Asymmetry strain induced superdomain structures in (101)-oriented Pb(Zr_0.2Ti_0.8)O₃and PbTiO₃

Ferroelectric materials in room temperature have attracted great scientific and technological interests due to its huge potential for applications in nonvolatile memory devices. Lead zirconate titanate (Pb(Zr_xTi_1-x)O_3, PZT) compounds, with remarkable ferroelectricity, is one of the most commonly studied system. Abundant previous researches have shown that ferroelectric domain structures of the PZT system would depend on the orientation of epitaxial substrate due to the stain effect. In this study, we investigated the domain structures of (101)-orientated tetragonal Pb(Zr_0.2Ti_0.8)O₃ (PZT) and PbTiO₃ (PTO) epitaxial films grown on cubic SrTiO₃ (110) substrates by vector piezoresponse force microscopy (vector-PFM). Interestingly, we observe superdomains with particular spontaneous polarizations on both PZT and PTO films which are under asymmetry strains from the substrate. However, comparing with those of (101)-orientated PTO, (101)-orientated PZT has more fine structures within one superdomain perioid, which are with polarization rotations along phi-direction observed by vector-PFM. As the result, we could further confirm the istrain effect break the in-plane symmetry of the PZT and PTO films and and lead to the superdomain structures.