Effect of oxygen cooling environment on the structural characteristics and dielectric properties of BaTiO₃ and SrTiO₃ thin films

The BaTiO₃ (BTO) and SrTiO₃ (STO) thin films have been fabricated on (La,Sr)CoO₃/MgO (100) single costal substrate by pulsed laser deposition (PLD). The effect of oxygen content in the BTO and STO lattices on their structural characteristics and dielectric properties has been investigated. The variation of the oxygen content was made In BTO and STO thin (10 nm) films by changing oxygen cooling pressure from 10^-3 Torr to 400 Torr. The lattice parameter of STO thin film was sensitive to the variation of the oxygen pressure while that of BTO thin film was not sensitive to the oxygen pressure. The volume of the STO thin film increased with decreasing the oxygen cooling pressure, which is attributed to the volume change caused by oxygen nonstoichiometry (deficiency). The dielectric constant of the STO thin film was insensitive to the oxygen cooling pressure. This result indicates that the dielectric constant of the STO thin film was not influenced by the oxygen deficiency, although the STO thin film was influenced by the oxygen environment and had oxygen deficient nonstoichiometry. Those results suggest that the lattice distortion is the most important factor to influence the dielectric property of specifically STO thin films. On the other hand, the BTO thin film was not susceptible to the change in the oxygen environment, resulting in insensitive lattice parameter and volume as well as the dielectric constant to the oxygen environment.