Confirmation of the dielectric polarization theory of anodic film formation: a voltage pulse technique for investigating Faradaic-current-driven polarization processes

Abstract

Potentiostatic voltage-pulse experiments, carried out on anodically formed tantalum oxide films, show directly the existence of a dielectric polarization process which is driven by the passage of ion-current. Furthermore, quantitative analysis of the data yields a value for the constant coupling the polarization rate to the ion-current density, of the same order as that obtained from galvanostatic field transients, a result expected if the dielectric polarization of the film makes a large contribution to the effective field causing film growth. This experiment provides, therefore, convincing evidence in support of the main tenet of the dielectric polarization theory for anodic film growth (the ion-current-driven polarization process) with some support for the effective-field postulate also provided.