The mechanical properties of compositionally modulated Au-Ni films were investigated by submicrometer depth-sensing indentation and by deflection of micrometer-scale cantilever beams. Films prepared by sputter deposition with composition wavelengths between 0.9 and 4.0 nm were investigated. Strength was found to be high and invariant with composition wavelength. Experimental and data analysis methods were developed to provide more accurate and precise measurements of elastic stiffness. Large enhancements in stiffness (the “supermodulus effect”) were not observed. Rather, relatively small but significant minima were observed at a composition wavelength of about 1.6 nm by both techniques. These variations were found to be strongly correlated with variations in the average lattice parameter normal to the plane of the film. Both structural and mechanical property variations are consistent with a simple model in which the film consists of bulk-like Au and Ni layers with interfaces of constant thickness.

A kinetic theory of ordering based on the path probability method was implemented in the pair (Bethe) approximation and used to study the kinetics of short- and long-range ordering in alloys with equilibrium states of B2, DO3, or B32 order. The theory was developed in a superposition approximation for a vacancy mechanism on a bcc lattice with first- (1nn) and second-nearest neighbor (2nn) pair interactions. Chained 1nn conditional probabilities were used to account for the entropy of 2nn pair configurations. Monte Carlo simulations of ordering were also performed and their results compared to predictions of the pair approximation. Comparisons are also made with predictions from an earlier kinetic theory implemented in the point (Bragg-Williams) approximation. For all three calculations (point, pair, and Monte Carlo), critical temperatures for B2 and DO3 ordering are reported for different 1nn and 2nn interaction strengths. The influence of annealing temperature on the kinetic paths through the space of B2, DO3, and B32 order parameters was found to be strong when the thermodynamic preferences for the ordered states were of similar strengths. Transient states of intermediate order were also studied. A transient formation of B32 order in an AB3 alloy was found when 2nn interactions were strong, even when B32 order was neither a Richards-Allen-Cahn ground state nor a stable equilibrium state at that temperature. The formation of this transient B32 order can be argued consistently from a thermodynamic perspective. However, a second example of transient B2 order in an AB alloy with equilibrium B32 order cannot be explained by the same thermodynamic argument, and we believe that its origin is primarily kinetic.

Microtubules are an interesting type of microstructure that resemble miniature drinking straws. Such tubular microstructures are found in nature. In addition, we and others have been investigating strategies for making synthetic analogs. We are especially interested in the idea of making metal microtubules. Four procedures for preparing metal microtubules are described in this paper. The general approach, called template-synthesis, entails using the pores in a microporous membrane as templates for forming the tubules. Microporous anodic aluminum oxide membranes and nuclear track-etch membranes are used as the template membranes. Gold and silver microtubules are made with outer diameters as small as 200 nm. These microstructures are characterized by scanning electron microscopy.

This work describes the formation of stoichiometric AlN films by single ion-beam sputtering of Al, using an ionized N2 (75%) + H2 (25%) mixture, onto substrates heated to 200 °C or above. The role of substrate temperature on film composition and properties is followed in the substrate temperature range between ambient and 250 °C. Infrared spectra of freshly prepared and 2 month old (aged in air) films demonstrate that substrate heating significantly affects the chemical nature of the resulting films. SEM and STM data, combined with IR and UV-visible spectral results, indicate that films formed at a substrate temperature of ≥200 °C are very smooth and highly resistant to attack by atmospheric gases. X-ray diffraction data show no diffraction peaks, indicating that the film is either amorphous or crystalline on a scale of less than 4 nm.

We have developed multilayer composite diamond coatings with improved adhesion and wear resistance on WC(Co) tool substrates. The coatings consist of a first layer of discontinuous diamond crystallites that are anchored to the WC(Co) substrate by an interposing layer of ceramic films. These films consist of TiC, TiN, SiC, Si3N4 or WC deposited to provide a conformal coverage on the first layer of diamond. A second or final layer of continuous diamond film is deposited to provide the cutting edge of the tool. The diamond film in the composite layers is deposited by hot filament chemical vapor deposition (HFCVD) and the interposing layer is deposited by laser physical vapor deposition (LPVD). The different parameters associated with the deposition of diamond and interposing layers are optimized to improve the adhesion and wear resistance. We have studied the adhesion characteristics by indentation tests in which the critical load for peeling of the diamond films is determined. Adhesion and wear resistance of the films are also tested using an overlap polishing on diamond paste with 5–6 μm particle size. The diamond and interposing layers in the composite are characterized by scanning electron microscopy and Raman spectroscopy. Results of improvement in adhesion and wear resistance are correlated with the quality of the diamond film and the interposing layer. Better accommodation of thermal stresses and strains in the composite layers has been shown to be responsible for improvement in the adhesion and wear resistance of the composite diamond films.

