PLASMA SOURCE ION-IMPLANTATION OF OXYGEN AND NITROGEN IN ALUMINUM

In a preliminary study we compare the surface properties of oxygen and nitrogen implanted in aluminum by the plasma source ion implantation (PSII) technique with beam line implantation of these elements. The acceleration voltage was 35 keV. Using PSII at these energies the areal density of the implanted species saturates at about 2 x 10(17) cm-2 for nitrogen and 4 X 10(17) cm-2 for oxygen. In the case of PSII with nitrogen, a relatively high concentration of oxygen is detected which is explained as due to the strong surface interaction with the oxygen contamination of the plasma. During PSII from a steady state oxygen plasma, the plasma surface interaction predominates the implantation. A surface layer of Al2O3 with a rough topology is formed. The surface hardness is lowered by this treatment. All other implanted samples show an increased dynamic hardness in a thin surface near layer of about 50 nm thickness in comparison to a nonimplanted sample. A maximum increase of the dynamic hardness by a factor 1.2 has been estimated for PSII with nitrogen and for PSII with oxygen from the plasma of the Townsend discharge.