DIELECTRIC-PROPERTIES OF ELECTRON-CYCLOTRON-RESONANCE-SPUTTERED (BA, SR)TIO3 FILMS

Structural and electrical properties of Ba0.55Sr0.45TiO3 thin films ar e investigated. Electron-cyclotron-resonance sputtering was used to de posit the 200-nm-thick films in Pt/Ba0.55Sr0.45TiO3/Pt/Ti/SiO2/Si stru ctures. A dielectric constant of 250 is obtained for the films deposit ed at 450 degrees C, and that of 350 after annealing at 650 degrees C for 30 min in O-2 gas. Although in Literature the Curie temperature of the ceramics with this composition is -15 degrees C, a broad peak ext ended across 0 degrees C is observed in the dielectric constant versus measurement temperature relationship. This result coincides with an i ncrease in the width of (200) diffraction peak after the annealing, su ggesting that some peak splitting to (200) and (002) due to tetragonal ity may occur at room temperature. The polarization versus electric fi eld curves for the annealed films also showed hysteresis before and af ter de-bias stress tests without correlation with an increase in leaka ge current. These experimental results suggest that the hysteresis doe s not result only from instability due to charge trapping. The tetrago nality caused by tensile stress is thought to be one of the origins fo r the hysteresis.