Containerless processing of YBa2Cu3O7−δ was performed using an aero-acoustic levitation technique. Upon solidification from the liquid, spheres of size 2.5 mm diameter undercooled and recalesced, forming tetragonal YBa2Cu3O7−δ directly from the melt. Subsequent to solidification processing, these samples were annealed to single phase YBa2Cu3O7−δ with orthorhombic symmetry as indicated by powder XRD, SQUID magnetometer measurements indicate a sharp superconducting transition at approximately 85 K. Magnetic Jc values, calculated using the Bean critical state model, indicate that the spheres can carry critical current densities on the order of 104 A cm−2. Microstructural characterization has been performed on both the as-solidified and annealed spheres.

The importance of the interactions between alloy atoms and topological defects for the thermodynamic properties of nanostructured alloys is pointed out. The McLean model for grain boundary segregation is extended to yield an expression for the total Gibbs free energy of an alloy polycrystal. This provides a simple conceptual basis for a qualitative discussion of the thermodynamic properties of nanocrystalline alloys. It is demonstrated that certain alloy poly- or nanocrystals may reach a metastable state, where the alloy is stable with respect to variation of its total grain boundary area.

High oxygen pressures have been achieved in a piston-cylinder apparatus using a double capsule assembly consisting of a sealed outer Au capsule, containing an oxygen source (KMnO4), and an inner, open Pt capsule containing the sample. Using this technique, La2CuO4 was annealed at 800 °C, 5–25 kbar for 2–4 h. Transposed temperature drop calorimetry at 704 °C was used to determine the enthalpy of oxidation, and weight loss measurements characterized the oxygen nonstoichiometry, δ, in La2CuO4+δ, in the high-pressure, oxygen-annealed samples. For samples analyzed at room temperature, x-ray diffraction measurements show that beyond δ ≍ 0.10–0.13, additional oxygen is accommodated in a perovskite-like LaCuO3−α phase. An analysis of the thermochemical measurements indicates that the nature of holes in La2CuO4+δ could change in the range of δ ≍ 0.03–0.06.16,17 It is further suggested that the observed change in the thermochemical behavior in the range of δ ≍ 0.03–0.06 could be the driving influence behind the spinodal decomposition of La2CuO4+δ at low temperatures (Dabrowski et al.10).

We describe a method for directly determining the strain state of passivated metal lines. Synchrotron radiation in the grazing incidence geometry is used to directly measure the in-plane interplanar spacing along the length and width of the lines, while the strain normal to the surface of the line is measured using conventional diffraction methods. The entire strain state is thereby defined. Previous work has measured out-of-plane reflections, fit them to a straight line as a trigonometric function of the angle of orientation, and extrapolated to determine the principal strains. The equivalence of the two x-ray methods on the same sample is demonstrated at room temperature before and after thermal cycling. For short time strain relaxation experiments during thermal cycling, measurement of the three principal strains leads to the direct calculation of the stress relaxation. We apply the strain determination technique to Al-0.5% Cu lines passivated with Si3N4 as the lines are thermally cycled from room temperature to 450 °C and back. The strain state, stress state, and strain relaxation of the lines are calculated at several temperatures during thermal cycling.

Analysis and sample preparation techniques for the bulge test have been improved to the point where the test can provide reliable and accurate measurements of the mechanical properties of thin films. Ag-Pd multilayer films of variable bilayer period were prepared for this study and characterized by cross-section transmission electron microscopy and by x-ray methods. The films were tested in the bulge test to determine their biaxial moduli. The data show no peak in biaxial modulus at a critical composition wavelength and no nonlinear elastic behavior. They do show a slight trend toward increasing elastic modulus with increasing strength of (111) crystallographic texture. These findings refute a previous report of the “supermodulus” effect in this system and add to the evidence that the effect is caused by artifacts of the mechanical testing technique. Methods for eliminating such artifacts are discussed.

The artificial layering of metals can change both physical and structural characteristics from the bulk. The stabilization of polymorphic metallic phases can occur on a dimensional scale that ranges from single overgrowth layers to repetitive layering at the nanoscale. The sputter deposition of crystalline titanium on nickel, as both a single layer and in multilayer form, has produced a face-centered cubic phase of titanium. The atomic structure of the face-centered cubic titanium phase is examined using high resolution electron microscopy in combination with electron and x-ray diffraction.

