Movement of Ions During the Anodic Oxidation of Aluminum

Abstract

In an extensive series of experiments, we have studied the movement of foreign atoms during the anodic oxidation of aluminum by introducing them into the surface layers of specimens by ion implantation at low energy (20–40 keV) and determining the depths of the implants after oxidation by means of Rutherford back-scattering analysis. Two different situations were investigated; each species was implanted into specimens covered only by natural air-formed oxide (≈ 0.5 µg/cm² thick) and into specimens covered by a pre-formed oxide 11 µg/cm² thick. In the former the greater part of the implanted atoms was located in the metal, in the latter they were entirely contained by the oxide layer; see Fig. 1. The depths of the implants after both the air-formed and pre-formed oxide films had been thickened anodically, were determined using a 2 MeV He beam in the manner described in detail in Ref. (1).