Ionic Current as a Function of Field in the Oxide during Plasma Anodization of Tantalum and Niobium

Abstract

The plasma anodization of tantalum and niobium in an oxygen d‐c glow discharge was confirmed to be analogous to anodization in aqueous solutions in that evidence was obtained that the ion current in the oxide was a function of field E in the oxide. Experimental data on were obtained using in situ ellipsometry to determine the thickness of oxide , and hence (using probe measurements to obtain the potential difference across the oxide) and from . The ellipsometry data are consistent with a two‐layer oxide, and this may indicate that both metal and oxygen ion motion is involved in the growth process.