Transmission electron microscopy was used to characterize microstructures of SiC densified using a transient liquid phase (resulting from the reaction of Al2O3 with Al4C3) by hot pressing at 1875 °C for 10 min in N2. High resolution electron microscopy showed that the SiC grain boundaries were free of glassy phases, suggesting that all liquid phases crystallized upon cooling. Phases that might be expected due to reactive sintering (i.e., AlN, Al2OC, Al2O3, Al4O4C, Al3O3N, or solid solutions of SiC, AlN, and Al2OC) were not observed. However, significant Al, Si, O, and C concentrations were found at all triple junctions of these rapidly densified ceramics.

Transmission electron microscopy (TEM) has been used to explore details of the structural phase transitions and corresponding microstructural features in the solid solution of Pb1−xBaxNb2O6 (PBN) tungsten bronze ferroelectrics at compositions embracing the morphotropic phase boundary between orthorhombic and tetragonal ferroelectric phases. In addition to the ferroelectric domain structures that were consistent with the expected symmetries, incommensurate ferroelastic phases were observed. The “onset” and “lock-in” transition temperatures are a function of the Pb/Ba ratio, and for lead-rich compositions it appears that the incommensurate distortion may occur above the ferroelectric Curie temperature in the paraelectric phase.

The relative energies of the related C11b, C40, and C54 crystal structures of group IV–VII transition-metal disilicides are obtained by ab initio self-consistent band-structure calculations using the augmented-spherical-wave (ASW) method. The structural energy differences among these three structures correlate strongly with d-band filling, with C40 being stabilized relative to C54 and C11b relative to C40 as the transition-metal d-electron count increases. The C40/C11b energy difference is <0.05 eV/atom only for CrSi2 and MoSi2. Relative C11b/C40/C54 energies are similar in magnitude to those obtained in previous studies of L12/D022/D023 competition in transition-metal aluminides.1,2 Calculations of the C49/C54 energetic competition are inaccurate; the differences in atomic coordination in these two structures are probably too large for the computational method to handle accurately. The total-energy results are interpreted by a detailed analysis of the electronic density-of-states (DOS) distributions. The stable structures do not correlate as strongly with DOS effects in the vicinity of the Fermi level as in the aluminides.

The near-interface structure of diamond films grown from a methane and hydrogen gas mixture by microwave plasma enhanced chemical vapor deposition has been studied. Freestanding diamond films grown on both silica and silicon at two different methane concentrations were analyzed by scanning and transmission electron microscopies, electron diffraction, Raman spectroscopy, and secondary ion mass spectroscopy. It was found that the substrate chemistry greatly influenced the nature of the carbon initially deposited on the substrate surface. Diamond formed large flat contact areas on silicon, whereas on silica a particulate type of intermediate layer formed first because of the chemical reactions occurring on and/or with the surface. It was found that the phase content of the films was greatly affected by the methane concentration in hydrogen. At the low (1.0% or less) methane concentrations in hydrogen, phase pure diamond formed; while at the high (5.0%) methane concentration in hydrogen, graphite and disordered carbon were codeposited along with diamond during the early growth stages. Silicon carbide was detected at the diamond interfaces which appeared in discrete areas on silica as opposed to a rather continuous layer as is believed to form on silicon.

Structures of some phases in the SrMnO3−x system accompanied by planar defect were studied using a high resolution electron microscope. A four-layer structure with a hexagonal unit cell was found to have an oxygen deficiency in some degree followed by planar defects normal to the c-axis which are classified into several types. On the basis of observed images showing an irregular stacking along the c-axis in the hexagonal unit, the distribution and the origin of the planar defect are discussed. A structure image showed the transformation of the four-layer phase into a nonstoichiometric state and a shear structure with a displacement vector of occurring between the face-sharing octahedra. Experiment by in situ observation during beam irradiation in an electron microscope indicates the process of the formation of the planar defect. A mechanism for the formation of the planar defect is proposed by which oxygen deficiency in face-sharing octahedra induces the displacement of SrO3 layers and oxygen octahedra which reduce the coordination number of Mn ions and the disruption of face-sharing octahedra.

