The ability of heavy-ion beams to enhance the adhesion of thin metallic films to substrates has been studied as a function of projectile species. Measurements of the adhesion enhancement of a thin gold film to substrates of tantalum and silicon (with native oxides) have been made for beams of 12C, 16O, 28Si, 35Cl, and 58Ni at 2.85 MeV/nucleon. The threshold dose required to pass the Scotch tape peel test was found for the Au-Ta system to be D th (cm−2) = 1017 (dE / dx)−3±0.2 where dE/dx is the electronic stopping power (MeV mg−1 cm−2) of the ion in Au. For the Au-Si system, Dth = 6×1018 (dE/dx)−4.1±0.3. The steep dependence of D th on dE/dx found here is in contrast with an earlier measurement for the Au-Ta system by Tombrello et al. The adhesion enhancement was observed to decrease with time after the bombardment in a manner suggesting that diffusion of atoms through the gold film is important. The possible importance of small concentrations of extraneous atoms at the interface is discussed.

Electrophotographic properties of chalcogenide materials are readily influenced by altering their composition and/or structure. Dark decay and cycle down of photoreceptors utilizing small particle generators are both directly proportional to average crystallite size (ACS). This paper describes a novel chemical method to control the ACS of Se, Te, and Sex Te1−x alloys. These chalcogenide materials are prepared as powders by the reduction or coreduction of SeIV and/or TeIV intermediates with hydrazine, in organic media. To control the ACS of precipitated chalcogens the reaction is carried out at the desired temperature. X-ray diffraction measurements are used to determine the ACS, homogeneity, and phase of these precipitated powders.

Amorphous Al80Cr20 films were made by coevaporation and by room temperature ion irradiation of the coevaporated films. The amorphous phase was transformed into the quasicrystalline state through two routes: thermal and ion beam assisted anneal. The intensity of the quasicrystalline electron diffraction pattern increases continuously within the annealing temperature range from 547°to 607°C. The starting state of the films (as-deposited or ion-irradiated codeposited) had no effect on the thermal transformation to the quasicrystalline state. Ion irradiation of the amorphous phase at 200°C produces a more complete set of icosahedral diffraction lines. Icosahedral AlCr has the same reciprocal lattice spacings as icosahedral AlMn.

The 27Al and the 55Mn nuclear magnetic resonance powder pattern lineshapes have been obtained in icosahedral and decagonal (T phase) Al-Mn quasiperiodic crystals, and are compared to that of orthorhombic Al6Mn. The quasiperiodic crystals yield much broader spectra with little resolved structure. The quadrupole and Knight shift parameters for the 55Mn resonance in orthorhombic Al6Mn have been determined as |vQ| = 0.76 MHz,Kax = −2.7 × 10−4, Kiso = + 5 × 10−3. The results imply that Al6Mn and the quasiperiodic crystals have similar electronic and magnetic properties.

Homogeneous single phase Mg32Al19Zn30 was melt spun to form flakes suitable for TEM examination. The nodular structure gave diffraction patterns with 5.3.2 icosahedral point group symmetry. The formation of the icosahedral phase is rationalized in terms of the Mg(AlZn)49 equilibrium structure. This structure is a Frank-Kasper phase. It has previously been established how such icosahedral order can be anticipated in the Frank-Kasper phases.

The evolution of the implant distribution during ion implantation at elevated temperatures has been theoretically studied using a comprehensive kinetic model. In the model foreign atoms, implanted into both interstitial and substitutional sites of the host lattice, could interact with implantation-induced point defects and with extended sinks such as the bombarded surface. The synergistic effects of preferential sputtering, radiation-enhanced diffusion, and radiation-induced segregation, as well as the influence of nonuniform defect production, were taken into account. The bombarded surface was allowed to move in either direction, − x or + x, depending on ion energy, i.e., on the competition between the rates of ion deposition and sputtering. The moving surface was accounted for by means of a mathematical technique of immobilizing the boundary. The ion implantation process was cast into a system of five coupled partial differential equations, which could be solved numerically using a suitable technique. Sample calculations were performed for two systems: Si+ and Al+ implantations into Ni. It has been known from previous studies that in irradiated Ni, Si atoms segregate in the same direction as the defect fluxes, whereas Al solutes migrate in the opposite direction. Thus the effects of different segregation mechanisms, as well as the influence of target temperature, ion energy, and implantation rate on the evolution of implant concentrations in time and space, could be examined with the present model.

Compound samples of NiAl3 as well as Ni23Al77 multilayered samples have been irradiated by either Xe or Ne ions to doses of 2 × 1015 Xe ions/cm2 and 1.3 × 106 Ne ions/cm2 at temperatures of 100 K, 300 K, and 373 K. In the case of compound irradiation, NiAl3 stability appears to be determined by regrowth kinetics and increased with lighter irradiating ion mass and higher irradiation temperature. The formation of NiAl3 by ion mixing Ni/Al multilayers was not affected by irradiating ion mass and appears to be limited by nucleation.

