Microstructure and 90° domain assemblages of Pb(Zr, Ti)O3//RuO2 capacitors as a function of Zr-to-Ti stoichiometry

Abstract

Planar microstructure, 90° domain configurations, and cross-sectional perovskite grain morphology were characterized for a series of Pb(Zr, Ti)O3//RuO2 thin film capacitors. Perovskite grain size increased substantially with increasing Zr concentration of the Pb(Zr, Ti)O3 (PZT) films, being on the order of 0.15 μm for PZT 20/80 films and 2.5 μm for PZT 50/50 films. While PZT 20/80 and PZT 30/70 films were single phase perovskite, the PZT 40/60 and 50/50 films contained a second phase with fluorite structure. The second phase matrix consisted of two nanophases, one having fluorite structure while the other was amorphous. Both the amorphous nanophase and the fluorite nanophase were Pb deficient compared to the perovskite phase. Differences in cross-sectional perovskite grain morphology were substantial for these materials, with the PZT 40/60 film being almost entirely columnar and the PZT 20/80 film exhibiting almost entirely granular morphology. Differences in 90° domain wall density were essentially negligible among the films, suggesting that if 90° domains were responsible for the differences in electrical properties, it is not due to 90° domain population.