A TiV system, which does not amorphize in an inert gas atmosphere, has been mechanically alloyed (MA) and mechanically ground (MG) using a planetary ball mill in a hydrogen and nitrogen atmosphere. The products were characterized by x-ray diffractometry, transmission electron microscopy, differential scanning calorimetry, and chemical analysis as a function of milling time and the gas pressure. Amorphization occurs by MA and MG in a hydrogen atmosphere and by MG in a nitrogen atmosphere. Amorphization by MA proceeds by the reaction between TiH2 and pure V in a hydrogen atmosphere, while it proceeds by MG by hydrogen and nitrogen absorption into the metastable β-TiV alloy and subsequent milling. The difference in the phase formation by MA and MG of the TiV system is discussed based on the gas absorption rate and the solubility of gases.

The early stages of phase formation during mechanical alloying of Ti/Al powder blends were investigated using x-ray diffraction and transmission electron microscopy. After the initial formation of an hep solid solution by the diffusion of Al into Ti, the first phase nucleated at the Ti/Al interface is a (partially) Ll2-ordered fcc phase with a crystallite size of about 10–30 nm. This observation is ascribed to the kinetics of phase formation and the energetic destabilization of the equilibrium intermetallic compounds during milling due to chemical and structural disordering. A mechanism of phase formation during mechanical alloying is proposed, and comparisons are made with the thermal annealing behavior of Ti/Al multilayered thin films.

Solid state reactions induced by high energy ball milling between Pd and Si have been studied. X-ray diffractometry and differential scanning calorimetry have been used to characterize the resulting phases. During milling, Pd and Si react by diffusion to form different phases depending on the Si content in the starting mixture. With a low Si content of 19 at. %, an amorphous phase forms of the same composition. On continued milling, this amorphous phase partially crystallizes into Pd9Si2 and Pd2Si compounds. With the Si content equal to or higher than 33 at. %, no amorphous phases were observed. Instead, the Pd2Si phase is produced. For powder composition corresponding to the stoichiometric compound Pd2Si (33 at. % Si), the Pd2Si forms and remains stable during further milling. With Si content equal to or higher than 50 at. %, the initially produced Pd2Si is destabilized by a reaction with the remaining Si to form PdSi, which is a metastable phase at the temperature of ball milling. It is very unlikely that an amorphous phase of a composition equal to or higher than 33 at. % Si could be produced by ball milling in the Pd-Si system. This is because the Pd2Si phase forms very easily through the reaction between Pd and Si, and this reaction competes effectively with glass formation.

Thin solid films of C60 and C70 have been used as nucleating layers for the growth of diamond thin films on a variety of substrate surfaces, including metal, insulator, and semiconductors. Compared to other forms of carbon, such as graphite, amorphous carbon, soot, etc., it is found that the nucleation density on a C70 film is equivalent to that of diamond seeds themselves. On the other hand, diamond nucleation on a C60 film is less favorable. We argue from our experiments that the reason for C70 film to have such favorable nucleating properties is its chemical stability and geometry. A working model is proposed to explain the nucleation of diamond on solid C70 films. Application of this work extending to the growth of diamond on a wide range of substrates is also discussed.

The influence of the ambient atmosphere on the synthesis of diamond by chemical vapor deposition using an oxygen-acetylene torch is investigated experimentally. Diamond synthesis in an air atmosphere is compared to that in an inert atmosphere. It is found that the quality of diamond deposited on substrates positioned in the burnt gases near the premixed flame of the torch (within 1 mm) is independent of the composition of the ambient gas. Farther downstream from the premixed flame in the feather region, however, diamond deposition is controlled by the combustion of incomplete products from the premixed flame with oxygen from the atmosphere. In this region diamond grows in an annulus on the substrate with an air atmosphere, but no film is grown with an inert atmosphere.

Optical and electrical measurements on nitrogen ion-implanted diamond-like carbon films are presented. Raman scattering measurements, which probe the crystallinity of the film surface, indicate that nitrogen implantation reduces the finite crystallographic order in the pristine carbon films. The absence of molecular vibrations in the infrared absorption spectra of the films argues against a polymeric structure of the ion-implanted films. Spectroscopic ellipsometry experiments determine the change in the optical constants of the carbon film due to nitrogen implantation. Electrical de conductivity measurements are interpreted within the framework of a schematic density of states picture of graphitic τ-electrons in an amorphous carbon system. Taken collectively, the optical and electrical measurements suggest that nitrogen implantation increases the density of localized states within the 1.5 eV bandgap of the quasi-amorphous carbon film, thereby reducing the bandgap and increasing the conductivity of the nitrogen-implanted films.

