Flexoelectricity in barium strontium titanate thin film

Flexoelectricity, the linear coupling between the strain gradient and the induced electric polarization, has been intensively studied as an alternative to piezoelectricity. Especially, it is of interest to develop flexoelectric devices on micro/nano scales due to the inherent scaling effect of flexoelectric effect. Ba_0.7Sr_0.3TiO₃ thin film with a thickness of 130 nm was fabricated on a silicon wafer using a RF magnetron sputtering process. The flexoelectric coefficients of the prepared thin films were determined experimentally. It was revealed that the thin films possessed a transverse flexoelectric coefficient of 24.5-μC/m at Curie temperature (∼28 °C) and 17.44-μC/m at 41 °C. The measured flexoelectric coefficients are comparable to that of bulk BST ceramics, which are reported to be 10-100-μC/m. This result suggests that the flexoelectric thin film structures can be effectively used for micro/nano-sensing devices.