AFM polarization studies of high-fatigue-endurance PZT thin film capacitors with modified Pt/RuO2 top electrodes

It has been recently shown that low leakage conduction and very good polarization fatigue performance with PZT ferroelectric thin films and Pt electrodes can be achieved by suitably adding a very thin layer of conductive oxide between the PZT and the top Pt-electrode. The particular dependence of the fatigue effect on the electric field is consistent with the earlier proposed scenario where the switching polarization suppression is determined by the relative properties of the top (TE) and bottom (BE) electrode interfaces and by the possibility of having or not, bipolar nucleation at both interfaces. In the present work it is attempted, by means of local polarization detection assisted by atomic force microscopy (AFM), to directly observe how the fatigued states are influenced by the presence of a RuO₂ thin layer between the Pt-TE and the PZT. The objective is to verify the validity of the above mentioned fatigue scenario based on the inhibition of domain nucleation, induced by electric charge injection in the near interface region of the ferroelectric film and to analyze the piezoelectric signal amplitude as a function of fatigue. The long-term objective is to disclose the microscopic fatigue mechanism