By the 90° laser light-scattering technique, it was possible to visualize ultrafine crystalline particles and to investigate their behavior in relation to the growth of KDP crystals in an aqueous solution. It was found that the scattered microparticles move randomly and exist inhomogeneously in the solution. The density of microparticles increases with increasing supersaturation. Whereas in the bulk solution, the movements of the particles are slow, as soon as they approach the crystal, they are rapidly sucked into the surface to within a certain distance, corresponding to the thickness of the diffusion boundary layer. On the growing surface, they move or shake themselves for a while, and eventually become invisible. The crystal growth rate increases proportionally with increasing the density of the microparticles and the supersaturation. The results suggest that they are subcritical crystalline particles which are formed in the KDP solution, and contribute to the crystallization of KDP from the aqueous solution.

We have measured stress variations with temperature as a function of film thickness and a given grain size in pure Al and Al–0.5% Cu films on Si substrates. The variation in thickness for a given grain size is brought about by using the same film and the repeated controlled growth and dissolution of a barrier anodic oxide which can be grown uniformly on the film. Stress measurements were made as a function of temperature by measuring wafer curvature after successively removing each 0.1 μm of Al film. The components of strengthening due to the film thickness and the presence of grain boundaries were separated by assuming that the flow stress of the film is simply the sum of these two components. It is found that strengthening due to film thickness varies inversely with the thickness, which is consistent with results obtained by us using laser-reflowed films in an earlier work. The Hall–Petch coefficients calculated from the strengthening due to the grain boundaries are slightly higher than those reported for bulk Al. However, it is also recognized that the variation of the flow stress as g−1, where g is the grain size, is more plausible than that predicted by the Hall–Petch relation (i.e., as g−1/2). The variations of these two components with temperature, and under tension and compression, are discussed.

MoSi2 is a promising high-temperature material with low density (6.3 g/cm3), high melting point (2020 °C), and good oxidation resistance at temperatures to about 1900 °C. However, in the intermediate temperature range between 400 and 600 °C, it is susceptible to a “pest” reaction which causes catastrophic disintegration by a combination of oxidation and fracture. In this study, we have used polycrystalline MoSi2, produced by arc-casting of the pure elements and by cold and hot pressing of alloy powders, to characterize the pest reaction and to determine the roles of composition, grain or phase boundaries, and physical defects on the oxidation and fracture of specimens exposed to air at 500 °C. It was found that pest disintegration occurs through transport of oxygen into the interior of the specimen along pre-existing cracks and/or pores, where it reacts to form MoO3 and SiO2. The internal stress produced during the formation of MoO3 results in disintegration to powder. Near the stoichiometric ratio, the susceptibility to pest disintegration increases with increasing molybdenum content and with decreasing density. Silicon-rich alloys were able to form protective SiO2 and showed no indication of disintegration, even at densities as low as 60%.

Diamond-hexagonal (dh) Ge has been produced by Vickers micro-indentation of a Ge single crystal and investigated by high resolution transmission electron microscopy (HREM). The results are consistent with the mechanisms that have been proposed earlier for the generation of dh Si. The hexagonal phase of these elemental semiconductors may be produced by two related mechanisms: (a) secondary twinning or (b) the intersection of two twins. The hexagonal germanium produced by both of these mechanisms has been observed and is presented in the present paper.

Stress-driven diffusive growth of voids in encapsulated interconnect lines is studied. By calculating the rate of growth of a single void in a passivated line subjected to an initial hydrostatic tension stress and by assuming that failure occurs when the void reaches a critical size, a model for failure of encapsulated interconnect lines by stress voiding can be developed. The model for the prediction of void growth and failure is based on two limiting kinds of void growth. In one limit, which applies at short times, radial displacements occur by diffusional flow processes around the growing void and relax the local hydrostatic tension stress. In the long time limit, vacancies flow to the void from distant parts of the line by diffusion along grain boundaries, thereby relaxing the stress in a growing section of the line. A model based on a combination of these behaviors leads to a failure law for aluminum lines of the form tfσ2/d = 1019.2 exp(Q/RT) where tf is the failure time in seconds, σ is the initial hydrostatic tension stress in the line in Pa, d is the grain size in meters, and the activation energy, Q = 80.9 kJ/mol, is close to that for grain boundary diffusion in aluminum. The model predictions appear to be in good agreement with the few experiments on stress voiding that have been conducted.

