Tuning structure in epitaxial Pb(Mg1/3Nb2/3)O3–PbTiO3 thin films by using miscut substrates

• Epitaxial growth of pure perovskite Pb (Mg1/3Nb2/3)O3–PbTiO3 on miscut SrTiO3.
• Significant broadening of the deposition window for pyrochlore-free films.
• Dependence of the structural parameters on the miscut angle.
• Films on different vicinal substrates show comparable ferroelectric properties.

Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) is one of the most promising ferroelectric material for actuator, dielectric and electrocaloric applications. However, oriented and phase pure thin films are essential to use the outstanding properties of these compounds. In this work it is demonstrated that the use of miscut substrates influences the growth mechanism leading to a significantly broader deposition window to achieve the required film quality. Therefore, epitaxial 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 films were grown by pulsed laser deposition on (001)-oriented single crystalline SrTiO3 (STO) substrates with a miscut angle between 0 and 15° towards the [100] direction using a conducting La0.7Sr0.3CoO3 buffer layer. The influence of the vicinal angle on the PMN–PT structure was studied by high resolution X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. A nearly pure perovskite phase growth with a cube-on-cube epitaxial relationship was obtained on all miscut STO substrates, whereas a significant volume fraction of the pyrochlore phase was present on the standard substrate. Reciprocal space measurements revealed a peak split of the perovskite reflections indicating structural variants of PMN–PT with different c/a ratios. An additional tilting of the PMN–PT planes with respect to the buffer layer was observed on some samples, which might be explained with the incorporation of dislocations according to the Nagai model. Polarization loops were measured in a temperature range between room temperature and 150 °C showing a sharp drop of the remanent polarization above 65 °C on vicinal substrates.