Ferroelectric properties of (Pb,La)TiO₃ thin films by multiple cathode sputtering

(Pb,La)TiO₃ (PLT, La/Ti=0.17, 0.20 and 0.24) thin films were prepared by multiple cathode rf-magnetron sputtering. Perovskite PLT could be obtained on various substrates at 460~540°C. The electrical properties of these films were investigated. The PLT thin films deposited on Pt/MgO substrate exhibited higher crystallinity, squarer hysteresis loops and higher remanent polarization (Pr) values compared to the films on the Pt/SiO₂/Si substrate. By lowering substrate temperature, ferroelectric properties were improved. By controlling the Pb/Ti incident ratio, thin films with different Pb contents were formed at 460°C. The Pb-deficient PLT film showed weak ferroelectric behaviour. While, the Pb-rich PLT film showed a saturated hysteresis loop. The fatigue resistance was increased with the Pb content. The relation between ferroelectric properties and the Pb content are discussed in terms of the build-up of space charge