Effect of metal electrodes on the steady-state leakage current in PZT thin film capacitors

The ferroelectric Ir/PZT/Pt and Au/PZT/Pt capacitor structures are studied by the electron beam induced current (EBIC) technique and the steady-state current–voltage dependencies. EBIC data reveal the change in the local field at the PZT/metal interfaces caused by migration of oxygen vacancies V_o^** under an action of applied electric field. Ir/PZT and Pt/PZT interfaces block V_o^** movement causing their accumulation near the cathode interface. An electrons injection from the metal cathode to the PZT leads to formation of induced p–n junction. The steady-state leakage current in this case is well described by modified equation for the p-n diode, which considers an action of the counter electric field caused by electrons injection. In the case of transparent for oxygen vacancies Au/PZT cathode oxygen vacancies leave the PZT bulk and current–voltage dependence demonstrates a region of negative differential conductivity at high electric fields. The proposed p–n junction formalism can be used for engineering of PZT-based devices.