Engineering of self-assembled domain architectures with ultra-high piezoelectric response in epitaxial ferroelectric films

Substrate clamping and inter-domain pinning limit movement of non-180 degrees domain walls in ferroelectric epitaxial films thereby reducing the resulting piezoelectric response of ferroelectric layers. Our theoretical calculations and experimental studies of the epitaxial PbZr(x)Ti(1-x)O(3) films grown on single crystal SrTiO(3) demonstrate that for film compositions near the morphotropic phase boundary it is posssible to obtain mobile two-domain architectures by selecting the appropriate substrate orientation. Transmission electron microscopy, X-ray diffraction analysis, and piezoelectric force microscopy revealed that the PbZr(0.52)Ti(0.48)O(3) films grown on (101) SrTiO(3) substrates feature self-assembled two-domain structures, consisting of two tetragonal domain variants. For these films, the low-field piezoelectric coefficient measured in the direction normal to the film surface (d(33)) is 200 pm V(-1), which agrees well with the theoretical predictions. Under external AC electric fields of about 30 kV cm(-1), the (101) films exhibit reversible longitudinal strains as high as 0.35 %, which correspond to the effective piezoelectric coefficients in the order of 1000 pm V(-1) and can be explained by elastic softening of the PbZr(x)Ti(1-x)O(3) ferroelectrics near the morphotropic phase boundary.