Characterization of calcium titanate thin films deposited on titanium with reactive sputtering and pulsed laser depositions

In the present study, characteristics of calcium titanate thin films deposited on titanium by reactive sputtering and pulsed laser deposition techniques were investigated. In both techniques, a calcium titanate target was used as a deposition source, and the titanium substrate was heated at 873 K during the deposition. The oxygen flow for the reactive sputtering was in the range of 1 to 10 sccm, and the oxygen pressure for the pulsed laser deposition was in the range of 0.13 to 13 Pa. The deposited films were crystallized into perovskite-type calcium titanate; furthermore, a titanium-dioxide layer formed in the interface between the film and substrate. In the film deposited by reactive sputtering with low oxygen flow, titanium-to-calcium ratio ([Ti]/[Ca]) is lower than that of stoichiometric calcium titanate due to the formation of calcium hydroxide. The ratio increases with an increase of oxygen flow, and the ratio of the film deposited with a 10-sccm oxygen flow was almost in accordance with that of stoichiometric calcium titanate. On the other hand, in the pulsed laser deposition, [Ti]/[Ca] ratios of the deposited film were almost in accordance with that of stoichiometric calcium titanate at the oxygen pressure under the present experimental condition. In both deposition techniques, the thickness of the titanium-oxide layer increased with an increase of the amount of oxygen gases. The results indicate that the pulsed laser deposition has an advantage for the preparation of the stoichiometric calcium titanate film without formation of a thick titanium-oxide layer.