Modification of titanium by ion implantation of calcium and/or phosphorus

Pretreatment of titanium by implantation of P and Ca is of interest in order to improve the quality of hydroxyapatite coatings used to enhance its biocompatibility. A near surface implantation of high doses of calcium results in an oxidation of the modified layer and the formation of CaO. By post-implantation annealing also Ca4Ti3O10 is formed. For deeper calcium implantations, precipitation of the metastable hexagonal modification of calcium has been observed instead of the cubic equilibrium phase. By high dose implantation of phosphorus, the implanted layer becomes partly amorphized. This hinders the reaction with oxygen during implantation and room temperature aging. The thickness of the surface oxide corresponds to the native oxide layer. For high dose double implantation with both elements, due to the strong swelling effect and the incorporation of oxygen, the second implant is shifted to the surface, if the energies are chosen so that the profiles should be overlapping by implantation into pure titanium. No indication for compound formation besides calcium oxide has been found as a result of the implantation. (C) 1999 Elsevier Science S.A. All rights reserved.