Reactions between manganese thin films and silicon substrates, annealed at relatively low temperatures (<430 °C), have been systematically investigated. Three phases, i.e., Mn3Si, Mn5Si3, and MnSi, were formed through a layered growth process. The formation sequence for these silicides was Mn3Si, MnSi, and then Mn5Si3. The unusual phenomena of coexistence of these three phases and simultaneous growth of two phases (MnSi and Mn5Si3) were also observed. A model has been proposed to explain the growth behavior. The formation sequence of Mn3Si, MnSi, and then Mn5Si3, and simultaneous growth of MnSi and Mn5Si3, can be explained by considering both thermodynamic and kinetic effects. Only those reactions that are thermodynamically allowed and kinetically preferred can take place. Kinetic preference is determined by the composition in the reaction region, which is controlled by the diffusion flux of the moving reactant. The proposed model is also compared with existing models.

Silicon carbide-based ceramics can be rapidly densified above approximately 1850 °C due to a transient liquid phase resulting from the reaction between alumina and aluminum oxycarbides. The resulting ceramics are fine-grained, dense, and exhibit high strength at room temperature. SiC hot pressed at 1875 °C for 10 min in Ar was subjected to creep deformation in bending at elevated temperatures between 1500 and 1650 °C in Ar. Creep was thermally activated with an activation energy of 743 kJ/mol. Creep rates at 1575 °C were between 10−9/s and 10−7/s at an applied stress between 38 and 200 MPa, respectively, resulting in a stress exponent of ≍1.7.

Polycrystalline diamond thin films have been deposited on single crystal silicon substrates at low temperatures (⋚ 600 °C) using a mixture of hydrogen and methane gases by high pressure microwave plasma-assisted chemical vapor deposition. Low temperature deposition has been achieved by cooling the substrate holder with nitrogen gas. For deposition at reduced substrate temperature, it has been found that nucleation of diamond will not occur unless the methane/hydrogen ratio is increased significantly from its value at higher substrate temperature. Selective deposition of polycrystalline diamond thin films has been achieved at 600 °C. Decrease in the diamond particle size and growth rate and an increase in surface smoothness have been observed with decreasing substrate temperature during the growth of thin films. As-deposited films are identified by Raman spectroscopy, and the morphology is analyzed by scanning electron microscopy.

The influence of implanted impurities (B, O, P, Ar, Xe, Pb, and Bi) on the rate of low-temperature (138 °C), solid-phase epitaxial growth (SPEG) of amorphized CoSi2 has been studied. SPEG rates of impurity-implanted CoSi2, as determined from time-resolved reflectivity measurements, were retarded for all impurities compared to that of Si-implanted CoSi2. The extent of retardation varied from a factor of 1.5 for P to 9.4 for Xe. Channeling measurements of impurity-implanted CoSi2 indicated that Xe and Bi atoms were located on nonsubstitutional lattice sites while ∼40% of Pb atoms occupied either substitutional sites or vacant interstitial cation sites following annealing. The presence of impurities did not affect the CoSi2 post-anneal crystalline quality, and no significant impurity diffusion was apparent at 138 °C from secondary-ion mass spectrometry measurements.

Electrical conduction in thick film resistors has been studied, and microstructures, especially around conducting RuO2 phases in a lead-borosilicate glass matrix in as-fired and high-voltage-surged thick film resistors, have been observed in detail using transmission electron microscopy. Lattice images of as-fired thick film resistors have suggested the presence of subtle structural modifications in the very thin area across the RuO2/glass interface, whereas in the glass matrix very small dot-like contrasts on the order of 1 nm were occasionally observed and were interpreted as being small crystallites or Ru clusters. Heavy electrical loadings of thick film resistors were found to induce the local formation of plate-like crystals in glass, which were identified by electron diffraction to be a slightly modified anorthite. The significance of these observations in terms of the conduction network and the degradation due to the electrical overloading of thick film resistors are discussed.

