Phase field study on the effect of substrate elasticity on tip-force-induced domain switching in ferroelectric thin films

Tip-force-induced domain switching in ferroelectrics has recently attracted extensive interest as it provides an alternative switching strategy that might ease the problems brought by electrical switching. From the viewpoint of mechanics, substrate elasticity can largely modify the tip-induced deformation of ferroelectric thin films. However, so far, discussions on the influence of substrate elastic properties on such domain switching still remain exclusive. Here, a phase-field model is employed to study the influence of substrate stiffness on the domain switching in BaTiO3 (BTO) thin films, with the strain and stress distributions in BTO thin films and substrates solved by the finite element method. The results demonstrate that the substrate stiffness and loading modes (i.e., pressing and sliding) have a great influence on the symmetry of strain and stress distributions. The switched domain size is highly dependent on the substrate stiffness and loading modes. The switching is more efficient for thin films on a softer substrate. Moreover, the domain could be switched more effectively by the sliding mode under relatively large forces. Our study thus provides a strategy to increase the mechanical switching efficiency of ferroelectric thin films via tuning the substrate elasticity.