The effect of strain and dead layer on the nonlinear electric-mechanical behavior of ferroelectric thin films

Strain (intrinsic and thermo) and dead layer are inevitable at the substrate–ferroelectric film interface. They significantly affects the properties of nanoscale devices. The effect of strain and dead layer on the nonlinear electric-mechanical behavior of ferroelectric thin films is investigated based on micromechanical domain-switching model. Strain enhances the Gibbs free energy of a domain, making the domains more unstable and domain switching more continuous. Due to the existence of the dead layer between the ferroelectric thin film and substrate, the dielectric constant values and the effective electric field decrease through the film, thus leading to the decrease of the remnant polarization and increase of the coercive field. Our model, in which strain and dead layer are taken into consideration, shows improved displacement and strain versus electric field loops that agree reasonably well with the experimental data. In addition, both the electric displacement hysteresis and strain butterfly loops under various stress load have also been investigated by our model.