Structure and properties of biomedical TiO₂ films synthesized by dual plasma deposition

Titanium metal and titanium alloys are among the most widely used materials in biomedical devices because of their relatively high corrosion resistance and good biocompatibility. It has been suggested that the physiochemical and dielectric properties of the surface native oxide play a crucial role in the biocompatibility. There is increasing evidence that titanium may be extensively released in vivo and, under certain conditions, accumulated in adjacent tissues or transported to distant organs. Therefore, it is necessary to synthesize thicker and denser TiO₂ films on titanium to enhance its biomedical properties. In this paper, we discuss our fabrication technique utilizing dual plasma generated by metal vacuum are and radio frequency. The films fabricated consist of rutile crystal, although the substrates are not heated. As the oxygen partial pressure is raised, the intensity of the (101) and (110) diffraction peaks increases, and that of the (002) diffraction peak decreases. The preferred orientation of the TiO₂ film shifts from (002) to (110) as a result of the competition between the surface free energy and ion bombardment. At low oxygen pressure, the TiO₂ grain growth is mainly affected by ion bombardment, whereas thermodynamic factors affect the film growth at higher oxygen partial pressure. When the oxygen partial pressure reaches 0.93 × 10^-2 Pa, further increase in the oxygen flow rate does not change the film composition. The film is completely oxidized and only comprises the TiO₂ phase. The microhardness of the TiO₂ films increases with the oxygen partial pressure and reaches a maximum value of 19 GPa at 1.7 × 10^-2 Pa.