A hydrogen–plasma reactive flush of the glow discharge reactor after boron–doped a–Si1−xCx : H film deposition has been used to reduce boron contamination of subsequently deposited intrinsic a–Si:H. Photoluminescence studies of p/i structures in a–Si: H show that the hydrogen–plasma process increases both the luminescence efficiency and the activation energy for the competing nonradiative recombination. The process also shifts the emission peak to higher energies by 25 meV.

A technique has been developed to measure the surface tension of thin foils under their own vapor pressure. The zero creep method of surface tension measurement is used in conjunction with laser interferometry. This technique allows very small sample strains to be measured. Sample length changes of the order of 0.3 μm were measured with the laser interferometer. The sensitivity of the laser interferometer/zero creep system allows the surface tension to be measured much closer to the Tammann temperature, which is approximately one-half the melting temperature (≍1/2 Tm) of the material. The system has been tested on thin Sn foils in air, and on thin Al and Ni foils under their own vapor pressure (vacuum).

The elastic plane strain Green's function calculated in earlier papers is modified to account for generalized plane strain and applied to calculating the stress and the displacement field in a bimaterial composite containing a free surface normal to the interface and subjected to an out-of-plane load. The result is obtained in terms of a closed integral representation which is evaluated numerically as well as analytically. The method is applied to a cubic solid containing a Σ-5 grain boundary and to fiber-reinforced laminated composites. The singularities in the stress are identified and discussed.

Severe microstructural damage has been observed in polycrystalline OFHC copper specimens thermally exposed to high pressure tritium gas at temperatures ⋚200 °C, but not at 300 °C. No such damage occurs in single crystal specimens exposed under identical conditions, regardless of temperature. In the polycrystals, the damage takes the form of very flat, crack-like intergranular cavities. It is found that the cavitation evolves slowly with time. For short exposure times, cavities as small as 0.1 μm are observed. In specimens subjected to the longest aging times, the cavities grow and link until entire grain boundary facets fail. The driving force for the growth of these cavities is attributed to the internal gas pressure of helium-3 generated by the decay of tritium. The growth kinetics of the cavity microstructure are described by a coupled grain boundary, surface self-diffusion process. The tritium exposure profoundly affects the mechanical properties of the polycrystalline material, inducing a severe loss in ductility. In concert with the observed ductility loss is a change in fracture morphology from transgranular ductile rupture to intergranular fracture. Examination of the resulting grain boundary facets reveals a dimple structure. The spacing of these dimples can be correlated with the spacing of the exposure-induced grain boundary cavities.

The modification of film properties in evaporated tungsten was studied as a function of deposition environment. Using concurrent argon ion bombardment of the growing film, the stress varied in the same manner at all ion energies and substrate temperatures. Initial increases in tensile stress are followed by a monotonic trend toward compressive stress, for all sets of films. On the other hand, the qualitative changes in film resistivity with concurrent bombardment were dependent on the ion energy and substrate temperature, showing increases at high temperature and energy and decreases at low temperature and energy. Changes in the microstructure and impurity content in deposited films were found to be strongly linked to stress and resistivity changes. The trend toward compressive stress induced by high levels of ion bombardment is primarily reflected in an increase in (110) orientation. Increased resistivity is related to decreased grain size, increased (110) texture, and increased levels of film argon and oxygen content. By choice of deposition conditions, both the resistivity and stress can be minimized.

The elastic interactions of dislocations and intergranular cracks in isotropic materials have been studied. In the first part of the paper, a model based on the Rice–Thomson theory is established under which the conditions for dislocation emission and crack propagation can be described in terms of an emission surface, cleavage surface, and loading line in the local k-space associated with a mixed mode intergranular crack. For a given crack, the local k-field changes with the emission of dislocations from the crack tip, which alters the balance of cleavage and emission. In the second part, we present experimental results of in situ TEM observations of intergranular cracks in molybdenum. Alternating brittle crack propagation and dislocation emission is observed. The number of emitted dislocations corresponding to each crack propagation is in good agreement with the calculated values.

