In (α + β) titanium alloys, the interface between the α and β phases has been widely studied, and many conflicting results have been published concerning the formation of an interface phase having an hcp or fcc crystalline structure. Several authors consider that this phase is an artifact and consists of a titanium hydride formed during thin foil preparation for TEM examination. This paper reports examinations by TEM and STEM of heat-treated Ti–6Al–4V alloy and two titanium molybdenum aluminides. The formation of an α/β interface phase is discussed as a function of composition heat-treatment and thin foil preparations. Particularly, for Ti–6Al–4V in a nonequilibrium state, a strong concentration gradient was revealed in the α/β interface, and a metastable interface phase enriched in beta-stabilizers with an fcc structure has been clearly characterized.

The deposition process at 500 °C with SiH4–GeH4–B2H6–He mixtures, which yields the amorphous Si–Ge–B alloy, was studied. Although in crystalline Si and Ge the maximum B content is limited to the solid solubility, any amount of B can uniformly be contained in amorphous Si–Ge–B. Thus, films with a B content up to 64 at.% have been prepared. The deposition rate of atoms, defined as the number of atoms deposited in a unit time interval, is obtained for each element by analyzing the growth rate together with the composition and the mass density of the film. When the SiH4 and the B2H6 partial pressures are constant, the Si and the B deposition rates are almost independent of the GeH4 partial pressure. In contrast, the Si deposition rate increases remarkably as the B2H6 partial pressure increases, even when the SiH4 partial pressure is maintained constant. A simple model is proposed for explaining the relationship between the Si and the B deposition rates.

The solidification behavior of Al65Cu20Co15 and Al65Cu15Co20 alloys was studied by means of scanning electron microscopy, energy-dispersive x-ray analysis, powder x-ray diffraction, and differential thermal analysis. Slowly cooled as well as rapidly cooled ingots of both alloys contained a decagonal quasicrystalline phase as dominant phase with additions of several minor normal-crystalline phases. The decagonal phase was found to solidify in a temperature range limited by two peritectic reactions involving phases of CsCl-type structure. Formation of AlCu and Al2Cu phases was also observed.

The microstructure of two metastable crystalline phases, which are formed during the first step of the crystallization process in Ni–Zr metallic glasses, was investigated by transmission electron microscopy. For the composition Ni33Zr67, crystallites with average size of 150 nm having the face-centered cubic E93 structure are formed. For the Ni42Zr58 composition, 100 nm size crystallites with a simple cubic unit cell, space group Pa3 are formed. The microstructure of the crystallites in the early stage of crystallization of the two phases is similar to globular morphology and internal striations.

We report first principles local density calculations for the metastable Al3Li intermetallic compound with cubic L12 crystal structure using the full-potential linearized augmented plane wave method. From the second derivative of the total energy as a function of volume, and generated tetragonal and trigonal lattice distortions, the elastic constants C11, C12, and C44 were derived yielding C11 = 158 GPa, C12 = 29.4 GPa, and C44 = 57.7 GPa. Because of the very high Young's modulus (E = 141 GPa) compared, for example, to pure Al (E = 66 GPa), it is suggested that Al3Li plays an important role in strengthening the Al–Li alloys. The calculated Young's modulus appears in good agreement with experimental estimates when the experimental values are extrapolated to 0 K. Although the Young's modulus of Al3Li is increased in comparison to Al, the calculated bulk modulus is decreased to a value of 72 GPa as compared to pure Al (82 GPa), in agreement with experiment. As a result, the Poisson ratio is reduced to ŝ = 0.173 as compared to the value 1/3 for an isotropic medium. Because of this and the high Young's modulus, the calculated Debye temperature ΘD at 0 K amounts to 672 K, which is substantially larger than ΘD for Al, which is about 400 K.

Fracture mechanics and mechanisms of a carbon fiber reinforced carbon matrix lamina composite are studied. The importance of microfracture processes of first matrix cracking, fiber bridging, and fiber pullout processes for toughening C/C-composites is emphasized, and then, the fiber bridging process of the composite is mainly focused through the measurement of the R-curve. The fiber bridging tractions are estimated by the Dugdale approach from which the superb stress shielding and excellent notch tolerance of the composite are demonstrated.

Irradiation of unsupported samples of hydrogenated amorphous silicon below 100 K with 360-MeV Xe ions results in macroscopically visible changes in sample dimensions. These changes have two different causes. Formation and growth of cavities lead to an isotropic increase of the specimen dimensions and to a drastic decrease of the mass density. Simultaneously plastic flow occurs, which produces additional but anisotropic changes of the specimen dimensions. The dimensions perpendicular to the beam grow whereas the dimension parallel to the ion beam shrinks. Neither effect saturates in the investigated fluence range (Φt < 1014 Xe/cm2) and both are absent in crystalline silicon. The effects are most likely provoked by electronic excitations and/or ionizations in the wake of the fast ions. With respect to plastic flow, a–Si:H behaves like metallic and oxide glasses. Formation of cavities and their growth, however, seem to occur only in tetrahedrally coordinated solids.

