Chemically prepared Pb(Zr,Ti)O3 thin films: the effects of orientation and stress

The effects of orientation and stress on chemically prepared Pb(Zr,Ti)O₃ (PZT) film properties have been determined. Systematic modification of the underlying substrate technology has made it possible to fabricate suites of films that have various degrees of orientation at a constant stress level, and to fabricate films that are in different states of stress but have similar orientation. Highly oriented films of the following compositions have been fabricated: PZT 60/40, PZT 40/60, and PZT 20/80. Remanent polarizations (≈60 μC/cm ²) greater than those of the best bulk polycrystalline ferroelectrics were obtained for PZT 40/60 films that were under compression and highly (001) oriented. Systematically varying orientation influenced ferroelectric properties, and the film stress also had a considerable effect. The sign of the film stress at the Curie point controlled the type of ferroelectric behavior exhibited by the films. Stress measurements as a function of thermal history indicated that the coefficient of thermal expansion of the paraelectric state was critical in determining the type of film ferroelectric behavior