Ferroelectric BaTiO3 thin films were deposited on Si by rf magnetron sputtering. A conductive oxide, RuO2, was used as the bottom electrode of the capacitors. The performance of the thin film capacitors was found to be a strong function of the surface and interface properties between ferroelectric BaTiO3 and the bottom electrode. A suitable capacitor configuration must be used to preserve the bottom electrode, to enhance the dielectric constant, and to reduce the leakage current density of the films. BaTiO3 thin film on the RuO2/Si substrate, where the BaTiO3 thin film has a bilayer structure of polycrystalline on microcrystalline, showed a dielectric constant of 125 at a frequency of 1 MHz, leakage current density of 10−6 A/cm2 at a field intensity of 2.5 × 105 V/cm, and a breakdown voltage above 106 V/cm.

Seven batches of a high-lead glass were used for the preparation of RuO2-based thick film resistors. Investigation of their electrical properties showed a lack of reproducibility of results whose origin was related to changes of the physicochemical properties of the glassy matrix. A systematic investigation of the glass batches, both in form of frit powders and screen printed and fired layers, was carried out with several spectroscopies to detect changes in composition and structure. The spectroscopic methods included x-ray Energy Dispersive Fluorescence (EDS), Scanning Electron Microscopy (SEM), Atomic Absorption (AA), diffuse optical reflection of the powders and specular reflection of the layers, optical transmission, and other complementary methods. The dissolution of Al, due to interaction between the glasses and the alumina substrate, as well as the diffusivity and solubility of Ag due to interaction with the Ag-bearing terminations were measured. The results demonstrated that, apart from small compositional differences, the various batches were characterized by differences in residual stresses, redox reactions, and “microstructure.” The latter was responsible for very notable differences in the optical properties of the glasses, which in turn are closely related with the difference in atomic solubility and diffusivity. Optical spectroscopies have been found to be a suitable means for testing reproducible preparation methods of glass frits for thick-film hybrid microelectronics.

The interface states in ZnO with impurities of transition-metals, Mn, Co, and Cu, were investigated by the DLTS (deep-level transient spectroscopy) measurements in ZnO/PrCoOx/ZnO junctions as model systems of ZnO ceramic varistors and by the SCF-Xα-SW molecular orbital calculations using simplified cluster models. The DLTS signals, correlated to the doping of Mn and Co, are obtained with ZnO/PrCox/ZnO junctions. The signals correspond to the interface states due to the transition-metal doping. Xα calculations indicate that the interface states attributed to the doping of transition-metals, Mn, Co, and Cu, in ZnO are created between the valence band and the conduction band, which consist of transition-metals 3d character. The impurities of transition-metals affect interface states as well as the adsorbed excess oxygen.

The microstructural development of Ti: LiNbO3 optical waveguides, as a function of annealing time and temperature, was studied by x-ray diffraction, scanning and transmission electron microscopy, and Auger electron spectroscopy. The microstructure evolves in three major stages: oxidation, precipitation and abnormal grain growth, and interdiffusion. The deposited Ti film is oxidized at low temperatures through a series of intermediate TiOx phases until complete oxidation to rutile TiO2 occurs at ∼500 °C. At intermediate temperatures, 500-800 °C, epitaxial precipitates of LiNb3O8 are formed at the rutile/LiNbO3 interface. At this stage abnormal grain growth occurs in the rutile film, causing multivariant epitaxy where all of the grains have a single orientation relationship to the substrate. Subsequent interdiffusion between TiO2 and LiNb3O8 produces a solid solution with the rutile structure which, at these temperatures, appears to coexist in equilibrium with the underlying lithium niobate substrate. This rutile solid solution serves as the source of Ti in the final stage of interdiffusion, which occurs only at higher temperatures (≳ 1000 °C), and leads to consumption of the rutile layer by the substrate. Structural models are discussed for epitaxial grain growth and interdiffusion.

The reaction of tetraethoxysilane (TEOS) and the subsequent deposition of SiOx on the basal plane and edges of highly oriented pyrolytic graphite (HOPG) were studied. Interfacial bonding and surface morphologies resulting from different reaction conditions were probed using scanning tunneling microscopy (STM), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), temperature programmed desorption (TPD), and high resolution electron energy loss spectroscopy (HREELS). The initial reaction of TEOS was found to occur at surface defects. STM images indicated that SiCx films do not grow layer-by-layer, confirming earlier indirect observations to that effect.

