AUGER-ELECTRON SPECTROSCOPY ROTATIONAL DEPTH PROFILING OF NI CR MULTILAYERS USING O2+ AND AR+ IONS

Ni/Cr multilayers with a total of 16 alternating Ni and Cr layers with a single-layer thickness of 30 nm on a smooth silicon substrate were depth profiled by Auger electron spectroscopy with and without sample rotation. The multilayers were sputtered with rastered O2+ and Ar+ ion beams, generated by a duoplasmatron ion source and having energies of 3 and 6 keV, at incidence angles of 45-degrees and 77-degrees. Sputte ring with O2+ ions improved the depth resolution with respect to the r esults obtained with Ar+ ions on stationary as well as on rotated samp les, except in the case of rotational depth profiling at 77-degrees. T he improvement observed during ion sputtering with O2+ ions at an inci dence angle of 45-degrees is ascribed to the formation of an amorphous layer of oxide, which diminished topographical and crystallinity effe cts. During rotational depth profiling of the Ni/Cr sample with O2+ io ns at 45-degrees an oxide layer with a thickness between 3 and 4 nm is formed. However, on the stationary and rotated samples ion sputtered with O2+ ions at 77-degrees, only the residue of an oxide layer was fo und. The optimal values of depth resolution obtained with rotational d epth profiling at a 77-degrees incidence angles are independent of the sputter depth, and are of the same order of magnitude for O2+ and Ar ions, lying between 3 and 5 nm. Use of a grazing angle of incidence d iminished the influence of ion mass, ion energy, recoil implantation, atomic mixing and chemical effects on the depth resolution, and sample rotation promoted a smoothing effect and reduced the microroughness o f the sample surface.