PINNING EFFECT OF LEAD LANTHANUM TITANATE THIN-FILMS DEPOSITED ON DIFFERENT SUBSTRATES

Pinning effect of lead lanthanum titanate (PLT) ferroelectric thin fil ms with excess PbO of 20 mol% has been studied for deposition on diffe rent substrates. Silicon, sapphire and quartz were used as substrates on which Pt/Ti or LaNiO3 thin films were deposited as bottom electrode s. Electron probe analysis results showed that there was still a certa in amount of excess Pb in PLT films after annealing at 550 degrees C f or 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 elect ron spectroscopy depth profile. It was shown that the substrates and t he bottom electrodes had significant effects on the content and distri bution of excess Pb in PLT films. The excess Pb and its accumulation a t the interface between the film and bottom electrode may act as pinni ng 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 we re high in PLT films deposited on Pt/Ti/Si, and considerable pinning e ffect 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 LaNiO 3/Si was very low and the pinning effect was hardly observed.