Thin films of CoSi2 have been grown on (111) substrates of Si, and studied using transmission electron microscopy. In 2nm films, steps initially on the substrate were found to be transformed into interfacial dislocations following deposition of the films. The Burgers vectors of the dislocations were consistent with ½<101>, which includes a component ½[111] perpendicular to the interface. The contrast behaviour of these dislocations exhibited characteristic effects, which are consistent with the short-range displacement field of the defects resembling that of a disclination dipole.

There is considerable interest at present in the mechanisms of tilting of epitaxial films, such that low index planes in layer and substrate have slightly different orientations. There are two primary causes of this effect: a) coherency strains and b) the action of misfit dislocations. It is important to distinguish between the two effects, particularly in the case of strained layers used for band-gap engineering. Using a recent formulation of the Frank-Bilby equation for the dislocation content of interfaces, it is shown how planes may be rotated in coherent layers due to both the Poisson effect and anisotropic misfit. An advantage of the Frank-Bilby equation is that it allows consideration of semicoherent layers. It is shown that a side effect of misfit dislocation introduction can be to introduce a further rotation of the epitaxial layer. Both these effects have been measured experimentally. The amount and the sense of rotation is compared to theory.

The relative misorientation (tilt) between the epilayer and substrate (400) lattice planes of InP epilayers grown by gas-source molecular beam epitaxy on (100) GaAs substrates misoriented towards the (110) plane was studied by high resolution x-ray diffraction. For the growth temperature of 490–500°C, the direction of the relative tilt was nearly coincident with the direction of the substrate lattice plane tilting. In contrary, when a buffer layer was deposited at a lower temperature of 400–450°C prior to growth, an azimuthal rotation of about 45° was found between the directions of the relative tilt and the substrate lattice plane tilting. In order to explain the results, a temperature-dependent anisotropic nucleation model is proposed.

In many materials, crystalline interfaces are facetted. The experimental evidence is that on each side of an interfacial ledge, or along the facets meeting along a common line, low energy atomic structural units are preserved which accommodate elastically angular or/and length misfit(s). Each facet can be considered as a Somigliana dislocation (SD) whose core is extended on the facet. The elastic displacement field of a SD is derived in an anisotropic continuum, for any orientation of the facet relative to a given Cartesian frame. From an atomic point of view, the translation state of the two crystals on each side of the facet is defined. The dislocation content attached to a ledge or a dihedral angle formed by two joining facets along a common side is also analyzed. The local elastic field related to these cases are derived and applications are presented for depicting the positions of the atomic columns in theoretical plots. Comparisons are made with some other theoretical works and HRTEM images. Examples illustrate the application of the Somigliana model to grain boundaries in hexagonal crystals (Mg, WC), and an interphase interface Ni3AI/Ni3Nb.

TiAI/Ti3AI colonies in an as-cast Ti-40 at.%AI alloy have been studied using HREM. Their microstructures consist mainly of alternating parallel lamellae of y (TiAI, L10) and α2 (Ti3AI, DO19) phases. The γ phase is often twinned with extended boundaries {111] parallel to the adjacent Ti3AI-TiAI interphase boundaries. The detailed atomic structures of the two possible (111)-γ σ3a and (111)γ σ3b twin boundaries have been observed as well as the facetted (0001)α2//(11)γ interphase boundaries. The facetted boundaries contain transformation dislocations whose elastic displacement fields conform well to the fields computed from the Somigliana dislocation model.

Results of recent studies of preferred orientations for metal/non-metal interface systems are presented and discussed in terms of some of the general concepts derived from interface structure models. The limitations of geometric models used to predict preferred orientations for metal/ionic crystal interfaces are demonstrated, and the effects of temperature and impurity segregation on the low energy interfaces for metal/glass interfaces are discussed.

Stresses are introduced in crystals at interphase boundaries where steps improve the registry of atoms. A model and mathematical analysis based on an approach previously taken by van der Merwe and Shiflet1–4 of the problem incorporating a coherent step are presented. Computed distributions of stresses, strains, dilatation and energy density in the form of contours and nets are given for a coherent monatomic step. It is concluded that the maximum stresses are quite large and the fields decay fairly rapidly with distance from the steps, the gradient of dilatation around steps will significantly affect diffusion kinetics of impurities and the strain energy seems too low to significantly enhance chemical processes.