Formation of End-of-Range (EOR) disorder was studied in (100)-oriented silicon, when subjected to amorphization by implantation of Ge+ ions, followed by a 10 s Rapid Thermal Annealing (RTA) at 1050 °C. XTEM, RBS/channeling, and SIMS were used to analyze Czochralski grown (CZ) silicon wafers with oxygen concentrations of 6.5, 7.0, and 8.0 × 1017/cm3 and Float Zone (FZ) silicon, as “low oxygen” wafers. Amorphization on neighboring parts of the 4″ wafers was made either by 60 keV Ge+ implantation or by 110 keV Ge+ implantation and by sequential (60 keV + 110 keV) Ge+ implantation. Parts of each wafer were additionally implanted with 13 keV boron. In FZ silicon, no defects were found for 60 keV Ge+ implantation and RTA at 1050 °C. For 110 keV Ge+ and sequential (60 keV + 110 keV) Ge+ implantation in FZ-silicon the majority of the samples showed perfect annealing. Two wafers, however, subjected to sequential implantation still contained defects but with a defect density that was one order of magnitude lower than for CZ wafers. For one of them, not even a continuous layer of defects was formed. In contrast, CZ wafers contained defect bands, except for the 60 keV Ge+ implantation [in accord with the findings of Ozturk et al., IEEE Trans. on Electronic Dev. 35, 659 (1988)]. The presence of boron had no visible effect on the defect structure.

We have analyzed the phase relationships in two titanium aluminides containing 3.4 at. % Mo with different aluminum compositions. The alloys were first homogenized in the β field, then cooled continuously at different cooling rates from 80 °C/s to 0.1 °C/s. The continuous cooling transformation diagrams (CCT) show that phase transformations and resulting microstructures are highly dependent on cooling rate. The microstructure consists of ordered α2 (DO19), ordered β0 (B2), and athermal ω (hexagonal) phases. The “tweed microstructure” is observed. The evolution of microhardness was determined as well as the relative partitioning of Al and Mo in (α2', α2) and β0 phases as a function of cooling rate.

Alloy films of Ni–Co and Ni–Cr of compositional ratios 1:1, 1:3, and 3:1 deposited by vapor deposition were studied by Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). Results of TEM analysis on the Ni–Co alloy films indicated that the films were face-centered cubic (fcc) in structure. XRD results confirmed the TEM observations. TEM analysis of Ni–Cr alloy films showed that the films were body-centered cubic (bcc) in structure. With increase in the Cr content more than 25%, the material contained a higher fraction of an amorphous phase. XRD studies provide limited information owing to the quasi-amorphous structure of the films of high Cr content.

The blunt tip geometry of the so-called nanoindenter is modeled by a spherical cap of various radii. The relation between area and penetration depth of the indenter is comparable with experimental results if the radius of the tip is about 1.0 μm. Simulation of indentation tests was carried out using the finite element method by incremental loading and unloading based on a continuum model. Good agreement with the experimental results for nickel is obtained also for a tip radius of 1.0 μm.

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 compression behavior of both the monolithic L12 compound Al22Fe3Ti8 and discontinuous composites obtained by incorporating ∼1 μm TiB2 particles was studied for various volume percent reinforcements as a function of temperature and at high temperatures as a function of strain rate. In this study, by varying the Fe and Ti contents, the nature and volume fraction of the minor phases coexisting with the dominant L12 phase were changed and were examined with and without TiB2 reinforcement. At high strain rates (10−4 s−1), the TiB2 reinforcements significantly enhance ambient and warm-temperature strength, although a crossover is observed at ∼1000 K, above which the monolithic material is stronger than the composite. At slow strain rates (10−7 s−1), representative of creep conditions, however, the TiB2-containing composites retain their superiority at least up to 1200 K. Power law fits of compressive flow stress at 1% strain versus strain rate yielded a stress exponent of ∼3.0 with an activation energy of 310 kJ/mol for the monolithic material. For the particulate composites (20 vol. % TiB2), the corresponding values were ∼5.0 and 465 kJ/mol, suggesting a change in the dominant deformation mechanism.

Binary and ternary quasicrystals have been successfully separated by means of quantum structural diagrams in the light of new experimental data, and new potential candidates for the quasicrystalline state are presented. A general and simple classification of alloy systems, consistent with the experimental data, is proposed, which allows predictions of any type of binary and ternary quasicrystals. Quantum coordinates are analyzed and interpreted, and suggestions are given for an improvement of the present method.

A simple phenomenological model is developed to explain, qualitatively, the observed temperature and ion flux dependences of either recrystallization or further amorphous growth of amorphous layers in semiconductors when exposed to ion irradiation. The model includes radiation assisted annealing processes and thermally modified amorphous zone production at the amorphous-crystal interface.