A thermochemical analysis is performed in the system Cu–In–S at 298 K. Free energies of the compounds In6S7, In2.8S4, CuInS2, CuIn5S8, and of the recently discovered CuIn2 have been estimated, the numerical values (kJ/mol) of which are −1043 ± 21, −556 ± 8.8, −315 ± 54, −1238 ± 113, and −51 ± 26. A consistent set of data is used for the calculation of the Gibbs triangle as well as of the predominance area diagram. The results are in nearly complete agreement with the measurements published recently, in particular with those using the nuclear method of perturbed angular correlations (PAC). The compound CuInS2, one of the possible base materials for thin film solar cells, is shown to equilibrate with nearly all of the compounds of the system. A nonvariant four-phase equilibrium CuIn2−InS–In–CuInS2 is found at about 298 K. It is noted where more precise data are needed.

An alumina (Al2O3) diffusion barrier coating to inhibit the interfacial reactions between boron-carbide-coated boron (B4C/B) fibers and a nickel-aluminide (Ni3Al) (IC-221) matrix was investigated. The alumina diffusion barrier was deposited on the B4C/B fibers using chemical vapor deposition. Also, Saphikon single-crystal Al2O3 fibers were used to demonstrate the compatibility between Al2O3 and Ni3Al. The detailed microstructures and chemical compositions of the fibers, coating, and matrix before and after various thermal exposures were analyzed using scanning electron microscopy, energy dispersive x-ray analysis, and ion microprobe mass analysis. The interfacial reaction products present after 6 h at 980 °C were characterized, and Ni was found to be the dominant diffusion species. The alumina diffusion barrier shows promise for effectively inhibiting the deleterious reactions between B4C/B fibers and the Ni3Al matrix. The uncoated B4C/B fibers were consumed by the matrix after fabrication alone, whereas the Al2O3 coated fibers demonstrated resistance to the matrix for 25 h at 880 °C and 6 h at 980 °C. The Saphikon fiber-reinforced Ni3Al composites demonstrated excellent compatibility after 50 h at 1000 °C. Zirconium (Zr)-rich precipitates on the order of 2 μm in diameter formed at the fiber interface after this exposure, but no gross reaction was indicated between the fiber and the matrix.

Rutherford backscattering (RBS)-ion channeling, transmission electron microscopy (TEM), and conversion electron Mössbauer spectroscopy (CEMS) have been used to determine the structure of α–Al2O3 implanted with iron at room temperature. Changes produced by post-implantation annealing in oxidizing and reducing atmospheres were followed using the same techniques. Implantation of 160 keV Fe at room temperature produces a damaged but crystalline microstructure for fluences as high as 1 × 1017 Fe/cm2. The iron resides in a variety of local environments: three Fe2+ components, one Fe0 component, and two Fe4+ components. The relative amount of each component varies with implantation fluence. Only the Fe0 component seems to be associated with second-phase formation. In this case, 2 nm diameter α-iron particles were detected by TEM studies. Recovery of implantation-induced disorder in the Al- and oxygen-sublattices occurs in two stages for annealing in oxygen and in one continuous stage for hydrogen-annealing. The end state for iron is Fe3+ for oxygen anneals and Fe0 for hydrogen anneals. The precipitated phases observed are those to be expected from the equilibrium phase diagrams.

Phases of the nominal composition Ni3MSb (where “M” represents aluminum, gallium, or indium) were found to occur in their respective ternary systems. They were analyzed by x-ray diffraction and were found to exhibit the B81.5′ crystal structure, similar to that of Ni3GaAs. These phases were shown by differential thermal analysis (DTA) to be stable between room temperature and their melting points, which were determined to be >1150 °C, 1066 °C, and 1091 °C for Ni3AlSb, Ni3GaSb, and Ni3InSb, respectively. An analysis of their respective constituent binary systems suggested that these phases were not true ternary compounds, but rather represented specific compositions of extensive solid solutions of constituent binary phases. Speculations were made as to the solution behavior of these phases. The Ni3MSb phases were predicted to form initially in nickel/MSb diffusion couples, in an analogy to what is observed in nickel/GaAs diffusion couples.