Scanning tunneling microscopy images of the (0001) plane of highly oriented pyrolytic graphite show defect regions consisting of an extensive network of partial dislocations that form extended and contracted nodes. The partial dislocations in hexagonal graphite enclose triangular regions (∼1000 nm on a side) of faulted material comprised of rhombohedral graphite. Electronic and elastic interactions of the tip with the HOPG surface are proposed to explain the observed image contrast between hexagonal and rhombohedral graphite.

The phase formation of elemental multilayered thin Al100−xNix films during 500 keV Xe+ irradiation has been investigated using transmission electron microscopy. The whole composition range has been covered for various substrate temperatures during the irradiation. At low temperatures, only structurally simple crystalline and amorphous phases are observed. Thermodynamic data for these simple phases were calculated using the CALPHAD method, and nonequilibrium phase diagrams were derived and discussed in the context of the experimental findings.

The effect of additional elements (Si and Co) on the behavior of copper polycrystalline alloy under static and dynamic compression was studied. Relations between the deformation microstructure and the mechanical behavior have been investigated. In the Cu–Si alloys, the SFE depends on additional element content and the SFE level controls the dissociation of perfect dislocations into partial ones. In the Cu–Co alloy, Co induces precipitation and the dislocation repartition is uniform if the precipitates are coherent. When the precipitates become semicoherent, there is formation of dislocation walls around the precipitates.

Iron-rich Fe–Cu–Si multilayers were made by alternately depositing pure elements in a high vacuum system. The as-deposited films were then subjected to 200 keV xenon ion irradiation to doses ranging from 2 × 1015 to 1.2 × 1016 Xe/cm2 at liquid nitrogen and room temperature. Transmission or scanning electron microscope and in situ energy dispersive spectroscopy were used to characterize the films. It was found that ion irradiation induced the formation of a new metastable phase in many irradiated films. The new phase was identified to be of fee structure with a lattice constant a = 0.423 nm. Strikingly, another phase reflecting sharp diffraction spots with 12-fold symmetry was also observed in a room temperature irradiated sample at a dose of 9 × 1015 Xe/cm2. The distribution of the diffraction spots was shown to be incommensurate and bore a close relationship with the metastable fee phase. Furthermore, scanning electron microscope examination revealed that many clusters with 5-fold symmetry emerged in the corresponding film. The sharp incommensurate diffraction patterns may be ascribed to some incommensurate or quasicrystalline order appearing in the ion-induced structures.

Three-dimensional chemical maps by Secondary Ion Mass Spectrometry (3D-SIMS), XPS spectroscopy, and SEM-EDAX microscopy were employed in order to investigate the effects of accelerated fatigue tests on crack formation in 95.5% Pb–2% Sn–2.5% Ag and 95% Pb–5% Sn solder joints. These alloys are used in the die bonding of electronic power device assemblies. The results show that cracks form by Sn-depletion from the inner regions of the soldered joint. Simultaneously, there is a recrystallization of the Pb-rich phase in the same regions of the joint. The crack occurs at a critical number of cycles when a Sn-depleted region is formed, yielding weaker inner layers with lower shear strength. A possible explanation of the Sn-depletion is also discussed.

This paper deals with the concept of microstructural engineering through donor and acceptor dopings within the grain and at the grain boundary of a polycrystalline semiconducting ceramic. These concepts are derived from an analysis of the “prebreakdown” and the “upturn” current-voltage characteristics of a ZnO varistor and from the construction of corresponding defect models as a function of donor and acceptor dopants at the grain and grain boundary. By using Li, Al, and Na as dopants, it is shown that the dopants can be grain or grain boundary specific in the ZnO microstructure and that they can act as donors, acceptors, or both, depending on the nature and concentration of dopants and their location on the host crystal lattice structure. In the case of the ZnO varistor, the grain and grain boundary properties can thus be tuned independently or concurrently by systematic engineering of the entire microstructure through defect dopings that are specific to the grain, grain boundary, or both. Following a detailed analysis of the defect models thus developed for the ZnO varistor, a set of ground rules are proposed for applying these concepts of donor and acceptor dopings at the grain and grain boundary to the general case of microstructural engineering in a polycrystalline semiconducting ceramic.

