Colossal Electromechanical Response in Antiferroelectric-based Nanoscale Multilayers

The pursuit of smaller, energy-efficient devices drives the exploration of electromechanically active thin films (<1 µm) to enable micro- and nano-electromechanical systems. While the electromechanical response of such films is limited by substrate-induced mechanical clamping, large electromechanical responses in antiferroelectric and multilayer thin-film heterostructures have garnered interest. Here, multilayer thin-film heterostructures based on antiferroelectric PbHfO₃ and ferroelectric PbHf_1-xTi_xO₃ overcome substrate clamping to produce electromechanical strains >4.5%. By varying the chemistry of the PbHf_1-xTi_xO₃ layer (x = 0.3-0.6) it is possible to alter the threshold field for the antiferroelectric-to-ferroelectric phase transition, reducing the field required to induce the onset of large electromechanical response. Furthermore, varying the interface density (from 0.008 to 3.1 nm^-1) enhances the electrical-breakdown field by >450%. Attaining the electromechanical strains does not necessitate creating a new material with unprecedented piezoelectric coefficients, but developing heterostructures capable of withstanding large fields, thus addressing traditional limitations of thin-film piezoelectrics.