Low-temperature deposition of (1 1 0) and (1 0 1) rutile TiO2 thin films using dual cathode DC unbalanced magnetron sputtering for inducing hydroxyapatite

Thin films of both (1 1 0) and (1 0 1) rutile titanium dioxide (TiO2) were synthesized using a dual cathode DC unbalanced magnetron sputtering at low temperature with various substrate bias voltages (Vsb) ranging between 0 and −150 V. The TiO2 film prepared with Vsb = 0 underwent heat treatment after deposition. It was observed that the (1 1 0) rutile phase was deposited on the film with Vsb below −50 V. Furthermore, the film showed high crystallinity after the heat treatment. However, when using Vsb above −50 V, the phase of film shifted to (1 0 1) due to the formation of high-energy particles on the surface. For in vitro testing, the samples were immersed in simulated body fluid (SBF) for 7 days. The heat-treated (1 1 0) rutile shows a poor distribution of hydroxyapatite (HA) formation, generally causing the stress effect. The film was prepared with Vsb = 50 V and observed to form higher crystallinity of HA.