Surface oxidation as a diffusion barrier for Al deposited on ferromagnetic metals

Grazing incidence x-ray reflectometry has been used to study surface oxidation as a diffusion barrier for Al deposited on ferromagnetic metals (Co, Fe, Ni, and ${\mathrm{Ni}}_{\mathrm{80}}{\mathrm{Fe}}_{\mathrm{20}}\mathrm{).}$ Samples of the form ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{\backslash 10 nm X\backslash 4 nm Al}$ with ${\mathrm{X=(Co, Fe, Ni, and Ni}}_{\mathrm{80}}{\mathrm{Fe}}_{\mathrm{20}}\mathrm{)}$ were investigated for X\Al intermixing. Surface oxidation was achieved by exposing the ferromagnetic layer to ${\mathrm{O}}_{\mathrm{2}}$ to oxidize the top two or three atomic layers before depositing the Al layer. Specular x-ray scans were used for the analysis. Samples of the form ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{\backslash 10 nm X\backslash 4 nm Au}$ were used to separate topographical roughness from intermixing. Surface oxidation was found to suppress the diffusion of Al into Co, Ni, and ${\mathrm{Ni}}_{\mathrm{80}}{\mathrm{Fe}}_{\mathrm{20}}$ but not into Fe.