Pinning effect of lead lanthanum titanate thin films deposited on different substrates

Pinning effect of lead lanthanum titanate (PLT) ferroelectric thin films with excess PbO of 20 mol% has been studied for deposition on different substrates. Silicon, sapphire and quartz were used as substrates on which Pt/Ti or LaNiO₃ thin films were deposited as bottom electrodes. Electron probe analysis results showed that there was still a certain amount of excess Pb in PLT films after annealing at 550°C for 1 h, and the amount of it was dependent on the substrate used. The distribution of excess Pb in the films was investigated by Auger electron spectroscopy depth profile. It was shown that the substrates and the bottom electrodes had significant effects on the content and distribution of excess Pb in PLT films. The excess Pb and its accumulation at the interface between the film and bottom electrode may act as pinning centers and have a pinning effect on domains, which can be observed by abnormal P-E hysteresis loops and abnormal C-V curves. The excess Pb content in the films and the accumulation of Pb at the interface were high in PLT films deposited on Pt/Ti/Si, and considerable pinning effect was observed. As LaNiO₃ would absorb most part of the excess Pb in PLT films, the content of excess Pb in the films deposited on LaNiO₃/Si was very low and the pinning effect was hardly observed.