A reverse martensitic phase transformation was observed in Nb-enriched Nb-Co multilayers induced by room temperature 200 ke V xenon ion mixing. Further experiments revealed that this bcc-fcc transition proceeds in two steps, i.e., bcc-hcp and hcp-fcc. A crystallographic model is proposed to explain the two-step transition through shearing and sliding, which are mediated by irradiation-induced defects and strain in the films. In addition, the existence of the hcp and fcc metastable states in the Nb-Co system was confirmed by high-temperature solid state interdiffusion of the corresponding multilayers.

By depositing thin films under conditions where intensity oscillations are observed in RHEED (reflection high-energy electron diffraction) spots, unit cell level multilayers of SrTiO3/BaTiO3 structures have been grown by pulsed laser ablation. High resolution TEM (transmission electron microscopy) and STEM (scanning transmission electron microscopy) observations of the deposits show that epitaxial multilayers with layer thicknesses of 1, 2, 4, 8, and 16 unit cells can be grown on [100] orientation SrTiO3 substrates. The superlattices show partial intermixing of the Sr and Ba for layer thicknesses less than 8 unit cells, but incomplete intermixing occurs even when the layers are only a single unit cell thick. From observations of the degree of intermixing at different depths in the deposit, it was determined that most of the intermixing takes place during deposition and not during subsequent annealing of the deposit. The 16 and 8 unit cell thick BaTiO3 layers were found to be tetragonal with the c-axis of the layers oriented normal to the substrate but with the a-axis strained to coherently match the SrTiO3 layers.

Zinc sulfide thin films were prepared by the Atomic Layer Epitaxy (ALE) process from zinc acetate and zinc chloride and studied by emanation thermal analysis (ETA). The effects of different precursors and growth temperatures were evident in the ETA curves. In the films grown from zinc acetate, thermally induced changes were detected below 95 °C and above 400 °C which can plausibly be attributed to a higher amount of volatiles and to a polymorphic transition, respectively. The cubic to hexagonal transition was confirmed by DSC. Doping with terbium distorts the crystal structure and causes the peaks to become poorly discernible.

The size distributions of aerosol particles generated in N2 and O2 at ambient atmospheric pressure by repetitive excimer laser ablation of solids have been measured in quasi-steady-state from 10 nm to 1 μm diameter with a differential mobility analyzer (DMA). A light scattering technique extended the range of measurable sizes up to 20 μm, beyond the upper limit of sizes observed in the aerosol. Irradiation near focus was required to observe metal particles above 0.1 μm diameter. YBCO ceramic (YBa2Cu3O7) produced copious smaller particles with mild focusing. For an ablated polymer, PMMA, particulate production increased and the size distribution altered shape with continued energy deposition.

Structural defects occurring on the {311} planes of single crystal silicon have been observed near the bottom oxide corner in silicon-on-insulator structures formed by selective epitaxial growth. These {311} defects exhibit a preferential orientation and are clustered near the silicon/silicon dioxide interface. This new observation provides an opportunity to study the mechanism of {311} defect generation in a system with discernible microstructure and stress state. High resolution electron microscopy combined with analytical and numerical three-dimensional stress modeling are used to show the dependence of these {311} defects on the local stress field, and to establish their origin in terms of a homogeneous dislocation nucleation model.

Undoped and lanthanide (La and Nd) doped Pb(ZrxTi1-x)03, i.e., PZT, ferroelectric thin films were prepared by metallorganic decomposition (MOD) and spin-coating. The precursors for making the undoped PZT films were derived from lead acetate, zirconium n-propoxide, and titanium isopropoxide. In addition, lanthanum acetylacetonate and neodymium acetate were introduced into the precursor solution to accomplish the doping of the corresponding elements. Both undoped and doped PZT films were coated onto Pt/Ti/Si02/Si and single-crystal sapphire substrates to various thicknesses and annealed at a range of temperatures and times. The effects of lanthanide dopants in PZT films were studied with regard to microstructure, Curie temperatures, crystal distortion, optical properties, and electrical properties. The results indicate that the addition of La and Nd dopants tends to enhance perovskite phase formation and improve the packing densities and electrical properties of PZT films.

In a new approach to sinter Al/AlN composites in an overpressure environment of Al, the effects of sintering temperature and Al content on the microstructure, density, shrinkage, and mass gain were investigated. Fracture behavior and toughness were correlated with microstructure and composition of Al/AlN composites.

A new mask-less electrode patterning method using a thermal transfer printing technique was investigated. Thermal ink ribbons were prepared, which included more than 50 vol. % conductive metal powder. Arbitrary electrode patterns were designed with a computer and printed out on a ceramic green sheet with a serial thermal printer. The ceramic green sheets with printed electrode patterns were stacked up and cofired to obtain a multi-layer ceramic capacitor.

