Reactions at the aluminum oxide-ferrite interface

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Sputter-deposited aluminum oxide films on NiZn ferrite substrates are used as passivation and insulation layers in fabricating magnetic recording devices. Auger electron spectroscopy and X-ray photoelectron spectroscopy have been used to monitor the changes on the Al 2O 3 target after being ion sputtered and the chemical reactions that take place between the deposited aluminum oxide and the ferrite substrate. Sputtering of Al 2O 3 target with pure argon preferentially removed some oxygen and, as a result, an oxygen-deficient aluminum oxide was formed on the target surface. During the initial aluminum oxide film growth on the ferrite surface, the sputtered species tended to satisfy its oxygen-deficient state by “stealing” oxygen from the neighboring environment. The reactions, therefore, resulted in the formation of a metallic iron phase on the ferrite surface, making the surface electrically conductive. Sputtering of the Al 2O 3 target with argon gas having an oxygen content of approximately 0.1% allowed the sputtered species to react with oxygen either in space or on the ferrite surface. This mechanism created a less reducing environment which did not allow metallic iron phase formation on the ferrite surface and thus the surface remained electrically non-conductive.