Preparation of epitaxial Pb(ZrxTi1−x)O3 thin films and their crystallographic, pyroelectric, and ferroelectric properties

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Lead zirconate-titanate (PZT) thin films with tetragonal and rhombohedral structures have been successfully grown with good epitaxy on MgO single crystals and on [100]-oriented platinum thin films by rf-magnetron sputtering. The PZT films were obtained by using sputtering targets with compositions of Pb(ZrxTi1−x)O3, where x=0.2–0.8. The tetragonal PZT thin films have a strong [001] orientation, and the rhombohedral ones are (100) oriented. Asymmetric D-E hysteresis loops were observed on the tetragonal films. Nearly symmetric loops were observed on the rhombohedral films and the rhombohedral loops around the morphotropic phase boundary had slim loops. The tetragonal thin films of x=0.45 have a spontaneous polarization of 45 μC/cm2, a remanent polarization of 40 μC/cm2, and a coercive field of 150 kV/cm. It was found that significant pyroelectric currents are detected on both [001]-oriented tetragonal and (100)-oriented rhombohedral PZT films even without a poling treatment, and the direction is the same in all specimens. The relative dielectric constant εr achieves a maximum at the morphotropic phase boundary, as occurs for PZT ceramics. The pyroelectric coefficient γ increases with increase of Zr content and reaches a peak near the phase boundary in the tetragonal thin films. On the other hand, for the rhombohedral films, γ drops around the phase boundary and increases upon increasing Zr content. Thin films of x=0.45 have εr of 400 and γ of 4.2×10−8 (C/cm2 K). These films will be suitable for use in piezoelectric transducers and pyroelectric infrared detectors.