Microstructure and grain size dependence of ferroelectric properties of BaTiO3 thin films on LaNiO3 buffered Si

BaTiO3 films were prepared by radio frequency sputtering on the LaNiO3/Si substrates and then annealed at different temperatures. The films exhibit a highly (1 0 0)-oriented structure and their grain size range from 14 to 55 nm after annealing. Polarization-reversal characteristics for different BaTiO3 films were measured. The results show that while obvious ferroelectricity is obtained for films with grain size larger than 22 nm, a weak ferroelectricity is still observed in BaTiO3 film of 14 nm grains, indicating that if a critical grain size exists for ferroelectricity it is less than 14 nm for polycrystalline BaTiO3 on LaNiO3/Si. The suppression of macroscopic ferroelectricity for BaTiO3 with finest grain size and the grain size dependence of remnant polarization and coercive field are also discussed in detail.