Dielectric properties of electron-cyclotron-resonance-sputtered (Ba, Sr)TiO3 films

Structural and electrical properties of Ba 0.55 Sr 0.45 TiO 3 thin films are investigated. Electron-cyclotron-resonance sputtering was used to deposit the 200-nm-thick films in Pt/Ba 0.55 Sr 0.45 TiO 3 /Pt/Ti/SiO 2 /Si structures. A dielectric constant of 250 is obtained for the films deposited at 450°C, and that of 350 after annealing at 650°C for 30min in O 2 gas. Although in literature the Curie temperature of the ceramics with this composition is -15°C, a broad peak extended across 0°C is observed in the dielectric constant versus measurement temperature relationship. This result coincides with an increase in the width of (200) diffraction peak after the annealing, suggesting that some peak splitting to (200) and (002) due to tetragonality may occur at room temperature. The polarization versus electric field curves for the annealed films also showed hysteresis before and after dc-bias stress tests without correlation with an increase in leakage current. These experimental results suggest that the hysteresis does not result only from instability due to charge trapping. The tetragonality caused by tensile stress is thought to be one of the origins for the hysteresis.