An early stage of diamond growth in hot-filament chemical vapor deposition on silicon substrates was examined by the high resolution electron microscope. “Pretreatment” of the substrate surfaces by diamond powder abrading was found to plant diamond seed crystals with a density of as high as 1011/cm2. These crystals provide sites for subsequent growth of diamond films. The CVD grown diamond particles tend to be cuboctahedra. Smaller particles in nanometer size are faultless, but larger ones of several tens of nanometers develop crystal faults. Some of them may originate from the seed crystals. Degradation of the diamond seed crystals due to the electron beam irradiation is discussed in terms of fabrication of diamond film.

A simple and practical method is described for determining the residual stress in vapor deposited thin films that are less than 1000 Å in thickness. The method relies on the evaporation of thin films onto prefabricated micro-cantilever beams of SiO2. The vertical deflection at the end of the beam is measured using an optical microscope to determine the average film stress with a resolution of 25 MPa. Calculations show that the vapor deposition of metal films onto these beams does not induce significant heating, so the thermal component of residual film stress is minimal. The micro-cantilever technique is used to measure the film stress in 500 Å films of Al, Ti, Pt, Au, Ni, and Ge. These measured values are compared to similar measurements reported in the literature.

A highly effective wetting agent and emulsifier, Triton X-100 detergent is introduced to metalorganic solutions. When applied to a substrate, this detergent/metalorganic solution promotes the formation of a uniform spin-on thin film with good adhesion. The precursor, copper formate film, was spin-deposited with a metalorganic solution prepared by a solvent mixture of methanol and Triton X-100 (50:1 by volume). KrF laser (248 nm) direct writing of high-purity copper patterns on glass and polyimide substrates has been achieved. When the laser beam is imaged through a slit device, periodic copper metal structures with a linewidth of ∼2.5 μm are observed, which may be attributed to result from Fraunhofer diffraction. A general process for casting homogeneous amorphous films on substrates from a solution of molecular or ionic metalorganics dissolved in the neutral or charged micelles is proposed.

Electrical characteristics of trench capacitors using RTO (Rapid Thermal Oxidation) oxides, nitroxides, and reoxidized nitroxides as the gate insulators are discussed. High temperature RTO is effective in preventing oxide thinning at the trench corner, and so the dielectric strength of trench capacitors is improved drastically. The mean time to failure (MTTF) of trench capacitors using RTO is more than ten times longer than that of trench capacitors using conventional furnaces. Using reoxidized nitroxides as the gate insulator, superior charge to breakdown (QBD) is obtained. RTP (Rapid Thermal Processing) is superior to the process using the conventional furnace for the gate insulators of trench capacitors. Improvements in temperature uniformity, repeatability, and lessening of slip line formation are essential for RTP equipment to be practical.

The problem of ice accretion and accumulation on critical structural components of fixed wing and rotary wing aircraft structures has in recent years engendered much interest. However, the mechanical properties of the accreted impact ices are at present not adequately known and, therefore, analytical modeling of this particular material is not possible. This paper proposes a technique for experimentally determining both the modulus of elasticity and tensile strength of ice. The feasibility and accuracy of the test technique were verified by determining the properties of laboratory grown ice. Results reveal a slight degradation of ice tensile strength with an increase in test temperature. The degradation in ice tensile strength is rationalized on the basis of competing mechanistic effects involving an incipient melting of the ice at the higher test temperature and a concomitant intrinsic variation in microstructural features due to variations in freezing rate. Application of the test technique to impact ices will soon be conducted inside an icing wing tunnel.

Thermal diffusivity of the sintered semiconductors was measured by the photopyroelectric (PPE) method. The measurement based on the phase-modulation frequency characteristics was shown to give superior results, eliminating errors expected in the conventional signal amplitude-distance characteristics measurements. Thermal diffusivities of the melt-grown and hot-pressed samples were found to be αmelt(c⊥) = 0.014 cm2/s, αmelt(c//) = 0.011 cm2/s, αhot(c⊥) = 0.012 cm2/s, and αhot(c//) = 0.008 cm2/s, depending on the relation between the c-axis direction of grain and thermal flow direction. The thermal diffusivity of the hot-pressed samples shows a strong dependence on the hot-press pressure through the orientation factor.

The effects of substituting Cu for either Ti or Al in Al3Ti were studied by the first-principles local density self-consistent linear muffin tin orbital method. The Cu atoms are found to strongly favor Al sites and to promote the stability of the L12 phase, in agreement with experiment. Surprisingly, the rigid band model is closely followed when Cu substitutes for Al. However, the structure of the density of states undergoes remarkable changes if Cu substitutes for Ti; a much weaker hybridization occurs in both L12- and DO22-like structures, giving rise to weaker binding effects. The modification of bond directionality upon Cu addition is determined by comparing the charge density for the structures calculated with those of pure Al3Ti. The effect of tetragonal distortion is also examined. By comparing with the bonding characteristics of pure Al3Ti in the L12 and DO22 structures, the addition of Cu to Al3Ti is found to be equivalent to the tetragonal distortion in DO22 Al3Ti as far as bonding is concerned, resulting in the stabilized L12-like structure for (AlCu)3Ti. The semi-empirical inverse relation between the structural stability and the density of states at Fermi energy is well established.

