Repassivation and ion migration in Pd-implanted TiO2 layers on Ti

TiO2 layers on Ti have been formed by anodic polarization. Implantation of 70 or 200 keV Pd+ ions yields a doped amorphous oxide. Subsequent repassivation by anodization to potentials below the formation potential causes recrystallization. This recrystallization starts at the interface with the underlying metal, demonstrating for the first time solid phase epitaxial regrowth under the influence of an electrical field. In the amorphous phase, the activation energy for ion migration is sufficiently lowered to result in three time thicker oxide layers than the original ones. During recrystallization also, Pd ions start migrating towards the surface and dissolve into the electrolyte. (author)