Self-propagating high-temperature synthesis (SHS), also called combustion synthesis, is useful for fabricating numerous ceramics. In the case of SiC, heat released from the exothermic reaction is not sufficient to completely convert the mixed reactants of constituent elements into SiC in the usual nonadiabatic experimental system. This disadvantage could be overcome by a new ignition process called, the “direct passing method of electric current.” By using this method, stoichiometric fine SiC powder could be obtained rapidly and efficiently with low electric power. This paper also involves the effect of particle size of Si and C initial reactant powders on conversion efficiency into SiC and also on particle size of SiC powder fabricated by this method.

Several novel oxides have been prepared by the decomposition of carbonate precursors of calcite structure of the general formulas Mn1−xMxCO3 (M = Mg,Co,Cd), Ca1−xMx'CO3, and Ca1−x−yMxMy”CO3

Determination of the amount of cubic and tetragonal phase in yttria–zirconia using high-angle XRD (x-ray diffraction) has been complicated by problems of resolution and interpretation. The evidence, from electron diffraction studies, for a c→t shear transformation also needs to be taken into account. Two compositions, a 3 and a 5.7 mol % Y2O3−ZrO2, were sintered and thermally treated at different temperatures between 1450°and 1700°C. X-ray diffraction traces revealed the anticipated tetragonal (400) and (004) reflections. The region of the diffraction pattern that was thought to arise from the cubic phase could be best interpreted as a second tetragonal phase t'. The original amount of cubic phase computed from the t' reflections showed good agreement with the phase diagram of Scott. The lattice parameters of the t' phase were determined, and the volume of the tetragonal (t') unit cell was calculated.

Electrical conduction in undoped and indium-doped ZnO films in as-deposited, vacuum-annealed and oxygen-annealed states has been studied. The as-deposited and oxygen-annealed films contain a large density (≥ 1017 m−2) of trap states due to chemisorbed oxygen at the grain boundaries. The role of these trap states has been analyzed in terms of the grain boundary carrier trapping model. The vacuum-annealed films are free of chemisorbed oxygen, and the conduction in these films is controlled by scattering due to ionized impurities and grain boundary barriers. In the case of undoped ZnO films, intrinsic trap states at the grain boundaries also play a significant role. The optical behavior of all films in the UV and visible regions is dielectric-like and the optical bandgap shows a dependence on free carrier concentration that is controlled by a bandgap narrowing effect due to electron-electron and electron-impurity interactions as well as the Moss-Burstein effect of bandgap widening. In the IR region the optical behavior is metal-like due to free-electron effects and follows the Drude model.

The approach to equilibrium of the grain structure and electrical properties has been studied in high-resistivity, As-implanted polycrystalline silicon films on thermally oxidized silicon wafers. Thermal annealing parameters are found to be critical in determining the film sheet resistance. Results from spreading resistance analysis, secondary ion mass spectroscopy, and transmission electron microscopy indicate that As diffusion down the grain boundaries into the film leads to a large fraction of the As being left in inactive grain boundary sites. Reactivation of the As is negligible when processing temperatures are 900 °C or lower. A relatively simple diffusion model has been developed that can fit the As concentration profile over the entire film thickness. This makes the model applicable to normal integrated circuit processing conditions where film thickness effects and nonequilibrium dopant distributions are important.

The reactions between bilayered Ni/Pt films and Si (100) substrates induced by thermal annealing and ion mixing were investigated. Thermal annealing of Si/Pt/Ni and Si/Ni/Pt samples led to layer reversal at low temperatures (∼ 300°to 400°C) and the formation of a ternary phase at high temperatures (∼ 700°C). These results are consistent with those reported in the literature. Ion mixing of both types of samples led to silicide formation without layer reversal. This effect is interpreted in terms of a change of moving species from metal (in thermal annealing) to Si (in ion mixing). The mixing efficiency between Pt and Ni is observed to be enhanced when Si is mixed together with these two metals.

The structural and electrical properties of a Nb-Si thin alloy film as a function of temperature have been studied by Auger electron spectrometry, Rutherford backscattering spectroscopy, transmission electron microscopies, and in situ electrical resistivity and Hall coefficient measurements. The NbSi2,8 films were deposited by double electron-gun coevaporation onto oxidized silicon. For electrical measurements samples of a van der Pauw pattern were made through metallic masks. In the as-deposited state the coevaporated alloy film was amorphous. Upon annealing a precipitous drop in resistivity near 270°C has been determined to be the amorphous to crystalline phase transformation. The kinetics of the transformation has been determined by isothermal heat treatment over the temperature range of 224°C to 252°C. An apparent activation energy of 1.90 eV has been measured. The nucleation and growth kinetics in the crystallization process show a change in the power of time dependence from 5.5 to 2.4. The microstructures of films at various states of annealing have been correlated to the resistivity change. The crystalline NbSi2 shows an anomalous metallic behavior. The resistivity (p) versus temperature curve has a large negative deviation from linearity (dfl) and it approaches a saturation value (psat) as temperature increases. The resistivity data are fitted by two empirical expressions put forth to explain the resistivity behavior in A15 superconductors at low and high temperatures. One is based on the idea that ideal resistivity must approach some limiting value in the regime where the mean free path becomes comparable to the interatomic spacing and the other is based on a selective electron-phonon assisted scattering. In spite of the wide temperature range of analysis, it is not possible to choose one of them due to the fact that the best fit in both cases is nearly the same. The Hall coefficient (RH) changes sign from negative above ∼250°K to positive below ∼ 250°K.

