Characterization of surface layers produced by ion implantation of nitrogen in bulk aluminium

Surface layers of overall extent less than 400 nm have been generated by ion implantation of nitrogen as N + or N + 2 at energies of 50 and 100 keV into high-purity aluminum sheet at ambient temperature. These layers have been characterized by Auger electron spectroscopy with concurrent ion etching, scanning electron microscopy of the surface, and transmission electron microscopy in plan and cross-section geometries. Rutherford backscattering spectrometry, particle-induced X-ray emission and nuclear reaction analysis were used to assess cumulative changes in surface composition. The surface composition was found to be determined by the combined effects of sputtering, ablation, and recoil implantation of both existing surface oxides and reactive species incorporated into the surface during the process of ion implantation. Regions of AlN could be identified in the subsurface at an ion dose of 1 × 10 17 N + 2 cm -2 at 50 keV. The apparently non-contiguous regions of AlN formed semi-coherently with parent aluminum grains. The reaction layer, containing AlN, residual aluminum metal and oxygen, was found to grow toward the original passivated metal surface with increasing ion dose.