Si samples (001) oriented have been implanted with 101774Ge/cm2 (17.7 at. % maximum Ge concentration) and then pulse annealed with either ruby or excimer (XeCl) lasers in the energy density range from 0.1 to 1.5 J/cm2. Compositional and structural characterization has been performed showing that for both laser wavelengths the final product of the annealing process is a single crystal characterized by a surface layer about 150 nm thick whose composition is Si0.9Ge0.1. While after ruby laser irradiations defects are present even in the fully recrystallized samples, after XeCl irradiations good strained layers in epitaxy to the underlying silicon crystals and free from misfit dislocations are produced. Structural characterization of the regrown films indicates that the governing factor for the recovery of the crystalline quality and for the “building up of strain” is the state of the implantation “end-of-range defect” layer. When this defected layer is not melted, textured columnar grains are formed. Upon melting of the end-of-range defect layer, a single crystal epitaxial layer under compressive strain is formed.

Since copper has some advantages relative to aluminum as an interconnection material, it is appropriate to investigate its mechanical properties in order to be prepared in advance for possible problems, such as the cracks and voids that have plagued aluminum interconnect systems. A model previously used to interpret the behavior of aluminum films proves to be, with minor modification, also applicable to copper. Although the thermal expansion of copper is closer to that of silicon and, consequently, the thermally induced strains are smaller, the much larger elastic modulus of copper results in substantially higher stresses. This has implications for the interaction of copper lines with dielectrics.

A 70-nm-thick, 19-μΩ · cm TiSi2 layer is formed using a Ti-ion implantation technique. TiN/TiSi2 double layers, whose surface morphology is superior to that obtained with conventional deposition and reaction techniques, can also be simultaneously formed by Ti-ion implantation into monocrystalline Si screened with the Si3N4 film. Discrete pn-junction diodes with a shallow TiSi2 layer and Ti-polycide-gate MOS capacitors are fabricated to determine the influences of Ti-ion implantation on electrical characteristics. The leakage current of the B-doped p+n junction and As/P-doped n+p junction with Ti-ion implanted silicide layer is low enough for device applications. Silicide formation on the gate polycrystalline-Si does not affect the breakdown electric field strength of a 20-nm-thick gate oxide. MOS capacitors showed normal C-V characteristics.

High temperature x-ray diffractometry (HT-XRD) and differential scanning calorimetry (DSC) measurements confirm that two kinds of structural phase transitions exist in LaGaO3. One is the first order transition from the orthorhombic to the rhombohedral structure at ∼150 °C. The other is the second order transition from the rhombohedral to the monoclinic structure from ∼750 °C to ∼1000 °C.

We have employed the Local Harmonic (LH) model and the Embedded Atom Method (EAM) to examine the structural and thermodynamic properties of a series of twelve [001] twist boundaries in gold for temperatures between 0 K and 700 K. For the majority of the grain boundary misorientations, metastable structures were observed with grain boundary energies that were typically less than 0.1% larger than the stable structures. Four of the twelve grain boundaries underwent first order structural phase transitions as seen by the crossing of the free energy versus temperature curves for the competing structures. Relatively small cusps or inflections in the grain boundary free energy versus misorientation curves were observed at Σ5 (36.87°) and Σ13 (22.62°) at low temperatures, at Σ13 (22.62°) and Σ17 (28.07°) at intermediate temperatures, and at Σ5 (36.87°) and Σ17 (28.07°) at elevated temperatures. A maximum in the grain boundary entropy versus misorientation was observed at Σ17 (28.07°) for all temperatures, and local minima were observed at Σ5 (36.87°) at low temperature and in Σ13 (22.62°) at high temperature. The excess volume associated with the grain boundary shows a roughly linear dependence on grain boundary free energy at each temperature examined. The room-temperature mean-square vibrational amplitude is approximately 25% larger than that for the bulk at the (002) plane adjacent to the boundary and decays to within 2% of the bulk value by the second (002) plane from the boundary. The room-temperature mean-square vibrational amplitude is dominated by the in-plane (parallel to the grain boundary) vibrations at the (002) plane nearest the grain boundary.

We have carried out a detailed investigation of the Al71Pd19Mn10 alloy by using a combination of experimental techniques (neutron diffraction, electron diffraction, high resolution electron microscopy, and electron probe microanalysis). This alloy contains only the perfect icosahedral phase. This icosahedral phase is stable from room temperature up to its melting, though a transient cubic metastable phase coexists with it during the heating. It grows directly from liquid without involving any crystalline phase. Its isothermal growths at different temperatures can well be described by the Avrami equation with exponent n = 1.85. Comparisons with the Al–Cu–Fe I phase have also been made. The growth velocity of both I phases is approximately 1 μm/min with ΔT around 10 K, much slower than that of the crystalline phases growing under the same condition. After the sample was maintained at near liquidus temperature for more than 10 h, element losses and Si contamination from the crucible changed the sample composition. In consequence, crystalline phases have formed during the subsequent cooling and made the growth of the icosahedral phase a eutectic reaction.