Ferroelectric domain configuration and piezoelectric responses in (001)-oriented PMN-PT films

(1−x)Pb(Mg1/3Nb2/3)−xPbTiO3 (x=0.3–0.35) ferroelectric thin films were prepared by pulsed laser deposition on (001) single crystal LaAlO3 substrates coated with YBa2Cu3O7 electrodes. X-ray diffraction (XRD) measurements showed the as-grown lead magnesium niobate (PMN)-lead titanate (PT) films are epitaxial and have a (001)-oriented perovskite structure. A scanning force microscope (SFM) was employed to probe the domain configuration and piezoelectric response of the films. A comparison of the topographic and domain images showed that the large grains possessed a polydomain configuration. The average value of the piezo-response signal implied that there was a net spontaneous polarization pointing towards the bottom electrode in the as-grown films, presumably due to the presence of an internal field. The piezo-response hysteresis loop obtained while the films were subjected to a dc bias voltage exhibited a behavior that was dependent on the PbTiO3 content, indicating that the mechanism behind the field-induced strain depended on the composition and structure.