A~BSTRACTThe formation of oxide films on resistively heated silicon in dry oxygen was followed in situ using a computer controlled ellipsometer. For (111)

The formation and oxidation of nickel hydroxide films under a variety of experimental conditions are studied using in situ ellipsometric measurements. Two forms of the hydroxide, which we assume to be the α and β forms reported by other workers, are found. The α‐ and β‐hydroxide layers are both transparent with real refractive indices of 1.52 and 1.46, respectively, at 6328Aå. Upon oxidation the two forms of hydroxide convert to different oxides, both of which absorb light. The process involved in the conversion of the β‐hydroxide appears to be similar to the process postulated for the charging of the nickel battery electrode.

The steady-state and transient conductivities of solutions of an ionic surfactant in a dielectric fluid were investigated experimentally over a wide range of applied voltages for various cell thicknesses. The observed nonlinear dependence of steady-state current density on applied field suggests the importance of dissociation-recombination processes in the bulk. The transient current response was found to depend markedly on the applied voltage conditions. On the first application of a field a steadily decreasing current was observed; reversing the polarity of the applied field produced a well-defined current peak. The peak times are not directly proportional to cell thickness or to the inverse of the applied field. Transient current behavior indicates a complex transport process involving bipolar ionic conduction in the bulk. In addition, conditions where space charge and electrohydrodynamic effects influence the transients are identified. The observed behavior is characteristic of many systems of weakly dissociating species in dielectric fluid.

No abstract

In situ ellipsometric measurements on the galvanostatic oxidation of tantalum, niobium, and tungsten show that both the refractive index and the thickness of the oxide change suddenly on changing the current applied to the film. For all three metals the thickness was found to increase linearly with the electric field, whereas both the refractive index and low frequency (1000 Hz) dielectric constant were found to decrease linearly with increasing field. The magnitudes of the changes in dielectric constant and refractive index that were detected experimentally, when compared with theoretical predictions using standard dielectric theory and the observed change in thickness, indicate that these changes are due to the variation in the density of the film with the applied field. The inclusion of the linear dependence of the dielectric constant on field into an effective field model of the ionic conduction process is shown to be a possible explanation of the curvature in the plot of ln(i) vs. E for the anodic oxidation process.