HIGH-DOSE IMPLANTATION OF YTTRIUM AND BARIUM IONS INTO COPPER - THE USE OF A SACRIFICIAL CARBON LAYER FOR ENHANCED RETENTION

High dose implantation of heavy ions is highly problematical, since th ese ions may have sputtering yields (S(y)) in excess of 30, with high doses leading to significant target erosion and a resultant loss of th e implanted species. Although the S(y) of heavy ions into metals can b e very high, the S(y) of those same ions into lighter materials is oft en quite low. We have been investigating a technique involving the use of thin (< 1000 angstrom) C coatings on metal targets, to act as slow ly sputtering ''sacrificial layers'' during heavy ion implants. Uncoat ed Cu samples were implanted with high doses (> 1.5 x 10(17) ions/cm2) of 400 or 600 keV Y and Ba ions. The retention in these samples was a pproximately 80% for the Y implantation but only approximately 10% for the Ba implantation. The Ba implants were then repeated into Cu targe ts coated with a thin (750 angstrom) layer of C. This yielded excellen t results, with Ba retentions close to 100%. Results of a SIMS study ( to examine C mixing) and X-ray diffraction to investigate phase format ion will also be discussed.