Silicon 〈111〉 single crystals were implanted with 70 keV Ar ions to the dose of 1017 ions/cm2. Next, the friction coefficient between a Si crystal and a hard steel ball was measured using a pin-on-disk setup in air and in vacuum. The wear tracks were measured using a surface profilometer. For measurements performed in vacuum, a strong influence of implantation on friction force and wear tracks was found. The microstructure of the samples was subsequently investigated using RBS, ERD, and x-ray diffraction (XRD) techniques. Micro-RBS measurements showed that Ar had been removed from the wear tracks, despite their continued exhibition of low friction.

Due to its interesting mechanical properties, silicon carbide is an excellent material for many applications. In this paper, we report on the mechanical properties of amorphous hydrogenated or hydrogen-free silicon carbide thin films deposited by using different deposition techniques, namely plasma enhanced chemical vapor deposition (PECVD), laser ablation deposition (LAD), and triode sputtering deposition (TSD). a-SixC1−x: H PECVD, a-SiC LAD, and a-SiC TSD thin films and corresponding free-standing membranes were mechanically investigated by using nanoindentation and bulge techniques, respectively. Hardness (H), Young's modulus (E), and Poisson's ratio (v) of the studied silicon carbide thin films were determined. It is shown that for hydrogenated a-SixC1−x: H PECVD films, both hardness and Young's modulus are dependent on the film composition. The nearly stoichiometric a-SiC: H films present higher H and E values than the Si-rich a-SixC1−x: H films. For hydrogen-free a-SiC films, the hardness and Young's modulus were as high as about 30 GPa and 240 GPa, respectively. Hydrogen-free a-SiC films present both hardness and Young's modulus values higher by about 50% than those of hydrogenated a-SiC: H PECVD films. By using the FTIR absorption spectroscopy, we estimated the Si-C bond densities (NSiC) from the Si-C stretching absorption band (centered around 780 cm−1), and were thus able to correlate the observed mechanical behavior of a-SiC films to their microstructure. We indeed point out a constant-plus-linear variation of the hardness and Young's modulus upon the Si-C bond density, over the NSiC investigated range [(4–18) × 1022 bond · cm−3], regardless of the film composition or the deposition technique.

The kinetics of silicon carbide (SiC) deposition, in a hot-wall chemical vapor deposition (CVD) reactor, were modeled by analyzing our own deposition rate data as well as reported results. In contrast to the previous attempts which used only the first order lumped reaction scheme, the present model incorporates both homogeneous gas phase and heterogeneous surface reactions. The SiC deposition process was modeled using the following reactions: (i) gas phase decomposition of methyltrichlorosilane (MTS) molecules into two major intermediates, one containing silicon and the other containing carbon, (ii) adsorption of the intermediates onto the surface sites of the growing film, and (iii) reaction of the adsorbed intermediates to form silicon carbide. The equilibrium constant for the gas phase decomposition process was divided into the forward and backward reaction constants as 2.0 × 1025 exp[(448.2 kJ/mol)/RT] and 1.1 × 1032 exp[(-416.2 kJ/mol)/RT], respectively. Equilibrium constants for the surface adsorption reactions of silicon-carrying and carbon-carrying intermediates are 0.5 × 1011 exp[(-21.6 kJ/mol)/RT] and 7.1 × 109 exp[(-33.1 kJ/mol)/RT], while the rate constant for the surface reaction of the intermediates is 4.6 × 105 exp[(-265.1 kJ/mol)/RT].

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.

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.

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.

The results of a study of point defects in MgS are presented. First we obtain empirical interionic potentials in the framework of a shell model and then calculate defect energies using the HADES and ICECAP simulation procedures. The calculated Schottky formation energy is 10.9 eV in comparison to the cation and anion Frenkel formation energies of 11.9 and 25.1 eV, respectively. The migration energy by the vacancy mechanism of the Mg2+ and S2− ions is predicted to be 2.5 and 3.4 eV, respectively. One-electron ICECAP calculations yield the optical absorption energy of 3.1 eV for the F+ center in MgS.

Samples of γ-Fe2O3 have been prepared from uniform α-Fe2O3 particles obtained by homogeneous hydrolysis in solution and directly by spray pyrolysis methods. The crystalline structure of these samples was analyzed by using x-ray and electron diffraction. It was concluded that, depending on the preparation method and parameters, different degrees of order in the distribution of vacancies were present. The study of the magnetic properties of these samples included the measurement of both intrinsic (saturation magnetization) and extrinsic properties (coercive force and magnetization behavior in the approach to saturation region). It was found that all the above-mentioned quantities depended on the degree of order in the distribution of vacancies.