Polycrystalline diamond films were produced in a microwave plasma assisted CVD reactor using CO as the carbon source gas. Reactor exhaust gas compositions were determined by mass spectrometry using 2–10% CO and 0–1.5% O2 in H2 feed gas mixtures. The chemistry involved in the gas phase is similar to that which occurs when diamond is grown using hydrocarbons as carbon source gases. A chemical mechanism for the oxidation of CH4 in flames appears to be applicable to this system. Addition of O2 to the reactor feed gas results in increased growth rates for low addition levels possibly due to activation of the diamond surface, while lower growth rates result at high addition levels due to oxidation of carbon from the surface and depletion of diamond growth precursors in the gas phase. The chemical reactions that take place in the plasma are similar to those that occur in flames and hot filament reactors, indicating that the plasma acts to induce reactions that are normally associated with high temperature combustion processes.

Space resolved, on-line spontaneous and stimulated emission, and CARS diagnostics have been employed on CH4/H2 mixtures excited by rf-discharge in order to investigate the chemical processes and the gas phase kinetics in the plasma. CH4 and H2 concentration and temperature have been monitored during the process as a function of main reaction parameters (rf-power, total pressure, CH4/H2 ratio). Formation of CH,H2, and H in excited states has been observed. On the basis of present spectroscopic data, a model for the gas-phase reactions accompanying the carbon film deposition is proposed.

AgGaSe2 crystals are useful for nonlinear optical applications after a post-growth heat-treatment in the presence of Ag2Se to eliminate an unavoidable precipitate phase that degrades their optical properties. To understand better the heat-treatment procedure, surface migration and volume diffusion were investigated in the Ag2Se–AgGaSe2 system using reactive diffusion couples which were analyzed by x-ray diffraction, optical microscopy, and electron probe microanalysis. Surface diffusivities of all mobile species were found to be much larger than volume diffusivities. Specific values determined were DsAg = 5.43 × 10−4 exp(-0.46 eV/kT) and DvAg = 2.40 × 10−7 exp(-0.84 eV/kT), where DsAg and DvAg are effective surface diffusivity and effective volume diffusivity of Ag, respectively. The corresponding diffusivities for Ga and Se were found to be almost the same, indicating that Ga and Se move together with Ag to maintain binary (Ag2Se and Ga2Se3) stoichiometry and electroneutrality. These findings are consistent with the pattern of annihilation of the second phase precipitates in the AgGaSe2 matrix during heat treatment.

A stochastic model for the MBE growth kinetic study of compound semiconductors is developed based on the master equation approach, the solid-on-solid restriction, and the quasi-chemical approximation. The developed model is suitable for the zinc blende crystals with 001 as the growth direction. In the modeling, the diamond cubic structure and the two sublattice nature of the zinc blende crystal are taken into account. The stochastic model is extended to compound semiconductor alloys such as GaAlAsSb to make it suitable for the MBE kinetic studies of alloys. Up to four elements with two in each sublattice can be accommodated. The presence of two elements in the same sublattice was taken into account. A procedure for the evaluation of the model parameters based on the available thermodynamic and experimental data is discussed. Advantages and limitations of the stochastic model over the available theoretical models are discussed.

In this part of the work (Part II), two typical applications of the stochastic model to the MBE growth kinetic studies are presented. The applications are the MBE growth kinetics of a hypothetical compound semiconductor, ab, and diamond cubic alloy, ax. In this study, the effect of the surface diffusion process on the MBE growth kinetics is analyzed. In the case of the compound, ab, the results of the present stochastic model are compared with that of a Monte Carlo simulation study in the temperature range of 600–850 K. The results of the two studies agree qualitatively. Higher substrate temperatures result in higher growth rate and growth front smoothness due to higher surface diffusion. Beyond 800 K, the growth rate and the growth front smoothness become independent of temperature because of the saturation of the interlayer diffusion process. In the case of the alloy studies, the kinetics of a hypothetical diamond cubic alloy in which the thermodynamics favors phase separation, is studied in the temperature range of 573–898 K. Below 648 K, due to negligible surface diffusion, there is no clustering of the alloy, but the surface roughness is very large. In the intermediate temperature range of 573–798 K, with increasing temperature, the surface diffusion increases, resulting in more clustering and less surface roughness. Above 798 K, due to very high surface diffusion, complete phase separation of the alloy and a smooth surface result.

The optical properties of polycrystalline CdSe films prepared using electroless deposition techniques are discussed. Refractive index measurements are reported for the wavelength region 400–2000 nm. Extinction and absorption coefficient measurements are reported for the strong absorption regime (450–750 nm). UV reflectance measurements are also discussed.

Mechanical and optical properties and structural characteristics are described for Si:N films with Al and O additions (SixAl1−xOyN1−y) deposited by reactive RF diode sputtering on Si and SiO2 substrates. The thermal and intrinsic stress components, elastic stiffness, coefficient of thermal expansion (CTE), and refractive index were measured for films ranging in thickness from ∼2 μm to 50 μm. Some structural and microstructural data were obtained using x-ray diffraction, optical and scanning-electron microscopy, and surface profilometry. Alloying Si:N with Al to form Si:Al:N greatly reduced the compressive intrinsic and total stress found in pure Si:N films on Si. Addition of O to the Si:Al:N moderately increased the intrinsic stress, decreased the elastic stiffness, and produced a smoother, more glassy (amorphous) film.

