Large Electromechanical Responses Driven by Electrically Induced Dense Ferroelastic Domains: Beyond Morphotropic Phase Boundaries

Piezoelectric materials based on ferroelectrics with a perovskite structure are among the most useful materials because they can convert electrical energy into mechanical energy and vice versa. Although piezoelectricity strongly depends on ferroelastic domain density, there are no general methods to controllably fabricate dense domain structures in ferroelectric films. Here, we report a mechanism to achieve a large piezoresponse based on an electrically induced dense ferroelastic domain structure in ferroelectric films. We demonstrate a large piezoelectric coefficient of 310 pm/V under both bipolar and unipolar electric fields, which is about 3 times larger than that in epitaxial single-crystalline thin films of tetragonal PbZr0.4Ti0.6O3 grown on silicon substrates. Analysis by a combination of in situ Raman and piezoresponse force microscopy suggests that the large piezoelectric response can be explained by the motion of dense ferroelastic domain walls. This mechanism provides a general method to enhance the piezoelectric properties of ferroelectric materials.