The kinetics of aluminum dissolution in etch pits and tunnels, in a 1 M HCl-3 M H 2 SO 4 solution at 70°C, were investigated. Dissolution current densities during growth of tunnels and pits, at potentials of roughly Ϫ0.8 and 1 V vs. Ag/AgCl respectively, were found to be approximately 6 A/cm 2 . Transient experiments using current step reductions during pitting, or anodic current pulses during tunnel growth, revealed strongly potential-dependent current densities up to 300 A/cm 2 . The results suggested that the dissolution rate is potential-dependent when measured on times scales of ϳ1 ms after potential disturbances, but insensitive to potential in quasi-stationary experiments. A kinetic model was presented assuming a monolayer or multilayer chloride layer on the aluminum surface, including kinetic expressions for transfer of Al ϩ3 and Cl Ϫ ions at the film/solution interface, and ionic conduction in the film. In agreement with experiments, the model yields constant or potential-dependent dissolution rates following a Butler-Volmer relation, depending on the time scale of experimental measurements. The large current densities in anodic transient experiments derived from high rates of Cl Ϫ incorporation during film growth.

Electron mobility in the growth direction was measured using space charge limited current techniques in device-type nin structure nanocrystalline Si:H and nanocrystalline Ge:H structures. The films were grown on stainless steel foil using either hot wire or remote plasma enhanced chemical vapor deposition techniques. Grain size and crystallinity were measured using x ray and Raman spectroscopy. The size of grains in films was adjusted by changing the deposition conditions. It was found that large ⟨220⟩ grain sizes (∼56nm)" role="

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A model for pit initiation during galvanostatic anodic etching of aluminum in acid chloride-containing solutions was developed. The predictions were compared to experimental potential transients and pit-size distributions. The model presumed that pits initiated from subsurface nanoscale voids, which were exposed by uniform corrosion. Void concentrations fit from potential transients depended on times of caustic and acid exposure before etching, in agreement with prior characterization of the voids by positron annihilation measurements. The model yielded realistic predictions of the effect of applied current density and temperature on the potential transients. The effective void concentration was found to increase with the chloride concentration in the etching solution; this suggested that higher chloride concentrations inhibit passivation of newly exposed voids, enhancing their survival probability. On the whole, the interfacial void model provided a promising quantitative description of pit initiation during anodic etching.

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