The optical absorption edge of the sol-gel derived borosilicate, silica, and phosphosilicate glasses containing heavy-metal oxides PbO and TeO2 exhibits a strong dependence on the temperature and composition. As the temperature is varied, a significant reversible thermochromic effect is observed in these glasses with a temperature coefficient as high as 10−3 eV/°C for most compositions, which is in general one magnitude of order greater than those of conventional semiconductor materials. The absorption edge of the glasses containing 10.24 wt. % PbTeO3 at room temperature was located at 3.76, 3.86, and 4.33 eV for the borosilicate, silica, and phosphosilicate glasses, respectively. With an increase in the heavy-metal concentration from 5.36 up to 18.62 wt. % in the borosilicate glasses, the absorption edge moved from 3.80 to 3.31 eV. On further increasing the concentration, the absorption edge no longer showed obvious red-shift. The observed optical characteristics were explained in view of the bond polarizability and structural coordination.

Titanium di- and sesquioxide films were epitaxially grown on the (001) surface of sapphire single-crystalline substrates by an activated reactive evaporation method. Formation range for each titanium oxide was determined as a function of oxygen pressure (Po2) by means of x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films prepared at Po2 ≥ 2.0 × 10−4 Torr were stoichiometric (100)-oriented rutile of TiO2, and with decreasing Po2 they would accommodate more and more Ti3+ ions in the rutile structure. At Po2 = 0.6 × 10−4 Torr, on the other hand, (001)-oriented Ti2O3 was formed and an electrical transition was clearly detected at about 400 K. However, the large lattice mismatch between the substrate and these films leads to a periodic introduction of misfit dislocations in the case of the TiO2 films and a mixing of stacking sequences for the Ti2O3 films.

Monolithic CoSi and TiB2 reinforced CoSi materials were produced by spray atomization and co-deposition. The creep behavior of both materials at elevated temperature was investigated. The unreinforced material of grain size ≍25 μm exhibited a stress exponent of three, activation energy for creep of 320 kJ/mole, dislocation substructure of homogeneously distributed dislocations, and inverse creep transients upon stress increases. These results suggest that the creep behavior of CoSi is controlled by a dislocation glide mechanism. In contrast, the reinforced material of a finer grain size (≍10 μm) exhibited a stress exponent of unity, activation energy for creep of 240 kJ/mole, and negligible creep transients upon stress increases, suggesting that the creep behavior of the reinforced material is controlled by a diffusional creep mechanism. The creep resistance of the reinforced material was lower than that for the unreinforced material. This is a result of the finer grain size and higher porosity in the reinforced material.

CuInSe2 thin film solar cells with an efficiency of about 10% were studied with a cross-sectional high resolution transmission electron microscope (HRTEM). The growth defects such as twins, stacking faults, and intergrowth phase in the CuInSe2 thin films were studied in detail. Polycrystalline CuInSe2 films were deposited on a Mo-coated glass substrate by using the three source evaporation system. The CuInSe2 film contains fivefold multiply twinned crystallites as well as a high density of twins in the {112} plane. The CuInSe2 film also contains intergrowth phase with a long range of periodicities of 10 Å parallel to the [112] direction of the chalcopyrite structure. The intergrowth phase composition is similar to the chalcopyrite phase. The structural model of the intergrowth phase is proposed on the basis of the high resolution electron micrograph.

A novel testing technique has been developed capable of measuring the interfacial fracture resistance, Γi, of thin ductile films on substrates. In this technique, the thin film on the substrate is stressed by depositing onto the film a second superlayer of material, having a large intrinsic stress, such as Cr. Subsequent processing defines a precrack at the interface between the film and the substrate. The strain energy available for driving the debond crack is modulated by varying the thickness of the Cr superlayer. Spontaneous decohesion occurs for superlayers exceeding a critical thickness. The latter is used to obtain Γi from elasticity solutions for residually stressed thin films. The technique has been demonstrated for Cu thin films on silica substrates.

CdS-silica xerogel composites were prepared from tetramethoxysilane, acidic water, and formamide mixtures homogenized by high power ultrasounds. Different concentrations of Cd(NO3)2 were added. CdS semiconductor nanoparticles were precipitated by H2S gas diffusion through the sonogel porous structure. Composite mechanical properties were enhanced by an impregnation process by the gel soaking in the same sol as-prepared. Textural parameters evolution is compared to the salt content in order to find the best performance to CdS nanocrystal growth. The impregnation process allows a better composite protection.

A thermochemical analysis is performed in the system Cu-In-S at 723 K. Free energies of In6,S7, In417S583, “In2S3”, Cu951In49, and CuIn5S8 have been estimated, the numerical values (kJ/mol) of which are −1285, −97 780, −481.1, −31 680, and −1444. The free energy (kJ/mol) of CuInS2 is calculated from the relation G° = (-306.1 ± 54.4) + 0.5092T −1.397 10−5T2 −0.09468T In T + 268.2T−1, which is obtained from published assessed standard formation enthalpy and specific heat and entropy data. The free energy of the Cu-In melt is taken from very new literature. A consistent set of data is used for the calculation of a tentative Gibbs triangle as well as of the corresponding predominance area diagram. The Gibbs triangle is calculated with the program thermo, the algorithm of which is given. The results are in agreement with the results of published measurements, also for the equilibria which involve the melt. The compound CuInS2, one of the possible base materials for thin film solar cells, is shown to equilibrate with most of the compounds of the system. Predictions are made how to prepare CuInS2 from Cu-In alloys and H2S/H2 gas mixtures. However, more experiments are necessary to establish the data, the experiments, and/or the results of the calculations.