The structure of the lowest energy interface between an hcp austeidte phase and an foc martensite phase of similar atomic volumes has been simulated by annealing a disordered region between the two perfect lattices until semi-coberent intergrowth occurred. The two structures were oriented so that the closepacked planes were parallel, and closepacked directions were aligned. The dynamics of this interface and the structure which it evolved as it moved was then studied by applying a transformation driving force through the use of an Embedded Atar Method potential. Initially the interface moved in a reconstructive, diffusive manner but eventually it developed a highly mobile, diffusionless form which moved at about one third of the shear sound velocity. The structure of this rapidly moving interface could be analyzed in terms of three different types of Shockley partials arranged in sequence, but passing at slightly different times. This structure agrees with some elements of a model previously proposed by Christian to describe the transformation in pure Co, and agrees with other elements of a proposal of Mcbreer, Lunggren and Franck to explain their observations of the transformation in 4He. Neither fully explain our observations.

Computer simulation of the atomic structure and movement of twinning dislocations in four twin boundaries in the h.c.p. metal α-Ti is described. These dislocations have the form of steps on the twin boundary, and whereas some have cores which are very widely spread over the interface, others are only an interatomic spacing or so across. These configurations are determined mainly by whether or not atomic shuffles are required to restore the h.c.p. crystal structure when the dislocation is introduced. The mobility of the dislocations is also controlled by the same effect, and is found to correlate well with experiment.

The initial stages of heteroepitaxial growth of Ge0.85 Si0.15 on Si(001) grown from Bi solution (liquid phase epitaxy) are studid by transmission electron microscopy. Stranski-Krastanov growth is observed to take place. After growth of a pseudomorphic Ge0.85 Si0.15 layer of 4 monolayer thickness, islands form and grow pseudomorphically up to a thickness of 30 nm. Then first misfit dislocations form. The formation process of these dislocations is analyzed and discussed in terms of half loop nucleation at the surface and dislocation glide. Evidence for glide on (110) planes is put forward.

A quantitative model of the effect of the selective growth on dislocation density has been developed and compared to experiments. It is concluded that the dominant dislocation nucleation source in the selective areas occurs at the specific heterogeneous sites at edges of the selective areas. This edge nucleation can be controlled by adjusting the orientation of the sidewalls.

The (001) GaSb/GaAs heterostructure reveals a nearly complete relaxation of the misfit strain. This relaxation is connected to the highly regular network of Lomer dislocations which is a consequence of island growth conditions.

In this paper we study the lattice-mismatch induced defect structures of InAs films grown on semi-insulating InP substrates using metal organic chemical vapor deposition. The defect structure studies were carried out on films of equal total thicknesses but for different duration for nucleation of a layer of InAs deposited at low temperature on the substrate. Misfit strain is caused by the inherent lattice mismatch of approximately three percent and this is partially relieved by the generation of misfit dislocations at the film/substrate interface. Transmission electron microscopy studies show the presence of an intrinsic strain and the generation of thermal etchpits at the heteroepitaxial interface. Our studies show that there is a direct correlation between the density of dislocations generated at the film/substrate interface and the duration of nucleation of the film on the substrate. Dislocation densities at the surface of the InAs films and at the heteroepitaxial interface differed by almost two orders of magnitude. High resolution electron microscopy reveals abrupt and sharp interfaces in films with thick nucleation layers and also confirms that the lattice mismatch is partially accommodated by the generation of misfit dislocations at the film/substrate interface.

Ion implantation and thermal oxidation are device fabrication processes that lead to perturbation of equilibrium point defects concentration in silicon. This study investigates the interaction between oxidation-induced point defects and type II dislocation loops intentionally introduced in silicon via ion implantation. The type II dislocation loops were introduced via Si implants into (100) Si wafers at 50 keV to a dose ranging from 2×1015 to 1×1016/cm2. The subsequent furnace annealing at 900 °C was done for times between 30 min and 4 hr in either a dry oxygen or nitrogen ambient. Plan-view transmission electron microscopy (PTEM) was used to characterize the increase in atom concentration bound by dislocation loops as a result of oxidation. The results show type II dislocation loops can be used as point defect detector and they are efficient in measuring oxidation-induced point defects. It is also shown that the measured net interstitials flux trapped by dislocation loops is linearly proportional to the total supersaturation of interstitials as measured by oxidation enhanced diffusion (OED) studies.

Poly-Si layers are used for various applications in integrated-circuit manufacturing technology. In most cases, the microstructure of the layers can have a significant impact on performance of the structures. In the present study, poly-Si layers implanted with 1E14 and 1E16 oxygen cm-2 were characterized using transmission electron-microscopy (TEM). Layers implanted with 1E16 cm-2 oxygen had exhibited lower variations in sheet-resistance for a given variation in post-implant anneal temperature. The microstructural behavior of the films was therefore of interest. TEM characterization showed differences in the microstructure of poly-Si implanted with 1E14 and 1E16 oxygen cm-2. Layers implanted with 1E14 doses showed a columnar grain-structure similar to as-deposited poly-Si layers. Grain-sizes were quite uniform and relatively small. Layers implanted with 1E16 doses showed a strongly defected grain-structure quite different from as-deposited poly-Si layers. The columnar structure had been largely destroyed. Grain-sizes were less uniform, with primarily large grains but also small grains being present. There are indications that the 1E16 samples had been amorphized by the implant and recrystallized by the anneal, but it is not clear from these samples whether this is the cause for the variation in resistance-behavior (between IE 14 and IE 16 samples). TEM micrographs are indicative of the presence of oxygen-bubbles in both sets of implanted specimens. The bubbles arise due to the oxygen implant. There is no noticeable correlation between poly-Si grain-boundaries and the bubbles.

