Direct piezoelectric properties of BiFeO3 epitaxial films grown by combinatorial sputtering

Abstract

We have proposed that BiFeO₃ films are suitable for piezoelectric vibration energy harvesting applications, because of the low dielectric permittivity and excellent ferroelectricity. In this paper, the improvement of the piezoelectric properties of the domain-engineered BiFeO₃ films was discussed. The (100) epitaxial films were prepared at growth temperatures between 500 and 650°C on Nb-doped (100) SrRuO₃ single crystals. The combinatorial sputtering method was employed in order to prevent Bi defects during high-temperature deposition. The domain structure and e_31,f piezoelectric coefficients of the films were characterized by a piezoelectric force microscopy and direct piezoelectric response, respectively. The highest e_31,f coefficient of -4.3 C/m² and figures of merit of 14 GPa were obtained in the film deposited at 600°C, which has the highest domain wall density. This suggests that the introduction of the domain walls is effective to enhance the piezoelectric properties of BiFeO₃ films.