Non-planar Morphology Research Articles

Oxidation of carbon fibers and films in ceramic matrix composites: A weak link process

Non-planar morphologies observed in the reaction front of carbon fibers or interphases receding into a ceramic matrix have been analyzed. A numerical simulation was used to evaluate the parameters which control the morphology of the receding carbon reaction front. The study has indicated that in addition to influencing the recession kinetics, the morphology of the reaction front contains information regarding the interplay between oxidation behavior and microstructural features of the carbon. The implications of non-planar morphology development in receding carbon constituents with respect to ceramic matrix composites are evaluated.

Interfacial Solid-State Oxidation Reactions In The Sn-Doped In2O3 On Si And Si0.85Ge0.15 Alloy Systems

AbstractWe have experimentally demonstrated that the interface between ITO and Si or Si0.85Ge0.15 is metastable, with silicon reducing ITO to form an amorphous oxide layer and In metal. A 400nm-thick ITO layer was deposited on two types of substrates: p-type, <100> silicon wafers and a silicon wafer with a 400nm-thick layer of Si0.85Ge0.15 grown by CVD. Annealing of the ITO/Si system resulted in the growth of a 5nm-thick planar, interfacial SiO2 layer and the formation of In metal in the ITO above the SiO2 layer. In contrast, annealing of the ITO/Si0.85Ge0.15 system produced an interfacial Si0.85Ge0.15O2 layer that was non-uniform in thickness and which had a non-planar surface morphology. As-deposited and annealed samples were characterized by HREM, EDS, and C-V measurements. Thermodynamic and kinetic arguments predicted both of the different reaction paths that were observed in the two systems.

Conditions for uniform growth of GaAs1−xPx superlattices

Nonplanar morphology and compositional inhomogeneity are observed in GaAs1−xPx superlattices when the phosphorus content is substantially different in adjacent sublayers. The main characteristic feature of the distortion is a series of ribbonlike regions running through the superlattice which etch at a faster rate and contain more phosphorus than the surrounding material and are also the source of clusters of dislocations. Morphological stability and a general decrease in dislocation density can be effected by decreasing the interlayer strain, i.e., compositional difference, between the superlattice sublayers.

Junction profiles of nonplanar polycrystalline CuxS/CdS solar cells

AES depth profiles were obtained from nonplanar CuxS/CdS solar cells fabricated by the ’’wet’’ ion exchange technique. The horizontal junction (cap) thickness was determined by utilizing a focused electron beam with a spot size less than the diameter of a single grain. This technique minimized the introduction of profile artifacts caused by the nonplanar junction morphology. The cap thickness was compared to the thickness determined by a conventional electrochemical analysis developed for CuxS. No correlation was found to exist between the two results. The AES depths ranged from 0.08 to 1.16 of the electrochemical result. The S peak shape was also investigated and the identification of the chemical state of the S was used to determine the location of the CuxS/CdS interface. This method agreed well with the crossover in the Cu and Cd profiles.

Crystal Growth and Segregation under Zero Gravity: Ge

Crystal growth and segregation in space were quantitatively investigated in a Bridgman‐type configuration. It was established that the segregation behavior is diffusion controlled without interference from residual gravity, G‐jitter, and surface tension gradients. Radial and longitudinal segregation effects were accounted for by a lateral diffusional dopant redistribution within the diffusion boundary layer brought about by the nonplanar morphology of the growth interface.

THE THERMODYNAMIC DESCRIPTION OF HETEROGENEOUS DISSIPATIVE SYSTEMS BY VARIATIONAL METHODS: I. A FORMULATION OF THE PRINCIPLE OF MINIMUM RATE OF ENTROPY PRODUCTION WITH APPLICATION TO CERTAIN STATIONARY HETEROGENEOUS CONVECTIVE SYSTEMS

The variational principle[Formula: see text]where, in terms of the system's independent thermodynamic forces, Xi, the rate of entropy production per unit volume is[Formula: see text]is known to describe the integral behavior of certain non-convective, steady (constrained) dissipative processes since the Euler–Lagrange equations corresponding to each degree of freedom define just sufficient steady state conditions to uniquely specify the configuration. It is herein demonstrated that this principle generates the Le Chatelier principle in the presence of constraints which are more general than previously considered. This has made possible the description of certain heterogeneous convective systems which were not previously amenable to unique thermodynamic analysis. In particular, the principle has been used to rationalize cellular or dendritic growth from the melt in alloys. The supporting observation is cited that the non-planar morphology, as compared to a planar one, leads to the maximum rate of conservation of available energy as solute segregation.