Phase Tailoring of Dense Tantalum Films for Improving Hardness of Titanium Implants Using Negative Substrate Bias During DC Sputtering at Low Temperature

This work reports the deposition of a dense α-Ta and β-Ta films to enhance the surface hardness and biocompatibility of Ti by applying a different negative substrate bias during direct current (DC) sputtering. When a Ta film was deposited with a negative substrate bias voltage of 70 V, the microstructure of the film exhibited a single β-Ta phase. Whereas, a negative substrate bias of 150 V resulted in the formation of a single α-Ta phase. The deposition of the dense Ta film onto Ti significantly improved the hardness of the Ti film. Specifically, β-Ta films possessed a hardness as large as 21.0 ± 1.5 GPa, substantially higher than that of bare Ti (3.6 ± 0.3 GPa) and α-Ta films (8.3 ± 0.3 GPa). Additionally, the obtained results also showed that bydepositing the dense Ta film, one can get the biocompatible surface.