Piezoelectric non-linearity in PbSc0.5Ta0.5O3 thin films

• Piezoelectric and dielectric non-linearity in epitaxial PbSc0.5Ta0.5O3 thin films.
• Observed dielectric and piezoelectric non-linearity cannot be explained by the Rayleigh model.
• Dielectric non-linearity in the PbSc0.5Ta0.5O3 films is tentatively explained as a manifestation of a percolation of the polar nano regions.

Epitaxial (001)-oriented PbSc0.5Ta0.5O3 (PST) thin films were deposited by pulsed laser deposition. Local piezoelectric investigations performed by piezoelectric force microscopy show a dual slope for the piezoelectric coefficient. A piezoelectric coefficient of 3 pm/V was observed at voltages up to 0.8 V. However, at voltages above 0.8 V, there is a steep increase in piezoelectric coefficient mounting to 23.2 pm/V. This nonlinear piezoelectric response was observed to be irreversible in nature. In order to better understand this nonlinear behavior, voltage dependent dielectric constant measurements were performed. These confirmed that the piezoelectric non-linearity is indeed a manifestation of a dielectric non-linearity. In contrast to classical ferroelectric systems, the observed dielectric non-linearity in this relaxor material cannot be explained by the Rayleigh model. Thus the dielectric non-linearity in the PST films is tentatively explained as a manifestation of a percolation of the polar nano regions.