Effect of electrodes on the phase evolution and microstructure of Pb(Zr0.53Ti0.47)O₃films

The crystallization behavior of PZT thin films deposited by the sol-gel process on RuO2/SiO2/Si and Pt/Ti/SiO2/Si was studied and compared. X-ray diffraction studies reveal that in both cases crystallization of the perovskite structure is preceded by pyrochlore formation. Transformation of the as-deposited amorphous film to the pyrochlore phase occurs at about 500°C on both Pt and RuO2 electrodes. In the case of films deposited on RuO2 electrodes, the pyrochlore phase persists to higher temperatures, up to 700°C, as TEM shows. In the case of films deposited on Pt, the pyrochlore phase is completely transformed to perovskite upon annealing at 700°C for 10 minutes. The morphology and microstructure of the films are strongly electrode dependent. Films grown on Pt are characterized by a high density of perovskite nuclei. The subsequent growth of these nuclei results in dense, phase-pure perovskite films. In contrast, films grown on RuO2 are characterized by a lower density of nuclei resulting in inhomogeneous films. Methods to improve the homogeneity of films grown on RuO2 by controlling the nucleation process are discussed.