Ferroelectric properties of Pb(Zi, Ti)O3 capacitor with thin SrRuO3 films within both electrodes

Ferroelectric properties of a Pb(Zi, Ti)O-3 (PZT) capacitor with thin SrRuO3(SRO) films within both electrodes were investigated in detail. Thin SRO films of 10 nm thickness markedly improve the electrical performance, such as switching charge (Qsw), saturation characteristics of the hysteresis curve and imprint performance even at an elevated temperature. It should also be noted that there was no Qsw degradation after 5 x 10(10) read/write cycles at 5 V. No leakage current increase after the test was observed. The results of transmission electron microscope (TEM and electron dispersive X-ray (EDX) analyses also showed that there is no diffusion of either Sr or Ru in the PZT film. The Qsw increase can be explained by the model in which excess oxygen ions existing in the SRO films drift into the PZT due to the external electric field where they fill the oxygen vacancies in the PZT near the interfaces. We confirmed that the proposed electrode structure was a key to realizing highly reliable ferroelectric random access memories (FRAMs).