Heat-Treatment of Anodic Oxide Films on Tantalum

The temperature dependence of capacitance for heat‐treated, anodized tantalum has been used as a means of scanning the conductivity profile across the film. This conductivity results from the extraction of oxygen from the oxide by the metal during heat‐treatment. The results show that subsequent reanodization at the formation voltage is a slow process which proceeds in a stepwise manner from the electrolyte side of the oxide film toward the underlying tantalum. The application of a small anodic d‐c bias gives a temporary conductivity profile which is similar to the permanent profile obtained by partial reanodization. Further evidence is given that the oxide conductivity is highest at the interface.