HIGH-DOSE PT ION-IMPLANTATION INTO STAINLESS-STEEL THROUGH A SACRIFICIAL CARBON LAYER - CARBON MIXING EFFECTS

It has been shown that a thin layer of C can effectively inhibit sputt ering from a metal target surface during ion implantation, enabling hi gh concentrations of an implanted species to be retained. However, som e of the C is mixed into the underlying metal by the energetic ions, a nd this increased surface C concentration may be detrimental to desire d surface properties. This study was carried out to determine whether the mixed region could be removed during the implant process through j udicious selection of C layer thickness, implanted ion energy and ion dose. Theoretical predictions using PROFILECODE suggested that a 1000 angstrom thick C layer should be fully removed by sputtering with a do se of 1.5 x 10(17) Pt cm-2. Higher doses should lead to erosion of the mixed layer. Stainless steel samples were coated with 300 and 1050 an gstrom C and implanted with 1500 keV Pt to doses between 0.1 and 1.9 x 10(17) Pt cm-2. Results of Rutherford backscattering spectrometry and secondary ion mass spectrometry showed the idea to be promising, alth ough sample heating during ion implantation resulted in extensive C mo vement into the bulk metal, well beyond the region where it could be r emoved by surface sputtering.