Mechanically induced ferroelectric switching in BaTiO₃ thin films

The ability to reverse or switch the polarization of a ferroelectric thin film through a mechanical force under an atomic force microscopy (AFM) tip offers the exciting possibility of a voltage-free control of ferroelectricity. One of the important metrics for characterizing such a switching process is the critical force F_c required to reverse a polarization. However, the experimentally measured values of F_c display a large uncertainty and vary significantly even for the same ferroelectric film. Here, using BaTiO₃ thin films as a model system, we systematically evaluate F_c using a combination of AFM-based experiments and phase-field simulations. In particular, we study the influence of the AFM tip radius, misfit strain, and film thickness on F_c as well as the interplay between the flexoelectric and piezoelectric effects. This work provides a deeper understanding on the mechanism and control of mechanically induced ferroelectric switching and thus guidance for exploring potential ferroelectric-based nanodevices based on mechanical switching.