Spatially resolved electron energy-loss data have been recorded at the interface between niobium and sapphire (α-Al2O3), a model metal/ceramic couple. The spatial-difference technique is used to extract interface specific components of the energy-loss near-edge structure (ELNES), which are dependent on the chemistry and bonding across the interface. Multiple scattering calculations of aluminum, oxygen, and niobium clusters were performed to simulate the measured Al L2,3 ELNES. Two samples fabricated by different techniques were examined. The first interface was made by diffusion bonding pure crystals. Its interface spectrum is identified with tetrahedral coordination of the Al ions at the interface. The calculations match the experimental edge structures, supporting the notion of aluminum to niobium metal bonding and concurring with a structural model in which the basal plane of sapphire at the interface is terminated by a full monolayer (i.e., 67% excess) of aluminum. The second sample was produced by molecular beam epitaxy. The spectrum of this interface is consistent with an atomistic structure in which the interfacial basal plane of sapphire is terminated by oxygen. An unoccupied band of states within the band gap of Al2O3 is observed, signifying chemical bonding between metal and ceramic.

Traditional CVD phase diagrams, which neglect the depletion effects in a hot wall reactor and assume the gaseous species concentrations at the substrate are the same as input concentrations, are at best valid for a cold wall reactor. Due to the constant change of gaseous species concentration along the length of the reactor, traditional CVD phase diagrams do not accurately predict the phases in the deposit on the substrate in a hot wall CVD system. In this paper, a new approach to calculate the local equilibrium CVD phase diagrams at the substrate is presented by coupling the depletion effects in a hot wall reactor to the equilibrium thermodynamic computer codes solgasmix-pv. The deposition of SiC using the gas system of methyltrichlorosilane (MTS)-hydrogen (H2) under low pressure was chosen for this study. Differences between the new CVD phase diagrams and the traditional phase diagrams for this gas system are discussed. The calculated CVD phase diagrams are also compared with the experimental data both from our own experiment and from the literature. The local equilibrium phase diagrams predicted the deposition of a single phase of SiC much better than those without the consideration of the depletion effects. The experimental regions for depositing single phase SiC are larger than the calculated local phase diagrams. This is attributed to the higher linear velocity of the gas flux under low pressure and the polarity of the Si carrying intermediate species.

The effects of boron additions (0 to 4000 wppm B) on the room temperature deformation behavior of Ni-24Al have been examined with both quasi-static deformation and short pulse duration shock loading. Changes in compressive yield strength and hardness with the amount of boron suggest that strengthening effects are more complicated than predicted by usual interstitial solid-solution strengthening considerations. The nature of the dislocations changes from SISF-dissociated superdislocations in the Ni-24Al base alloy to APB-dissociated dislocations with the additions of small amounts of boron. Therefore, the observed variation in strength with boron additions reflects a solid-solution strengthening contribution from the interstitial boron coupled with a “softening” effect arising from the greater mobility of the APB-bounding partials relative to the SISF-bounding partials. It is suggested that this “softening” is a necessary prerequisite for enhanced ductility in Ni3Al. In addition, the grain boundary fracture strength must be increased by boron additions. While this may occur through an increased grain boundary cohesive strength due to boron segregation, it is also expected that the interaction of the dislocations with the grain boundaries will be significantly altered as the nature of the dislocations changes. The lack of a “boron effect” in Ni-25Al, the so-called stoichiometric effect, can be attributed to a diminished “softening”, combined with the rapid solid-solution strengthening observed in this alloy.

The electrochemical codeposition of In and Sb from a novel low temperature molten salt electrolyte is reported. The melt, which consists of InCl3 and 1-methyl-3-ethylimidazolium chloride, allows the codeposition to be accomplished at 45 °C. XPS shows that InSb can be deposited from this system. Electrochemical experiments are provided along with an interpretation that draws on the importance of In(I) species in the melt.

It is well known that mechanical properties of commercial stainless steel are improved by alloying with nitrogen. In this study a series of nitrogenated commercial 201 stainless steel alloys with nitrogen levels as high as 2.6 wt. % were obtained by melting in a hot-isostatic-pressure furnace using nitrogen as the pressurizing gas. Nitrogen concentrations in excess of 1.25 wt. % formed a series of different chromium nitride precipitates and morphologies depending upon the nitrogen concentration. Five different nitrogen levels were fabricated using the same processing conditions recommended for 201 stainless steel including hot-and cold-working, and heat-treating at two different temperatures. Tensile strength of the nitrogenated materials at each processing step was related to the interstitial nitrogen concentration and the presence or absence of precipitates. The presence of chromium precipitates did reduce the fracture ductility and changed the fracture features. This U.S. Bureau of Mines study shows that increasing the nitrogen concentration in commercial steels above their current level has positive effects on mechanical properties as long as the nitrogen solubility level is not exceeded and chromium nitride precipitates begin to form.