Beyond 100% Contribution of Domain Switching to Piezoelectric Response in (100)/(001)-Oriented Tetragonal Multidomain Pb(Zr, Ti)O₃ Films Epitaxially Grown on Si substrates

Piezoelectric responses have been widely discussed based on two contributions: the intrinsic response from the deformation of the crystal lattice and the extrinsic response, including domain switching. In this study, tetragonal (100)/(001)-oriented Pb(Zr,Ti)O3 films with thicknesses of 400 and 1800 nm and different volume fractions of (001)-oriented domains were epitaxially grown on various substrates via pulsed laser deposition. The changes in crystal lattice and domain fraction under an applied electric field were systematically investigated using in situ X-ray diffraction. The intrinsic and extrinsic piezoelectric responses were evaluated quantitatively and separately. The out-of-plane lattice parameters of the (100)-oriented domains for both thicknesses of the tetragonal (100)/(001)-oriented Pb(Zr,Ti)O3 films decreased under the applied electric field, which is not conventionally considered for the piezoelectric response, whereas the change in the out-of-plane lattice parameter of the (001)-domains was relatively small. These phenomena arise from the clamping of the films by the underlying substrates. Owing to this shrinkage, the contribution of the extrinsic piezoelectric response owing to domain switching from the (100)- to the (001)-oriented domain to the overall piezoelectric response exceeded 100%. Furthermore, the relationship between non-180° ferroelastic domain switching and the lattice strain when a piezoelectric response occurs was investigated.