A Very Precise Sectioning Method for Measuring Concentration Profiles in Anodic Tantalum Oxide

Abstract

Concentration profiles can be measured by removing thin uniform layers from the surface of a solid and determining the amount of the species left after the removal of each layer. The precision of such measurements depends on four factors: the thinness of the layers removed, the accuracy with which their thickness can be measured, the uniformity of the layers, and the accuracy with which the amount of the species present may be determined. The present paper describes a sectioning technique for anodic tantalum oxide, based, on slow dissolution of the oxide in almost saturated with . Layers as thin as 5Aå have been repeatedly and reproducibly removed, and the standard error in the total thickness removed is effectively about 3Aå for the purpose of profile measurements. Furthermore, the layers are removed with extreme uniformity. In effect, therefore, anodic oxide films on tantalum can be sectioned almost atom layer by atom layer.