Chemical vapor deposition of aluminum films using tri-isobutyl aluminum on Si(111) wafers has been studied from the viewpoint of structural and electrical properties of Al films as a function of substrate temperature (Ts). The epitaxial relation of Al on Si is found to be very sensitive to Ts, thus changing from Al(100)))Si(111) with Al[1$\overline 1$0]))Si[11$\overline 1$] to Al(111)))Si(111) with Al[1$\overline 1$0]))Si[1$\overline 1$0] around 410 °C in the course of increasing Ts. The epitaxial relation is mainly determined at the initial stage of the deposition, but in some cases the relation changes with increasing film thickness. Above 420 °C, single-crystalline Al(111) is grown on Si(111), which has resistivity as low as the bulk value, high reflectivity, and a very flat surface.

The site occupancy of ternary atoms in three L12-structured intermetallic phases, Al62.5+XTi25−Y(Fe, Ni, or Cu)12.5–Z found in three laser processed intermetallic systems was studied by the axial ALCHEMI (Atom Location by Channeling Enhanced Microanalysis). The ternary atoms in all three intermetallic phases were found preferentially to occupy the Al sublattices, although slight differences in occupancy among them were detected. A simple extrapolation method of calculating delocalization correction factors for various characteristic x-ray emissions was described, which was proved to be practically useful in ALCHEMI analyses. In order to compare the axial ALCHEMI analysis with the planar ALCHEMI in an experimental perspective, the planar ALCHEMI analysis was also carried out on the phase alloyed with Cu, which showed results in broad agreement with those of the axial ALCHEMI analysis on the same phase. Nevertheless, owing to much weaker channeling effects the planar ALCHEMI analysis gave apparently worse statistics in its results. In the end, various sources of errors in the ALCHEMI analyses at the present stage are discussed.

The intermetallic compound Al3Sc is a trialuminide with the L12 structure, which deforms easily in compression at room temperature, with yield stresses around 100 MPa. As shown by single crystal compression experiments, slip occurs on {111} planes. In tension Al3Sc fractures transgranularly in a brittle manner. The predominant cleavage plane is {011}. In a scanning electron microscope (SEM) numerous cleavage steps, which are aligned in three major crystallographic directions, are observed. The fracture surfaces almost always show microscopic waviness along the traces of intersecting slip planes. Regions that are flat within the experimental resolution of the SEM are only occasionally observed. Some of the cleavage steps consist of {111} or {001} planes, but others are not distinctly crystallographic. Plastic deformation involving dislocation motion or twinning may have occurred at these steps. Reactions among different types of steps are also observed. One type of cleavage pattern found is strikingly similar to the typical appearance of fracture surfaces of fcc or fcc related materials after stress corrosion cracking. However, this particular pattern is only rarely observed in Al3Sc and can therefore not be taken as evidence for stress corrosion cracking in this material. Our observations indicate that an interpretation of cleavage fracture in Al3Sc in terms of surface energies alone is unlikely to be successful. Similarly, any criterion that categorizes its fracture behavior into either fully brittle or fully ductile is faced with difficulties. A full understanding of the fracture morphology of Al3Sc will therefore require detailed atomistic simulations.

Tensile strength and Young's modulus were determined for vapor-grown carbon fibers (VGCF's) prepared from benzene in Linz–Donawitz converter gas (LDG) by the floating catalyst method. The tensile strength decreased with increasing diameter and volume and depended strongly on whether the fiber was straight or crooked. The average tensile strength of straight fibers was 2.05 GPa, while that of crooked fibers was 1.09 GPa. The latter broke at bends in the fiber where they acted as defects. The average Young's modulus of straight fibers was 163 GPa, while that of crooked fibers was a little higher at 197 GPa. VGCF's prepared in LDG appeared to have comparable mechanical properties to those grown in hydrogen.