Raman microprobe studies of pulsed laser damaged TiO2 films deposited using three different methods are reported. Phase transformation and redeposition of coating materials were observed in selected regions of amorphous films deposited by ion beam sputtering and electron beam evaporation. Preferential removal of a specific phase or transformation to a second phase were observed in reactively sputtered films. Some damage sites exhibited regions of stress heterogeneity which can be explained in terms of the return electron stream model of plasma/target interaction and rapid quenching.

Surface planarity and epi/SiO2 interface characteristics of selective epitaxial growth (SEG) and epitaxial lateral overgrowth (ELO), deposited at 800–950 °C/10 or 25 Torr, have been studied for micron-sized structures. SEG at 860 °C showed superior planarity and reduced ratio of facet width to epi thickness, compared to higher deposition temperatures. Data showed that epi/SiO2 interface defects are greatly reduced for structures parallel to (100) and/or by adding HCl to the source gas, compared to interfaces positioned at standard orientation (110) on a (100) substrate. The transition from SEG to ELO in view of the facet orientations will be discussed. To correlate structural with electrical data, n+/p diodes were fabricated on as-grown and polish planarized SEG. Leakage current values of approximately 100 nA/cm2 could be measured. These are comparable to similar n+/p junctions fabricated on conventional epi.

X-ray diffraction from a synchrotron source was employed in an attempt to identify the crystal structures in zirconia ceramics produced by the sol-gel method. The particles of chemically precipitated zirconia, after calcination below 600 °C, are very fine, and have a diffracting particle size in the range of 7–15 nm. As the tetragonal and cubic structures of zirconia have similar lattice parameters, it is difficult to distinguish between the two. The tetragonal structure can be identified only by the characteristic splittings of the Bragg profiles from the “c” index planes. However, these split Bragg peaks from the tetragonal phase in zirconia overlap with one another due to particle size broadening. In order to distinguish between the tetragonal and cubic structures of zirconia, three samples were studied using synchrotron radiation source. The results indicated that a sample containing 13 mol% yttria-stabilized zirconia possessed the cubic structure with a0 = 0.51420 ± 0.00012 nm. A sample containing 6.5 mol% yttria stabilized zirconia was found to consist of a cubic phase with a0 = 0.51430 ± 0.00008 nm. Finally, a sample which was precipitated from a pH 13.5 solution was observed to have the tetragonal structure with a0 = 0.51441 ± 0.00085 nm and c0 = 0.51902 ± 0.00086.

Conventional and high resolution electron microscopy (HREM) were used to study the structure of {113} defects in high-dose oxygen implanted silicon. The defects are created with a density of 1011 cm−2 below the buried oxide layer in the substrate region. The HREM images of the {113} defects are similar to the ribbon-like defects in bulk silicon. It is proposed that there is a third possible structure of the defects, in addition to coesite and/or hexagonal structures. Portions of some defects exhibit the original cubic diamond structure which is twinned across {115} planes. The atomic model shows that the {115} interface is a coherent interface with alternating five- and seven-membered rings and no dangling bonds.

We have implanted Nd and Er ions into x- and z-cut LiNbO3 single crystals. Rutherford backscattering spectrometry and channeling shows the recrystallization of the host during annealing and the rare earth diffusion. Nd and Er have different solubilities and different diffusion constants in LiNbO3. The solubility is strongly temperature dependent. The diffusion is substitutional, fastest parallel to c-axis of the LiNbO3 crystal and characterized by an activation energy of approximately 3.6 eV.

A Ni3Al-based alloy containing Cr is examined after preparation by Osprey deposition. The microstructure consists of solidified spherical regions showing cellular segregation interspersed with regions of finer, equiaxed segregation morphology. The segregation structure is characterized by cell interiors rich in aluminum and poor in chromium, while the cell walls are poor in aluminum and rich in chromium. This segregation pattern is the inverse of that expected, based on earlier melt spinning experience, and is explained in terms of the undercooling of the melt prior to solidification. Very high temperature annealing is required to homogenize the material, despite the use of this rapid solidification process for material fabrication.