Solid state interfacial reactions of Ti3Al with Si3N4 and SiC have been studied via both bulk and thin film diffusion couples at temperatures of 1000 and 1200 °C. The nature of reactions of Ti3Al with Si3N4 and SiC was found to be similar. Only limited reactions were detected in samples reacted at 1000 °C. In the Ti3Al/Si3N4, layered reaction products consisting of mainly titanium silicide(s), titanium-silicon-aluminide, and titanium-silicon-nitride were formed; in the Ti3Al/SiC, the reaction product was primarily titanium-silicon-carbide. In both cases, silicon was enriched near the surface region, and aluminum was depleted from the reacted region. Reactions at 1200 °C resulted in a drastic change of the Si distribution profiles; the enrichment of Si in near surface regions was no longer observed, and the depletion of Al became more extensive. Titanium nitride and titanium-silicon-carbide were the major reaction products in the Ti3Al/Si3N4 and Ti3Al/SiC reactions, respectively. Mechanisms of driving the variation of Si, N, and C diffusion behavior (as a function of temperature) and the depletion of Al from the diffusion zone are suggested. It is proposed that reactions of Ti3Al with Si3N4 and SiC lead to in situ formation of a diffusion barrier, which limits the diffusion kinetics and further reaction. The thermodynamic driving force for the Ti3Al/Si3N4 reactions is discussed on the basis of Gibbs free energy.

A Zr-modified polycarbosilane has been obtained reacting a zirconium alkoxide with a polycarbosilane. This new preceramic polymer has been nitridated in flowing ammonia up to 1000 °C. The conversion process of the polymer precursor to the Si–N–Zr–O ceramic has been followed mainly by FT-IR, XRD, and TEM investigations. The formation of the Si–N–Si network starts at 600 °C. At 1000 °C the system can be described as an amorphous silicon nitride ceramic in which very fine zirconia-based particles are dispersed. Increasing the temperature to 1300 °C results in the crystallization of t-ZrO2 microcrystals (35 Å in size). At higher temperatures the crystallization of the silicon nitride matrix into β–Si3N4 has been observed.

Very small NiFe2O4 particles between 1 and 4 nm in size have been observed in an Fe-doped NiO sample quenched during early stages of spinel precipitation. The differences between the crystal structure of NiFe2O4 and NiO made it possible to use three different TEM imaging techniques to observe these very small particles. These very small particles are distributed throughout the volume of the sample and hence were not produced by specimen preparation. The large concentration of the very small precipitates compared with the much larger but less numerous growing precipitates indicates that the very small precipitates are actually embryos which form due to compositional fluctuations. The critical size for spinel nucleation was estimated to be 4.3 nm based on the distribution in the size of very small particles. The embryos are bounded by 〈111〉 planes with an octahedral morphology which is the minimum energy morphology.

The major problem in the NiMn2O4 system has been the determination of the valencies and the cation distribution between the two sublattices of the inverse spinel structure, in which both manganese and nickel can adopt more than one valence state. X-ray photoelectron spectroscopy (XPS) was used to elucidate the valence distribution of the manganese and nickel ions. The results showed that identification of the three Mn and two Ni species in the nickel manganite phase is possible, enabling the validity of crystal structure configurations, proposed in the literature, to be assessed. A small amount of copper, added as CuO to the system, was found to be present in both monovalent and divalent states, the Cu+ ions inducing the creation of the large amount of tetravalent Mn observed. This led to a larger number of sites for electron hopping, the mechanism of conduction, and consequently the electrical conductivity of the Cu doped material is much higher than the undoped NiMn2O4.

Ceramic (Sr1−xCax)2CuO3 samples have been prepared with x = 0.00, 0.25, 0.50, 0.55, 0.75, and 1.00 in order to study the change in lattice constants with the ratio of Sr/Ca. This phase is frequently an impurity phase in the fabrication of Bi–Sr–Ca–Cu–O superconductors, and it is important to be able to connect the lattice constants with stoichiometry. The behavior of the lattice constants closely follows Vegard's law.

Crack morphology in brittle materials exposed to thermal shock is studied by means of Monte Carlo simulations based on simple three-dimensional lattice systems. Thermal shock-induced crack growth is modeled as a series of processes of storage, release, and transfer of strain energies in the system of grains. Special attention is devoted to the crack pattern on the surface exposed to thermal shock and the crack penetration in the direction perpendicular to the surface. The dependences of the crack pattern and the crack penetration on the grain boundary strength and the temperature difference of thermal shock are explored through the simulations. The results of the simulations are qualitatively consistent with crack features in available experimental reports.

Scanning tunneling microscope observations of gold-coated polymer fracture surfaces are reported. We compare nm-scale surface features of poly(methyl methacrylate) (PMMA) fractured under three different loading conditions: in tension at room temperature, in tension at liquid nitrogen temperature, and in the double torsion geometry at room temperature (slow crack growth). Fracture surfaces of polystyrene and polycarbonate loaded in tension at room temperature are also described. Each of these surfaces shows distinctive nm-scale features which we interpret in terms of the interaction between craze growth (fibril formation) and crack growth along the craze boundary. The resolution of these images is sufficient to greatly complement other fractographic studies.