Tuning Susceptibility via Misfit Strain in Relaxed Morphotropic Phase Boundary PbZr_1-xTi_xO₃ Epitaxial Thin Films

Epitaxial strain is a powerful tool to manipulate the properties of ferroelectric materials. But despite extensive work in this regard, few studies have explored the effect of epitaxial strain on PbZr_0.52Ti_0.48O₃. Here we explore how epitaxial strain impacts the structure and properties of 75 nm thick films of the morphotropic phase boundary composition. Single-phase, fully epitaxial films are found to possess "relaxed" or nearly "relaxed" structures despite growth on a range of substrates. Subsequent studies of the dielectric and ferroelectric properties reveal films with low leakage currents facilitating the measurement of low-loss hysteresis loops down to measurement frequencies of 30 mHz and dielectric response at background dc bias fields as large as 850 kV/cm. Despite a seeming insensitivity of the crystal structure to the epitaxial strain, the polarization and switching characteristics are found to vary with substrate. The elastic constraint from the substrate produces residual strains that dramatically alter the electric-field response including quenching domain wall contributions to the dielectric permittivity and suppressing field-induced structural reorientation. These results demonstrate that substrate mediated epitaxial strain of PbZr_0.52Ti_0.48O₃ is more complex than in conventional ferroelectrics with discretely defined phases, yet can have a marked effect on the material and its responses. The role of epitaxial strain in affecting the properties of PbZr_0.52Ti_0.48O₃ films is explored. Complex domain structures and property evolution are found despite films possessing nearly "relaxed" structures indicating that the elastic constraint from the substrate produces residual strains that dramatically alter the electric-field response including quenching domain wall contributions to the dielectric permittivity and suppressing field-induced structural reorientation.