THE USE OF AN AL SACRIFICIAL LAYER TO IMPROVE RETENTION DURING HIGH-DOSE PT ION-IMPLANTATION INTO NI

Our previous work [Clapham, Whitton, Ridgway, Hauser, and Petrovic, J. Appl. Phys. 72, 4014 (1992) and Clapham, Whitton, and Ruck, Nucl. Ins trum. Methods B 80/81, 501 (1993)] has shown that the sputtering limit ation often associated with high-dose, heavy ion implantation into met als can be overcome by using a thin (angstrom 1000 angstrom) C sacrifi cial layer. This layer, which is deposited on the surface prior to imp lantation, sputters slowly during bombardment, thus protecting the und erlying target. The present study further investigates the potential o f the sacrificial layer technique, using Al as a sacrificial layer on a Ni target implanted with high doses (to 7 X 10(17) ionS/cm2) of 5 Me V Pt ions. The Al layer was found to be very effective in enhancing re tention of the implanted Pt, with 100% retention and a maximum concent ration of 19 at. % Pt achieved for the highest dose. This compares wit h a saturation concentration of approximately 10 at. % Pt when no sacr ificial layer was used. The mixing behavior of Al into Ni was consiste nt with other studies conducted at lower ion energies. The temperature region of radiation-enhanced diffusion was established, and the phase Ni3Al was found to be present in the Al/Ni mixed region after Pt bomb ardment.