Perovskite phase stabilization in epitaxial Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ films by deposition onto vicinal (001) SrTiO₃ substrates

We report the perovskite phase stabilization of 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-PT) epitaxial thin films by deposition onto miscut substrates. Films were grown on (001) SrTiO₃ substrates with miscut angles from O to 8 degrees toward the [100] direction using 90° off-axis magnetron sputtering. Films on high miscut substrates (>4°) showed almost the pure perovskite phase in both x-ray diffraction and transmission electron microscopy image, and were nearly stoichiometric. In contrast, films on exact (001) SrTiO₃ contained a high volume fraction of pyrochlore phases with Pb deficiency. Atomic force microscopy reveals that films on 8° miscut substrates have a much smoother surface morphology than those on exact (001) SrTiO₃. Cross-sectional transmission electron microscopy images reveal that the pyrochlore phases nucleate on top of the perovskite phase, and that the amount of the pyrochlore phases increase with film thickness. A film on an 8° miscut substrate exhibits a polarization hysteresis loop with a remnent polarization of 20 μC/cm² at room temperature.