Ion-channeling and transmission electron microscopy (TEM) techniques were used to examine the microstructure of single-crystal Y2O3 stabilized cubic zirconia (YSZ) after implantation with 240 keV Xe+ ions. The observed microstructure was related to Knoop indentation hardness measurements. These measurements showed an increase in hardness for low ion-doses, reaching some maximum value, then a decrease in hardness at higher doses. In the hardening regime, below 7.5 × 1015 Xe+/cm2, point defects and dislocation networks were observed by TEM. Ion-channeling showed a corresponding increase in damage as a function of ion-dose. For doses between 7.5 × 1015 and 3 × 1016 Xe+/cm2 the hardness falls, and the amount of damage, measured with ion-channeling, reaches a limiting value at less than complete damage. In this dose range the Xe concentration continues to increase beyond the dose where the amount of damage saturates. For high doses, greater than 3 × 1016 Xe+/cm2, where softening of the zirconia occurs, additional reflections appear in the electron diffraction pattern that are consistent with the lattice parameter of solid Xe. A diffuse ring is also visible; this is believed to be due to the presence of fluid Xe. Both ion-channeling and TEM show that a significant amount of monocrystalline zirconia remains even up to doses of 1 × 1017 Xe+/cm2. There is also evidence for the presence of recrystallized zirconia at the high doses. Since so much crystalline material remains, it seems that amorphization of the zirconia is not the dominant cause of the softening at high doses.

The nature and rates of erosion of diamond, graphite, and diamond-like carbon (DLC) films exposed to oxygen plasmas were evaluated by comparison of surface morphological changes and weight losses. The RF plasma oxidation at ambient temperature caused severe etching of graphite and DLC specimens, while causing only minor damage to diamond film surfaces. The results suggest that erosion by low energy ions is very selective to the sp2 and sp states compared to the sp3 state of carbon. The selectivity of etching by oxygen plasma is significant, as compared to what has been reported for hydrogen in atomic and ionic states, or for oxidation at elevated temperatures in molecular oxygen. These observations have significant implications to the synthesis of diamond films by chemical vapor deposition (CVD) as well as to the application of diamond film coatings on graphite or other substrates for protection against energetic atomic oxygen prevailing in the low earth orbits (LEO).

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.

Silicon wafers have been implanted with As+ ions at an energy of 100 keV and a dose of 1 × 1017 cm−2 and subsequently annealed at 1050°for 15 min. This results in a peak As concentration of 7 × 1021 cm−3, which is far beyond the solid solubility value of arsenic in silicon at this annealing temperature. Rod-like precipitates, dislocations, and small precipitate-like defects have been observed by transmission electron microscopy. From the analysis of several diffraction patterns taken on a number of rod-like particles at different tilt angles, it has been unambiguously found that they have the structure of the monoclinic SiAs compound previously reported in literature. The stoichiometry of the precipitates has been confirmed by x-ray microanalysis. To our knowledge, this is the first time that this SiAs phase is detected in As+-implanted silicon.

The distribution and chemistry of hydrides produced in single and dual phase alloys with a composition near TiAl have been investigated by using a combination of TEM and x-ray diffraction techniques. The alloys were exposed at 650 °C to 13.8 MPa of gaseous H2 for 100 h. In the single-phase gamma alloy, large hydrides preferentially nucleated on the grain boundaries and matrix dislocations and a population of small hydrides was distributed throughout the matrix. X-ray and electron diffraction patterns from these hydrides indicated that they have an fcc structure with a lattice parameter of 0.45 nm. EDAX analysis of the hydrides showed that they were enriched in Ti. The hydrides were mostly removed by vacuum annealing at 800 °C for 24 h. On dissolution of the hydrides, the chemistry of hydride-free regions of the grain boundary returned to the matrix composition, suggesting that Ti segregation accompanied the hydride formation rather than Ti enrichment causing the formation of the hydride. The hydrogen content in the two-phase (γ-α2) alloy was approximately three times that of the single phase alloy, which was presumably a consequence of the presence of the α2-Ti3Al phase in the two-phase alloy. The hydrides in the two-phase material were shown by x-ray diffraction to have an fcc structure and were removed on annealing in vacuum at 800 °C for 24 h.

Chemical vapor deposition (CVD) of titanium oxide films has been performed for the first time under ultra-high vacuum (UHV) conditions. The films were deposited through the pyrolysis reaction of titanium isopropoxide, Ti(OPri)4, and in situ characterized by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). A small amount of C incorporation was observed during the initial stages of deposition, through the interaction of precursor molecules with the bare Si substrate. Subsequent deposition produces pure and stoichiometric TiO2 films. Si–O bond formation was detected in the film-substrate interface. Deposition rate was found to increase with the substrate temperature. Ultra-high vacuum chemical vapor deposition (UHV-CVD) is especially useful to study the initial stages of the CVD processes, to prepare ultra-thin films, and to investigate the composition of deposited films without the interference from ambient impurities.