Ferroelectric thin film microstructure development and related property enhancement

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Abstract
Factors that control phase evolution, microstructural development and ferroelectric domain assemblage are evaluated for chemically prepared lead zirconate titanate (PZT) thin films. Zirconium to titanium stoichiometry is shown to strongly influence microstructure. As Ti content increases, there is an apparent enhancement of the perovskite phase nucleation rate, grain size becomes smaller, and the amount of pyrochlore phase, if present, decreases. While the pyrochlore matrix microstructure for near morphotropic phase boundary composition thin films consists of two interpenetrating nanophases (pyrochlore and an amorphous phase); the pyrochlore microstructure for PZT 20/80 films deposited on MgO substrates is single phase and consists of 10 nm grains. Zirconium to titanium stoichiometry also has a substantial influence on process integration. Near morphotropic phase boundary films exhibit extensive reaction with underlying TiO2 diffusion barriers; conversely, there is no chemical reaction for identically processed PZT 20/80 thin films. We have attempted to directly correlate the optical quality of PZT thin films to the following microstructural features: 1) presence of a second phase, 2) domain orientation, and 3) nanometer surface morphology.