Dopant species can interact in different ways with interfaces, layers of varied microstructures, and with extended-defects. An understanding of such interactions is relevant to semiconductor processing and device-fabrication. In this study, the behavior of phosphorus-implanted silicon wafers was characterized using transmission electron microscopy (TEM), for as-implanted as well as post-implant rapid thermal-anneal (RTA) conditions. The top layers of as-implanted wafers were found to be amorphized. A correlation was seen between the presence of the amorphous-to-crystalline silicon interface and a drop in phosphorus concentrations in depth-profiles obtained using SIMS (secondary-ion mass-spectrometry). Reasons for the drop in concentration are explored, one of which is a higher diffusivity for phosphorus in amorphous silicon than in crystalline silicon. The top layers of wafers subjected to a RTA had recrystallized. A band of extended defects was present in the vicinity of the original amorphous-to-crystalline silicon interface. A correlation was seen between the presence of these defects and a secondary peak in phosphorus concentrations (in depth profiles) obtained using SIMS. These effects are explained in terms of gettering of phosphorus to the extended-defects. The band of extended-defects consists of dislocation loops, point-defect clusters, and extended dislocations that arise due to coalescing of point defects followed by annealing of the resulting extended-defects. The point-defects themselves arise from the implantation.

We describe PC- based software which calculates grazing incidence X-ray reflectivity profiles from model thin film structures, including interface grading. We discuss the mathematical principles of the model and benchmark tests for speed of operation on two PC compatible machines are presented. Curvature of the specimen results in selective loss of fringe visibility at low scattering vectors and is treated rigorously. We discuss the treatment of roughness and use a generalized formula that is valid at large and small values of the reflectivity; its effects are illustrated using the program.

The mechanical behavior of polycrystalline intermetallic compounds are often strongly influenced by the properties of the interfaces present. A classic example of this is the intergranular fracture exhibited by polycrystalline Ni3Al, and the dramatic increase in ductility upon the addition of small amounts of boron. It has been proposed that boron may promote the transmission of slip across grain boundaries by inducing the formation of a local region of compositional disorder. The results of experimental efforts to characterize the effect of boron on the structure and chemistry of these grain boundaries are summarized. Recent high resolution transmission electron microscopy studies using oriented bicrystals are described which indicate that there is no apparent change in the compositional ordering to within 0.5 nm from the boundary. These experimental results are compared with the results of atomistic calculations which have been used to examine the effect of stoichiometry and boron content on the energy and degree of ordering of these boundaries. The proposed mechanisms of intergranular fracture in Ni3Al are discussed based on this experimental and theoretical work.

Atomic structures of grain boundaries in Ni3Al and Cu3Au has been studied using a Monte Carlo relaxation technique and many body central force potentials to describe interatomic forces. The purpose of this work is to investigate the temperature dependence of the compositional order in the boundary region for both stoichiometric and non-stoichiometric alloys. In the former case the boundaries in Ni3Al remain ordered up to very high temperatures while boundaries in Ni3Al disorder at relatively low temperatures. In the non-stoichiometric case, the surplus of nickel in the bulk leads to segregation to grain boundaries and to a significant chemical disordering in the boundary region. The surplus of aluminum also leads to segregation but without disordering in the boundary region. Using these results we discuss the intrinsic brittleness of grain boundaries in Ni3Al as well as the effect of stoichiometry on the intergranular brittleness.

In this paper the structure of a (011)-Σ=3 twist boundary in ordered Cu3Au is analysed geometrically. Wrong nearest-neighbour bonds can be avoided by facetting on an atomic scale along common {112} planes, together with a rigid-body translation parallel to one of the facets as measured in earlier work. In the specimen different translational states were found in different areas of the [165]-Σ=3 boundary by transmission electron microscopy (TEM). One of the translations was in agreement with the model, the other was associated with a presumably energetically more unfavourable structure. The in situ observation at 230 °C of the motion of the dislocation separating the different boundary areas was associated with a transformation of the boundary structure with the higher energy into the more favourable structure. Therefore, it is likely that the driving force of the dislocation motion was a difference in boundary energy.