Crystal structure and optical properties of TiO₂ thin films prepared by reactive RF magnetron sputtering

In sputtering deposition process of TiO₂, metal Ti or sintered TiO₂ target is used as deposition source. In this study, we have compared the characteristic of target materials. When TiO₂ target was used, stoichiometric TiO₂ films was deposited under the Ar atmosphere containing 1.0% of oxygen. The highest sputtering rate under this atmosphere was 3.9nm/min at 3.4W/cm². But, sintered TiO₂ target is fragile and cannot endure higher density of input power than 3.4W/cm². On the other hand, Ti target needs higher oxygen concentration (8%) in sputtering gas atmosphere for obtaining rutile/anatase. Even though Ti target can be input twice power density of 7.9W/cm², the highest deposition rate for Ti target was 1.4/nm, which was ∼35% of the highest rate for TiO₂ target. Then we have study out the composite target consisting of Ti plate and TiO₂ chips. Using the composite target, stoichiometric TiO₂ films were prepared in the rate of 9.6nm/min at 6.8 W/cm² under the atmosphere of Ar/2.5%O₂. Furthermore, we have found that the TiO₂ films obtained from the composite target consisted of about 100% anatase, whereas TiO₂ films obtained from other target have rutile dominant structure. The optical band gap energy of the film is determined by using the Tauc plot. The calculated band gap energies for the films deposited by Ti target and composite target were 2.95 and 3.24eV, which are equivalent to that of rutile and anatase structure, respectively.