Different properties of the mixtures of polyethylene with carbon black modified by the implantation of Sb+ ions were studied. Chemical changes of polymer were examined by IR- and UV-visible spectroscopy. Sheet resistivity as a function of sample temperature was studied. Depth profiles of implanted Sb atoms and incorporated oxygen were determined by the Rutherford backscattering technique. The percolation threshold of unimplanted mixtures is found at 4.5 and 5 wt. % of carbon black. As a result of ion implantation, the polymer is oxidized and conjugated double bonds are produced. The mixtures with carbon black concentration above percolation threshold exhibit metal-like conductivity. For the mixtures below percolation threshold, the measurements of resistivity versus temperature dependence indicate semiconductor type conductivity and charge transport via a variable range-hopping mechanism.

Synthesis of zirconium tetramethylheptanedione [Zr(thd)4] was optimized. Purity of Zr(thd)4 was confirmed by melting point determination, carbon, and hydrogen elemental analysis and proton nuclear magnetic resonance spectrometer (NMR). By using Zr(thd)4, excellent quality ZrO2 thin films were successfully deposited on single-crystal silicon wafers by metal-organic chemical vapor deposition (MOCVD) at reduced pressures. For substrate temperatures below 530 °C, the film deposition rates were very small (⋚1 nm/min). The film deposition rates were significantly affected by (i) source temperature, (ii) substrate temperature, and (iii) total pressure. As-deposited films are carbon free. Furthermore, only the tetragonal ZrO2 phase was identified in as-deposited films. The tetragonal phase transformed progressively into the monoclinic phase as the films were subjected to a high-temperature post-deposition annealing. The optical properties of the ZrO2 thin films as a function of wavelength, in the range of 200 nm to 2000 nm, were also reported. In addition, a simplified theoretical model which considers only a surface reaction was used to analyze the deposition of ZrO2 films. The model predicated the deposition rates well for various conditions in the hot wall reactor.

The stresses that arise in compositionally modulated Au-Ni thin films as a result of the constraint of the substrate were determined from the curvatures of micrometer-scale bilayer cantilever beams consisting of a silicon dioxide layer upon which the metal film had been deposited. These substrate interaction stresses were found to vary strongly with the wavelength of the composition modulation. Simulations of the bulge test show that such stresses can account for the major features of the “supermodulus effect” as artifacts of the analysis method.

The morphology and the growth mechanism of lithium borate crystals from the vitreous state have been studied for various compositions, X = B/(Li + B), from 0.62 to 0.75. Crystalline phases and morphology of grown crystals varied with the composition. Octahedral and/or spherical Li2B4O7 crystals are seen in the specimen with X = 0.62, 0.64, 0.67, and 0.68. The spherical crystal is composed of an octahedral core and fibrous crystals. The size of the core varied with the composition of the starting glass, X. The fibrous crystal growth is supposed to arise from the morphological instability due to the compositional variation caused by the solute pileup at the growth interface.

The pyrochlore to perovskite transition in sputtered PZT thin films has been studied using SEM and XRD. The films were annealed in the temperature range between 350 °C and 750 °C, and the transition temperature for pyrochlore to perovskite transition was found to be around 525 °C. Isothermal annealing was used to study the nucleation and growth kinetics of the perovskite phase. The results showed a linear growth rate for the perovskite phase, thereby indicating an interface controlled process. Also, the growth was found to be isotropic in two dimensions parallel to the plane of the substrate. The nucleation of the perovskite phase was found to be random. The effective activation energy of the perovskite transition was found to be 494 kJ/mol using Avrami's approach.

Nanocomposites involving iron particles in silica glass matrix have been synthesized by the hot pressing of suitably reduced precursor gel powders. The metal particles have diameters in the range 3.8 to 10.2 nm. An almost four orders of magnitude resistivity range at room temperature has been obtained by such changes in particle diameters. The resistivity in the temperature range 200-340 K shows a fractional temperature dependence with an average value of n ∼ 0.69. The resistivity changes in this temperature region can be explained on the basis of an electron tunneling mechanism.

