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. (C) 2008 Elsevier Ltd. All rights reserved.