We present the first known systematic mapping of quantum well and tunnel barrier thicknesses in a resonant tunneling structure by transport measurements. The technique derives a 1 Å averaged resolution for quantum well and barrier thicknesses, independently for the quantum well and adjacent tunnel barriers. Contour maps of the structure reveal an asymmetric shallow ring growth structure for one of the epilayers. Current-voltage characteristics and temperature dependence of the resonant tunneling structures will also be discussed.

Temperature-dependent chemical interactions between Au and nine III-V compound semiconductors (III = Al,Ga,In and V = P,As,Sb) have been calculated using bulk thermodynamic properties. Enthalpic considerations alone are insufficient to predict metal/ compound semiconductor reactivities. The entropy of vaporization of the group V elements is shown to be an extremely important driving force for chemical reactions involving the III-V's, since it enables several endothermic reactions to occur spontaneously under certain temperature and pressure conditions. Plots of either Gibbs' free energies of reaction or equilibrium vapor pressure of the group V element versus temperature are used to predict critical reaction temperatures for each of the systems studied. These plots agree extremely well with previous experimental observations of thin film reactions of Au on GaAs.

The Au-Ga-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb ternaries were surveyed using x-ray powder diffraction to determine which metallic phases exist at equilibrium with the III-V compound semiconductors. In closed, small-volume systems (i.e., formation of gas-phase products was prevented), Au does not react with GaAs but does react with the other III-V's investigated to produce Au-group III intermetallic compounds and another solid phase containing the group V element. However, each semiconductor formed pseudobinary systems with at least two different intermetallic compounds. The bulk phase diagrams determined in this study provide frameworks within which much of the experimental data in the literature concerning the products of reactions at Au/III-V interfaces can be understood.

Raman scattering from the ∼ 1600 cm−1 graphitic phonons is used to study the stage evolution of graphite-H2SO4 in the first ∼ 1000 Å of the bulk during electrochemical intercalation. The Raman results are compared to staging kinetics in the deep bulk studied previously by 00/ x-ray diffraction. For low cell currents, which establish quasiequilibrium conditions, the c-face surface of the highly oriented pyrolytic graphite (HOPG) in contact with the reactant rapidly changes stage index to n − 1 just as the bulk completes stage n. We conclude that the intercalant must cross the c-face plate boundary of the HOPG, probably entering at either grain boundaries, microcracks, or steps in the plate surface. During stage transitions, the Raman lines are observed to remain Lorentzian in shape, with constant width, indicating that an ordered stage n − 1 compound grows at the expense of an ordered stage n compound. In studies of partially submerged HOPG plates, the surface above the acid level is found to stage last, although the plate surface just below the acid level stages first. Lateral diffusion of the sulfate anions from regions below, to regions above the acid level, is apparently impeded for reasons that are not understood. During portions of the electrochemical reaction requiring only hydrogen rearrangement in the intercalate layers (“overcharging”), Raman spectra taken from above and below the acid level are observed to evolve in concert, indicating the protons are not similarly impeded.

Pulses of Q-switched Nd-YAG radiation have been used to remove polysilicon target links during the implementation of laser programmable redundancy in the fabrication of silicon memory. The link is encapsulated by transparent dielectric films that give rise to important optical interference effects modifying the laser flux absorbed by the link and the silicon substrate. Estimates of these effects are made on the basis of classical plane-wave procedures. Thermal evolution of the composite structure is described in terms of a finite-difference form of the three-dimensional heat diffusion equation with a heat generation rate having a Gaussian spatial distribution of intensity and temporal shapes characteristic of commercial lasers. Temperature-dependent thermal diffusivity and melting of the polysilicon link are included in the computer modeling. The calculations account for the discontinuous change in the link absorption coefficient at the transition temperature. A threshold temperature and corresponding pressure, sufficiently high to rupture the dielectric above the link and initiate the removal process, are estimated by treating the molten link as a hard-sphere fluid. Numerical results are presented in the form of three-dimensional temperature distributions for 1.06 and 0.53 μm radiation with pulse energies 3.5 and 0.15μJ, respectively. Similarities and differences between heating effects produced by long (190 ns FWHM/740 ns duration) and short (35 ns FWHM/220 ns duration) pulses are pointed out.

This paper describes the effect of cyclic loading upon the compressive strength, the stress-strain relationship, and the energy absorption and dissipation characteristics of short concrete columns (stub columns) at various slow strain rates. Comparison is made with columns loaded monotonically at similar strain rates. The columns were confined laterally by high-tensile steel bolts, inserted horizontally in two orthogonal directions through preformed ducts; the annular space between ducts and bolts was grouted with high-strength epoxy resin. Both steel and concrete deformational response was measured. Significant enhancement of the strength and ductility of the concrete was obtained. Columns displayed large energy absorption and dissipation capacity under cyclic loading. The validity of an envelope curve to describe cyclic behavior is discussed.