Structure and properties of titanium oxide layers prepared by metal plasma immersion ion implantation and deposition

Coating with titanium oxides is a promising method to improve the blood compatibility of materials to be used for medical implants. Ti oxide layers were deposited on oxidized Si from a plasma produced by cathodic arc evaporation under addition of oxygen to the ambient near the substrate. In dependence on the deposition parameters amorphous and nanocrystalline structures, crystalline layers composed of anatase and brookite as well as layers dominated by the rutile phase have been obtained. The activation of the plasmatic clotting cascade was only minimally influenced by the crystal size and the crystallite structure of the titanium oxide films. As a trend, amorphous, nanocrystalline and fine-grained layers show higher clotting times than well crystallized rutile films. Ion implantation of Cr or P strongly influences the clotting time. Contrasting tendencies in the dependence of clotting time and platelet adhesion on the microstructure of the Ti oxide have been found, however, for P+-doped rutile both, enhanced clotting time and improved platelet adhesion, are observed. Platelet adherence and activation always show similar trends.