Impurity Distributions in Anodic Films on Tantalum

Anodization of tantalum in electrolytes containing phosphorus or fluorine ions resulted in the incorporation of a quantity of these elements into the anodic film. While phosphorus was concentrated in the outer portions of such films, fluorine was attracted to the oxide/metal interface. We employed an ion microprobe mass spectrometer to examine the concentration profiles of these elements in films formed by a variety of anodization procedures. These experiments demonstrated the usefulness of the IMMS as a tool for such work and, in addition, furnished information on the characteristics of both film growth and the distribution and movement of these impurities. The influence of fluorine‐rich layers at the oxide/metal interface on the adherence of the anodic films was also shown.