Leakage currents in ferroelectric thin films

The main mechanisms of leakage currents in thin lead zirconate titanate (PZT) ferroelectric films prepared by the sol-gel method are discussed. Four specific regions are determined in I-V dependencies. At very weak fields (10-20kV/cm), the current falls with the voltage increase as a result of depolarization. In the low fields region (about 70-100kV/cm), the leakage current decreases with the decrease of voltage ramp speed and its components are the ohmic and displacement currents. In the high fields region (130kV/cm), the leakage current increases with the decrease of step voltage ramp in contrast to the previous case. Possible conductivity mechanisms are the Poole- Frenkel emission and hopping conduction. In the transition region between above-mentioned ones (from 80-90 to approximate to 130kV/cm), an abrupt unstable increase of current is observed caused by breakdown of reverse bias Schottky barrier. Depolarization currents are studied for sol-gel PZT films prepared at different preparation conditions.