.

High-resolution transmission electron microscopy (HRTEM) is used to reveal fine structures of amorphous silicon induced by Vickers indentation and its interface with unindented silicon matrix. Deformation microtwins at the interface and continuous transition from lattice structure of crystal into amorphous structure at the interface are observed. Within the amorphous silicon near the periphery of the indented region, there are many clusters characterized by distorted silicon lattice. A possible mechanism of lattice-distortion-induced amorphization at the periphery of indented silicon is suggested. All the indentations are performed at ambient temperature.

The photoacoustic (PA) spectra for the porous silicon samples irradiated during or after anodization are reported. The difference between the spectra for the irradiation conditions is discussed. The light irradiation time dependence of the PA spectra is shown. The irradiation after anodization causes the samples to luminesce in the blue region and enhances the photoluminescence signal intensity around 600 nm. It also reduces the PA signal intensity in the shorter wavelength region. The irradiation during the anodization causes enhancement only in the red-region luminescence.

Rod-shaped samples of YBa2Cu3O6+x (Y123) with different contents of Y2BaCuO5 (Y211) are textured by the partial-zone melting method in order to produce single-domain specimens. The microstructure and magnetic properties of the samples are analyzed as a function of the Y211 initial addition. Y211 precipitates are more homogeneously distributed and smaller, and the superconducting properties of the sample also improve, so when the initial content of Y211 increases, Jc values are high. Texture analysis is carried out by the x-ray pole figure technique.

We investigated the relationship between the structure and misorientation angle of (001) twist grain boundaries in Bi2Sr2Ca1Cu2Oy/Ag composite tapes processed in different oxygen partial pressures (PO2 = 0.01, 0.21, and 1 atm). Large-angle misoriented twist boundaries (>10°) essentially had no amorphous layers at the interface, and the misorientation angles of these boundaries mostly corresponded to low-energy misorientations. This large-angle misoriented boundary structure was independent of PO2. Small-angle misoriented twist boundaries (<10°), on the other hand, corresponded to high-energy misorientations and sometimes had amorphous layers at the interface. The population of the small-angle boundary with an amorphous layer was very low in the tape processed in PO2 = 1 atm. This suggests that high PO2 during the heat treatment is effective in the improvement of grain coupling, and hence, to increase critical current density.

We report the stability of TlBa2CaCu2O7 and Tl2Ba2CaCu2O8 on LaAlO3(100) epitaxial thin films, under a variety of conditions. All films are stable in acetone and methanol and with repeated thermal cycling to cryogenic temperatures. Moisture, especially vapor, degrades film quality rapidly. These materials are stable to high temperatures in either N2 or O2 ambients. While total degradation, resulting from Tl depletion, occurs at the same temperatures for both phases, 600 °C in N2 and 700 °C in O2, the onset of degradation occurs at somewhat lower temperatures for TlBa2CaCu2O7 than for Tl2Ba2CaCu2O8.

A commercial Al–Li alloy, in which the superplastic microstructure is developed by “strain-assisted continuous recrystallization” in early stages of flow, was studied using positron annihilation lifetime spectroscopy. Results revealed that exposing the material to a temperature of 525 °C (optimal temperature of superplastic deformation for this alloy) led to agglomeration of single vacancies into vacancy clusters of size of approximately four vacancies. Evidence for superplastic strain-induced cavitation was not found at 450 °C up to an elongation of 432% and at 525 °C up to 341%, the initial strain rate of deformation in both cases being 1.0 ×10−3 s−1. These results have practical significance.

Ion implantation was used to form compound semiconductor nanocrystal precipitates of ZnS, CdS, and PbS in both glass and crystalline matrices. The precipitate microstructures and size distributions were investigated by cross-sectional transmission electron microscopy techniques. Several unusual features were observed, including strongly depth-dependent size variations of the ZnS precipitates and central void features in the CdS nanocrystals. The morphology and crystal structure of the nanocrystal precipitates could be controlled by selection of the host material. The size distribution and microstructural complexity were significantly reduced by implanting a low concentration of ions into a noncrystalline host, and by using multi-energy implants to give a flat concentration profile of the implanted elements.

This paper presents the results of a systematic investigation of structure and formation of the interface between gold and trimethylcyclohexane polycarbonate, particularly concerning interface evolvement during gold evaporation and the influence of evaporation rate, substrate temperature, and subsequent annealing. The means of investigation were cross-sectional transmission electron microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy. Extensive metal diffusion into the polymer and cluster formation near the interface were observed at deposition rates of the order of one monolayer per minute and below. The penetration depth is strongly temperature dependent. At high evaporation rates metal aggregation at the surface prevents cluster formation inside the polymer. No diffusion into the polymer was observed from metal films deposited at room temperature after extensive annealing at elevated temperatures.

The deformation behavior of melt-textured Y1Ba2Cu3O7-x (YBCO) prepared by the vertical gradient freeze (VGF) method was investigated by high temperature deformation experiments at temperatures ranging from 850 to 950 °C. The experiments were performed in an atmosphere of pure oxygen under uniaxial pressure with constant strain rates in the range from 1 × 10−5 to 5 − 10−4 s−1. An analysis of the dependence of the steady state flow stress on the strain rate and the deformation temperature reveals that the predominant deformation mechanism is dislocation glide and climb controlled by climb at Y-211 particles and that no significant grain boundary sliding occurs. Furthermore, transmission electron microscopy observations of deformed and undeformed samples support a deformation mechanism based on dislocation movement. The total fracture strain, however, does not depend on the temperature or strain rate. Scanning electron microscopy investigations of the fracture faces of samples deformed until fracture reveal that fracture does not occur within the Y-123 matrix but along platelet boundaries. An improvement of the fracture behavior is expected by introducing large Y-211 particles interconnecting neighboring platelets.