Effect of bottom electrodes on microstructures and electrical properties of sol-gel derived Pb(Zr0.53Ti0.47)O3 thin films

Lead zirconate titanate (PZT) thin films were fabricated by adding 15 mol.% excess of Pb to the starting solution and spin coating onto Pt/Ti/SiO2/Si and Ir/IrO2/SiO2/Si substrates. The effect of bottom electrodes on the microstructures, crystalline phases and electrical properties of the PZT thin films was investigated. It was found that the films deposited on Pt/Ti bottom electrode consisted of perovskite phase without pyrochlore phase, whereas the films deposited on the Ir/IrO2 bottom electrode consisted of mainly perovskite phase with a small amount of pyrochlore phase. Bottom electrodes were also found to influence the preferred orientation and microstructure as well as the surface morphology of the PZT films. The Pt/Ti bottom electrode favored a (100) orientation and fine-grained structure as well as a smooth surface, whereas the Ir/IrO2 bottom electrode favored a random orientation, non-uniform structure and rough surface. High-resolution electron microscopy observation reveals that there is an intermediate layer of IrO2 at the PZT/Ir interface. This indicates that the intermediate layer of IrO2 influenced the orientation and microstructure of the PZT films on the Ir/IrO2, bottom electrode. Ferroelectricity was investigated by observing the polarization hysteresis loops, The remanent polarization and saturation polarization of the PZT films on the Ir/hO(2) bottom electrode were smaller than those of the PZT films on the Pt/Ti bottom electrode. The difference between the dielectric and the ferroelectric properties in these PZT films was correlated to their crystalline phases and microstructure. (C) 2002 Elsevier Science B.V. All rights reserved.