In this paper the finite element method is used to explore the mechanics of the microindentation process. In the simulations discussed, aluminum and silicon are investigated both in their bulk forms and in thin film-substrate combinations. Among the quantities readily computed using this approach and given in this paper are hardness (computed using actual contact area), contact stiffness, effective composite modulus, and surface profile under load. Importantly, this investigation builds on previous work by providing a more critical examination of the amount of pileup (or sink-in) around the indenter in the fully loaded configuration, as well as the variation of the actual contact area during indenter withdrawal. A key conclusion of this study is that finite element simulations do not support the widely used assumption of constancy of area during unloading (for either bulk materials or thin film systems). Furthermore, the amount of pileup or sink-in can be appreciable. The implication of these findings is that for many situations the commonly used straight-line extrapolation of a plastic depth may render an estimate for the contact area that is quite distinct from the actual area. This assertion is demonstrated herein through comparison of hardnesses calculated using actual contact area with values calculated using the straight-line extrapolation of plastic depth.

Direct writing of iron lines on glass and Al2O3 has been achieved by CW CO2 laser-driven pyrolytic dissociation of volatile iron pentacarbonyl liquid. Since a very high organometallic molecular density is realized in the solution, use of a liquid precursor has enabled deposition of micron-thick iron films at the writing speeds of 10–400 mm s−1, which are significantly higher as compared to those achievable by the conventional CVD method. The iron stripes deposited on the glass substrate at the laser power density of 5.3 kW cm−2 and the writing speed of 100 mm s−1 are found to have a resistivity of about 580 μohm-cm. These stripes have been found to have an integral bond with the substrate due to the interface reaction.

Polycrystalline diamond thin films have been selectively grown on silicon, silicon dioxide, silicon nitride, tantalum, molybdenum, alumina, and sapphire substrates using selective damaging by ultrasonic agitation. Processes were developed to selectively damage the substrates by ultrasonic agitation in methanol containing diamond particles of typical size 90 μm. Optical and scanning electron microscopy is used to study selectivity and morphology of as-grown diamond thin films.

The evolution of radiation damage and of dopant profiles in Si samples subjected to self-annealing implantation with 160 keV As+ ions, under various transient heating conditions, depending on the beam current density, has been investigated. For temperatures in excess of 880 °C, the formation of voids is evidenced by Transmission Electron Microscopy observations. They are located in a layer extending from the surface over a depth of about 0.8 of the ion projected range, Rp (≃110 nm), while extended interstitial-type defects are observed in the region below. With increasing temperature (due to increasing beam power density and/or irradiation time), voids tend to anneal in the near surface region, while they survive and grow in a region about 40 nm thick, centered at a depth of about 50 nm, where an anomalous peak in the dopant profile is developed. The annealing of the extended interstitial-type defects at depths ≥Rp, which becomes appreciable for T ≥ 1050 °C, is coupled to a large enhancement of dopant diffusivity in the same region. It is argued that the local vacancy supersaturation, which leads to void formation, and the corresponding interstitial excess in the deeper region, which leads to extended defect formation, are a natural consequence of the collision kinetics of the displacement process, as suggested by Monte Carlo simulations reported in the literature. The evolution of damage and the anomalies in the redistribution of dopant, observed by increasing the temperature, are described as the result of the increase in the population of mobile point defects and of their influence on the mechanism of As diffusion in the different regions of the implanted layer.

Thermodynamic properties of the melts of several Al–Y and Al–Fe–Y alloys are studied by means of calibrated differential thermal analysis. The results can be used to optimize process parameters of rapid solidification which are important for glass formation in the Al-based alloys. Close examinations of the melt-spun alloys show that the process parameters, particularly the temperature of the melts, will influence not only the amorphicity and the chemical short-range order but also the crystallization process of the glasses. A key point of glass formation in the Al-based alloys is found to be related to the content in the melts of a certain amount of the intermetallic compounds which are gradually dissolved in the premelted α Al matrix.