Piezoelectric properties of epitaxial Ba0.6Sr0.4TiO3 thin films

The nonlinear piezoelectric response of epitaxial Ba0.6Sr0.4TiO3 thin films is investigated theoretically using a modified thermodynamic model based on the Landau-Devonshire-type phenomenological theory. The effective piezoelectric coefficients of Ba0.6Sr0.4TiO3 thin films grown on MgO substrate and LaAlO3 substrate as a function of the external field and film thickness are calculated. Analysis shows that an optimum nonlinear piezoelectric coefficient can be obtained by adjusting the substrate material and film thickness especially in the vicinity of critical thickness. Besides, the impact of deposition temperature on the effective piezoelectric coefficient is also exhibited. It is suggested that there is much stronger electric field dependence for a lower deposition temperature.