We have investigated the binding and diffusion pathways for atomic hydrogen in diamond using the semiempirical atom superposition and electron delocalization molecular orbital (ASED-MO) theory. The bond-centered site has been found to be more stable than the tetrahedral and hexagonal interstitial sites due to the formation of a low-lying band-gap orbital which takes the promoted electron. A second hydrogen binds even more stably to the nearby antibonding site with additional stabilization of the now doubly occupied band gap orbital. The bond-centered hydrogen is predicted to migrate along the high-density (110) planes in the diamond lattice with an activation barrier of 1.9 eV. A carbon atom vacancy is found to attract interstitial H which bind to dangling orbitals on the surrounding C atoms. These bond strengths decrease as up to a maximum of four H atoms enters the vacancy. A hydrogen atom in a vacancy is found to increase the activation energy for vacancy migration.

Electronic structure calculations are used to study the bonding at diamond/BeO interfaces. The {110} interface between zinc blende BeO and diamond is used as a representative model for general reconstructed interfaces characterized by an equal amount of Be–C and O–C bonds. The interface energy is calculated to be 2 J/m2 and combined with the estimated free surface energies to obtain an estimate of the adhesion energy. It is found to be close to the adhesion of BeO to itself, but somewhat lower than that of diamond to itself. The effects of the 7% lattice mismatch on the total energy and the band structure for a biaxially strained pseudomorphic diamond film are investigated. The effect of misfit dislocations, expected to occur for thicker films, on the adhesion energy is estimated to be lower than 10%. The bulk properties, such as equilibrium lattice constant, bulk modulus, cohesive energy, and band gap of BeO are shown to be in good agreement with experimental values and previous calculations. The valence-band offset is calculated to be 3.9 eV and found to take up most of the large band gap discontinuity. The nature of the bonding is discussed in terms of the local densities of states near the interface. The interface localized features are identified in terms of Be–C and O–C bonding and antibonding states.

Yttrium aluminum garnet (YAG) powders were synthesized by normal and reverse strike precipitation from a mixed solution containing aluminum and yttrium nitrates. The precipitates were characterized by FTIR, DTA, and TGA techniques. The amorphous precipitates were crystallized under various atmospheres (air, argon, hydrogen) at different temperatures and the product analyzed by x-ray diffraction. Only reverse strike precipitation followed by crystallization in hydrogen consistently yielded phase pure YAG.

Particles of gadolinium iron garnet, Gd3Fe5O12, were produced primarily by an aerosol spray pyrolysis technique starting with solutions of gadolinium and iron nitrates. The as-prepared particles were polydisperse solid spheres. Average diameters in the range 0.05 to 0.8 μ could be obtained by variation of the initial solution concentration. Larger particles to 2 μ were created by direct, non-aerosol, pyrolysis of the solutions. Heat treatment caused sintering and particle coalescence and yielded ∼95% garnet phase. The reaction time to create the garnet phase scaled with the square of the particle diameter, the smallest particles transforming the quickest. Magnetic measurements showed bulk behavior for the saturation magnetization, but the coercivity could be varied with particle size with a maximum near the single domain size.

Time-resolved reflectivity and Rutherford backscattering spectroscopy were used to investigate the effects of regrowth environments on the thermally induced solid phase epitaxial (SPE) regrowth of amorphous near-surface layers produced by ion implantation of single-crystal SrTiO3. Water vapor in the regrowth atmosphere was found to alter both the apparent rate and activation energy of the SPE regrowth. For relatively dry atmospheres, a single constant regrowth rate is observed at any given temperature, and the activation energy is 1.2 ± 0.1 eV. When the concentration of H2O vapor in the atmosphere is increased, however, the regrowth activation energy effectively decreases to ∼0.95 eV. When regrown in atmospheres containing H2O vapor, the SrTiO3 amorphous layer exhibits two distinct stages of SPE regrowth as compared to the single rate found for dry anneals. This two-stage process apparently results from the diffusion of H/OH from the regrowth atmosphere at the surface of the crystal through the amorphous layer to the regrowing crystalline/amorphous interface.

Deposits of nitrides and oxides of Al and Ti have been produced by laser irradiation of Al and Ti targets in air, N2, and NH3 + N2 gases. Microstructure and constituent phases in these deposits have been examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray diffractometry (XRD). The distribution of metalloid elements has been investigated by Rutherford backscattering spectrometry (RBS). On the basis of the results of these examinations, the nitride and oxide deposits have been shown to be formed by reactions between ambient gas and metal-melt or metal-vapor which take place during pulse laser irradiation.

The growth of sputter-deposited MoS2 thin films is investigated by high-resolution transmission electron microscopy. Pure high-temperature grown films are compared with H2O-contaminated films and amorphous annealed films. In the first case, the films are oriented. They have a first interface layer with crystallites having their (002) planes parallel with the substrate. The subsequent growth leads to the already described lamellar structure, with flakes perpendicular to the substrate. This structure can be explained in terms of a local branching process during crystal growth. The orientation relations between the crystallites in the parallel layer and the lamellae are determined. The local structure at the root of the lamellae, as well as at the interface, is investigated by image calculation. Water contamination in the plasma is shown to result in an amorphization of the interfacial region, followed by lamellar growth. Amorphous films annealed under vacuum do not show a lamellar structure, but have isotropic crystallization. In each of these cases, the mechanism determining the film structure is different.

Several copper vanadium oxide melts were tested for possible application as the active medium in phase-change optical data storage devices. These materials were melted in the bulk and then quenched. Their phase development was characterized to help determine their applicability to optical data storage. It was found that they satisfy many of the criteria necessary for successful phase-change data storage; further studies of their behavior in thin film geometry would be warranted.

This paper compares the luminescence spectra of Eu3+ in sol-gel derived silica samples heated at different temperatures, following the densification process from wet gel to compact silica glass. Lifetimes, linewidths, and Stark splittings of the transitions were used to study the structural evolution of the gel network.

Thermodynamic calculations were performed for chemical vapor deposition in the Al–B–Ti–N–H–Cl–Ar system in order to determine the feasibility of multiphase deposition. Reagent species used were BCl3, AlCl3, TiCl4, NH3, H2, and Ar; B2 was substituted for BCl3 to determine changes in deposition efficiency. Temperature and input molar concentrations were varied over a range of values to establish relationships among solid deposits. Through deposition diagrams, molar efficiency plots, and partial pressure graphs, several two and three phase regions were found to exist. The calculations indicate that the following dispersed phase composites could be prepared: A1N + BN + TiN, BN + TiN, BN + TiB2, BN + TiB2 + TiN, and TiB2 + TiN.

Rising T- (or R-) curve behavior is increasingly being used in order to improve the mechanical reliability of ceramic materials. In this study, the possibility of inducing such behavior using residual compressive stresses is analyzed. The T-curves obtained for certain residual stress profiles induce crack stability when the stress minima (compressive stress maxima) lie away from the surface of the sample. The consequences of this stabilization on the strength characteristics are a significant reduction in the strength variability and strength insensitivity to the initial flaw size. In addition to these desirable features, considerable strengthening is also obtained. Hence, suitably engineered compressive stress profiles are shown to be a novel and alternative means of enhancing mechanical reliability.