Negative-pressure enhanced ferroelectricity and piezoelectricity in lead-free BaTiO3 ferroelectric nanocomposite films

Abstract

Due to environmental concerns and the increasing drive towards miniaturization of electronic circuits and devices, lead-free ferroelectric films with low leakage current and robust ferroelectric and piezoelectric properties are highly desired. The preferred alternative, BaTiO₃, is non-toxic and has ferroelectric properties, but its high leakage current, poor ferroelectricity and piezoelectricity and low Curie temperature of ∼130 °C in thin film form are obstacles for high-temperature practical applications. Here, we report that a negative-pressure-driven enhancement of ferroelectric Curie temperature and effective piezoelectric coefficient are achieved in (111)-oriented BaTiO₃ nanocomposite films. The enhanced ferroelectric and piezoelectric properties in the emergent monoclinic BaTiO₃ are attributed to the sharp vertical interface and 3D tensile strain that develops upon interspersing stiff and self-assembled vertical Sm₂O₃ nanopillars through the film thickness. Our work also demonstrates that fabricating oxide films through (111)-oriented epitaxy opens up new avenues for the creation of new phase components and exploration of novel functionalities for developing oxide quantum electronic devices.