Fatigue anisotropy in pulsed laser deposited PYbN-PT thin films

Heterostructures consisting of a (100) LaA1O₃ (LAO) or (111) SrTiO₃ (STO) substrate, a SrRuO₃ (SRO) metallic oxide bottom electrode, and a (1-x) Pb[Yb_1/2Nb_1/2]O₃ - x PbTiO₃ (PYbN-PT, x∼0.5 or 0.6) ferroelectric thin film were grown by the pulsed laser deposition process. The films were perovskite structured, with orientations that ranged from highly '001'_pc-oriented PYbN-PT/SRO/LAO to highly '111'_pc-oriented PYbN-PT/SRO/STO multi-layer systems. According to the crystal orientation, the ferroelectric and fatigue characteristics of such as-grown planar capacitors vary significantly. In particular, '001'_pc-heteroepitaxial thin films result in fatigue-free capacitors up to 10¹¹ cycles while '111'_pc-oriented heterostructures exhibit a marked degradation of the switchable polarization by ac voltage cycling. These data agree with recent findings of fatigue anisotropy in relaxor ferroelectric-PbTiO₃ single crystals. This orientation dependence may result from differences in the domain configuration and switching process.