AUGER-ELECTRON PROFILES OF CHEMICAL-ELEMENT DISTRIBUTION IN THE ANODIC ALUMINUM-OXIDE FILM FORMED IN A CITRIC-ACID ELECTROLYTE

Profiles of element distribution in an anodic aluminum oxide film formed in a citric-acid electrolyte have been investigated by Auger electron spectroscopy in combination with ion sputtering. It has been found that the principal chemical elements (aluminum, oxygen, and carbon) are distributed nonuniformly across the thickness of the anodic oxide film. The carbon concentration decreases monotonically from the surface into the interior of the film. At the oxide/metal interface, the element concentration in the film gradually decreases and the concentration of unoxidized aluminum gradually increases. These observations are attributed to the specific cellular structure of the anodic oxide film.