Sputter deposition of calcium phosphate/titanium dioxide hybrid thin films

The application of either hydroxyapatite (HA) or titanium dioxide (TiO₂) as coatings onto existing bioinert materials has been explored as the key route for enhancing the surface properties of hard tissue implant devices. However, it has been proposed that composite HA/TiO₂ coatings may provide significant advantages for the application of such surfaces. This work reports on the surface properties of such composite HA/TiO₂ surfaces produced by the sputter deposition of HA onto a titanium surface and their subsequent thermal processing using either post deposition (PDA) or in situ annealing (ISA). For both the PDA and ISA coatings, a hybrid nature was only achieved in the uppermost surface region after annealing at 700 °C. It was observed that the Ca/P ratio decreased with increasing annealing temperature for the PDA coatings and that the coating annealed to 700 °C had a value of 1.82 ± 0.07, which was closest to stoichiometric HA. In comparison, the Ca/P ratio of the ISA samples increased with increasing annealing temperature. It has been shown that the resultant coatings have surface properties that are dependent on the annealing profiles employed, and that a temperature of 700 °C is required in order to create a Ca–P/TiO₂ hybrid surface.