Substrate effect on in-plane ferroelectric and dielectric properties of Ba0.7Sr0.3TiO3 thin films

Heteroepitaxial Ba0.7Sr0.3TiO3thin films were grown on (LaAlO3)0.3(Sr2AlTaO6)0.35(001) (LSAT) and SrTiO3(001) (STO) single crystal substrates using pulsed laser deposition (PLD). X-ray diffraction characterization revealed a good crystallinity and a pure perovskite structure for films grown on both LSAT and STO substrates. The in-plane ferroelectric and dielectric properties of the films were studied using interdigital electrodes (IDE). The film grown on LSAT substrate exhibited an enhanced in-plane ferroelectricity, including a well-defined P-E hysteresis loop with the remnant polarization Pr= 10.5 μC/cm2and a butterfly-shaped C-V curve. Nevertheless, only a slim hysteresis loop was observed in the film grown on STO substrate. Curie temperature Tcof the film grown on LSAT substrate was found to be ∼105°C, which is nearly 70°C higher than that of the bulk Ba0.7Sr0.3TiO3ceramics. Tcof the film grown on STO substrate has almost no change compared to the bulk Ba0.7Sr0.3TiO3ceramics. The dielectric tunabilities were found to be 64% and 52% at 1 MHz for the films grown on LSAT and STO substrates, respectively.