Oxide thin films formed during rotational AES sputter depth profiling ofNi/Cr multilayers using oxygen ions

Ni/Cr multilayers composed of 16 alternating Ni and Cr layers with a single-layer thickness of 30 nm on a smooth silicon substrate were AES sputter depth profiled using rastered 6 keV O2+ ions. The formation of Ni and Cr oxide thin films was investigated on rotated samples in dependence on the incidence angle of O2+ ions in the range between 33° and 77°. The surface concentration of oxygen and the thickness of the oxide thin film decreased with the angle increase. The quasi-amorphous oxide film with a thickness of a few nanometers, which can diminish the topographical effects, was found only on the samples that were ion sputtered at lower angles. However, on the rotated samples depth profiled at grazing incidence angles only the residue of an oxide thin film was found and the improvement of depth resolution is attributed to the reduction of the other ion-beam-angle-dependent effects.