Enhanced in-plane ferroelectricity in Ba0.7Sr0.3TiO3 thin films grown on MgO (001) single-crystal substrate

Abstract

Highly oriented Ba0.7Sr0.3TiO3 thin films were grown on MgO (001) single-crystal substrate using pulsed-laser deposition and the in-plane ferroelectric properties of the film were evaluated. X-ray diffraction characterization revealed a good crystallinity and tensile in-plane stress in the film. A well-defined ferroelectric hysteresis loop with Pr=9.5μC∕cm2 was observed along the (100) direction, which implied an enhanced in-plane ferroelectricity in the Ba0.7Sr0.3TiO3 thin film in comparison with the Ba0.7Sr0.3TiO3 ceramics. Curie temperature of the film was found to be ∼88°C, which is nearly 50°C higher than that of the Ba0.7Sr0.3TiO3 ceramics. The butterfly-shaped C-V characteristic curve also evidenced the enhanced in-plane ferroelectric property in the film, and a large dielectric tunability of 69% was found at 1MHz under a moderate dc bias field. The observation of enhanced ferroelectricity along the in-plane direction in the highly oriented Ba0.7Sr0.3TiO3 thin film was explained in terms of the increased tetragonality (a∕c=1.016) induced by the lattice misfit strain.