Nickel aluminides exhibit limited ductility and toughness at room temperature. One way to improve these characteristics is by adding ceramic reinforcements to the matrix. In this paper, we have studied the combustion synthesis of Ni3Al and Ni3Al-matrix composites, using the self-propagating high-temperature synthesis (SHS) mode. First, studies of the Ni3Al synthesis were carried out by quenching the reaction during its progress, which revealed the mechanism of the synthesis. The influence of Al2O3 and SiC whiskers or particulates, and B4C particulates added to the reaction mixture prior to combustion synthesis, was investigated next. It was found that, in general, reinforcements are heat sinks and limit the propagation of the reaction. Also, whiskers impede the flow of formed liquid to a larger extent than do particulates. Al2O3 is inert and matrices reinforced with up to 2 wt. % Al2O3 are composed essentially of Ni3Al grains. However, both B4C and SiC react with the Ni-Al matrix and lead to complex phases. In particular, B4C readily forms a Ni-Al-B liquid phase and disrupts dramatically the progress of the Ni3Al matrix synthesis.

Thermally induced solid-state reactions between a 70 nm Pt film and a single-crystal (001) β-SiC substrate at temperatures from 300 °C to 1000 °C for various time durations are investigated by 2 MeV He backscattering spectrometry, x-ray diffraction, secondary ion mass spectrometry, scanning electron microscopy, and cross-sectional transmission electron microscopy. Backscattering spectrometry shows that Pt reacts with SiC at 500 °C. The product phase identified by x-ray diffraction is Pt3Si. At 600–900 °C, the main reaction product is Pt2Si, but the depth distribution of the Pt atoms changes with annealing temperature. When the sample is annealed at 1000 °C, the surface morphology deteriorates with the formation of some dendrite-like hillocks; both Pt2Si and PtSi are detected by x-ray diffraction. Samples annealed at 500–900 °C have a double-layer structure with a silicide surface layer and a carbon-silicide mixed layer below in contact with the substrate. The SiC—Pt interaction is resolved at an atomic scale with high-resolution electron microscopy. It is found that the grains of the sputtered Pt film first align themselves preferentially along an orientation of {111}Pt//{001}SiC without reaction between Pt and SiC. A thin amorphous interlayer then forms at 400 °C. At 450 °C, a new crystalline phase nucleates discretely at the Pt-interlayer interface and projects into or across the amorphous interlayer toward the SiC, while the undisturbed amorphous interlayer between the newly formed crystallites maintains its thickness. These nuclei grow extensively down into the substrate region at 500 °C, and the rest of the Pt film is converted to Pt3Si. Comparison between the thermal reaction of SiC-Pt and that of Si–Pt is discussed.

Epitaxial β-SiC (3C) films were grown on (0001) 6H-SiC and 15R-SiC substrates by chemical vapor deposition (CVD). TEM characterization revealed that films on both substrates exhibited large areas of atomically flat, coherent interfaces. However, when 3C-SiC films were grown on 6H substrates, double position boundaries (DPB's) were frequently observed, and islands of 6H were occasionally embedded in the predominantly 3C film. In contrast, films of 3C-SiC grown on 15R substrates exhibited relatively few DPB's and only occasional islands of 15R. A model of interlay er interactions in SiC was applied to predict the atomic structures at both 3C/6H and 3C/s15R interfaces, and these predictions were consistent with experimental observations of the interfaces by TEM. The observed interface structures and defect distributions were attributed to a microscopic kinetic mechanism of terrace growth. Consideration of step energies and growth kinetics led to the prediction that DPB's can be avoided by growing 3C-SiC films on 15R-SiC substrates.

Epitaxial TiN/V0.3Nb0.7N superlattices with a 1.7% lattice mismatch between the layers were grown by reactive magnetron sputtering on MgO(001) substrates. Superlattice structure, crystalline perfection, composition modulation amplitudes, and coherency strains were studied using transmission electron microscopy and x-ray diffraction. Hardness H and elastic modulus were measured by nanoindentation. H increased rapidly with increasing Λ, peaking at H values ≍75% greater than rule-of-mixtures values at Λ ≍ 6 nm, before decreasing slightly with further increases in Λ. A comparison with previously studied lattice-matched TiN/V0.6Nb0.4N superlattices, which had nearly identical composition modulation amplitudes, showed a similar H variation, but a smaller H enhancement of ≍50%. The results suggest that coherency strains, which were larger for the mismatched TiN/V0.3Nb0.7N superlattices, were responsible for the larger hardness enhancement. The results are discussed in terms of coherency strain theories developed for spinodally decomposed materials. Nanoindenter elastic modulus results showed no significant anomalies.